(For a listing of all microsystems-related projects at UMD, please visit the UMD Microsystems Initiative.)

Active projects

Inkjet-fabricated paper-based SERS devices for chemical and biological sensing

Stephen Restaino, Qian Zhang (previously Veemoon Yu and Eric Hoppmann)

As a bio/chemical sensing technique, surface enhanced Raman spectroscopy (SERS) offers sensitivity comparable to that of fluorescence detection while providing highly specific information about the analyte. The high sensitivity of SERS detection results from the localized plasmons generated at the surface of noble metal nanostructures upon excitation by resonant electric fields at optical frequencies. Although single molecule identification with SERS was demonstrated over a decade ago, today a need exists to develop practical solutions for point-of-sample and point-of-care SERS systems. Recently, we demonstrated the fabrication of SERS substrates by inkjet printing silver and gold nanostructures onto paper and other similar membranes. Using a low-cost commercial inkjet printer, we deposited silver nanoparticles with micro-scale precision to form SERS-active biosensors. Using these devices, we have been able to achieve detection limits comparable to conventional nanofabricated substrates. Furthermore, we have leveraged the fluidic properties of paper to enhance the performance of the SERS devices while also enabling unprecedented ease of use, which is critical for extending chemical and biological analytics from central labs out into the field. We are currently investigating the use of these paper-based SERS sensors for both chemical and biological sensing applications

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    Eric P. Hoppmann, Wei W. Yu, and Ian M. White, Multiplex detection of DNA targets using polymerase chain reaction (PCR) and paper surface enhanced Raman spectroscopy (SERS) chromatography, Applied Spectroscopy, 68, 909-915, 2014. DOI:10.1366/14-07451.

    Eric P. Hoppmann, Wei W. Yu, and Ian M. White, Inkjet-printed fluidic paper devices for chemical and biological analytics using surface enhanced Raman spectroscopy, Journal of Selected Topics in Quantum Electronics, 20, 7300510, 2014. DOI:10.1109/JSTQE.2013.2286076.

    Eric P. Hoppmann, Wei W. Yu, and Ian M. White, Highly sensitive and flexible inkjet printed SERS sensors on paper, Methods, 63, 219-224, 2013. DOI:10.1016/j.ymeth.2013.07.010.

    Wei W. Yu and Ian M. White, Chromatographic separation and detection of target analytes from complex samples using inkjet printed SERS substrates, Analyst, 138, 3679-3686 2013. DOI:10.1039/C3AN00673E.

    Wei W. Yu and Ian M. White, Inkjet-Printed Paper-Based SERS Dipsticks and Swabs for Trace Chemical Detection, Analyst, 138, 1020-1025, 2013. DOI:10.1039/C2AN36116G.

    Analyst front cover

    Wei W. Yu and Ian M. White, Inkjet Printed Surface Enhanced Raman
    Spectroscopy Array on Cellulose Paper, Anal. Chem. 82, 9626 - 9630, 2010. DOI:10.1021/ac102475k

Simplified sample preparation for microfluidic PCR

Imaly Nanayakkara (previously Kunal Pandit)

We have invented a process that dramatically reduces the hands-on time and complexity of PCR sample preparation. This may be the key factor that finally enables PCR-based molecular diagnostics to be utilized in near-patient applications. Publications are pending.

Amplified biosensors

Stephen Restaino, John Goertz, Hieu Nguyen, Ken Sharp, Sean Virgile

We are investigating novel bio-active materials that enable amplified sensing read-outs, thus boosting sensing performance by orders of magnitude, which may lead to new diagnostic applications that are not possible with today's commercial technologies. Publications are in progress.

Paper-based diagnostics for at-home health care

Adriel Sumathipala

This research effort has seen the development of an ultra-low cost, rapid, and on-site tests for the detection of two discrete biomarkers of cardiac disease, oxidized low-density lipoprotein (ox-LDL) and total blood cholesterol. The first and recently discovered biomarker, ox-LDL, has been found to have a stronger correlation with cardiac disease than any other biomarker; yet, tests for this vital biomarker are inaccessible to most, available at only a handful of labs and costing upwards of $250. Using non-enzymatic, electrochemical detection mechanisms, this research was able to successfully detect and differentiate ox-LDL from native LDL. Moreover, this test was able to detect the lipid peroxides of ox-LDL in its earliest stages, whereas the more expensive, antibody based assays detect ox-LDL in its last stages. The concentration of the second and traditional biomarker, cholesterol, was analyzed via an enzymatic assay constructed by an inkjet printer, enabling rapid and scalable production. The ink-jet technology developed can be harnessed for applications in sensing environmental toxins, food safety, and integrated personalized health statistics.

Previous projects

Optofluidic SERS in nanoporous microchannels for chemical and macromolecule detection

Soroush Yazdi

We integrated surface enhanced Raman scattering assays into microfluidic channels to enable highly automated, portable, and sensitive chemical and biomolecular analysis tools.

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    Soroush H. Yazdi and Ian M. White, Multiplexed detection of aquaculture fungicides using a pump-free optofluidic SERS microsystem, Analyst, in press, DOI:10.1039/C2AN36232E.

    Soroush H. Yazdi and Ian M. White, A nanoporous optofluidic microsystem
    for highly sensitive and repeatable SERS detection, Biomicrofluidics 6,
    014105, 2012. DOI:10.1063/1.3677369.

    Soroush H. Yazdi and Ian M. White, An Optofluidic SERS Microsystem for Sensitive and Repeatable On-Site Detection of Chemical Contaminants, Analytical Chemistry, in press, DOI:10.1021/ac301747b.

    Soroush H. Yazdi and Ian M. White, Multiplexed detection of aquaculture fungicides using a pump-free optofluidic SERS microsystem, Analyst, in press, DOI:10.1039/C2AN36232E.

Interfacial effects in droplet PCR.

Kunal Pandit

We investigated the pendant drop technique as a method for assessing the performance of surfactants for droplet PCR. In the process, we identified a surfactant that significantly outperformed the current state of the art for on-chip droplet PCR.

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    Kunal R. Pandit, Paul E. Rueger, Richard V. Calabrese, Srinivasa R. Raghavan, and Ian M. White, Assessment of surfactants for efficient droplet PCR in mineral oil using the pendant drop technique, Journal of Colloids and Surfaces B: Biointerfaces, 126, 489-495, 2015. DOI:10.1016/j.colsurfb.2015.01.001

Microfluidic enrichment and recovery of targeted cells.

Jeff Burke, I-Jane Chen

We developed microfluidic techniques to enrich and recover targeted cell types using microfluidics.

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    Jeffrey M. Burke, Rebecca E. Zubajlo, Elisabeth Smela, and Ian M. White, High-throughput particle separation and concentration using spiral inertial filtration, Biomicrofluidics, in press, DOI:10.1063/1.4870399.

On-chip analysis of CTC tumorigenicity.

Katayoon Saadin, Jeff Burke

The mechanisms by which circulating tumor cells (CTCs) can form metastatic tumors are not well understood.  We developed microsystems to enable the study of isolated CTCs to elucidate the tumor initiation process.

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    Katayoon Saadin, Jeffrey M. Burke, Neerav P. Patel, Rebecca E. Zubajlo, and Ian M. White, Enrichment of tumor-initiating breast cancer cells within a mammosphere-culture microdevice, Biomedical Microdevices, DOI:10.1007/s10544-013-9755-y.

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