Fabrication of a Flexible Three-Dimensional Hybrid Directional Lead for Deep Brain Stimulation and Control of Micturition Reflex in Rats

A miniaturized three-dimensional (3D) cylindrical directional lead was fabricated through micro-electromechanical system (MEMS) technology and used to investigate micturition control via a rodent model. After verifying the feasibility of the design with a simulation tool, the directional lead was fabricated in two steps: (1) patterning a gold layer on the polydimethylsiloxane substrate and insulating it with SU-8 and (2) wrapping the film electrode around a polyimide tubing to form the 3D cylinder. The fabricated lead was characterized by measuring its bending stiffness and impedance and was tested on the micturition control of stimulated rats. The rats were randomly divided into two groups: concentric lead stimulation (Con-stim) and directional lead stimulation (Dir-stim). The lead exhibited a considerably lower bending stiffness than conventional leads. The impedances of the channels on the fabricated lead were 138, 73, 46, 87, 100, and 111
$\text{k}\Omega $
at 1 kHz. During the stimulation, the intercontraction interval and voiding volume were increased in both rat groups, while the inhibition effect remained after the stimulation in the Dir-stim group. The difference in these results means that the difference of E-field distribution induced by two different leads can affect the modulating effects. MEMS technology can overcome the limitations of conventional fabrication methods and can be used in conjunction with a wrapping technique to construct the miniaturized 3D lead with a complex patterned electrode. This novel 3D lead will allow advanced brain research in small animals, ultimately expanding deep brain modulation.