Redox‐Active Iron‐Citrate Complex Regulated Robust Coating‐Free Hydrogel Microfiber Net with High Environmental Tolerance and Sensitivity

TLDR

Stretchable hydrogel microfibers are promising ionic conductors for skin‑like sensing, yet fabricating coating‑free, water‑retaining conductive microfibers with balanced spinnability and strength remains challenging. The authors aim to use the redox chemistry of Fe‑citrate to overcome this fabrication challenge in continuous draw‑spinning of poly(acrylamide‑co‑sodium acrylate) hydrogel microfibers and nets. They implement continuous draw‑spinning from a water/glycerol solution, incorporating Fe‑citrate to produce coating‑free, water‑retaining conductive microfibers. The resulting microfibers are ionically conductive, highly stretchable, uniform with tunable diameters, and exhibit anti‑freezing, water‑retaining, and environmentally intelligent properties, with stiffness and ionic conductance responsive to humidity, UV light, and strain, enabling highly sensitive environmental perception.

Abstract

Abstract Stretchable hydrogel microfibers as a novel type of ionic conductors are promising in gaining skin‐like sensing applications in more diverse scenarios. However, it remains a great challenge to fabricate coating‐free but water‐retaining conductive hydrogel microfibers with a good balance of spinnability and mechanical strength. Here the old yet significant redox chemistry of Fe‐citrate complex is employed to solve this issue in the continuous draw‐spinning process of poly(acrylamide‐ co ‐sodium acrylate) hydrogel microfibers and microfiber nets from a water/glycerol solution. The resultant microfibers are ionically conductive, highly stretchable, and uniform with tunable diameters. Furthermore, the presence of redox‐reversible Fe‐citrate complex and glycerol endows the fibers with good anti‐freezing, water‐retaining, and environmentally intelligent properties. Humidity and UV light can finely mediate the stiffness of hydrogel microfibers; conversely, the ionic conductance of microfibers is also responsive to light, humidity, and strain, which enables the highly sensitive perception of environmental changes. The present draw‐spinning strategy provides more possibilities for coating‐free conductive hydrogel microfibers with a variety of responsive and sensing applications.