INTEGRATED MICROFLUIDIC DEVICE FOR DROPLET MANIPULATION

Droplets based microfluidic systems have a big potential for the miniaturization of processes for bioanalysis. In the form of droplets, reagents are used in discrete volume, enabling high-throughput chemical reactions as well as single-cell encapsulation. Microreactors of this type can be manipulated and applied in bio-testing. In this work we present a platform for droplet generation and manipulation by using dielectrophoresis force. This platform is an integrated microfluidic device with a dielectrophoresis (DEP) chip. The microfluidic device generates microdroplets such as water in oil emulsion

Electrorotation of arbitrarily shaped micro-objects: modeling and experiments

International audienceIn this paper, we study the electrorotational behaviorof non-spherical micro-objects. We extend a controlorientedmodel of general dielectrophoresis to incorporate alsothe hydrodynamics so that we can predict the motion of nonsphericalmicro-objects in fluidic environments. Such mathematical(computational) model enables model-based feedbackcontrol of a position and orientation of particles by real-time(online) computation of voltages applied to the electrodes. Weuse the measured data from experiments with electrorotation ofan artificial micro-object having a Tetris-like shape, to evaluatethe performance of the proposed model. We also demonstrate thequalitative difference in behavior from the commonly performedelectrorotation of a sphere advocating the necessity for modelbasedcontrol. Further analysis of the simulation results for otherthan the experimentally explored scenarios provides additionaluseful insight into the electrorotational behavior of non-sphericalobjects

Control-oriented model of dielectrophoresis and electrorotation for arbitrarily shaped objects

International audience"The most popular modeling approach for dielectrophoresis (DEP) is the effective multipole (EM) method. Yet nowadays, in an unrestricted source electric field, a general multipolar description of the potential caused by their charge distribution is only available for spherical objects. We present a method for computing such multipolar representation of arbitrarily shaped objects polarized by arbitrary electric fields. The method is based on numerical solutions of Laplace equation for the potential and the orthonormality of spherical harmonics. We show how the superposition principle holding for the potential can be utilized to construct a basis of solutions, from which the total potentical can be composed in real time. It is then possible to calculate the DEP forces and torques for arbitrarily shaped objects under the influence of arbitary electric fields in fractions of a second, which is needed in model-based control applications. This contrasts with the Maxwell stress tensor-based numerical method. We validate the proposed method against reference numerical solutions and analyse the importance of the higher-order multipolar moments using a sample case of a Tetrisshaped micro-object placed inside a quadrupolar micro-electrode array and exposed to electrorotation. The implementation of the model in Matlab and Comsol are offered for free download.

Dynamical Modelling and Position Control of Ultrasonic Piezoelectric Positioning Stage

The paper describes development of a feedback position controller for a new type of monolithic "hybrid" ultrasonic motor. The goal of the controller design was to demonstrate the main advantage of this piezoelectric motor – high speed and high accuracy at the same time. Tracking of 1 mm steps with 30 nm error in down to 100 ms has been achieved