Fabrication of an Active PCB-MEMS Microfluidic Chip for CHO Cells Characterization by Electrochemical Impedance Spectroscopy

This paper reports the use of laser ablation for the fabrication of a microfluidic device with integrated electrodes on a printed circuit board (PCB-MEMS). The fabricated novel device has flame retardant (FR)-4 resin as substrate, copper (Cu) as active material, and SU-8 polymer as a structural material. The resolution, repeatability, and simplicity achieved in this approach, along with the low cost of the involved materials and methods, enable an affordable micromachining technique with a rapid fabrication-test cycle to develop active microfluidic systems on a chip. Furthermore, an Electrochemical Impedance Spectroscopy (EIS) analysis was performed at different Chinese Hamster Ovary (CHO) cell concentrations (105 to 108 cfu ml-1) to validate device assembly and functionality. The electrical properties of the system were characterized and discussed through a proposed equivalent circuit model comprising five passive elements. The model describes ohmic and non-ideal capacitive behavior of the cytoplasm and membrane of the CHO cells as well as the suspending medium and electrical connections of the device. Likewise, two characteristic times associated with relaxation processes caused by a change in the path of charge transport through the cells are determined.