Ultra-Fast Micro-Actuation using Thermal Bubble-Driven Micro-Pumps

Taking inspiration from the Mantis shrimp, we seek to develop a new class of micro-actuators for micro-robots that are both (a) ultra-fast and (b) high force. To date, these two criteria are difficult to achieve in micro-robotic actuators but have applications in both legged and winged micro-robots. In this work, we explore the use of a new class of micro-actuation technology, thermal bubble-driven micro-pumps, as an ultra-fast and high force micro-actuator. Thermal bubble-driven micro-pumps are essentially high-power thermal inkjet resistors. A current pulse heats the surface of the resistor to 300 °C in microseconds causing explosive boiling of an interfacial fluid layer which forms a high pressure (10’s atm) vapor bubble. This vapor bubble is then harnessed to perform mechanical work. When the high-power resistor is actuated, the high-pressure vapor bubble causes the thin membrane to deflect. To investigate experimentally, a stroboscopic imaging system was developed to perform high-speed imaging (2 Mfps); additionally, a Polytec laser vibrometer was used to probe the transient membrane deflection during actuation. We found that the maximum membrane deflection was 57 um and reached a maximum velocity of 15.2 m/s with a maximum acceleration of 2 x 10⁷ m/s². For comparison, a Mantis shrimp strike has a maximum velocity of 22.35 m/s and a maximum acceleration of 1.5 x 10⁵ m/s². In general, we envision thermal bubble-driven micro-pumps as a viable means to enable ultra-fast micro-actuation for micro-robotics.