Wireless Battery-Free Broad-Band Sensor for Wearable Multiple Physiological Measurement

Multiple sensing devices are needed for physiological signals with different intensities and frequencies, which may decrease the reliability of the wearable system. Here, we presented a multiband physiological signal-sensing system (MPSS) with a single strain sensor showing ultrasensitivity and wide bandwidth based on laser-induced graphene (LIG). By controlling the microstructures and thickness of the LIG/polydimethylsiloxane (PDMS) film, a maximum gauge factor of 456.51 was obtained. Also, the response frequency of the sensor ranges from 0 to 500 Hz, which covers the frequency of almost all of the physiological signals generated by the human body. A flexible wireless and battery-free circuit was fabricated based on near-field communication technology. Real-time monitoring of physiological signals with frequencies of 0.2–200 Hz, including respiration, pulse waves at the carotid artery, radial artery, and fingertip, heart sounds, and human voice, was realized by simply attaching the sensor on the skin surface at different body locations without applying any pressure. Given the ultrasensitivity and wide bandwidth of the sensor, the subtle details of the physiological signals, such as the difference between central and peripheral pulse waves and the first and second heart sounds, were clearly identified. The effects of temperature, humidity, and body movement on the MPSS performance were also examined. The integrated wearable sensor is potentially useful in smart electronics, health care, and telemedicine.