Flexible microscale tactile display with liquid-to-gas phase-change actuator array

Flexible tactile displays have gained significant attention for their ability to deliver tactile feedback to users, complementing widely used visual displays and auditory output devices. However, previously reported tactile displays have limited spatial resolutions because they are mostly confined to centimeter-scale sizes, restricting the provision of sophisticated tactile feedback. We developed a microscale flexible actuator using water as a liquid phase-change material (PCM), which exhibits a large volumetric expansion upon phase transition from liquid to vapor. The actuator consisted of a flexible microheater, PCM, and stretchable elastomer membrane. A scalable batch fabrication process was used to form PCM chambers localized within the heater regions. Microscale PCM actuators have a thickness of less than 200 μm, making them easy to attach to curved surfaces. The device achieves a response time of 600 ms and a displacement of 580 μm and operates at a low power consumption of 300 mW. Integrating this tactile display with a commercial virtual-reality headset for visual feedback enables immersive multisensory information delivery to users.