Catechol/Pyrogallol-Modified Chitosan Composite Conductive Hydrogel as Strain Sensor for Human Movement Monitoring

Conductive hydrogels have great application and development value in the field of functional materials including flexible wearable devices, electronic skin and health detectors. Herein, chitosan (CS) was firstly modified with 3,4-dihydroxybenzaldehyde and 2,3,4-trihydroxybenzaldehyde, respectively, through the Schiff base reaction and NaBH3CN reduction, and the resulting products (CCS and PCS) with improved water solubility were then used as the cross-linking agents for polyvinyl alcohol (PVA) to fabricate the corresponding CCS/PVA and PCS/PVA composite hydrogels through the freezing-thawing method. AlCl3 was further introduced into the two composite systems to give the hydrogels good conductivity. As flexible strain sensors, both CCS/PVA/AlCl3 and PCS/PVA/AlCl3 hydrogels could monitor human movements such as finger bending, wrist rotation, elbow bending, foot rotation and nodding. In addition, the conductive hydrogels can also respond regularly to small facial movements such as mouth opening-closing cycle and frowning. In general, the present CCS/PVA/AlCl3 and PCS/PVA/AlCl3 conductive hydrogels are expected to have good application prospect in smart wearable devices and other functional fields.