ABSTRACT
The trade-off between high sensitivity and wide detection range remains a challenge for flexible capacitive pressure sensors. Gradient structure can provide continuous deformation and lead to a wide sensing range. However, it simultaneously augments the distance between two electrodes, which diminishes the variation in the relative distance and results in a decreased sensitivity. Herein, a conformal design is introduced into the gradient structure to construct a flexible capacitive pressure sensor. The gradient conformal dome structure is fabricated by a simple reverse dome adsorption process. Taking advantage of the progressive deformation behavior of the gradient dielectric, and the significant improvement of relative distance variation between two electrodes from the conformal design, the sensor achieves a sensitivity of 0.214 kPa-1 in an ultrabroad linear range up to 200 kPa. It maintains high-pressure resolution under the preload of 10 and 100 kPa. Benefiting from the rapid response and excellent repeatability, the sensor can be used for physiological monitor and human motion detection, including arterial pulse, joint bending, and motion state. The gradient conformal design strategy may pave a promising avenue to develop pressure sensors with high sensitivity and wide linear range.
ABSTRACT
A microstructured surface has been applied in self-powered triboelectric pressure sensors to increase the charge-carrying sites and enhance the output performance. However, the microstructure increases the distance between the electrode and the triboelectric layer, and its influence on the output performance is unknown. Herein, we proposed a dome-conformal electrode strategy for a self-powered triboelectric nanogenerator (TENG) pressure sensor. With a simple reverse-dome adsorption process, an ultrathin triboelectric layer and Ag electrode can be made conformal to the dome PDMS structure. The TENG sensor is constructed with paper as a positive triboelectric layer. Compared with the device based on nonconformal structure, the conformal design strategy endows the device with a faster charge transfer and enhanced output voltage. By doping with BaTiO3, the outermost triboelectric layer can be easily modified to improve its ability of sustaining charge, and an ultrathin PDMS layer is coated on the triboelectric layer to expand the triboelectric polarity difference between two triboelectric layers so as to enhance the output voltage. The synergistic effects enable the optimized TENG sensor with a sensitivity of 0.75 V/kPa in the low-pressure region (0-26 kPa) and 0.19 V/kPa in the high-pressure range (26-120 kPa). Its application in human motion detection, grabbing water beakers, and noncontact distance testing has been demonstrated. This work provides a route such as a conformal structure design strategy to enhance the output performance of a microstructure-based TENG sensor.