Oligosaccharide toughened polyacrylamide hydrogel for high sensitivity strain sensor

Abstract

Conductive hydrogels are promising for wearable electronics and human-machine interfaces due to their stretchability, conductivity, and stimulus responsiveness. However, their utility is often limited by the brittleness of their cross-linked networks. To address this, hydroxyl-rich oligosaccharides are incorporated into the polyacrylamide network in this work. The oligosaccharides form extensive hydrogen bonds with the polymer matrix, which enhances interchain interactions and facilitates efficient energy dissipation. This produces a hydrogel exhibiting an elongation of 1200%, a fracture stress of 1000 kPa, and a toughness of 600 kJ·m-2, representing a 3.75-fold improvement. Based on this tough hydrogel matrix, a high-sensitivity strain sensor is constructed using an ionic/electronic dual-conduction strategy. The addition of KCl creates stable ion-conducting channels, whereas the incorporation of multi-walled CNTs forms a percolating electron-conducting network. The synergistic effect elevates the gauge factor from 1.55 to 6.25, i.e. a 3.03 fold improvement-and achieves a rapid response time of 0.265-0.306 s. The present work thus offers a viable approach to flexible strain sensors with high sensitivity and a broad sensing range.