Transforming the way cancer vaccines are designed and made

A new way to significantly increase the potency of almost any vaccine has been developed by researchers from the International Institute for Nanotechnology (IIN) at Northwestern University. The scientists used chemistry and nanotechnology to change the structural location of adjuvants and antigens on and within a nanoscale vaccine, greatly increasing vaccine performance. The antigen targets the immune system, and the adjuvant is a stimulator that increases the effectiveness of the antigen.

The scientists used chemistry and nanotechnology to change the structural location of adjuvants and antigens on and within a nanoscale vaccine, greatly increasing vaccine performance. The antigen targets the immune system, and the adjuvant is a stimulator that increases the effectiveness of the antigen.

The study will be published Jan. 30 in Nature Biomedical Engineering.

"The work shows that vaccine structure and not just the components is a critical factor in determining vaccine efficacy," said lead investigator Chad A. Mirkin, director of the IIN. "Where and how we position the antigens and adjuvant within a single architecture markedly changes how the immune system recognizes and processes it.

Mirkin also is the George B. Rathmann Professor of Chemistry at the Weinberg College of Arts and Sciences and a professor of medicine at Northwestern University Feinberg School of Medicine.

This new heightened emphasis on structure has the potential to improve the effectiveness of conventional cancer vaccines, which historically have not worked well, Mirkin said.

Mirkin's team has studied the effect of vaccine structure in the context of seven different types of cancer to date, including triple-negative breast cancer, papillomavirus-induced cervical cancer, melanoma, colon cancer and prostate cancer to determine the most effective architecture to treat each disease.

Conventional vaccines take a blender approach

With most conventional vaccines, the antigen and the adjuvant are blended and injected into a patient. There is no control over the vaccine structure, and, consequently, limited control over the trafficking and processing of the vaccine components. Thus, there is no control over how well the vaccine works.

"A challenge with conventional vaccines is that out of that blended mish mosh, an immune cell might pick up 50 antigens and one adjuvant or one antigen and 50 adjuvants," said study author and former Northwestern postdoctoral associate Michelle Teplensky, who is now an assistant professor at Boston University. "But there must be an optimum ratio of each that would maximize the vaccine's effectiveness."

Enter SNAs (spherical nucleic acids), which are the structural platform -- invented and developed by Mirkin -- used in this new class of modular vaccines. SNAs allow scientists to pinpoint exactly how many antigens and adjuvants are being delivered to cells. SNAs also enable scientists to tailor how these vaccine components are presented, and the rate at which they are processed. Such structural considerations, which greatly impact vaccine effectiveness, are largely ignored in conventional approaches.

Vaccines developed through 'rational vaccinology' offer precise dosing for maximum effectiveness

This approach to systematically control antigen and adjuvant locations within modular vaccine architectures was created by Mirkin, who coined the term rational vaccinology to describe it. It is based on the concept that the structural presentation of vaccine components is as important as the components themselves in driving efficacy.

"Vaccines developed through rational vaccinology deliver the precise dose of antigen and adjuvant to every immune cell, so they are all equally primed to attack cancer cells," said Mirkin, who also is a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. "If your immune cells are soldiers, a traditional vaccine leaves some unarmed; our vaccine arms them all with a powerful weapon with which to kill cancer. Which immune cell 'soldiers' do you want to attack your cancer cells?" Mirkin asked rhetorically.

Building an (even) better vaccine

The team developed a cancer vaccine that doubled the number of cancer antigen-specific T cells and increased the activation of these cells by 30% by reconfiguring the architecture of the vaccine to contain multiple targets to help the immune system find tumor cells.

The team investigated differences in how well two antigens were recognized by the immune system depending on their placement -- on the core or perimeter -- of the SNA structure. For an SNA with optimum placement, they could increase the immune response and how quickly the nanovaccine triggered cytokine (an immune cell protein) production to boost T cells attacking the cancer cells. The scientists also studied how the different placements affected the immune system's ability to remember the invader, and whether the memory was long-term.

"Where and how we position the antigens and adjuvant within a single architecture markedly changes how the immune system recognizes and processes it," Mirkin said.

The most powerful structure throws two punches to outsmart the wily, mutating tumor

The study data show that attaching two different antigens to an SNA comprising a shell of adjuvant was the most potent approach for a cancer vaccine structure. It led to a 30% increase in antigen-specific T-cell activation and doubled the number of proliferating T cells compared to a structure in which the same two antigens were attached to two separate SNAs.

These engineered SNA nanostructures stalled tumor growth in multiple animal models.

"It is remarkable," Mirkin said. "When altering the placement of antigens in two vaccines that are nearly identical from a compositional standpoint, the treatment benefit against tumors is dramatically changed. One vaccine is potent and useful, while the other is much less effective."

Many current cancer vaccines are designed to primarily activate cytotoxic T cells, only one defense against a cancer cell. Because tumor cells are always mutating, they can easily escape this immune cell surveillance, quickly rendering the vaccine ineffective. The odds are higher that the T cell will recognize a mutating cancer cell if it has more ways -- multiple antigens -- to recognize it.

"You need more than one type of T cell activated, so you can more easily attack a tumor cell," Teplensky said. "The more types of cells the immune system has to go after tumors, the better. Vaccines consisting of multiple antigens targeting multiple immune cell types are necessary to induce enhanced and long-lasting tumor remission."

Another advantage of the rational vaccinology approach, especially when used with a nanostructure like an SNA, is that it's easy to alter the structure of a vaccine to go after a different type of disease. Mirkin said they simply switch out a peptide, a snippet of a cancer protein with a chemical handle that "clips" onto the structure, not unlike adding a new charm to a bracelet.

Path to most effective vaccine for any cancer type

"The collective importance of this work is that it lays the foundation for developing the most effective forms of vaccine for almost any type of cancer," Teplensky said. "It is about redefining how we develop vaccines across the board, including ones for infectious diseases."

In a previously published paper, Mirkin, Teplensky and colleagues demonstrated the importance of vaccine structure for COVID-19 by creating vaccines that exhibited protective immunity in 100% of animals against a lethal viral infection.

"Small changes in antigen placement on a vaccine significantly elevate cell-to-cell communication, cross-talk and cell synergy," Mirkin said. "The developments made in this work provide a path forward to rethinking the design of vaccines for cancer and other diseases as a whole."

Read more at Science Daily

Turning the spotlight on cells in tissues so RNA can tell their story

A new advance overcomes present limitations in spatial transcriptomics with a DNA nanotechnology-driven method called 'Light-Seq.' Light-Seq allows researchers to 'geotag' the full repertoire of RNA sequences with unique DNA barcodes exclusive to a few cells of interest. These target cells are selected using light under a microscope via a fast and effective photocrosslinking process, and their RNAs made available to next-generation sequencing with the help of a new DNA nanotechnology-driven technique. This entire process can then be repeated for different cell populations in the same sample.

Under the microscope, researchers often observe different cell types organizing themselves in peculiar patterns within tissues, or sometimes a rare cell type that stands out by occupying a unique position, exhibiting an unusual shape, or expressing a specific biomarker molecule. To determine the deeper meaning of their observations, they have developed approaches to also access cells' gene expression patterns (transcriptomes) by analyzing the gene-derived RNA molecules present within them, which they can match with cells' shapes, spatial positions, and molecular biomarkers.

However, these "spatial transcriptomics" approaches still only capture a fraction of a cell's total RNA molecules, and cannot deliver the depth and quality of analysis provided by single-cell sequencing methods, which were developed to investigate the transcriptomes of individual cells isolated from tissues or biofluids via next-generation sequencing (NGS) techniques. Nor do they allow researchers to only home in on specific cells based on their location in a tissue, which would greatly facilitate the pursuit of disjointed cell populations, or rare, difficult-to-isolate cells like rare brain cells with unique functions, or immune cells that invade tumors. In addition, because the original tissue environment is disrupted, many spatial transcriptomics and all single-cell sequencing methods prevent researchers from revisiting their samples to perform follow-up analysis, and they are costly because they require specialized instruments or reagents.

A new advance made at the Wyss Institute for Biologically Inspired Engineering at Harvard University now overcomes these limitations with a DNA nanotechnology-driven method called "Light-Seq." Light-Seq allows researchers to "geotag" the full repertoire of RNA sequences with unique DNA barcodes exclusive to a few cells of interest. These target cells are selected using light under a microscope via a fast and effective photocrosslinking process.

