Low-Cost Flexible Piezoelectric Sensors for Real-Time Tactile Monitoring and Energy Harvesting

This work presents comprehensive investigation and demonstration of flexible piezoelectric tactile sensors for IoT-enabled electronic skin (E-skin) applications. These sensors were fabricated using a solution-processed thin film of poly (vinylidene fluoride-trifluoro ethylene), i.e. P(VDF-TrFE) sandwiched between low cost copper (Cu)-cladded polyamide (PI) sheets, and exhibited extremely low response time < 20 ms for ultra-soft finger touch. Excellent sensitivity of ~1.34 V/N was extracted by measuring the finger tapping force, with high peak-to-peak output voltage (V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P-P</sub>) response of ~6.2 V for a touch with force of ~4.5 N. E-skin functionality was investigated by attaching these sensors to various parts of body such as fingers, knee, hand, wrist, and neck. Maximum response for neck movement with VP-P value of 5.12 V was achieved. Real-time sensing of tactile activities was demonstrated through array of sensors integrated with IoT cloud. Moreover, excellent energy harvesting capabilities of these devices were verified by charging a 22 μF capacitor through a bridge rectifier circuit upon repeated finger tapping for 20 s to 1.2 V. Our investigations indicate that these solution-processed flexible tactile sensors can be useful for demonstration of IoT enabled self-powered flexible E-skin for robotics applications.