Glass-based BioMEMS devices for optically excited cell impedance measurement

Abstract

This paper presents for the first time the design and fabrication of BioMEMS devices for living cells' electrochemical impedance measurement under optical excitation. An interdigitated electrode design is adopted in order to increase the sensitivity of living cells' impedance measurement. The magnitudes of the parasitic components were calculated and their influence on the chip performance was simulated. It is shown that our glass-based realization enables a very good performance up to a measurement frequency of 10 MHz when the solution resistance is 1 MΩ. The main difficulties that had to be solved in the fabrication process were related to adhesion and patterning of the various metal films, and especially to developing the correct bonding recipe. Unlike most of the reported data, no direct bonding was employed in the realization of our devices, but rather an intermediary polymer layer (e.g. SU8 or BCB) was used. The impedance of the devices with living yeast cells are measured with and without laser excitation at 532 nm. The laser excitation also redistributes the cells, and the suspending cells in the PBS buffer settle down much quicker after the light excitation. © 2006 Elsevier B.V. All rights reserved.