With the help of a new DNA nanotechnology, the barcoded RNA sequences are then translated into coherent DNA strands, which can then be collected from the tissue sample and identified using NGS. The Light-Seq process can be repeated with different barcodes for different cell populations within the same sample, which is left intact for follow-up analysis. With a performance comparable to single-cell sequencing methods, it significantly broadens the depth and scope of investigations possible on a tissue sample. The method is published in Nature Methods[BB1] .

"Light-Seq's unique combination of features fills an unmet need: the ability to perform imaging-informed, spatially prescribed, deep-sequencing analysis of hard, if not impossible-to-isolate cell populations or rare cell types in preserved tissues, with one-to-one correspondence of their highly refined gene expression state with spatial, morphological, and potentially disease-relevant features," said Peng Yin, Ph.D., one of four corresponding authors and a Core Faculty member at the Wyss Institute, where his group developed Light-Seq. "It thus has potential to fast-forward the biological discovery process in various biomedical research areas." Yin is also a Professor of Systems Biology at Harvard Medical School (HMS).

From barcoding in situ to sequencing ex situ

The Light-Seq project was spearheaded by Jocelyn (Josie) Kishi, Ph.D., Sinem Saka, Ph.D., and Ninning Liu, Ph.D. in Yin's group at the Wyss, and Emma West, Ph.D. in Constance Cepko's lab at HMS. Previously, Kishi and Saka had developed SABER-FISH as a spatial transcriptomics method for imaging gene expression directly in intact tissues (in situ). "With SABER-FISH, we still were orders of magnitude away from capturing cells' complete gene expression programs, with many thousands of different RNA molecules per cell. RNA molecules are just too densely packed to be captured in their entirety using present imaging techniques," said co-first and co-corresponding author Kishi. "Light-Seq solves this problem by combining high-resolution barcode labeling with full-transcriptome sequencing via NGS, giving us the best of both worlds and additional key advantages." At the time of the study, Kishi was a Wyss Technology Development Fellow on Yin's team, and is now pursuing a path toward commercializing Light-Seq together with some of her co-authors.

"To specifically sequence the cells in custom-selected locations of intact tissue samples, we developed a new approach for photocrosslinking DNA barcodes to copies of RNA molecules, and a DNA nanotechnology-powered procedure that makes them and their attached RNA sequences readable by NGS," said co-first author Liu, a Postdoctoral Fellow in Yin's group who previously co-developed a parallelized DNA barcoding platform for a super-resolution imaging method called "Action-PAINT" that also became one of the core components of Light-Seq.

First, DNA primers "base-pair" with RNA molecules in cells, and are extended to create copies of the RNA sequences called complementary DNA sequences (cDNAs). Then, DNA barcode strands containing an ultrafast photocrosslinker nucleotide are in turn base-paired to the cDNAs in the cells. These become permanently linked together when a target cell is lit up under the microscope through a stencil-like optical device that keeps other, non-target cells in the microscopic field in the dark and thus spares them from the photocrosslinking reaction. After washing the barcoded DNA sequences out of cells that were not permanently linked in situ, the procedure can be repeated with different barcodes and light patterns to label more regions of interest.

"To be able to integrate this barcoding workflow with NGS, we engineered a new stitching reaction that is based on DNA nanotechnology. This innovation allows us to convert our barcoded cDNAs into contiguous readout sequences. We can then extract the complete collection of barcode-bearing cDNA sequences from the sample, and analyze them with standard NGS techniques," explained Saka, one of the study's corresponding authors who is currently a Group Leader at the European Molecular Biology Laboratory in Heidelberg, Germany. "Ultimately, each barcode traces the full transcriptome readout back to the pre-selected cells in the tissue sample, which remains intact for subsequent analyses. This provides us the unique chance to revisit the exact same cells after sequencing for validation or further exploration."

Eying complex tissues and rare cells

Following the first validation of Light-Seq in cultured cells, Yin's team wanted to apply it to a complex tissue and partnered up with the group of Constance Cepko, Ph.D. at HMS. Cepko is one of the study's corresponding authors and the Bullard Professor of Genetics and Neuroscience in the Blavatnik Institute at HMS, and investigates the development of the retina as a model of the nervous system. Kishi, Saka, and Liu joined forces with West in Cepko's group to apply Light-Seq to cross-sections of the mouse retina and profile three major layers with different functions. The researchers reached a sequence coverage comparable to single-cell sequencing methods, and found that thousands of RNAs were enriched between the retina's three major layers. They also showed that after sequence extraction, the tissue samples remained intact and could be further imaged for proteins and other biomolecules.

"Taking Light-Seq to the extreme, we were able to isolate the full transcriptome of a very rare cell type, known as 'dopaminergic amacrine cells' (DACs), which is extremely hard to isolate because of its intricate connections to other cells in the retina, by retrieving merely four to eight individually barcoded cells per cross-section," said West. DACs are involved in regulating the eye's circadian rhythm by fine-tuning visual perception to different light exposures during the day-night cycle. "Light-Seq also picked up RNAs that were specifically expressed in DACs at low levels, as well as dozens of DAC-specific biomarker RNAs that, to our knowledge, had not been described before, which opens new opportunities to study this rare cell type," added West, who at the time of the study was a graduate student and then Postdoctoral Fellow with Cepko, and has now joined Kishi in her Light-Seq commercialization effort.

Opening the field of spatial transcriptomics up to NGS also adds information on the level of a single RNA species. "Our sequencing data clearly showed that Light-Seq can determine natural variations in the structure of RNAs. Going forward, we're very interested in using Light-Seq to better understand the interplay between the immune system, disease-propagating cells, and different therapeutic strategies such as gene and cell therapy," said Kishi.

Read more at Science Daily

Researchers take step toward developing 'electric eye'

Georgia State University researchers have successfully designed a new type of artificial vision device that incorporates a novel vertical stacking architecture and allows for greater depth of color recognition and scalability on a micro-level. The new research is published in the top journal ACS Nano.

"This work is the first step toward our final destination-to develop a micro-scale camera for microrobots," says assistant professor of Physics Sidong Lei, who led the research. "We illustrate the fundamental principle and feasibility to construct this new type of image sensor with emphasis on miniaturization."

Lei's team was able to lay the groundwork for the biomimetic artificial vision device, which uses synthetic methods to mimic biochemical processes, using nanotechnology.

"It is well-known that more than 80 percent of the information is captured by vision in research, industry, medication, and our daily life," he says. "The ultimate purpose of our research is to develop a micro-scale camera for microrobots that can enter narrow spaces that are intangible by current means, and open up new horizons in medical diagnosis, environmental study, manufacturing, archaeology, and more."

This biomimetic "electric eye" advances color recognition, the most critical vision function, which is missed in the current research due to the difficulty of downscaling the prevailing color sensing devices. Conventional color sensors typically adopt a lateral color sensing channel layout and consume a large amount of physical space and offer less accurate color detection.

Researchers developed the unique stacking technique which offers a novel approach to the hardware design. He says the van der Waals semiconductor-empowered vertical color sensing structure offers precise color recognition capability which can simplify the design of the optical lens system for the downscaling of the artificial vision systems.

Ningxin Li, a graduate student in Dr. Lei's Functional Materials Studio who was part of the research team, says recent advancements in technology make the new design possible.

"The new functionality achieved in our image sensor architecture all depends on the rapid progress of van der Waals semiconductors during recent years," says Li. "Compared with conventional semiconductors, such as silicon, we can precisely control the van der Waals material band structure, thickness, and other critical parameters to sense the red, green, and blue colors."

The van der Waals semiconductors empowered vertical color sensor (vdW-Ss) represent a newly-emerged class of materials, in which individual atomic layers are bonded by weak van der Waals forces. They constitute one of the most prominent platforms for discovering new physics and designing next-generation devices.

"The ultra-thinness, mechanical flexibility, and chemical stability of these new semiconductor materials allow us to stack them in arbitrary orders. So, we are actually introducing a three-dimensional integration strategy in contrast to the current planar micro-electronics layout. The higher integration density is the main reason why our device architecture can accelerate the downscaling of cameras," Li says.

The technology currently is patent pending with Georgia State's Office of Technology Transfer & Commercialization (OTTC). OTTC anticipates this new design will be of high interest to certain industry partners. "This technology has the potential to overcome some of the key drawbacks seen with current sensors, says OTTC's Director, Cliff Michaels. "As nanotechnology advances and devices become more compact, these smaller, highly sensitive color sensors will be incredibly useful."

Researchers believe the discovery could even spawn advancements to help the vision-impaired one day.

"This technology is crucial for the development of biomimetic electronic eyes and also other neuromorphic prosthetic devices," says Li. "High-quality color sensing and image recognition function may bring new possibilities of colorful item perception for the visually impaired in the future."

