DEP Actuation

Dielectrophoresis force (DEP force) is the force induced on a polarizable particle suspended in a non-uniform electric field. Based on the analysis of the dielectrophoretic behavior of particles, it has been demonstrated that DEP is an effective means for micro-manipulation, deposition and micro assembly. To move a micro-particle using DEP force or to control its trajectory by changing the electric potential, it is necessary to know its behavior under DEP and its trajectory.    

 

 

Figure: experimental electrode used to apply the dielectrophoretic motion.

 

A hybrid method is proposed in Minarob team to simulate the 3D behavior of micro particles under DEP force, in function of the electric potential applied on the electrodes. Indeed, because of the large variety of electrodes and their geometric complexity, it would be highly difficult to directly integrate analytic equations. This method is based on merging preprocessed FEM simulations and analytic equations. Physicals equations are computed in order to define the link between the electric potential and the DEP force. Consequently, based on the database built by few FEM simulations, our simulator is able to provide the trajectory whatever are the electric potentials applied on the electrodes. This approach enables to improve the simulation’s time. Each iteration consists of the use of the equations linking the electric potential to the electric field and then to the DEP force. FEM software can simulate complex geometries but the simulation time remains high and especially when the potential change frequently. By using FEM simulator as a preprocessing simulation and integrating physical law in a specific simulator, the time of simulation can be highly reduced.

 

Modeling and closed loop strategy of DEP systems using vision feedback have been proposed in Minarob team. By simulating the 3D behavior of micro particles under DEP force, in function of the electric potential applied on the electrodes and using the vision capture, the system is ready to include the feedback block. The problem which is faced is the large difference between the high dynamics of the system (respond time around 1ms) and the low speed rate of the vision capture (around 1 image per 10 ms). A predictive control strategy based on the feedback of the vision sensor and a model of the DEP force has been proposed and 2D trajectory control has been achieved experimentally inside a petri dish.