Wearable and Ultrasensitive Strain Sensor Based on High-Quality GaN pn Junction Microwire Arrays.

With the rapid growth in wearable electronics sensing devices, flexible sensing devices that monitor the human body have shown great promise in personalized healthcare. In the study, high-quality GaN pn junction microwire arrays with different aspect ratios and large-area uniformity are fabricated through an easy, repeatable fabrication process. The piezoelectric coefficient (d33 ) of GaN pn junction microwire arrays increases from 7.23 to 14.46 pm V-1 with the increasing of the aspect ratio, which is several times higher than that of GaN bulk material. Furthermore, flexible ultrasensitive strain sensor based on GaN microwires with the highest d33 is demonstrated to achieve the maximum open circuit voltage of 10.4 V, and presents excellent durability with stable output signals over 10 000 cycles with a response time of 50 ms. As a flexible and wearable sensor attached to the human skin, the GaN microwire pn junction arrays with such a high degree of uniformity can precisely monitor subtle human pulse and motions, which show great promise in future personalized healthcare.