Read more at Science Daily

Scientists use nanotechnology to detect bone-healing stem cells

 Researchers at the University of Southampton have developed a new way of using nanomaterials to identify and enrich skeletal stem cells -- a discovery which could eventually lead to new treatments for major bone fractures and the repair of lost or damaged bone.

Working together, a team of physicists, chemists and tissue engineering experts used specially designed gold nanoparticles to 'seek out' specific human bone stem cells -- creating a fluorescent glow to reveal their presence among other types of cells and allow them to be isolated or 'enriched'.

The researchers concluded their new technique is simpler and quicker than other methods and up to 50-500 times more effective at enriching stem cells.

The study, led by Professor of Musculoskeletal Science, Richard Oreffo and Professor Antonios Kanaras of the Quantum, Light and Matter Group in the School of Physics and Astronomy, is published in ACS Nano -- an internationally recognised multidisciplinary journal.

In laboratory tests, the researchers used gold nanoparticles -- tiny spherical particles made up of thousands of gold atoms -- coated with oligonucleotides (strands of DNA), to optically detect the specific messenger RNA (mRNA) signatures of skeletal stem cells in bone marrow. When detection takes place, the nanoparticles release a fluorescent dye, making the stem cells distinguishable from other surrounding cells, under microscopic observation. The stem cells can then be separated using a sophisticated fluorescence cell sorting process.

Stem cells are cells that are not yet specialised and can develop to perform different functions. Identifying skeletal stems cells allows scientists to grow these cells in defined conditions to enable the growth and formation of bone and cartilage tissue -- for example, to help mend broken bones.

Among the challenges posed by our ageing population is the need for novel and cost-effective approaches to bone repair. With one in three women and one in five men at risk of osteoporotic fractures worldwide, the costs are significant, with bone fractures alone costing the European economy €17 billion and the US economy $20 billion annually.

Within the University of Southampton's Bone and Joint Research Group, Professor Richard Oreffo and his team have been looking at bone stem cell based therapies for over 15 years to understand bone tissue development and to generate bone and cartilage. Over the same time-period, Professor Antonios Kanaras and his colleagues in the Quantum, Light and Matter Group have been designing novel nanomaterials and studying their applications in the fields of biomedical sciences and energy. This latest study effectively brings these disciplines together and is an exemplar of the impact collaborative, interdisciplinary working can bring.

Professor Oreffo said: "Skeletal stem cell based therapies offer some of the most exciting and promising areas for bone disease treatment and bone regenerative medicine for an aging population. The current studies have harnessed unique DNA sequences from targets we believe would enrich the skeletal stem cell and, using Fluorescence Activated Cell Sorting (FACS) we have been able to enrich bone stem cells from patients. Identification of unique markers is the holy grail in bone stem cell biology and, while we still have some way to go; these studies offer a step change in our ability to target and identify human bone stem cells and the exciting therapeutic potential therein."

Professor Oreffo added: "Importantly, these studies show the advantages of interdisciplinary research to address a challenging problem with state of the art molecular/cell biology combined with nanomaterials' chemistry platform technologies."

Professor Kanaras said: "The appropriate design of materials is essential for their application in complex systems. Customizing the chemistry of nanoparticles we are able to program specific functions in their design.

"In this research project, we designed nanoparticles coated with short sequences of DNA, which are able to sense HSPA8 mRNA and Runx2 mRNA in skeletal stem cells and together with advanced FACS gating strategies, to enable the assortment of the relevant cells from human bone marrow.

"An important aspect of the nanomaterial design involves strategies to regulate the density of oligonucleotides on the surface of the nanoparticles, which help to avoid DNA enzymatic degradation in cells. Fluorescent reporters on the oligonucleotides enable us to observe the status of the nanoparticles at different stages of the experiment, ensuring the quality of the endocellular sensor."

Both lead researchers also recognise that the accomplishments were possible due to the work of all the experienced research fellows and PhD students involved in this research as well as collaboration with Professor Tom Brown and Dr Afaf E-Sagheer of the University of Oxford, who synthesised a large variety of functional oligonucleotides.

The scientists are currently applying single cell RNA sequencing to the platform technology developed with partners in Oxford and the Institute for Life Sciences (IfLS) at Southampton to further refine and enrich bone stem cells and assess functionality. The team propose to then move to clinical application with preclinical bone formation studies to generate proof of concept studies.

Read more at Science Daily

Spaghetti-like, DNA 'noodle origami' the new shape of things to come for nanotechnology

A DNA origami with an emoji-like smiley face.

For the past few decades, scientists have been inspired by the blueprint of life, DNA, as the shape of things to come for nanotechnology.

This burgeoning field is called DNA origami. Scientist borrowed its moniker from the paper artists who conjure up birds, flowers and planes from imaginatively folding a single sheet of paper.

Similarly, DNA origami scientists are dreaming up a variety of shapes -- at a scale one thousand times smaller than a human hair -- that they hope will one day revolutionize computing, electronics and medicine.

Now, a team of Arizona State and Harvard scientists has invented a major new advance in DNA nanotechnology. Dubbed "single-stranded origami," their new strategy uses one long, thin noodle-like strand of DNA, or its chemical cousin RNA, that can self-fold -- -without even a single knot -- into the largest, most complex structures to date.

And, the strands forming these structures can be made inside living cells or using enzymes in a test tube, allowing scientists the potential to plug-and-play with new designs and functions for nanomedicine -- -like tiny, nanobots playing doctor and delivering drugs within cells to the site of injury.

"I think this is an exciting breakthrough, and a great opportunity for synthetic biology as well," said Hao Yan, a co-inventor of the technology, director of the ASU Biodesign Institute's Center for Molecular Design and Biomimetics, and the Milton Glick Professor in the School of Molecular Sciences.

"We are always inspired by nature's designs to make information-carrying molecules that can self-fold into the nanoscale shapes we want to make,"

As proof of concept, they've pushed the envelope to make Emoji-like smiley faces, hearts, triangle shapes -- 18 shapes in total -- that significantly expand the design studio space and material scalability for so-called, "bottom-up" nanotechnology.

Size matters

To date, DNA nanotechnology scientists have had to rely on two main methods for making spatially addressable structures with finite dimensions.

The first was molecular bricks, small, short pieces of DNA that can fold together to make a single structure. The second method was scaffolded DNA, where a single strand is shaped into a structure by using helper strands of DNA, that staple the structure into place.

"These two methods are not very scalable in terms of synthesis," said Fei Zhang, a senior co-author on the paper. "When you have so many short pieces of DNA, you can't replicate it using biological systems. One way around this is to engineer one long strand that could fold itself into any design or architecture."

Furthermore, each method has been limited because as the size of the structure increases, the ability to fold correctly becomes more challenging.

Now, there is a new third way.

For Yan and his team to make their breakthrough, they had to go back to the drawing board, which meant looking at nature again for inspiration. They found what they were looking for with a chemical cousin of DNA, in the form of complex, RNA structures.

The complex RNA structures discovered to date contain single-stranded RNA molecules that self-fold into structures without any topological knots. Could this trick work again for single-stranded DNA or RNA origami?

They were able to crack the code of how RNA makes structures to develop a fully programmable single-stranded origami architecture.

"The key innovation of our study is to use DNA and RNA to construct a structurally complex yet knot-free structure that can be folded smoothly from a single strand," Yan said. "This gave us a design strategy to allow us to fold one long strand into complex architecture."

"With help from a computer scientist in the team, we could also codify the design process as a mathematically rigorous formal algorithm and automate the design by developing a user-friendly software tool," said Yan.

The algorithm and software were validated by the automated design and experimental construction of six distinct DNA ssOrigami structures (four rhombuses and two heart shapes).

Form and function

It's one thing to make crafty patterns and smiley faces with DNA, but critics of DNA origami have been wondering when the practical applications would come about.

Now, these are possible. "I think we are much closer to real practical applications of the technology," said Yan. "We are actively looking at the first nanomedicine applications with our ssOrigami technology."

They were also able to demonstrate that a folded ssOrigami structure can be melted and used as a template for amplification by DNA copying enzymes in a test tube and that the ssOrigami strand can be replicated and amplified via clonal production in living cells.

"Single-stranded DNA nanostructures formed via self-folding offer greater potential of being amplifiable, replicable, and clonable, and hence the opportunity for cost-efficient, large-scale production using enzymatic and biological replication, as well as the possibility for using in vitro evolution to produce sophisticated phenotypes and functionalities," said Yan.

