Electrochemical actuator with a short response time: A new actuation regime

• A new regime of alternating polarity electrochemical actuator is described.
• Gas termination happens just in 10 μs due to combustion of gases.
• Minimal degradation of electrodes is observed.

The lack of fast and strong microactuators is a well-recognized problem in the MEMS community. Electrochemical actuators can develop high pressure but they are notoriously slow. Water electrolysis produced by short voltage pulses of alternating polarity can overcome the problem of slow gas termination due to spontaneous ignition of the reaction between hydrogen and oxygen in nanobubbles. An actuation regime with the termination time as short as 100 μs was demonstrated previously. Here we describe a new actuation regime, for which the gas pressure is relaxed just in 10 μs and a minimal degradation of the electrodes is observed. The actuator consists of a microchamber filled with an electrolyte and covered with a flexible silicon nitride membrane. The membrane bends outward when the pressure in the chamber increases. The new regime is characterized by the appearance of short-lived microbubbles in between the electrodes. Fast termination of gas and high pressure developed in the chamber are related to a high density of nanobubbles in the chamber. The physical processes happening in the chamber are discussed as well as problems that have to be resolved for practical applications of this actuation regime. The actuator can be used as a driving engine for microfluidics.