Smart Shoe Based on Battery-Free Bluetooth Low Energy Sensor

In this work, we propose a smart shoe integrated with a very-low power wireless sensor node operating in Bluetooth Low Energy (BLE) 5.0 standard. The sensor node consists of a miniaturized printed inverted-F antenna, an accelerometer and a gyroscope being placed at the bottom of the shoe to measure footstep-length, running speed and foot landing angle. The maximum power consumption of the sensor is 11 mW and it is sustained by a triboeletric nanogenerator (TENG) which generates power from the friction causing by user's motion itself and an energy storage circuit. The triboelectric energy harvester, having the size of 6 cm × 6 cm, is made of multiple pairs of triboelectric materials can harvest up to 32 mW/m2, enough to supply the sensor node.