These same design rules could be used for DNA's chemical cousin, RNA.

A key design feature of single-stranded origami (ssOrigami) is that the strand can be made and copied in the lab and in living cells and subsequently folded into designer structures by heating and cooling the DNA.

To make it inside the lab, they used the photocopier of cloning sequences, called PCR, to replicate and produce ssDNA.

Inside living cells, they first placed it inside a mule of molecular cloning, called a plasmid, after it was placed into a common lab bacteria called E. coli cells. When they treated the bacteria with enzymes to free up the ssDNA, they could isolate it, and then fold it into its target structure.

"Because plasmid DNA can be easily replicated in E. coli, the production can be scaled up by growing a large volume of E. coli cells with low cost," said Yan. This gets around the constraint of having to synthesize all of the DNA in the lab from scratch, which is far more expensive.

It also moves them in a direction now, where they can potentially make the structures inside of cells.

"Here we show bacteria to make the strand, but still need to do thermal annealing outside the bacteria to form the structure," said Yan. "The ideal situation would be to design an RNA sequence that can get transcribed inside the bacteria, and fold inside the bacteria so we can use bacteria as a nanofactory to produce the material."

Here, they demonstrated a framework to design and synthesize a single DNA or RNA strand to efficiently self-fold into an unknotted compact ssOrigami structure that approximates any arbitrary user-prescribed target shape.

"Its single-strandedness enabled the demonstration of facile replication of the strand in vitro and in living cells, and its programmability allowed us to codify the design process and develop a simple web-based automated design tool."

A new design school

In the software, made through a collaboration with BioNano Research Group, Autodesk Research, first, the user selects a target shape, which is converted into pixelated representation. The user can upload a 2D image or draw a shape using a 2D pixel design editor.

The user can optionally add DNA hairpins or loops, which can serve as surface markers or handles for attaching external entities. The pixels are converted into DNA helical domains and locking domains to do the folding. The software will then generate ssOrigami structures and sequences, and the user can view the molecular structure via an embedded molecular viewer. Finally, the DNA sequence is assigned to the cycle strand, and the expected folded structure manufactured in the lab and visually confirmed by viewing it under a powerful microscope that are the eyes of nanotechnology, atomic force microscopy, or AFM.

Read more at Science Daily

New window into the nanoworld

This is Vedran Jelic, PhD student at the University of Alberta and lead author on a new paper pioneering microscopy at terahertz frequencies.

For the first time ever, scientists have captured images of terahertz electron dynamics of a semiconductor surface on the atomic scale. The successful experiment indicates a bright future for the new and quickly growing sub-field called terahertz scanning tunneling microscopy (THz-STM), pioneered by the University of Alberta in Canada. THz-STM allows researchers to image electron behaviour at extremely fast timescales and explore how that behaviour changes between different atoms.

"We can essentially zoom in to observe very fast processes with atomic precision and over super fast time scales," says Vedran Jelic, PhD student at the University of Alberta and lead author on the new study. "THz-STM provides us with a new window into the nanoworld, allowing us to explore ultrafast processes on the atomic scale. We're talking a picosecond, or a millionth millionth of a second. It's something that's never been done before."

Jelic and his collaborators used their scanning tunneling microscope (STM) to capture images of silicon atoms by raster scanning a very sharp tip across the surface and recording the tip height as it follows the atomic corrugations of the surface. While the original STM can measure and manipulate single atoms -- for which its creators earned a Nobel Prize in 1986 -- it does so using wired electronics and is ultimately limited in speed and thus time resolution.

Modern lasers produce very short light pulses that can measure a whole range of ultra-fast processes, but typically over length scales limited by the wavelength of light at hundreds of nanometers. Much effort has been expended to overcome the challenges of combining ultra-fast lasers with ultra-small microscopy. The University of Alberta scientists addressed these challenges by working in a unique terahertz frequency range of the electromagnetic spectrum that allows wireless implementation. Normally the STM needs an applied voltage in order to operate, but Jelic and his collaborators are able to drive their microscope using pulses of light instead. These pulses occur over really fast timescales, which means the microscope is able to see really fast events.

By incorporating the THz-STM into an ultrahigh vacuum chamber, free from any external contamination or vibration, they are able to accurately position their tip and maintain a perfectly clean surface while imaging ultrafast dynamics of atoms on surfaces. Their next step is to collaborate with fellow material scientists and image a variety of new surfaces on the nanoscale that may one day revolutionize the speed and efficiency of current technology, ranging from solar cells to computer processing.

Read more at Science Daily

Liquid Metal Circuits and Atomic Microchips Could Be the Future of Electronics

In recent years, scientists have been very interested indeed about the concept of two-dimensional materials, sometimes called 2D materials or single-layer materials. As the name suggests, these are structures so thin — down to a single layer of atoms — that they've functionally abandoned the third dimension altogether.

The single-layer variant of carbon known as graphene is the rock star of this particular class of materials, which chemical engineers hope will power the next generation of super-small semiconductors. The tricky part is getting these atomically skinny two-dimensional materials to "plug in" to traditional three-dimensional manufacturing systems.

News out of Australia this week is pointing things in an interesting direction by incorporating liquid metals and a kind of nanoscale version of rust.

Research published today in the journal Nature Communications describes a new technique for creating integrated circuits that are just a few atoms in thickness. The process could potentially allow microchip companies to manufacture circuit wafers as thin as 1.5 nanometers. How skinny is that? Pretty skinny. Consider that a standard sheet of paper is about 100,000 nanometers thick.

"This is a truly revolutionary development," said lead researcher Kourosh Kalantar-zadeh, in an email exchange from his offices at the Royal Melbourne Institute of Technology in Australia. "Our idea will be one of the first steps toward translation of the 2D world into real electronic technologies."

The specifics get complicated indeed — quantum physics are involved — but the essential gist is this: The new technique leverages certain atomic properties of metals with a relatively low melting point — gallium and indium, if you're keeping score at home. These metals naturally form a thin layer of oxide on their surface when in an oxygenated environment. This oxide, a kind of nanoscale variation of rust, can then be transferred onto a pre-treated electronic wafer, creating individual transistors.

"We use nature itself to form atomically thin, self-limiting oxides with no extra manipulation," Kalantar-zadeh said. "It is the force of nature that produces them perfectly and with no ripples and steps. Because the technology comes from the simplest observation in nature, it will impact technologies very rapidly as it is simple, understandable, and easy to implement."

And just in time, too, according to Kalantar-zadeh, who believes the process represents the next big advance for electronics.

"The fundamental technology of car engines has not progressed since 1920 and now the same is happening to electronics," he said in a statement accompanying the research publication. "Mobile phones and computers are no more powerful than five years ago.

"That is why this new 2D printing technique is so important — creating many layers of incredibly thin electronic chips on the same surface dramatically increases processing power and reduces costs. It will allow for the next revolution in electronics."

Read more at Discovery News

Dressing up like a peacock: Bright colors by nanotechnology

The blue tarantula (Poecilotheria metallica) inspired researchers to produce non-iridescent structural colors.

Colors are produced in a variety of ways. The best known colors are pigments. However, the very bright colors of the blue tarantula or peacock feathers do not result from pigments, but from nanostructures that cause the reflected light waves to overlap. This produces extraordinarily dynamic color effects. Scientists from Karlsruhe Institute of Technology (KIT), in cooperation with international colleagues, have now succeeded in replicating nanostructures that generate the same color irrespective of the viewing angle.

In contrast to pigments, structural colors are non-toxic, more vibrant and durable. In industrial production, however, they have the drawback of being strongly iridescent, which means that the color perceived depends on the viewing angle. An example is the rear side of a CD. Hence, such colors cannot be used for all applications. Bright colors of animals, by contrast, are often independent of the angle of view. Feathers of the kingfisher always appear blue, no matter from which angle we look. The reason lies in the nanostructures: While regular structures are iridescent, amorphous or irregular structures always produce the same color. Yet, industry can only produce regular nanostructures in an economically efficient way.

Radwanul Hasan Siddique, researcher at KIT in collaboration with scientists from USA and Belgium has now discovered that the blue tarantula does not exhibit iridescence in spite of periodic structures on its hairs. First, their study revealed that the hairs are multi-layered, flower-like structure. Then, the researchers analyzed its reflection behavior with the help of computer simulations. In parallel, they built models of these structures using nano-3D printers and optimized the models with the help of the simulations. In the end, they produced a flower-like structure that generates the same color over a viewing angle of 160 degrees. This is the largest viewing angle of any synthetic structural color reached so far.

