Micro-array development for cell secretion studies

We are focusing on the development of a biochip which will enable massively parallel amperometric measurements on single cells for exocytosis studies. Initial prototypes have been fabricated with picoliter-sized wells which roughly conform to the shape of the cells. The electrochemical measurement using the prototype devices can capture a large fraction, approximately 80%, of the catecholamine release with millisecond temporal resolution. With this prototype device, cells must be manually positioned into the micro-wells by a micromanipulator. Therefore, two new designs incorporating three dimensional microfluidic structures have been developed for automatic cell positioning. One design is based on thin silicon diaphragms with picoliter-sized well arrays, while another has 1mum silicon nitride membranes. Both designs have through-membrane holes and are designed in such a way that the cells will be automatically positioned onto electrodes once a suitable pressure differential is applied between the two sides of the thin diaphragms. Details of the microfabrication process for both designs will be presented in this paper as well as results of automatic cell positioning tests.