pressure sensors

flexible

strain sensing

strain sensor

conductive hydrogels

gauge factor

strain sensors

self healing

soft sensors

ACS Applied Polymer Materials

Conductive hydrogels have shown great potential for fabricating flexible and wearable sensors, especially strain/pressure sensors to monitor human motion/health. In practice, the use of conductive hydrogel-based sensors is often limited because of hydrogels’ poor mechanical properties and low sensitivity. In the present article, a composite hydrogel comprising acrylamide, N-(3-aminopropyl) methyl acrylamide hydrochloride, and polydopamine-coated reduced graphene oxide is prepared. The dynamic covalent and noncovalent interactions that exist in the hydrogel matrix including C–N bonds, intra-/intermolecular hydrogen bonds and NH3+–π interaction, and π–π interactions rendered the hydrogels with superior fracture stress (496.4 ± 85.9 kPa) and ductility (1156.9 ± 110.1%). Also, prepared hydrogels have excellent cytocompatibility and show appropriate adhesion to the skin, showcasing their potential in fabricating wearable devices. On the basis of these facts, hydrogel-based strain/pressure sensors that cause a change in resistance when strain or pressure is applied are fabricated. The fabricated sensors show a high strain sensitivity in the strain range of 0–800% where, at a subtle strain (100%), the gauge factor reached 5.4. In addition, sensors are also responsive to pressure with a sensitivity of −0.74% kPa–1 in the range from 0 to 10 kPa. The fabricated strain/pressure sensors have the cyclic ability and self-healing property at room temperature. As a proof-of-concept, the sensors are shown to monitor movements of the elbow, knee, fingers, and wrists as well as sense the vocal cord vibration.

Highly Strong, Stretchable, and Conductive Reduced Graphene Oxide Composite Hydrogel-Based Sensors for Motoring Strain and Pressure