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Virginia Chu

Bio: Virginia Chu is an academic researcher from Princeton University. The author has contributed to research in topics: Amorphous silicon & Silicon. The author has an hindex of 24, co-authored 226 publications receiving 2083 citations.


Papers
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Journal ArticleDOI
TL;DR: A PDMS microchannel-based, colorimetric, autonomous capillary chip provides a multiplexed and semi-quantitative immunodetection assay and was successfully validated for these 3 mycotoxins in a corn-based feed sample after a simple sample preparation procedure.

52 citations

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TL;DR: An integrated microfluidic device for the simultaneous matrix clean-up, concentration and detection based on aqueous two-phase systems can help the development of point-of-care devices that can directly deal with real samples in complex matrices without the need for extra extraction processes and equipment.
Abstract: Immunoassays are fast and sensitive techniques for analyte quantification, and their use in point-of-care devices for medical, environmental, and food safety applications has potential benefits of cost, portability, and multiplexing. However, immunoassays are often affected by matrix interference effects, requiring the use of complex laboratory extraction and concentration procedures in order to achieve the required sensitivity. In this paper we propose an integrated microfluidic device for the simultaneous matrix clean-up, concentration and detection. This device consists of two modules in series, the first performing an aqueous two-phase extraction (ATPE) for matrix extraction and analyte pre-concentration, and the second an immunoassay for quantification. The model analyte was the mycotoxin ochratoxin A (OTA) in a wine matrix. Using this strategy, a limit of detection (LoD) of 0.26 ng mL−1 was obtained for red wine spiked with OTA, well below the regulatory limit for OTA in wines of 2 ng mL−1 set by the European Union. Furthermore, the linear response on the logarithmic concentration scale was observed to span 3 orders of magnitude (0.1–100 ng mL−1). These results are comparable to those obtained for the quantification of OTA in plain buffer without an integrated ATPE (LoD = 0.15 ng mL−1). The proposed method was also found to provide similar results for markedly different matrices, such as red and white wines. This novel approach based on aqueous two-phase systems can help the development of point-of-care devices that can directly deal with real samples in complex matrices without the need for extra extraction processes and equipment.

50 citations

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TL;DR: The reduction to the microscale does not greatly affect the antibody extraction yield when compared with macroscale results, but it does reduce the operation time, demonstrating the potentiality of this approach to process optimization.

50 citations

Journal ArticleDOI
TL;DR: Novel findings show that PEG–ammonium sulfate ATPE is a promising system for primary HIV-VLP recovery and demonstrate the potential of a miniaturized ATPE for massive parallelization (scale-out) at the preparative scale or integrated in analytical miniaturization systems.

46 citations

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TL;DR: In this paper, a hybrid magnetoresistive (MR) spin valve sensor was used to detect dc magnetic fields at high frequency microelectromechanical system using a (MEMS) microcantilever structure with integrated magnetic flux guide.
Abstract: Low frequency 1∕f noise in magnetoresistive (MR) spin valve sensors was suppressed by modulating an external dc magnetic field at high frequency microelectromechanical system using a (MEMS) microcantilever structure with an integrated magnetic flux guide. With this hybrid MR∕MEMS device, direct detection of dc magnetic fields in the sensor high frequency thermal noise regime was achieved. The microcantilever was actuated using a gate electrode by applying an ac voltage with frequency f, causing it to oscillate at 2f. Measurements show detection of a dc magnetic field at 2f frequency (400kHz), where sensor 1∕f noise is two orders of magnitude lower than dc.

43 citations


Cited by
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Journal ArticleDOI
TL;DR: A review of the field of biosensors can be found in this article, where the authors discuss the reasons for success, some of the more exciting emerging technologies, and speculates on the importance of sensors as a ubiquitous technology of the future for health and the maintenance of wellbeing.
Abstract: This review is based on the Theophilus Redwood Medal and Award lectures, delivered to Royal Society of Chemistry meetings in the UK and Ireland in 2012, and presents a personal overview of the field of biosensors. The biosensors industry is now worth billions of United States dollars, the topic attracts the attention of national initiatives across the world and tens of thousands of papers have been published in the area. This plethora of information is condensed into a concise account of the key achievements to date. The reasons for success are examined, some of the more exciting emerging technologies are highlighted and the author speculates on the importance of biosensors as a ubiquitous technology of the future for health and the maintenance of wellbeing.

1,160 citations

Journal ArticleDOI
TL;DR: In this article, the authors present several classes of inorganic semiconductor materials that can be used to form high-performance thin-film transistors for large area, flexible electronics.
Abstract: This article reviews several classes of inorganic semiconductor materials that can be used to form high-performance thin-film transistors (TFTs) for large area, flexible electronics. Examples ranging from thin films of various forms of silicon to nanoparticles and nanowires of compound semiconductors are presented, with an emphasis on methods of depositing and integrating thin films of these materials into devices. Performance characteristics, including both electrical and mechanical behavior, for isolated transistors as well as circuits with various levels of complexity are reviewed. Collectively, the results suggest that flexible or printable inorganic materials may be attractive for a range of applications not only in flexible but also in large-area electronics, from existing devices such as flat-panel displays to more challenging (in terms of both cost and performance requirements) systems such as large area radiofrequency communication devices, structural health monitors, and conformal X-ray imagers.

813 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize the main models that describe the lifetime dependence on bias voltage or carrier density, and find that there are two complementary approaches to clarify the structure of the lifetime.
Abstract: The electron lifetime τn in dye-sensitized solar cells (DSC) is a central quantity to determine the recombination dynamics in the solar cell. It can be measured by several methods: impedance spectroscopy, IMVS, stepped time transients, and open-circuit voltage decays. The paper aims at a better understanding of this fundamental parameter. We summarize the main models that describe the lifetime dependence on bias voltage or carrier density, and find that there are two complementary approaches to clarify the structure of the lifetime. The first is to treat the lifetime as a product of the chemical capacitance and recombination resistance. This approach is important because the resistance largely determines steady state operation characteristics of the solar cell close to open-circuit voltage. The second approach is based on a kinetic model that describes in detail the different processes governing the decay of the carrier population in a measurement of τn. The lifetime is composed of a trapping factor and a...

700 citations

Journal ArticleDOI
TL;DR: The aim of this review is to overview the basics of ATPS, optimization and its applications, and shows that it has also been successfully used in the detection of veterinary drug residues in food, separation of precious metals, sewage treatment and a variety of other purposes.
Abstract: Aqueous two-phase system (ATPS) is a liquid-liquid fractionation technique and has gained an interest because of great potential for the extraction, separation, purification and enrichment of proteins, membranes, viruses, enzymes, nucleic acids and other biomolecules both in industry and academia Although, the partition behavior involved in the method is complex and difficult to predict Current research shows that it has also been successfully used in the detection of veterinary drug residues in food, separation of precious metals, sewage treatment and a variety of other purposes The ATPS is able to give high recovery yield and is easily to scale up It is also very economic and environment friendly method The aim of this review is to overview the basics of ATPS, optimization and its applications

507 citations

Journal ArticleDOI
TL;DR: In this paper, the authors take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances.
Abstract: We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of rela...

477 citations