Polyelectrolyte microgels-enhanced double-crosslinking polyacrylamide hydrogel sensing with stretchable, transparent, and fast response

The development of medical sensor materials is progressing towards flexibility, wearability, and intelligence. Hydrogel, a new type of medical material, possesses excellent mechanical properties, high flexibility, and good biocompatibility. It is expected to become the foundation of a new generation of wearable devices. However, traditional hydrogels have limitations in recovery, conductivity, and stability, which restricts their practical applications as sensors. To address these limitations, this study presents a novel approach by preparing polyelectrolyte microgels (PMs) to reinforce conventional polyacrylamide (PAAm) hydrogels. The resulting double cross-linker hydrogel (DC-PMs/PAAm), containing PMs and N, N’-methylenebis (acrylamide) as cross-linkers, exhibits good transparency (90% at 550 nm) and mechanical properties (147 kPa, 880%). Notably, the DC-PMs/PAAm hydrogel demonstrates graded sensitivity factors in different strain ranges (GF at 0–150%, 150–350%, and 350–800% strain, were 2.47, 5.34, and 9.01, respectively). In addition, the hydrogel has a fast response time of 150 ms, which can detect large and subtle movements of the human body in real-time. Furthermore, DC-PMs/PAAm hydrogel maintains a stable resistance change rate during 1000 rapid cycles (100% strain) monitoring. Therefore, it is expected to be used as wearable device in the medical and health fields.