A three-dimensional shape memory alloy microelectrode with clipping structure for insect neural recording

A microelectrode, with clipping structure for neural recording from a free-moving insect, was designed and fabricated using a shape memory alloy (SMA) thin film. The SMA thin films (titanium nickel; Ti-48 at.%Ni) are deposited by RF magnetron sputtering and patterned by HF-HNO/sub 3/ wet etching. The transformation temperatures of the SMA thin films were measured at 54/spl deg/C (A*) and 50/spl deg/C (M*). The SMA microelectrode consists of a "hook" structure (720 /spl mu/m/spl times/480 /spl mu/m) and two "C"-shape probes (600 /spl mu/m/spl times/70 /spl mu/m). The electrode impedance is about 5 k/spl Omega/ at 1 kHz. The desired three-dimensional (3D) shape is given to the electrode by a bonded wire. The clinging force of the electrode to the nerve is enhanced by the 3-D structures. The SMA microelectrode can clip a nerve cord tightly. The damages of the nerve by thermal actuation of the clip are not observed by physiological analysis. The neural activity from a living insect was successfully recorded with this SMA microelectrode.