A Microfluidic Device Based on Standing Surface Acoustic Waves for Sorting and Trapping Microparticles

Microfluidic devices can provide innovative means to handle and control the transport of (bio)particles within a fluid flow. The advantage of microscale devices is that different components can be integrated in a single chip at low cost, with a negligible power consumption, compared to alternative solutions. In this work, a numerical investigation is developed on the use of standing surface acoustic waves (SAWs) generated within a microfluidic channel in order to manipulate microparticles. Far-field waves are generated via inter-digital transducers (IDTs), travel on the surface of a piezoelectric substrate and finally interfere in the channel, giving rise to a standing wave solution in terms of acoustic pressure. Results are reported for different geometries of the channel, to define the sensitivity of the acoustic pressure field to the relevant geometric features of the channel. This investigation shows how the acoustic radiation and drag forces interact with each other to move and focus the particles, possibly leading to a separation of heterogeneous ones, and generally provide a way to manipulate them at a small scale

Manipulation and Optical Detection of Colloidal Functional Plasmonic Nanostructures in Microfluidic Systems

The very strong optical resonances of plasmonic nanostructures can be harnessed for sensitive detection of chemical and biomolecular analytes in small volumes. Here we describe an approach towards optical biosensing in microfluidic systems using plasmonic structures (functionalized gold nanoparticles) in colloidal suspension. The plasmonic nanoparticles provide the optical signal, in the form of resonant light scattering or absorption, and the microfluidic environment provides means for selectively manipulating the nanoparticles through fluid dynamics and electric fields. In the first part we discuss recent literature on functionalized colloidal particles and the methods for handling them in microfluidic systems. Then we experimentally address aspects of nanoparticle functionalization, detection through plasmonic resonant light scattering under dark-field illumination and the electrokinetic behavior of the particles under the action of an alternating electric field

High Density Cell Microarray Based on Dielectrophoresis Traps Induced by a Matrix of Singularities

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Fast concentration gradient generator on a cell biochip for toxicology applications

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A microfluidic device with removable packaging for the real time visualisation of intracellular effects of nanosecond electrical pulses on adherent cells

Dalmay, C De Menorval, M A Francais, O Mir, L M Le Pioufle, B England Lab on a chip Lab Chip. 2012 Oct 16;12(22):4709-15. doi: 10.1039/c2lc40857k.The biological mechanisms induced by the application of nanosecond pulsed electric fields (nsPEFs: high electrical field amplitude during very short duration) on cells remain partly misunderstood. In this context, there is an increasing need for tools that allow the delivering of such pulses with the possibility to monitor their effects in real-time. Thanks to miniaturization and technology capabilities, microtechnologies offer great potential to address this issue. We report here the design and fabrication of a microfluidic device optimized for the delivery of ultra short (10 ns) and intense (up to 280 kV cm(-1)) electrical pulses on adherent cells, and the real time monitoring of their intracellular effects. Ultra short electric field pulses (nsPEFs or nanopulses) affect both the cell membrane and the intracellular organelles of the cells. In particular, intracellular release of calcium from the endoplasmic reticulum was detected in real time using the device, after exposure of adherent cells to these nsPEFs. The high intensity and spatial homogeneity of the electric field could be achieved in the device thanks to the miniaturization and the use of thick (25 mum) electroplated electrodes, disposed on a quartz substrate whose transparency allowed real time monitoring of the nsPEFs effects. The proposed biochip is compatible with cell culture glass slides that can be placed on the chip after separate culture of several days prior to exposure. This device allows the easy exposure of almost any kind of attached cells and the monitoring in real time while exposed to nsPEFs, opening large possibilities for potential use of the developed biochips

Advanced etching of silicon based on deep reactive ion etching for silicon high aspect ratio microstructures and three-dimensional micro- and nanostructures

International audienceDifferent processes involving an inductively coupled plasma reactor are presented either for deep reactive ion etching or for isotropic etching of silicon. On one hand, high aspect ratio microstructures with aspect ratio up to 107 were obtained on sub-micron trenches. Application to photonic MEMS is presented. Isotropic etching is also used either alone or in combination with anisotropic etching to realize various 3D shapes. (c) 2005 Elsevier Ltd. All rights reserved

In vitro and in silico study of cell growth in porous scaffold under dynamic flow

International audienceThe use of bioreactors for cultivating bone-forming cells on a three-dimensional porous scaffold material resolves mass transport limitations and provides physical stimuli, increasing the overall proliferation and differentiation of cells. Despite the recent and significant development of bioreactors for tissue engineering, the underlying mechanisms leading to improved bone substitutes remain mostly unknown. Previous studies have shown that numerical simulations can be a powerful tool to predict tissue development in complex environments. However, current models often present a poor representation of local physics and comparisons with experiments generally do not lead to a quantitative agreement. In order to experimentally reproduce the fluid flow through a porous scaffold, three-dimensional, micro-architectured micro-fluidic chambers have been designed. Osteoblast cells have been cultivated in micro-systems with and without flow, and cell proliferation dynamics have been monitored with image analyzing. Simultaneously, a numerical model has been developed in order to predict cell growth under fluid flow. Cell population dynamic is simulated using a three-dimensional cellular automaton, while the fluid flow is described using the Lattice-Boltzmann method (LBM). Experiments and numerical results show the influence of fluid induced shear stress on cell proliferation

Discrete model combined with mimetic microfluidic chips to study cell growth in porous scaffold under flow conditions.

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