A flat interface nerve electrode with integrated multiplexer.

One of the goals of peripheral nerve cuff electrode development is the design of an electrode capable of selectively activating a specific population of axons in a common nerve trunk. Several designs such as the round spiral electrode or the flat interface nerve electrode (FINE) have shown such ability. However, multiple contact electrodes require many leads, making the implantation difficult and potentially damaging to the nerve. Taking advantage of the flat geometry of the FINE, multiplexers were embedded within the cuff electrode to reduce the number of leads needed to control 32 channels. The circuit was implemented on a polyimide film using off-the-shelf electronic components. The electronic module was surface-mounted directly onto the electrode's flat substrate. Two circuit designs were designed, built, and tested: 1) a single supply design with only two wires but limited to cathodic-first pulse and 2) a dual-supply design requiring three lead wires but an arbitrary stimulation waveform. The electrode design includes 32 contacts in a 1 mm x 8 mm opening. The contact size is 300 microm x 400 microm with access resistance less than 1 k ohm. This electrode is not intended for long-term use, but developed as a feasibility study for future development using low-water-absorption materials such as liquid crystal polymer and an application specific integrated circuit.