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Roda Nur1 Naoji Matsuhisa1 Zhi Jiang1 Md Osman Goni Nayeem1 Tomoyuki Yokota1 Takao Someya1

1, The University of Tokyo, Tokyo, , Japan

Wearable sensors are a vital component in wearable electronics, since they are responsible for transducing external stimuli into electronic signals. In particular, strain sensors are needed for applications involving motion detection and the monitoring of vital bio-signals. Capacitive-type strain sensors are excellent candidates for practical applications due to their excellent linearity, high stretchability, and low hysteresis. However, a huge limitation of this sensor is its low sensitivity due to the constraints of the parallel-plate capacitor structure under applied strain operations. At best due to theoretical limitations, this structure can achieve a gauge factor (sensitivity) of 1. Here, we present a design technique to enhance the sensitivity in capacitive-type strain sensors through using thin Au film electrodes. We achieved a best gauge factor (GF) slightly above 3 over a high stretchability of 140% strain with great linearity and negligible hysteresis. We further found that the gauge factor of this strain sensor is tunable through varying the film thickness of the electrode. The enhanced sensitivity in capacitive-type strain sensors allows for the opportunity to distinguish subtle motions more sensitively for reliable and practical wearable applications.

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