(334a) 3D Carbon Cages for Dielectrophoretic-Based Bioparticle Separation/Concentration Applications

Víctor H. Pérez-González,^1,2 Vinh Ho,² Lawrence Kulinsky,² Blanca H. Lapizco-Encinas,³ Sergio O. Martínez-Chapa,¹Marc Madou,^2,4*

1 BioMEMS Research Chair, Tecnológico de Monterrey, Monterrey, NL, México.

2 Mechanical & Aerospace Engineering, University of California, Irvine, Irvine, CA, US.

3 Microscale Bioseparations Laboratory and Department of Chemical Engineering, Tennessee Technological University, Cookeville, TN, US.

4 Ulsan National Institute of Science and Technology, World Class University Program, Ulsan 689-79, South Korea.

*Correspondence author. Email: mmadou@uci.edu

Dielectrophoresis (DEP) is an electrokinetic phenomenon where the movement of a polarizable particle is due to its interaction with a spatially-non-uniform electrical field. The magnitude and direction of this movement depends upon the interaction between an induced electrical dipole and the electrical field, and also, on the relation between the dielectric properties of the particle and the suspending medium in which the particle is immersed. The microfluidic research community has become interested in DEP because of its wide range of biological applications: particle manipulation, filtration, separation, concentration, and characterization. There are two main directions in DEP-based microfluidics: metal-electrode based DEP, and insulator based DEP (iDEP). In metal-electrode based DEP, planar interdigitated fingers are employed to generate a non uniform electrical field in a microchannel. This 2D approach comes with some limitations; for instance, only particles in close vicinity of the microchannel floor will experience DEP, leaving most of the sample bulk unaffected. In iDEP, insulating obstacles are fabricated within the microfluidic channel and an electrical field is generated along the channel. The insulating obstacles deform the electrical field, creating zones of high concentration of field lines; iDEP has the advantage of affecting the complete sample since the obstacles are three-dimensional. Nonetheless, it also has some disadvantages, the most important of which is the requirement of high applied voltages, sometimes surpassing 1000 V. This not only creates Joule heating that can damage the sample, but also has safety concerns and requires expensive voltage sources. Carbon electrode based DEP (CarbonDEP) is a novel approach to microparticle manipulation. Carbon DEP brings together the advantages of both, electrode based DEP and iDEP. Through the photolithography and pyrolysis of organic precursors, 3D Carbon structures are developed that can be employed as electrodes for DEP applications. Carbon has a wider electrochemical stability window than most materials employed in metal-electrode based DEP. Carbon is also biocompatible, making it attractive for biotechnology applications. This work presents new developments in the areas of separation and concentration of microparticles in DEP-based microfluidic platforms. Simulation work was carried out employing COMSOL Multiphysics to analyze the electric field distribution within a microchannel for different electrode geometries. Results from simulations allowed for optimizing the electrode geometry design. Carbon posts were fabricated over planar Carbon leads as in previous CarbonDEP works, with the difference that planar Carbon links were fabricated over the Carbon posts, giving rise to Carbon cages, resulting in an increase in particle trapping efficiency. Carbon cages were tested with polystyrene particles with diameters ranging from 500 nm to 4 µm. It was found that Carbon cages allow for a higher dielectrophoretic effect in the bulk of the sample. Applications of this work include, but are not limited to, environmental monitoring, food safety control, clinical analysis, and clean energy production.