Wireless Human Motion Detection with a Highly Sensitive Wearable Pressure Sensing Technology

Wireless flexible sensing devices using inductive-capacitive (LC) resonator-enabled transmission technologies are attractive in the areas of human motion detection, health inspection, and implantable medical devices. However, challenges remain in LC-based wireless sensing devices, including low device sensitivity/resolution and slow signal readout speed based on sweeping excitation frequencies. Herein, an LC resonator-based wireless pressure sensing technology (LC-WPS) is proposed for flexible contact pressure measurements in a real-time manner. It includes a fully flexible passive LC pressure sensor and a signal-reading circuit for wireless communication with the sensor and real-time data processing. The passive sensor detects external pressure by the changes in resonant frequency. Importantly, by optimizing the design of the LC resonator in the sensor, the LC-WPS converts the pressure-dependent resonant frequency into circuit output voltage to a great extent, achieving a high sensitivity (1.23 x 10(-2) kPa(-1)) and resolution (54 Pa) within a pressure range of 0-15 kPa. In addition, the LC-WPS utilizes a single operating frequency (i.e., 13.56 MHz) instead of sweeping the operating frequencies to identify the sensor resonant frequency, featuring fast and real-time data analysis and processing. Real-time monitoring of human motions, such as laryngeal movement, neck bending and wrist rotation, is demonstrated, verifying the applicability of the LC-WPS in the fields of wearable medical care and sports biomechanics.