Low-cost ultra-stretchable strain sensors for monitoring human motion and bio-signals

Abstract

The emerging need for interactive wearable devices has been a driving force for the development of flexible electronics. Due to their ability to conform to the complex nature of the human physique, stretchable strain sensors have been extensively used to measure bio-signals and monitor human motion. Here, a new fabrication method of a piezo-resistive strain sensor is introduced, and the ability of the sensor to measure the human heartbeat and track a wide range of human motion is demonstrated. The sensor is fabricated by infusing graphene nano-flakes into a rubber-like adhesive pad. The fabricated sensor is highly stretchable and can withstand strain up to 350%. Even after 10,000 cycles of stretching and relaxing a robust and stable electrical response is maintained. Furthermore, the gauge factor of the sensor ranges from 2 to upto 160; which in turn allows the sensor to monitor a great variety of human motions. Hence, three wearable devices are developed using the fabricated graphene-based strain sensor to measure human knee movement, finger movement and heartbeat through the radial artery. The sensor is also used in a robotic haptic application to control a robotic finger. These experiments demonstrate the applicability of the sensor for real-time monitoring, specifically in wearable human interactive devices.