3D Printing of Highly Robust and Bioadhesive Strain Sensors for Human Motion Monitoring

Strain sensors based on Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hydrogels have attracted extensive attention in various fields such as wearable devices and epidermal electronics. However, developing high-performance strain sensors with excellent mechanical properties, strong adhesion, and advanced processing compatibility remains a significant challenge. In this study, a high-performance strain sensor is fabricated by 3D printing a novel Polyvinyl alcohol (PVA)-PEDOT:PSS-Hydroxypropyl methylcellulose (HPMC)-dopamine hydrochloride (DA-HCl) (PPHD) composite ink. The PPHD ink exhibits favorable rheological properties, making it suitable for direct ink writing (DIW) 3D printing, thereby enabling pattern customization and personalized fabrication. The hydrogel printed from this ink exhibits high toughness (>2 MJ·m⁻ 3 ) and strong adhesion (38 kPa). When further assembled into a strain sensor, the device demonstrates a fast response time of 200 ms, high linearity (R 2 = 0.99), and stable performance under 1000 cyclic loading and various frequency conditions, allowing for real-time monitoring of diverse human motions. This work establishes a conductive hydrogel strain sensing platform that integrates printability, strong adhesion, and excellent mechanical performance, and it is successfully applied in gesture recognition using a three-channel system. The outstanding performance of the PPHD hydrogel-based strain sensor holds great promise for a wide range of bioelectronic applications, such as wearable electronics and electronic skin.