As the key of flexible electronic devices, flexible sensing devices can transducer physical or environmental stimuli into detectable electrical signals, which have attracted increasing attention due to their great potential applications in displays, robotics, advanced therapies, and energy harvesting devices [1-5]
. In particular, flexible sensing devices can be wearable on human body or clothing to continuously monitor body signals, such as temperature, pulse, heart rate, motions, and respiration [6-8]
. To obtain various functions, wearable flexible sensors should have some special characteristics, for example, good flexibility, desirable stretch ability, biocompatibility, good stability, and high sensitivity [9-11]
Pressure is ubiquitous in the nature and human body, so flexible pressure sensors can be used to detect low and medium pressure (1-100 kPa) to track human activity and monitor personal health [12-14]
. Typically, flexible pressure sensors consist of active pressure or strain sensing components, flexible substrates, and conductive electrodes. Generally, elastic polymers, such as poly(dimethlsiloxane) (PDMS), polyethylene terephthalate (PET), polyimide (PI), and rubber, are commonly used as the flexible substrates. Due to the good flexibility, strechability, stability, and biocompatibility, PDMS is the best choice. The suitable active sensing components materials play an important role in fabricating sensors with good performance, which include carbon nanotubes (CNTs), graphene, carbon black, conductive polymers, and nanostructures (nanoparticles, nanowires, nanograting). In some conditions, the flexible substrates and active components will be integrated into one layer [15-18]
Based on wording mechanism, the flexible pressure sensors can be classified into capacitive-type [19,20]
, piezoelectricity-type [21,22]
, and piezoresistive-type sensors [23,24]
, which can convert pressure signals into resistance, voltage, or current changes with advantages of simple sensing process, easy read-out system, and large detection range. However, the sensitivity, limit of detection, detection range, response time, stability, reliability, and complicated and high cost fabrication process are still a challenge for flexible wearable sensing systems.
In 2006, Z. L. Wang et al. proposed triboelectric nanogenerator (TENG) based on couple effects of electrification and electrostatic induction, which can achieve remarkable electric output under the external mechanical pressure at low cost and relatively simple structure [25-28]
. The related researches about TENG with good performance of energy harvesting, electrical properties, high power density, and rapid response are conducted, which has potential applications in high sensitivity and self-powered sensing systems.
Here, we have constructed a flexible PDMS pressure sensor based on TENG, in which the PDMS nanostructures thin film serve as the triboelectric layer to fabricate high sensitivity and self-powered wearable sensors. A simple and low-cost fabrication method for PDMS nanostructures film based on soft nanoimprint lithography is developed. When the pressure in applied on the nanostructures layer, triboelectrostatic charges are induced. The experimental measurement of the electrical performance of TENG sensors is up to sensitivity of 0.8 V/kPa at frequency of 5 Hz. This study results provide an approach for self-powered sensing, with potential applications in military surveillance, artificial intelligence, health care.