An Ultra-Stretchable and Highly Sensitive Photoelectric Effect-Based Strain Sensor: Implementation and Applications

High performance strain sensors have recently attracted considerable attention because of their applications in human motion detection, soft robotics, and human-machine interface. However, it remains some challenges in achieving satisfactory features (e.g., high sensitivity, high stretchable, linearity, and easy fabrication) for soft strain sensors. Inspired by the working principle of the eye's adaptation to different light luminance, this paper presents an ultra-stretchable, highly sensitive and high linear strain sensor based on the photoelectric effect. The sensor has a simple structure which is made of light-emitting diode (LED), photosensitive element, silicone rod, and sensor shell. When the silicone rod is stretched, the light's shielding area becomes larger, causing the increase of light luminous received by the photosensitive element. Hence, the sensitivity of the sensor can be tuned by changing luminance of LED and the amplification factor. Experiments demonstrate that the sensor has a high sensitivity (the maximum gauge factor was 1050), wide strain-sensing range (the max sensing range was up to 800%), high linearity range (from 100% to 300%), good repeatability (decreased by 5.48% over 5000 cycles at the wide tensile strain of 0 - 300%), low drift, and high signal-to-noise ratio (over 60dB). The proposed strain sensor has been applied in the bending detection of the wrist and finger, the recording of the human moving patterns, and the human's pulse counting. The sensor can be further fabricated into a data glove for detecting the human hand movement.