ESE Ph.D. Thesis Defense: “Microscopic Surface Electrochemical Actuators for Voltage-Tunable Optical Elements”

Surface electrochemical actuators (SEAs) harness ion-induced surface stress changes to produce large bending deformations at the microscale. They have previously been applied in microrobot locomotion and microbattery validation, demonstrating their versatility as low-voltage microscopic actuators. Here, we extend their functionality by showing that ultra-thin platinum membranes (10 nm thick, 10–100 µm wide), fabricated via low-temperature lithographically patterned atomic layer deposition, can undergo voltage-driven buckling displacements of several hundred nanometers in aqueous electrolyte. These out-of-plane motions, controlled within ±150 mV of applied bias, span the full visible wavelength range when integrated as the movable membrane of an optical resonator. The buckling mechanics are characterized using atomic force microscopy and finite element analysis, while we also develop a hyperspectral imaging method to optically reconstruct the device topology. The actuators operate with response times on the order of tens of milliseconds and exhibit static power consumptions below a nanowatt, while remaining directly compatible with CMOS circuitry. By coupling surface-stress–driven mechanics with electronic control, these buckling-enabled actuators (BEAs) provide a pathway toward compact, low-power, voltage-tunable optical elements for applications in reflective displays and holography.