Micro Device for Bio-Particle Positioning in a Confined Microfluidic Volume Using Carbon MEMS and Dielectrophoretic Forces
Authors: Pilloni Oscar , Benítez José Luis , Oropeza-Ramos Laura 
Published: February 2020

Experiments on micron sized bio particles (bio compatible micro particles, cells) are limited by the manipulation techniques used to position particles in a zone of interest, like the focus point of an optical system, a micro electrode for an electrical measurement, a tridimensional cellular scaffold or a reaction chamber for a chemical process.
We introduce a device that would aid in the precise positioning of micron sized bio particles inside a microfluidic channel, using a combination of individually addressable 3D electrodes and planar electrodes based on carbon micro electro mechanical systems (C-MEMS) to induce dielectrophoretic (DEP) forces 1,2.
The proposed device uses a series of carbon-based 3D electrodes and a matrix of planar electrodes produced by the pyrolysis of a common photoresist (SU-8) 3. The electrodes are built on a fused silica substrate to enable the view of experiments trough optical microscopy.
Our hypothesis consist in that by using the electrodes to exert a pulsed DEP force, coplanar to the substrate by the 3D electrodes and orthogonal to the substrate by the planar electrodes, it is possible to precisely position a bio particle in a confined microfluidic volume at low flow rates 4.
These types of electrodes are chosen because they can induce a DEP force by applying small electric potentials (~ 10 V) due to the fact that are immersed in the carrying fluid. Pulsed DEP was selected due to its low cost implementation and because it is able to affect bio particles positions while maintaining their viability 5.
The manufacturing process requires the use of traditional techniques of photolithography to 3D pattern photoresist and a carefully tailored pyrolysis process to obtain the desired electrode features 6.
In order to validate the device, the resistivity of the carbon films is measured, cyclic voltammetry is used to characterize the electrochemical behavior of the electrodes, electrode half-cell potential stability is tested over time, particle image velocimetry is used to analyze the flow inside the micro channel and the spatial position of a target particle is monitored using optical microscopy while it is manipulated using DEP force 7. Finally, these results are compared with those obtained in the simulation and theoretical design of the proposed micro-platform.
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