Apart from the multi-layered structure and rotational symmetry, it is the hierarchical structure from micro to nano that ensures homogeneous reflection intensity and prevents color changes.

Via the size of the "flower," the resulting color can be adjusted, which makes this coloring method interesting for industry. "This could be a key first step towards a future where structural colorants replace the toxic pigments currently used in textile, packaging, and cosmetic industries," says Radwanul Hasan Siddique of KIT's Institute of Microstructure Technology, who now works at the California Institute of Technology. He considers short-term application in textile industry feasible.

Read more at Science Daily

Seeing the invisible: Visible light superlens made from nanobeads

Conceptual drawing of nanoparticle-based metamaterial solid immersion lens (mSIL) (b) Lab made mSIL using titanium dioxide nanoparticles (c) SEM image of 60 nm sized imaging sample (d) corresponding superlens imaging of the 60 nm samples by the developed mSIL.

Nanobeads are all around us- and are, some might argue, used too frequently in everything from sun-screen to white paint, but a new ground-breaking application is revealing hidden worlds.

A paper in Science Advances provides proof of a new concept, using new solid 3D superlenses to break through the scale of things previously visible through a microscope.

Illustrating the strength of the new superlens, the scientists describe seeing for the first time, the actual information on the surface of a Blue Ray DVD. That shiny surface is not as smooth as we think. Current microscopes cannot see the grooves containing the data- but now even the data itself is revealed.

Led by Dr Zengbo Wang at Bangor University, UK and Prof Limin Wu at Fudan University, China, the team created minute droplet-like lens structures on the surface to be examined. These act as an additional lens to magnify the surface features previously invisible to a normal lens.

Made of millions of nanobeads, the spheres break up the light beam. Each bead refracts the light, acting as individual torch-like minute beam. It is the very small size of each beam of light which illuminate the surface, extending the resolving ability of the microscope to record-breaking levels. The new superlens adds 5x magnification on top of existing microscopes.

Extending the limit of the classical microscope's resolution has been the 'El Dorado' or 'Holy Grail' of microscopy for over a century. Physical laws of light make it impossible to view objects smaller than 200 nm -- the smallest size of bacteria, using a normal microscope alone. However, superlenses have been the new goal since the turn of the millennium, with various labs and teams researching different models and materials.

"We've used high-index titanium dioxide (TiO2) nanoparticles as the building element of the lens. These nanoparticles are able to bend light to a higher degree than water. To explain, when putting a spoon into a cup of this material, if it were possible, you'd see a larger bend where you spoon enters the material than you would looking at the same spoon in a glass of water," Dr Wang says.

"Each sphere bends the light to a high magnitude and splits the light beam, creating millions of individual beams of light. It is these tiny light beams which enable us to view previously unseen detail."

Wang believes that the results will be easily replicable and that other labs will soon be adopting the technology and using it for themselves.

The advantages of the technology is that the material, titanium dioxide, is cheap and readily available, and rather than buying a new microscope, the lenses are applied to the material to be viewed, rather than to the microscope.

Read more at Science Daily

'Sticky waves: ' molecular interactions at the nanoscale

Like the gravitational forces that are responsible for the attraction between the Earth and the moon, as well as the dynamics of the entire solar system, there exist attractive forces between objects at the nanoscale.

These are the so-called van der Waals forces, which are ubiquitous in nature and thought to play a crucial role in determining the structure, stability and function of a wide variety of systems throughout the fields of biology, chemistry, physics and materials science.

"To put it simply, every molecular system and every material in nature experiences these forces," said Robert A. DiStasio Jr., assistant professor of chemistry and chemical biology in the College of Arts and Sciences. "In fact, we are finding that their influence is quite extensive, and includes protein-drug interactions, the stability of the DNA double helix, and even the peculiar adhesion properties of the gecko's foot."

When compared with the covalent bond (which involves the sharing of electron pairs between atoms), van der Waals forces are relatively weak and arise from instantaneous electrostatic interactions between the fluctuating electron clouds that surround microscopic objects. However, these forces are still quantum mechanical in origin and have posed a substantial challenge for both theory and experiment to date.

In a paper in the March 11 issue of Science, DiStasio and collaborator Alexandre Tkatchenko of the University of Luxembourg and the Fritz Haber Institute have put forth a new proposition for describing van der Waals forces among objects at the nanoscale.

Generally speaking, there are two schools of thought regarding these forces. The prevailing description of van der Waals interactions among most chemists and biologists is the picture of two induced electric dipoles, similar to the N and S poles of a magnet, representing the uneven distributions of positive and negative charges. The picture espoused by many physicists, however, centers around the fact that wavelike vacuum fluctuations are responsible for the van der Waals interactions among larger macroscopic objects.

In their work, DiStasio and Tkatchenko demonstrate that these fundamental forces between nanostructures must also be described by the electrostatic interactions between wavelike (or delocalized) charge density fluctuations instead of the aforementioned particle-like (or local) induced dipoles. They believe their work could help to bridge the gap between these two belief systems, and help scientists understand and control the interactions between objects at the nanoscale.

"Our work is demonstrating that there is a much wider variety of systems, such as nanostructured systems, where you have to think about the van der Waals force in terms of interactions between waves instead of interactions between particles," Tkatchenko said.

Paul McEuen, the John A. Newman Professor of Physical Science and director of the Kavli Institute at Cornell for Nanoscale Science, sees the duo's research as an important first step in a long, complicated journey to what McEuen half-jokingly characterized as "solving biology."

"It sounds like a rather boring problem, but it's actually a deeply important problem, the way biomolecules assemble and so on," said McEuen. "It's a hugely important problem, especially for someone like me, who's a nano-guy, but it's going to take time to solve."

Read more at Science Daily

Unique 2-level cathode structure improves battery performance

Building a better battery is a delicate balancing act. Increasing the amounts of chemicals whose reactions power the battery can lead to instability. Similarly, smaller particles can improve reactivity but expose more material to degradation. Now a team of scientists from the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, Lawrence Berkeley National Laboratory, and SLAC National Accelerator Laboratory say they've found a way to strike a balance--by making a battery cathode with a hierarchical structure where the reactive material is abundant yet protected.

Test batteries incorporating this cathode material exhibited improved high-voltage cycling behavior--the kind you'd want for fast-charging electric vehicles and other applications that require high-capacity storage. The scientists describe the micro-to-nanoscale details of the cathode material in a paper published in the journal Nature Energy January 11, 2016.

"Our colleagues at Berkeley Lab were able to make a particle structure that has two levels of complexity where the material is assembled in a way that it protects itself from degradation," explained Brookhaven Lab physicist and Stony Brook University adjunct assistant professor Huolin Xin, who helped characterize the nanoscale details of the cathode material at Brookhaven Lab's Center for Functional Nanomaterials.

X-ray imaging performed by scientists at the Stanford Synchrotron Radiation Lightsource (SSRL) at SLAC along with Xin's electron microscopy at CFN revealed spherical particles of the cathode material measuring millionths of meter, or microns, in diameter made up of lots of smaller, faceted nanoscale particles stacked together like bricks in a wall. The characterization techniques revealed important structural and chemical details that explain why these particles perform so well.

The lithium ion shuttle

Chemistry is at the heart of all lithium-ion rechargeable batteries, which power portable electronics and electric cars by shuttling lithium ions between positive and negative electrodes bathed in an electrolyte solution. As lithium moves into the cathode, chemical reactions generate electrons that can be routed to an external circuit for use. Recharging requires an external current to run the reactions in reverse, pulling the lithium ions out of the cathode and sending them to the anode.

Reactive metals like nickel have the potential to make great cathode materials--except that they are unstable and tend to undergo destructive side reactions with the electrolyte. So the Brookhaven, Berkeley, and SLAC battery team experimented with ways to incorporate nickel but protect it from these destructive side reactions.

They sprayed a solution of lithium, nickel, manganese, and cobalt mixed at a certain ratio through an atomizer nozzle to form tiny droplets, which then decomposed to form a powder. Repeatedly heating and cooling the powder triggered the formation of tiny nanosized particles and the self-assembly of these particles into the larger spherical, sometimes hollow, structures.

Using x-rays at SLAC's SSRL, the scientists made chemical "fingerprints" of the micron-scale structures. The synchrotron technique, called x-ray spectroscopy, revealed that the outer surface of the spheres was relatively low in nickel and high in unreactive manganese, while the interior was rich in nickel.

"The manganese layer forms an effective barrier, like paint on a wall, protecting the inner structure of the nickel-rich 'bricks' from the electrolyte," Xin said.

