Integrated Multiplexer for Nerve Electrodes

Multiple contact nerve cuff electrodes require many leads, making their implantation difficult and potentially damaging to the nerve. Therefore the design of circuits capable of reducing the number of wires is crucial to the development of a device that can be implanted in patients. The flat interface nerve electrode (FINE) was developed to allow selective recording and selective stimulation capabilities. We report here the design of multiplexers embedded within the cuff electrode that can reduce the number of leads needed to control thirty two channels. The electrode design includes thirty-two contacts in a 1mmx8mm opening. Each contact size is 300μm x400μm with access resistance less than 1kW. The control circuit was implemented on a polyimide film using off the-shelf surface mounted electronic components. The electronic module was mounted directly onto the electrode’s flat substrate. Two control circuit implementations for the control of the thirty two channels 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. These circuit designs allow a significant reduction of the number of leads required for the control of the electrode. However, the hermetic sealing of the devices has not yet been implemented. (Funding was provided the National Institutes of Health, grant number 5R01NS032845-14.)