A modular micromachined high-density connector system for biomedical applications

This paper presents a high-density, modular, low-profile, small, and remova ble connector system developed using micromachining technologies for biomed ical applications. This system consists of a silicon or polyimide electrode with one end in contact with the biological tissue and its back-end suppor ted in a titanium base (12.5 mm in diameter and 2.5 mm in height) that is f ixed on the test subject. An external glass substrate (6 x 6 x 0.75 mm(3)), which supports a flexible polyimide diaphragm and CMOS buffers, is attache d to the titanium base whenever electrical contact is required. The polyimi de flexible diaphragm contains high-density gold electroplated pads (32 pad s, each having an area of 100 x 100 mu m(2) and separated by 150 mu m) whic h match similar pads on the electrode back-end. When vacuum is applied betw een the two, the polyimide diaphragm deflects and the corresponding gold pa ds touch, therefore, establishing electrical connection. In vitro electrica l tests in saline solution have been performed on a 32-site connector syste m demonstrating <5 Omega contact resistance, which remained stable after 70 connections, and -55 dB crosstalk at 1 kHz between adjacent channels. In v ivo experiments have also confirmed the establishment of multiple contacts and have produced simultaneous biopotential recordings from the guinea pig occipital cortex.