But how were the lithium ions still able to enter the material to react with the nickel? To find out, Xin's group at the CFN ground up the larger particles to form a powder composed of much smaller clumps of the nanoscale primary particles with some of the interfaces between them still intact.

"These samples show a small subset of the bricks that form the wall. We wanted to see how the bricks are put together. What kind of cement or mortar binds them? Are they layered together regularly or are they randomly oriented with spaces in between?" Xin said.

Nanoscale details explain improved performance

Using an aberration-corrected scanning transmission electron microscope--a scanning transmission electron microscope outfitted with a pair of "glasses" to improve its vision--the scientists saw that the particles had facets, flat faces or sides like the cut edges of a crystal, which allowed them to pack tightly together to form coherent interfaces with no mortar or cement between the bricks. But there was a slight misfit between the two surfaces, with the atoms on one side of the interface being ever so slightly offset relative to the atoms on the adjoining particle.

"The packing of atoms at the interfaces between the tiny particles is slightly less dense than the perfect lattice within each individual particle, so these interfaces basically make a highway for lithium ions to go in and out," Xin said.

Like tiny smart cars, the lithium ions can move along these highways to reach the interior structure of the wall and react with the nickel, but much larger semi-truck-size electrolyte molecules can't get in to degrade the reactive material.

Read more at Science Daily

Mechanical properties of nanomaterials are altered due to electric field

Mechanical properties of nanomaterials can be altered due to the application of voltage, University of Wyoming researchers have discovered.

The researchers, led by TeYu Chien, a UW assistant professor in the Department of Physics and Astronomy, determined that the electric field is responsible for alterating the fracture toughness of nanomaterials, which are used in state-of-the-art electronic devices. It is the first observed evidence that the electric field changes the fracture toughness at a nanometer scale.

This finding opens the way for further investigation of nanomaterials regarding electric field-mechanical property interactions, which is extremely important for applications and fundamental research.

Chien is the lead author of a paper, titled "Built-in Electric Field Induced Mechanical Property Change at the Lanthanum Nickelate/Nb-doped Strontium Titanate Interfaces," that was recently published in Scientific Reports. Scientific Reports is an online, open-access journal from the publishers of Nature. The journal publishes scientifically valid primary research from all areas of the natural and clinical sciences.

Other researchers who contributed to the paper are from the University of Arkansas, University of Tennessee and Argonne National Laboratory in Argonne, Ill.

Chien and his research team studied the surfaces of the fractured interfaces of ceramic materials, including lanthanum nickelate and strontium titanate with a small amount of niobium. The researchers revealed that strontium titanate, within a few nanometers of the interfaces, fractured differently from the strontium titanate away from the interfaces.

The two ceramic materials were chosen because one is a metallic oxide while the other is a semiconductor. When the two types of materials come into contact with each other, an intrinsic electric field will automatically be formed in a region, known as the Schottky barrier, near the interface, Chien explains. The Schottky barrier refers to the region where an intrinsic electric field is formed at metal/semiconductor interfaces.

The intrinsic electric field at interfaces is an inevitable phenomenon whenever one material is in contact with another. The electric field effects on the mechanical properties of materials are rarely studied, especially for nanomaterials. Understanding electric field effects is extremely important for applications of nanoelectromechanical system (NEMS), which are devices, such as actuators, integrating electrical and mechanical functionalities on the nanoscale.

For NEMS materials made in nanoscale, understanding the mechanical properties affected by electric fields is crucial for full control of device performance. The observations in this study pave the way to better understand the mechanical properties of nanomaterials.

"The electric field changes the inter-atomic bond length in the crystal by pushing positively and negatively charged ions in opposite directions," Chien says. "Altering bond length changes bond strength. Hence, the mechanical properties, such as fracture toughness."

Read more at Science Daily

Nanostructured metal coatings let the light through for electronic devices

Light and electricity dance a complicated tango in devices like LEDs, solar cells and sensors. A new anti-reflection coating developed by engineers at the University of Illinois at Urbana Champaign, in collaboration with researchers at the University of Massachusetts at Lowell, lets light through without hampering the flow of electricity, a step that could increase efficiency in such devices.

The coating is a specially engraved, nanostructured thin film that allows more light through than a flat surface, yet also provides electrical access to the underlying material -- a crucial combination for optoelectronics, devices that convert electricity to light or vice versa. The researchers, led by U. of I. electrical and computer engineering professor Daniel Wasserman, published their findings in the journal Advanced Materials.

"The ability to improve both electrical and optical access to a material is an important step towards higher-efficiency optoelectronic devices," said Wasserman, a member of the Micro and Nano Technology Laboratory at Illinois.

At the interface between two materials, such as a semiconductor and air, some light is always reflected, Wasserman said. This limits the efficiency of optoelectronic devices. If light is emitted in a semiconductor, some fraction of this light will never escape the semiconductor material. Alternatively, for a sensor or solar cell, some fraction of light will never make it to the detector to be collected and turned into an electrical signal. Researchers use a model called Fresnel's equations to describe the reflection and transmission at the interface between two materials.

"It has been long known that structuring the surface of a material can increase light transmission," said study co-author Viktor Podolskiy, a professor at the University of Massachusetts at Lowell. "Among such structures, one of the more interesting is similar to structures found in nature, and is referred to as a 'moth-eye' pattern: tiny nanopillars which can 'beat' the Fresnel equations at certain wavelengths and angles."

Although such patterned surfaces aid in light transmission, they hinder electrical transmission, creating a barrier to the underlying electrical material.

"In most cases, the addition of a conducting material to the surface results in absorption and reflection, both of which will degrade device performance," Wasserman said.

The Illinois and Massachusetts team used a patented method of metal-assisted chemical etching, MacEtch, developed at Illinois by Xiuling Li, U. of I. professor of electrical and computer engineering and co-author of the new paper. The researchers used MacEtch to engrave a patterned metal film into a semiconductor to create an array of tiny nanopillars rising above the metal film. The combination of these "moth-eye" nanopillars and the metal film created a partially coated material that outperformed the untreated semiconductor.

"The nanopillars enhance the optical transmission while the metal film offers electrical contact. Remarkably, we can improve our optical transmission and electrical access simultaneously," said Runyu Liu, a graduate researcher at Illinois and a co-lead author of the work along with Illinois graduate researcher Xiang Zhao and Massachusetts graduate researcher Christopher Roberts.

The researchers demonstrated that their technique, which results in metal covering roughly half of the surface, can transmit about 90 percent of light to or from the surface. For comparison, the bare, unpatterned surface with no metal can only transmit 70 percent of the light and has no electrical contact.

Read more at Science Daily

Halloysite: Finally a promising natural nanomaterial?

a) This image shows loading clay nanotubes with drug from saturation solution. b,c) Mixing with drug solution, pumping out air, and pulling in drug molecules, washing, and loaded tubes.

Yuri Lvov and Rawil Fakhrullin of Bionanotechnology Lab, Kazan Federal University, in cooperation with Wencai Wang and Liqun Zhang of State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology have recently presented in Advanced Materials a broad scope of application of halloysite clay tubes .

Halloysite is a natural biocompatible nanomaterial available in thousands of tons at low price, which makes it a good candidate for nanoarchitectural composites. In chemical composition they are similar to kaolin and can be considered as rolled kaolin sheets with inner diameter of 10-20 nm, outer diameter of 40-70 nm and a length of 500-1500 nm. The internal side of halloysite is composed of Al2O3 while the external is mainly SiO2.

The inner lumen of halloysite may be adjusted by etching to 20-30% of the tube volume and used as natural nanocontainer for loading and sustained release of chemical agents. These ceramic nanotubes form a "skeleton" in the bulk polymers, enhancing the composite strength and adhesivity. These "skeleton bones" may be loaded with active compounds, like real bones are loaded with marrow, providing additional functionality for polymers (antimicrobial, anti-aging, anticorrosion, and flame-retardancy).

Halloysite tubes can encase enzymes for longer storage, higher temperature, and extended functionality, while the tube's opening allows for delivery of small substrate molecules into the tube interior for biocatalysis. Loading DNA into halloysite is another prospective research direction. As functional nanoblocks, halloysite tubes may be used for building on biological cells, like the formation of spore-like microbial shells providing microorganisms with additional functions.

In vitro and in vivo studies on biological cells and worms indicate the safety of halloysite, and furthermore, it can store and release molecules in a controllable manner, making these tiny containers attractive for applications in drug delivery, antimicrobial materials, self-healing polymeric composites, and regenerative medicine.

