Abstract
It is still a challenge to fabricate flexible pressure sensors that possess high sensitivity, ultralow detection limit, wide sensing range, and fast response for intelligent electronic devices. We here demonstrate superelastic and highly pressure-sensitive polyimide (PI)/reduced graphene oxide (rGO) aerogel sensors with unique honeycomb structure, which were designed and fabricated using a bidirectional freezing technique. This unique honeycomb structure with large aspect ratio is composed of aligned thin lamellar layers and interconnected bridges. The combination of the aligned lamellar layers and the bridges endows the aerogel sensors with high pressure sensitivity (1.33 kPa(-1)), ultralow detection limit (3 Pa), broad detection range (80% strain, 59 kPa), fast response time (60 ms), and excellent stability during cycling (over 1000 cycles). Remarkably, the aerogel sensors maintain stable piezoresistive performance at -50 °C, 100 °C, and 200 °C in air, indicating promising potential applications in harsh environments. Owing to the high sensitivity and wide sensing range, the aerogel sensors have been used to detect a full-range of human motion including small-scale motion monitoring (wrist pulse, blowing, puffing) and large-scale movement monitoring (finger bending, elbow bending, walking, running). These advantages make the composite aerogels attractive for high-performance flexible pressure sensors and wearable electronic devices.