Flexible and wearable devices with the capabilities of both detecting and generating mechanical stimulations are critical for applications in human-machine interfaces, such as augmented reality (AR) and virtual reality (VR). Herein, a flexible patch based on a sandwiched piezoelectret structure is demonstrated to have a high equivalent piezoelectric coefficient of d33 at 4050 pC/N to selectively perform either the actuating or sensing function. As an actuator, mechanical vibrations with a peak output force of more than 20 mN have been produced, similar to those from the vibration mode of a modern cell phone, and can be easily sensed by human skin. As a sensor, both the pressure detection limit of 1.84 Pa for sensing resolution and excellent stability of less than 1% variations in 6000 cycles have been achieved. The design principle together with the sensing and driving characteristics can be further developed and extended to other soft matters and flexible devices.

Dr. Junwen Zhong is a postdoctoral researcher in University of California, Berkeley, and is working with Prof. Liwei Lin at Berkeley Sensor & Actuator Center (BSAC). He received his B.S. degree (2011) and PhD degree (2016) from Huazhong University of Science and Technology, China. He majors in flexible generators, self-powered systems, active sensors, and mechanical actuators. He has published 7 patents, 1 book chapter and over 22 papers, among which 10 papers were published as the first author. Some of his papers were published in Energy & Environmental Science, Advanced Materials, ACS Nano, and Nano Energy, with over 1270 citations. Some of his researching works have been reported by Nature Nanotechnology, Scientific American, Chemical & Engineering, News, Nano Werk as highlights.

Smart phones, cars, and wearable activity trackers are just a few examples of products with sensors based on technologies pioneered at the Berkeley Sensor & Actuator Center, a Graduated NSF Industry/University Cooperative Research Center for Micro/Nanoelectromechanical Sensors & Systems (MEMS/NEMS). New research at BSAC will have even greater impacts on consumer, industrial, and medical products.