3D printed microstructured ultra-sensitive pressure sensors based on microgel-reinforced double network hydrogels for biomechanical applications

• Published in: Materials horizons 2023-10, Vol.1 (1), p.4232-4242
• Main Authors: Zheng, Jingxia, Chen, Guoqi, Yang, Hailong, Zhu, Canjie, Li, Shengnan, Wang, Wenquan, Ren, Jiayuan, Cong, Yang, Xu, Xun, Wang, Xinwei, Fu, Jun
• Format: Article
• Language: English
• Subjects: 3-D printers; Biomechanics; Fracture toughness; Human motion; Hydrogels; Inks; Microgels; Moisture content; Polyelectrolytes; Pressure sensors; Sensitivity; Sensor arrays; Sensors; Sol-gel processes; Spatial distribution; Tensile strength; Three dimensional printing; Wearable technology
• ISSN: 2051-6347; 2051-6355
• DOI: 10.1039/d3mh00718a

Hydrogel-based wearable flexible pressure sensors have great promise in human health and motion monitoring. However, it remains a great challenge to significantly improve the toughness, sensitivity and stability of hydrogel sensors. Here, we demonstrate the fabrication of hierarchically structured hydrogel sensors by 3D printing microgel-reinforced double network (MRDN) hydrogels to achieve both very high sensitivity and mechanical toughness. Polyelectrolyte microgels are used as building blocks, which are interpenetrated with a second network, to construct super tough hydrogels. The obtained hydrogels show a tensile strength of 1.61 MPa, and a fracture toughness of 5.08 MJ m −3 with high water content. The MRDN hydrogel precursors exhibit reversible gel-sol transitions, and serve as ideal inks for 3D printing microstructured sensor arrays with high fidelity and precision. The microstructured hydrogel sensors show an ultra-high sensitivity of 0.925 kPa −1 , more than 50 times that of plain hydrogel sensors. The hydrogel sensors are assembled as an array onto a shoe-pad to monitor foot biomechanics during gaiting. Moreover, a sensor array with a well-arranged spatial distribution of sensor pixels with different microstructures and sensitivities is fabricated to track the trajectory of a crawling tortoise. Such hydrogel sensors have promising application in flexible wearable electronic devices. 3D printed microstructured pressure sensors based on microgel-reinforced double network hydrogels show high toughness and sensitivity, and are used to fabricate a flexible sensor array for biomechanical and motion tracking applications.