Flexible pressure sensors emerge for important applications in wearable electronics, with increasing requirements for high sensitivity, fast response, and low detection limit. However, there is still a challenge in this field, that is, how to maximize both the electrical performance and mechanical stretchability simultaneously. Here, we report a straightforward and cost-effective method to fabricate highly stretchable and sensitive capacitive pressure sensor arrays. It features a unique design of integrating the icicle-shaped liquid metal film electrode and reliable processing of the liquid metal and elastomer. Under an external load, the deformation of the elastic bump structure dramatically results in an increase in the overlapping area of the electrodes and a decrease in the separation distance, offering a new capacitive sensing scheme with an enhanced sensitivity. Our sensor has been demonstrated with a high sensitivity of 39% kPa-1 in the range of 0-1 kPa, limit of detection as low as 12 Pa, hysteresis error of 8.46% at a maximum pressure of 25 kPa, and stretchability up to 94% strain without any failure. The arrayed sensor has been successfully applied to force measurements on a curved surface, contour mapping of external loads, and monitoring of contact pressures under various cervical postures.
Keywords: biomedical applications; capacitance; liquid metal; pressure sensors; wearable electronics.