Cedric Hurth

Publications (15) View all

• Article: A tuneable array of unique steady-state microfluidic gradients.

  Matthew D Estes, Cedric Hurth, Matthew Barrett, Frederic Zenhausern
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  ABSTRACT: We report an on-chip gradient generator that has been designed, modelled, fabricated, and characterized to facilitate temporal tuning of several unique gradients in parallel for multiple applications. This design allows for steady state programming of the intensities across multiple orders of magnitude while producing exponential, linear, and logarithmic gradient profiles. The magnitude of the gradients is controlled through regulating the ratio of the two on-chip flow inlets without the need for valves or other active mixers. On-chip binding of biotin by a fluorescent streptavidin complex creates a diffusive barrier that regulates access to the gradient inlets, providing a second orthogonal mechanism for regulating the microgradient intensities. The device is also characterized using an on-chip enzymatic reaction to produce an array of tuneable product concentrations within the various microchannels.
  Physical Chemistry Chemical Physics 05/2013; · 3.57 Impact Factor
• Article: Direct loading of polymer matrices in plastic microchips for rapid DNA analysis: a comparative study.

  Cedric Hurth, Jian Gu, Maurice Aboud, Matthew D Estes, Alan R Nordquist, Bruce McCord, Frederic Zenhausern
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  ABSTRACT: We report the design and performance validation of microfluidic separation technologies for human identification using a disposable plastic device suitable for integration into an automated rapid DNA analysis system. A fabrication process for a 15-cm long hot-embossed plastic microfluidic devices with a smooth semielliptical cross section out of cyclic olefin copolymer is presented. We propose a mixed polymer solution of 95% w/v hydroxyethylcellulose and 5% w/v polyvinylpyrrolidone for a final polymer concentration of 2.5 or 3.0% to be used as coating and sieving matrix for DNA separation. This formulation allows preparing the microchip without pretreatment in a single-loading step and provides high-resolution separation (≈1.2 bp for fragments <200 bp), which is superior to existing commercial matrices under the same conditions. The hot-embossed device performance is characterized and compared to injection-molded devices made out of cyclic olefin copolymer based on their respective injector geometry, channel shape, and surface charges. Each device design is assessed by fluorescence videomicroscopy to evaluate the formation of injection plugs, then by comparing electropherograms for the separation of a DNA size standard relevant to human identification.
  Electrophoresis 08/2012; 33(16):2604-11. · 3.30 Impact Factor
• Article: Clinical diagnostic of pleural effusions using a high-speed viscosity measurement method

  Cedric Hurth, Katherine Klein, Lena van Nimwegen, Ronald Korn, Krishnaswami Vijayaraghavan, Frederic Zenhausern
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  ABSTRACT: We present a novel bio-analytical method to discriminate between transudative and exudative pleural effusions based on a high-speed video analysis of a solid glass sphere impacting a liquid. Since the result depends on the solution viscosity, it can ultimately replace the battery of biochemical assays currently used. We present results obtained on a series of 7 pleural effusions obtained from consenting patients by analyzing both the splash observed after the glass impactor hits the liquid surface, and in a configuration reminiscent of the drop ball viscometer with added sensitivity and throughput provided by the high-speed camera. The results demonstrate distinction between the pleural effusions and good correlation with the fluid chemistry analysis to accurately differentiate exudates and transudates for clinical purpose. The exudative effusions display a viscosity around 1.39 ± 0.08 cP whereas the transudative effusion was measured at 0.89 ± 0.09 cP, in good agreement with previous reports.
  Journal of Applied Physics 08/2011; 110(3):034701-034701-6. · 2.17 Impact Factor
• Article: Direct Probing of Electrical Double Layers by Scanning Electrochemical Potential Microscopy

  Cedric Hurth, Chunzeng Li, Allen J. Bard
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  ABSTRACT: We report the direct experimental measurement of electrical double layer profiles on metallic (Pt foil) and insulator (SiO2 on Si) surfaces in a dilute electrolyte with no added redox mediator by scanning electrochemical potential microscopy (SECPM). An important consideration in these measurements is fabrication of the probe (tip), and experimental details are given for the reproducible preparation of suitable polyethylene-coated PtIr nanoelectrodes. A small amount of silver was electrodeposited on these tips to stabilize them for sensitive potentiometric measurements. A Pt foil surface and an oxide-grown Si(100) wafer in 10 μM KCl were approached to record the potential distribution in the vicinity of the surface. The advantages and limitations of SECPM are compared to conventional current-sensing techniques.
  03/2007;
• Article: Reduction of the cantilever hydrodynamic damping near a surface by ion-beam milling

  A. Maali, T. Cohen-Bouhacina, C. Jai, C. Hurth, R. Boisgard, J. P. Aime, D. Mariolle, F. Bertin
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  ABSTRACT: In this work, we evaluate the influence of the cantilever width on the hydrodynamic drag force. To do so, we present an experimental analysis of the thermal motion in air and liquid of a commercial and modified by focused ion-beam (FIB) milling silicon nitride cantilevers. From the thermal noise spectrum, we extract the damping for different cantilever-sample distances. We show that the hydrodynamic force due to the drag can be reduced by almost an order of magnitude when reducing the cantilever width. With the FIB modification (milling) one can still use conventional atomic force microscope heads with a significant reduction of the hydrodynamic forces.
  Journal of Applied Physics 02/2006; · 2.17 Impact Factor