Preparation and Sensing Properties of Highly Robust Conductive Hydrogels

In recent years, conductive hydrogels have attracted significant attention in the field of flexible wearable sensors. However, traditional conductive hydrogel-based sensors suffer from insufficient mechanical properties, severely limiting their application in flexible sensors. Therefore, enhancing the mechanical properties of conductive hydrogels is essential for flexible sensing applications. Poly(vinyl alcohol) /poly(ethyleneimine) -sodium sulfate (PVA/PEI-Na₂SO₄) hydrogels were successfully prepared using the directional freezing technique and salting-out effect, showing excellent mechanical properties. During the directional freezing process, the polymer chains in the PVA/PEI hydrogels were arranged orderly along the ice crystal growth direction. This ordered structure improved the mechanical properties of the hydrogels. By immersing the hydrogel in a sodium sulfate solution, the density of the hydrogel network structure increased through the salting-out effect, further enhancing its mechanical properties and endowing the hydrogel with ionic conductivity. The results demonstrated that the PVA/PEI-Na₂SO₄ hydrogel exhibited high compressive strength (5.98 MPa) and excellent force-electrical response properties, with stable electrical signals output during 100 external load-unload cycles. The PVA/PEI-Na₂SO₄ hydrogel developed in this study has potential applications in flexible sensing and finger muscle rehabilitation.