Tag Archives: University of California Los Angeles

Self-assembling liquid lenses used in optical microscopy to reveal nanoscale objects

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A Jan. 21, 2013 news item on Azonano highlights some research on microscope and self-assembling lenses done at University of California Los Angeles (UCLA),

By using tiny liquid lenses that self-assemble around microscopic objects, a team from UCLA’s Henry Samueli School of Engineering and Applied Science has created an optical microscopy method that allows users to directly see objects more than 1,000 times smaller than the width of a human hair.

Coupled with computer-based computational reconstruction techniques, this portable and cost-effective platform, which has a wide field of view, can detect individual viruses and nanoparticles, making it potentially useful in the diagnosis of diseases in point-of-care settings or areas where medical resources are limited.

The UCLA Jan. 20, 2013 news release, written by Matthew Chin and which originated the news item, explains why another microscopy technique is needed for viewing objects at the nanoscale,

Electron microscopy is one of the current gold standards for viewing nanoscale objects. This technology uses a beam of electrons to outline the shape and structure of nanoscale objects. Other optical imaging–based techniques are used as well, but all of them are relatively bulky, require time for the preparation and analysis of samples, and have a limited field of view — typically smaller than 0.2 square millimeters — which can make viewing particles in a sparse population, such as low concentrations of viruses, challenging.

To overcome these issues, the UCLA team, led by Aydogan Ozcan, an associate professor of electrical engineering and bioengineering, developed the new optical microscopy platform by using nanoscale lenses that stick to the objects that need to be imaged. This lets users see single viruses and other objects in a relatively inexpensive way and allows for the processing of a high volume of samples.
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At scales smaller than 100 nanometers, optical microscopy becomes a challenge because of its weak light-signal levels. Using a special liquid composition, nanoscale lenses, which are typically thinner than 200 nanometers, self-assemble around objects on a glass substrate.

A simple light source, such as a light-emitting diode (LED), is then used to illuminate the nano-lens object assembly. By utilizing a silicon-based sensor array, which is also found in cell-phone cameras, lens-free holograms of the nanoparticles are detected. The holograms are then rapidly reconstructed with the help of a personal computer to detect single nanoparticles on a glass substrate.

The researchers have used the new technique to create images of single polystyrene nanoparticles, as well as adenoviruses and H1N1 influenza viral particles.

While the technique does not offer the high resolution of electron microscopy, it has a much wider field of view — more than 20 square millimeters — and can be helpful in finding nanoscale objects in samples that are sparsely populated.

Here a citation for and a link to the research article,

Wide-field optical detection of nanoparticles using on-chip microscopy and self-assembled nanolenses by Onur Mudanyali, Euan McLeod, Wei Luo, Alon Greenbaum, Ahmet F. Coskun, Yves Hennequin, Cédric P. Allier, & Aydogan Ozcan. Nature Photonics (2013) doi:10.1038/nphoton.2012.337 Published online: 20 January 2013

The article is behind a paywall.

Synaptic electronics

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There’s been a lot about the memristor, being developed at HP Labs, at the University of Michigan, and elsewhere, on this blog and significantly less on other approaches to creating nanodevices with neuromorphic properties by researchers in Japan and in the US. The Dec. 20, 2012 news item on ScienceDaily notes,

Researchers in Japan and the US propose a nanoionic device with a range of neuromorphic and electrical multifunctions that may allow the fabrication of on-demand configurable circuits, analog memories and digital-neural fused networks in one device architecture.

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… Now Rui Yang, Kazuya Terabe and colleagues at the National Institute for Materials Science in Japan and the University of California, Los Angeles, in the US have developed two-, three-terminal WO3-x-based nanoionic devices capable of a broad range of neuromorphic and electrical functions.

The originating Dec. 20, 2012 news release from Japan’s International Center for Materials draws a parallel between the device’s properties and neural behaviour,  explains the ‘why’ of the process, and mentions what applications the researchers believe could be developed,

The researchers draw similarities between the device properties — volatile and non-volatile states and the current fading process following positive voltage pulses — with models for neural behaviour —that is, short- and long-term memory and forgetting processes. They explain the behaviour as the result of oxygen ions migrating within the device in response to the voltage sweeps. Accumulation of the oxygen ions at the electrode leads to Schottky-like potential barriers and the resulting changes in resistance and rectifying characteristics. The stable bipolar switching behaviour at the Pt/WO3-x interface is attributed to the formation of the electric conductive filament and oxygen absorbability of the Pt electrode.

As the researchers conclude, “These capabilities open a new avenue for circuits, analog memories, and artificially fused digital neural networks using on-demand programming by input pulse polarity, magnitude, and repetition history.”

For those who wish to delve more deeply, here’s the citation (from the ScienceDaily news item),

Rui Yang, Kazuya Terabe, Guangqiang Liu, Tohru Tsuruoka, Tsuyoshi Hasegawa, James K. Gimzewski, Masakazu Aono. On-Demand Nanodevice with Electrical and Neuromorphic Multifunction Realized by Local Ion Migration. ACS Nano, 2012; 6 (11): 9515 DOI: 10.1021/nn302510e

The news release does not state explicitly why this would be considered an on-demand device. The article is behind a paywall.

There was a recent attempt to mimic brain processing not based in nanoelectronics but on mimicking brain activity by creating virtual neurons. A Canadian team at the University of Waterloo led by Chris Eliasmith made a sensation  with SPAUN (Semantic Pointer Architecture Unified Network) in late Nov. 2012 (mentioned in my Nov. 29, 2012 posting).