Read more at Science Daily

Uniting classical and quantum mechanics: Breakthrough observation of Mott transition in a superconductor

An international team of researchers, including the MESA+ Institute for Nanotechnology at the University of Twente in the Netherlands and the U.S. Department of Energy's Argonne National Laboratory, announced today in Science the observation of a dynamic Mott transition in a superconductor.

The discovery experimentally connects the worlds of classical and quantum mechanics and illuminates the mysterious nature of the Mott transition. It also could shed light on non-equilibrium physics, which is poorly understood but governs most of what occurs in our world. The finding may also represent a step towards more efficient electronics based on the Mott transition.

Since its foundations were laid in the early part of the 20th century, scientists have been trying to reconcile quantum mechanics with the rules of classical or Newtonian physics (like how you describe the path of an apple thrown into the air--or dropped from a tree). Physicists have made strides in linking the two approaches, but experiments that connect the two are still few and far between; physics phenomena are usually classified as either quantum or classical, but not both.

One system that unites the two is found in superconductors, certain materials that conduct electricity perfectly when cooled to very low temperatures. Magnetic fields penetrate the superconducting material in the form of tiny filaments called vortices, which control the electronic and magnetic properties of the materials.

These vortices display both classical and quantum properties, which led researchers to study them for access to one of the most enigmatic phenomena of modern condensed matter physics: the Mott insulator-to-metal transition.

The Mott transition occurs in certain materials that according to textbook quantum mechanics should be metals, but in reality turn insulators. A complex phenomenon controlled by the interactions of many quantum particles, the Mott transition remains mysterious--even whether or not it's a classical or quantum phenomenon is not quite clear. Moreover, scientists have never directly observed a dynamic Mott transition, in which a phase transition from an insulating to a metallic state is induced by driving an electrical current through the system; the disorder inherent in real systems disguises Mott properties.

At the University of Twente, researchers built a system containing 90,000 superconducting niobium nano-sized islands on top of a gold film. In this configuration, the vortices find it energetically easiest to settle into energy dimples in an arrangement like an egg crate--and make the material act as a Mott insulator, since the vortices won't move if the applied electric current is small.

When they applied a large enough electric current, however, the scientists saw a dynamic Mott transition as the system flipped to become a conducting metal; the properties of the material had changed as the current pushed it out of equilibrium.

The vortex system behaved exactly like an electronic Mott transition driven by temperature, said Valerii Vinokur, an Argonne Distinguished Fellow and corresponding author on the study. He and study co-author Tatyana Baturina, then at Argonne, analyzed the data and recognized the Mott behavior.

"This experimentally materializes the correspondence between quantum and classical physics," Vinokur said.

"We can controllably induce a phase transition between a state of locked vortices to itinerant vortices by applying an electric current to the system," said Hans Hilgenkamp, head of the University of Twente research group. "Studying these phase transitions in our artificial systems is interesting in its own right, but may also provide further insight in the electronic transitions in real materials."

The system could further provide scientists with insight into two categories of physics that have been hard to understand: many-body systems and out-of-equilibrium systems.

"This is a classical system that which is easy to experiment with and provides what looks like access to very complicated many-body systems," said Vinokur. "It looks a bit like magic."

As the name implies, many-body problems involve a large number of particles interacting; with current theory they are very difficult to model or understand.

"Furthermore, this system will be key to building a general understanding of out-of-equilibrium physics, which would be a major breakthrough in physics," Vinokur said.

The Department of Energy named five great basic energy scientific challenges of our time; one of them is understanding and controlling out-of-equilibrium phenomena. Equilibrium systems--where there's no energy moving around--are now understood quite well. But nearly everything in our lives involves energy flow, from photosynthesis to digestion to tropical cyclones, and we don't yet have the physics to describe it well. Scientists think a better understanding could lead to huge improvements in energy capture, batteries and energy storage, electronics and more.

Read more at Science Daily

Nanoparticles: Small but unique

Scientists at Chalmers University of Technology have developed a new way to study nanoparticles one at a time, and have discovered that individual particles that may seem identical in fact can have very different properties. The results, which may prove to be important when developing new materials or applications such as hydrogen sensors for fuel cell cars, will be published in Nature Materials.

"We were able to show that you gain deeper insights into the physics of how nanomaterials interact with molecules in their environment by looking at the individual nanoparticle as opposed to looking at many of them at the same time, which is what is usually done," says Associate Professor Christoph Langhammer, who led the project.

By applying a new experimental approach called plasmonic nanospectroscopy, the group studied hydrogen absorption into single palladium nanoparticles. They found that particles with exactly the same shape and size may exhibit differences as great as 40 millibars in the pressure at which hydrogen is absorbed. The development of sensors that can detect hydrogen leaks in fuel cell powered cars is one example of where this new understanding could become valuable in the future.

"One main challenge when working on hydrogen sensors is to design materials whose response to hydrogen is as linear and reversible as possible. In that way, the gained fundamental understanding of the reasons underlying the differences between seemingly identical individual particles and how this makes the response irreversible in a certain hydrogen concentration range can be helpful," says Christoph Langhammer.

Others have looked at single nanoparticles one at a time, but the new approach introduced by the Chalmers team uses visible light with low intensity to study the particles. This means that the method is non-invasive and does not disturb the system it is investigating by, for example, heating it up.

"When studying individual nanoparticles you have to send some kind of probe to ask the particle 'what are you doing?'. This usually means focusing a beam of high-energy electrons or photons or a mechanical probe onto a very tiny volume. You then quickly get very high energy densities, which might perturb the process you want to look at. This effect is minimized in our new approach, which is also compatible with ambient conditions, meaning that we can study nanoparticles one at a time in as close to a realistic environment as possible," says Christoph Langhammer.

Even though they have now reached the level where their results are ready to be published, Christoph Langhammer believes they have just scratched the surface of what their discovery and developed experimental methodology will lead to in relation to further research. He hopes that they have helped to establish a new experimental paradigm, where looking at nanoparticles individually will become standard in the scientific world.

Read more at Science Daily

Solar water-splitting technology developed

Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.

The technology, which is described online in the American Chemical Society journal Nano Letters, relies on a configuration of light-activated gold nanoparticles that harvest sunlight and transfer solar energy to highly excited electrons, which scientists sometimes refer to as "hot electrons."

"Hot electrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy," said lead researcher Isabell Thomann, assistant professor of electrical and computer engineering and of chemistry and materials science and nanoengineering at Rice. "For example, most of the energy losses in today's best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat."

Capturing these high-energy electrons before they cool could allow solar-energy providers to significantly increase their solar-to-electric power-conversion efficiencies and meet a national goal of reducing the cost of solar electricity.

In the light-activated nanoparticles studied by Thomann and colleagues at Rice's Laboratory for Nanophotonics (LANP), light is captured and converted into plasmons, waves of electrons that flow like a fluid across the metal surface of the nanoparticles. Plasmons are high-energy states that are short-lived, but researchers at Rice and elsewhere have found ways to capture plasmonic energy and convert it into useful heat or light. Plasmonic nanoparticles also offer one of the most promising means of harnessing the power of hot electrons, and LANP researchers have made progress toward that goal in several recent studies.

Thomann and her team, graduate students Hossein Robatjazi, Shah Mohammad Bahauddin and Chloe Doiron, created a system that uses the energy from hot electrons to split molecules of water into oxygen and hydrogen. That's important because oxygen and hydrogen are the feedstocks for fuel cells, electrochemical devices that produce electricity cleanly and efficiently.

To use the hot electrons, Thomann's team first had to find a way to separate them from their corresponding "electron holes," the low-energy states that the hot electrons vacated when they received their plasmonic jolt of energy. One reason hot electrons are so short-lived is that they have a strong tendency to release their newfound energy and revert to their low-energy state. The only way to avoid this is to engineer a system where the hot electrons and electron holes are rapidly separated from one another. The standard way for electrical engineers to do this is to drive the hot electrons over an energy barrier that acts like a one-way valve. Thomann said this approach has inherent inefficiencies, but it is attractive to engineers because it uses well-understood technology called Schottky barriers, a tried-and-true component of electrical engineering.

"Because of the inherent inefficiencies, we wanted to find a new approach to the problem," Thomann said. "We took an unconventional approach: Rather than driving off the hot electrons, we designed a system to carry away the electron holes. In effect, our setup acts like a sieve or a membrane. The holes can pass through, but the hot electrons cannot, so they are left available on the surface of the plasmonic nanoparticles."

