For safety reasons, commercial neural implants use charge-balanced biphasic pulses to interact with target neurons using metal electrodes. Short biphasic pulses are used to avoid irreversible electrochemical reactions at the electrode-tissue interfaces. Biphasic pulses are effective at exciting neurons, but quite limited in inhibiting their activity. In contrast, direct current can both excite and inhibit neurons, however delivered to metal electrodes, it causes toxic electrochemical reactions. We recently introduced Safe Direct Current Stimulator (SDCS) technology, which can excite or inhibit neurons without violating the safety criteria. Instead of direct current, SDCS generates an ionic direct current (iDC) from a biphasic input signal using a network of fluidic channels and mechanical valves. A key enabler towards transforming SDCS concept from a benchtop design to an implantable neural prosthesis is the design of a miniature valve. In this work, we present poly-dimethylsiloxane (PDMS) based elastomeric valves, squeeze valve (SV) and plunger valve (PV) capable of being actuated using a shape memory alloy wire.
Keywords: PDMS; ionic direct current; microfluidic valve; neural inhibition; shape memory alloy.