A Flexible Pressure Sensor With Parallel Fiber Structure for Wireless Capsule Detection

With the rapid development of science and technology, flexible pressure sensors with high sensitivity and excellent stability have generated considerable attention due to their potential applications. However, the challenge of achieving high sensitivity persists in the development of pressure sensors. Polyaniline (PANI) has been widely used in various fields as a sensing material owing to its simple preparation and good electrical conductivity. In this study, a pressure sensor with a sandwich structure was developed to sensitively monitor body signals. The micro-nano fiber mats were prepared by electrospinning of thermoplastic polyurethane (TPU). The constructed parallel TPU mats (P-TPU) and staggered TPU mats (S-TPU) possess a nonwoven structure with a fiber diameter of ( $0.68~\pm ~0.14$ ) $\mu $ m and ( $1.02~\pm ~0.24$ ) $\mu $ m, respectively. PANI was grown in situ on the mat to form a conductive layer. After stacking S-TPU fiber mats bonded with commercial medical polyurethane (PU) films and orderly conductive mats to form a PANI-coated mat/S-TPU mat structure, another layer of the S-TPU mats was also packed for the construction of a sandwich-structured piezoresistive sensor. The device could tolerate more than 10 000 pressing cycles without affecting its sensing capability. The human body-attached experiments further demonstrated that the sensor could real-time monitor actions of finger/arm bending and cheek swelling and holding their breath, speaking-caused throat vibration, and moving of the gastrointestinal tract. The electrospinning method could be used as a cost-effective strategy with a simple preparation process to obtain flexible piezoresistive sensors with good skin compatibility and powerful pressure-sensing capabilities.