The setup features three layers of materials. The bottom layer is a thin sheet of shiny aluminum. This layer is covered with a thin coating of transparent nickel-oxide, and scattered atop this is a collection of plasmonic gold nanoparticles -- puck-shaped disks about 10 to 30 nanometers in diameter.

Read more at Science Daily

Unlocking nanofibers' potential

Nanofibers -- polymer filaments only a couple of hundred nanometers in diameter -- have a huge range of potential applications, from solar cells to water filtration to fuel cells. But so far, their high cost of manufacture has relegated them to just a few niche industries.

In the latest issue of the journal Nanotechnology, MIT researchers describe a new technique for producing nanofibers that increases the rate of production fourfold while reducing energy consumption by more than 90 percent, holding out the prospect of cheap, efficient nanofiber production.

"We have demonstrated a systematic way to produce nanofibers through electrospinning that surpasses the state of the art," says Luis Fernando Velásquez-García, a principal research scientist in MIT's Microsystems Technology Laboratories, who led the new work. "But the way that it's done opens a very interesting possibility. Our group and many other groups are working to push 3-D printing further, to make it possible to print components that transduce, that actuate, that exchange energy between different domains, like solar to electrical or mechanical. We have something that naturally fits into that picture. We have an array of emitters that can be thought of as a dot-matrix printer, where you would be able to individually control each emitter to print deposits of nanofibers."

Tangled tale

Nanofibers are useful for any application that benefits from a high ratio of surface area to volume -- solar cells, for instance, which try to maximize exposure to sunlight, or fuel cell electrodes, which catalyze reactions at their surfaces. Nanofibers can also yield materials that are permeable only at very small scales, like water filters, or that are remarkably tough for their weight, like body armor.

The standard technique for manufacturing nanofibers is called electrospinning, and it comes in two varieties. In the first, a polymer solution is pumped through a small nozzle, and then a strong electric field stretches it out. The process is slow, however, and the number of nozzles per unit area is limited by the size of the pump hydraulics.

The other approach is to apply a voltage between a rotating drum covered by metal cones and a collector electrode. The cones are dipped in a polymer solution, and the electric field causes the solution to travel to the top of the cones, where it's emitted toward the electrode as a fiber. That approach is erratic, however, and produces fibers of uneven lengths; it also requires voltages as high as 100,000 volts.

Thinking small

Velásquez-García and his co-authors -- Philip Ponce de Leon, a former master's student in mechanical engineering; Frances Hill, a former postdoc in Velásquez-García's group who's now at KLA-Tencor; and Eric Heubel, a current postdoc -- adapt the second approach, but on a much smaller scale, using techniques common in the manufacture of microelectromechanical systems to produce dense arrays of tiny emitters. The emitters' small size reduces the voltage necessary to drive them and allows more of them to be packed together, increasing production rate.

At the same time, a nubbly texture etched into the emitters' sides regulates the rate at which fluid flows toward their tips, yielding uniform fibers even at high manufacturing rates. "We did all kinds of experiments, and all of them show that the emission is uniform," Velásquez-García says.

To build their emitters, Velásquez-García and his colleagues use a technique called deep reactive-ion etching. On either face of a silicon wafer, they etch dense arrays of tiny rectangular columns -- tens of micrometers across -- which will regulate the flow of fluid up the sides of the emitters. Then they cut sawtooth patterns out of the wafer. The sawteeth are mounted vertically, and their bases are immersed in a solution of deionized water, ethanol, and a dissolved polymer.

Read more at Science Daily

Tuning friction to the point where it disappears may boost development of nanomachines

Friction is all around us, working against the motion of tires on pavement, the scrawl of a pen across paper, and even the flow of proteins through the bloodstream. Whenever two surfaces come in contact, there is friction, except in very special cases where friction essentially vanishes -- a phenomenon, known as "superlubricity," in which surfaces simply slide over each other without resistance.

Now physicists at MIT have developed an experimental technique to simulate friction at the nanoscale. Using their technique, the researchers are able to directly observe individual atoms at the interface of two surfaces and manipulate their arrangement, tuning the amount of friction between the surfaces. By changing the spacing of atoms on one surface, they observed a point at which friction disappears.

Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT, says the ability to tune friction would be helpful in developing nanomachines -- tiny robots built from components the size of single molecules. Vuletic says that at the nanoscale, friction may exact a greater force -- for instance, creating wear and tear on tiny motors much faster than occurs at larger scales.

"There's a big effort to understand friction and control it, because it's one of the limiting factors for nanomachines, but there has been relatively little progress in actually controlling friction at any scale," Vuletic says. "What is new in our system is, for the first time on the atomic scale, we can see this transition from friction to superlubricity."

Vuletic, along with graduate students Alexei Bylinskii and Dorian Gangloff, publish their results today in the journal Science.

Friction and force fields

The team simulated friction at the nanoscale by first engineering two surfaces to be placed in contact: an optical lattice, and an ion crystal.

The optical lattice was generated using two laser beams traveling in opposite directions, whose fields add up to form a sinusoidal periodic pattern in one dimension. This so-called optical lattice is similar to an egg carton, where each peak represents a maximum electric potential, while each trough represents a minimum. When atoms travel across such an electric field, they are drawn to places of minimum potential -- in this case, the troughs.

Vuletic then engineered a second surface: an ion crystal -- essentially, a grid of charged atoms -- in order to study friction's effects, atom by atom. To generate the ion crystal, the group used light to ionize, or charge, neutral ytterbium atoms emerging from a small heated oven, and then cooled them down with more laser light to just above absolute zero. The charged atoms can then be trapped using voltages applied to nearby metallic surfaces. Once positively charged, each atom repels each other via the so-called "Coulomb force." The repulsion effectively keeps the atoms apart, so that they form a crystal or lattice-like surface.

The team then used the same forces that are used to trap the atoms to push and pull the ion crystal across the lattice, as well as to stretch and squeeze the ion crystal, much like an accordion, altering the spacing between its atoms.

An earthquake and a caterpillar

In general, the researchers found that when atoms in the ion crystal were regularly spaced, at intervals that matched the spacing of the optical lattice, the two surfaces experienced maximum friction, much like two complementary Lego bricks. The team observed that when atoms are spaced so that each occupies a trough in the optical lattice, when the ion crystal as a whole is dragged across the optical lattice, the atoms first tend to stick in the lattice's troughs, bound there by their preference for the lower electric potential, as well as by the Coulomb forces that keep the atoms apart. If enough force is applied, the ion crystal suddenly slips, as the atoms collectively jump to the next trough.

"It's like an earthquake," Vuletic says. "There's force building up, and then there's suddenly a catastrophic release of energy."

The group continued to stretch and squeeze the ion crystal to manipulate the arrangement of atoms, and discovered that if the atom spacing is mismatched from that of the optical lattice, friction between the two surfaces vanishes. In this case, the crystal tends not to stick then suddenly slip, but to move fluidly across the optical lattice, much like a caterpillar inching across the ground.

For instance, in arrangements where some atoms are in troughs while others are at peaks, and still others are somewhere in between, as the ion crystal is pulled across the optical lattice, one atom may slide down a peak a bit, releasing a bit of stress, and making it easier for a second atom to climb out of a trough -- which in turn pulls a third atom along, and so on.

Read more at Science Daily

Laser technique for low-cost self-assembly of nanostructures

Researchers from Swinburne University of Technology and the University of Science and Technology of China have developed a low-cost technique that holds promise for a range of scientific and technological applications.

They have combined laser printing and capillary force to build complex, self-assembling microstructures using a technique called laser printing capillary-assisted self-assembly (LPCS).

This type of self-assembly is seen in nature, such as in gecko feet and the salvinia leaf, and scientists have been trying to mimic these multi-functional structures for decades.

The researchers have found they can control capillary force -- the tendency of a liquid to rise in narrow tubes or be drawn into small openings -- by changing the surface structure of a material.

"Using laser printing techniques we can control the size, geometry, elasticity and distance between tiny pillars -- narrower than the width of a human hair -- to get the self-assembly that we want," lead author of a study published in the Proceedings of the National Academy of Science , Swinburne's Dr Yanlei Hu, said.

Ultrafast laser printing produces an array of vertical nanorods of varying heights. After the laser process, the material is washed in a development solvent using a method similar to traditional darkroom film processing. The gravity-governed capillary force difference creates pillars of unequal physical properties along different axes.

"A possible application of these structures is in on-chip micro-object trap-release systems which are in demand in chemical analysis and biomedical devices," co-author Dr Ben Cumming said.

The researchers demonstrated the ability of the LPCS structures to selectively capture and release micro-particles.

Read more at Science Daily