A modular micromachined high-density connector system for biomedical applications

This paper presents a high-density, modular, low-profile, small, and removable connector system developed using micromachining technologies for biomedical applications. This system consists of a silicon or polyimide electrode with one end in contact with the biological tissue and its back-end supported in a titanium base (12.5 mm in diameter and 2.5 mm in height) that is fixed 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 attached to the titanium base whenever electrical contact is required. The polyimide flexible diaphragm contains high-density gold electroplated pads (32 pads, each having an area of 100 x 100 mu m(2) and separated by 150 mu m) which match similar pads on the electrode back-end. When vacuum is applied between the two, the polyimide diaphragm deflects and the corresponding gold pads touch, therefore, establishing electrical connection. In vitro electrical tests in saline solution have been performed on a 32-site connector system demonstrating <5 Omega contact resistance, which remained stable after 70 connections, and -55 dB crosstalk at 1 kHz between adjacent channels. In vivo experiments have also confirmed the establishment of multiple contacts and have produced simultaneous biopotential recordings from the guinea pig occipital cortex.