NERCS—a great nano acronym (Nanosystems ERCs)—engineering research centers

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It’s a bit complicated, isn’t it? Here’s the straight scoop from the Sept. 11, 2012 news item on Nanowerk,

The National Science Foundation (NSF) recently awarded $55.5 million to university consortia to establish three new Engineering Research Centers (ERCs) that will advance interdisciplinary nanosystems research and education in partnership with industry.

Over the next five years, these Nanosystems ERCs, or NERCS, will advance knowledge and create innovations that address significant societal issues, such as the human health and environmental implications of nanotechnology. At the same time, they will advance the competitiveness of U.S. industry. The centers will support research and innovation in electromagnetic systems, mobile computing and energy technologies, nanomanufacturing, and health and environmental sensing.

“The Nanosystems ERCs will build on more than a decade of investment and discoveries in fundamental nanoscale science and engineering,” said Thomas Peterson, NSF’s assistant director for engineering. “Our understanding of nanoscale phenomena, materials and devices has progressed to a point where we can make significant strides in nanoscale components, systems and manufacturing.”

Here are some specifics about the three new centers (from the news item),

The NSF Nanosystems Engineering Research Center for Advanced Self-Powered Systems of Integrated Sensors and Technology (ASSIST), led by North Carolina State University, will create self-powered wearable systems that simultaneously monitor a person’s environment and health, in search of connections between exposure to pollutants and chronic diseases.

The NSF Nanosystems Engineering Research Center for Nanomanufacturing Systems for Mobile Computing and Mobile Energy Technologies (NASCENT), led by the University of Texas at Austin, will pursue high-throughput, reliable, and versatile nanomanufacturing process systems, and will demonstrate them through the manufacture of mobile nanodevices.

The NSF Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS), led by the University of California Los Angeles, will seek to reduce the size and increase the efficiency of components and systems whose functions rely on the manipulation of either magnetic or electromagnetic fields.

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The NERCs will be a part of NSF’s contributions to the National Nanotechnology Initiative, which is a government-wide activity designed to ensure that investments in this area are made in a coordinated and timely manner and to accelerate the pace of revolutionary nanotechnology discoveries. A long-term view for nanotechnology research and education needs is documented in the 2010 NSF/WTEC report, “Nanotechnology Research Directions for Societal Needs in 2020”.

You can find the 614 pp. “Nanotechnology Research Directions for Societal Needs in 2020” PDF written in 2010 here.

Free the rats, mice, and zebrafish from the labs—replace them with in vitro assays to test nanomaterial toxcicity

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The July 9, 2012 Nanowerk Spotlight article by Carl Walkey (of the University of Toronto) focuses on research by Dr. André Nel and his coworkers at the California NanoSystems Institute (CNSI) and the University of California Los Angeles (UCLA) on replacing small animal model testing for nanomaterial toxicity with in vitro assays,

Currently, small animal models are the ‘gold standard’ for nanomaterial toxicity testing. In a typical assessment, researchers introduce a nanomaterial into a series of laboratory animals, generally rats or mice, or the ‘workhorse’ of toxicity testing – zebrafish (see: “High content screening of zebrafish greatly speeds up nanoparticle hazard assessment”). They then examine where the material accumulates, whether it is excreted or retained in the animal, and the effect it has on tissue and organ function. A detailed understanding often requires dozens of animals and can take many months to complete for a single formulation. The current infrastructure and funding for animal testing is insufficient to support the evaluation of all nanomaterials currently in existence, let alone those that will be developed in the near future. This is creating a growing deficit in our understanding of nanomaterial toxicity, which fuels public apprehension towards nanotechnology.

Dr. André Nel and his coworkers at the California NanoSystems Institute (CNSI) and the University of California Los Angeles (UCLA) are taking a fundamentally different approach to nanomaterial toxicity testing.

Nel believes that, under the right circumstances, resource-intensive animal experiments can be replaced with comparatively simple in vitro assays.  The in vitro assays are not only less costly, but they can also be performed using high throughput (HT) techniques. By using an in vitro HT screening approach, comprehensive toxicological testing of a nanomaterial can be performed in a matter of days. Rapid information gathering will allow stakeholders to make rational, informed decisions about nanomaterials during all phases of the development process, from design to deployment.

I’ve excerpted a brief description of Nel’s approach,

Rather than using in vitro systems as direct substitutes for the in vivo case, Nel is using a mechanistic approach to connect cellular responses to more complex biological responses, attempting to employ mechanisms that are engaged at both levels and reflective of specific nanomaterial properties.

“You need to align what you test at a cellular level with what you want to know at the in vivo” says Nel. “If oxidative stress at the cellular level is a key initiating element, then by screening for this outcome in cells you more are likely to yield something more predictive of the in vivo outcome. We can do a lot of our mechanistic work at an implementation level that allows development of predictive screening assays.”

By measuring many relevant mechanistic responses, and integrating the results, Nel believes that the in vivo behavior of a nanomaterial can be accurately predicted, provided that enough thinking goes into the devising the systems biology approach to safety assessment.

According to Walkey’s article, this approach could result in a ‘reverse’ nanomaterial development process,

Nel’s approach will influence not only the way in which nanomaterial toxicity is assessed, but also the way in which nanomaterials are developed. Currently, nanomaterials are designed to meet the need of a particular application. Toxicity is then evaluated retrospectively. Formulations that exhibit unacceptable toxicity at that point may be abandoned after a significant investment in development. Because Nel’s approach generates toxicity information much faster than traditional techniques, it will be possible to integrate toxicity during the design of a new nanomaterial. The proactive characterization of nanomaterial toxicity will provide feedback during the design process, producing formulations that maximize efficacy and minimize risk.

This is a very interesting article (illustrated with images and peppered with accessibly explanations of the issues) for anyone following the ‘nanomaterial toxicology’ story.