Electrolysis-based Parylene Balloon Actuators for Movable Neural Probes

Abstract

In order to track a specific neuron and keep good sampling neural signals during chronic implantation, the neural probes are highly desired to have moving capability. This paper presents a novel electrolysis-based parylene balloon actuator fabricated with MEMS technology. The actuator is integrated with silicon probe to make it movable. A new fabrication technology has been developed to build a parylene balloon structure with silicon spring structure, electrolysis electrodes and electrolyte inside. By applying little current to electrolysis electrodes, high pressure is generated inside the parylene balloon by electrolysis. The spring structure is stretched with the parylene balloon expansion. Therefore the neural probe is moved by the actuation. The electrolysis actuator can generate large stain and pressure, requires modest electrical power and produces minimal heat. Due to the large volume expansion obtained via electrolysis, the small actuator can create a large force. The new electrolysis actuators for movable neural probes have been fabricated and validated.

Electrolysis-based parylene-balloon actuators

“…PDMS is much more permeable than parylene, so it does not significantly affect the total permeability. The electrolyte used in this case is a 0.25 M solution of MgSO 4 . The maximum displacement obtained is 11.5 μm, corresponding to a force of 28.75 mN.…”

“…Electrolysis as a method of actuation has been already demonstrated [1,2], and it has been employed in various applications, such as electrolysis pumps for microfluidics [3] and actuation of movable neural probes [4]. The main advantage of this kind of actuators is their ability to provide large force and displacement, while requiring low actuation voltage and low power.…”

MEMS electrolytic inchworms for movable neural probe applications

“…This chapter illustrates the design, fabrication, and testing of the monolithic devices. The work on these devices was started by C. Pang [26,83] and continued by the author.…”

“…The first version of the device features a single balloon actuator fabricated behind a silicon neural probe [83] (Figure 3-1). The device is based on a silicon frame with two sections: a probe section and a spring section.…”

Parylene-membrane piezoresistive pressure sensors with XeF<inf>2</inf>-etched cavity

“…These constraints arise from the application these pressure sensors are mainly designed for, i.e. integration into electrolysisbased parylene balloon actuators for movable neural probes [6]. The sensors are designed to be placed inside the electrolysis chamber, where the pressure generated by the electrolysis gas-phase products needs to be monitored.…”