Carrageenan‐Based Ionically Conductive Hydrogel With High Stretchability, Adhesion, and Self‐Healing Properties, and Piezoionicity for Flexible Sensor Application

ABSTRACT Hydrogels are promising polymeric materials for development of flexibly wearable sensors. This study constructed a κ‐carrageenan (κ‐CG) based hydrogel with dual network of manganese ions crosslinking with κ‐CG, and interacted with polyacrylamide and lithium bis((trifluoromethyl)sulfonyl)azanide. The hydrogel displayed not only high stretchability and fatigue resistance but also excellent adhesive and self‐healing properties due to the formation of multiple dynamic bonds. The hydrogel exhibited piezoionicity because of the differences in migration rates of chloride ions (Cl ⁻ ) and lithium ions (Li ⁺ ) (Cl ⁻ < Li ⁺ ) under mechanical pressure, which was applied as piezoresistive sensor for monitoring human motions (e.g., knee and wrist movement) with rapid response and stability. Moreover, the hydrogel exhibited good conductivity owing to the migrations of anions and cations, which was applied as piezoresistive sensor for monitoring human motions with high sensitivity and stability, as well as emergency communication and covert information transmission via Morse code. An intelligent hand‐gesture recognition by integrating the piezoresistive sensing with a deep‐learning algorithm could recognize the finger‐bending signals with accuracy more than 93%. This stretchable, adhesive, and self‐healing hydrogel with good conductivity and piezoionicity has great potential for development of flexible sensors for human motion monitoring and human‐machine interaction.