Mechanical strong stretchable conductive multi-stimuli-responsive nanocomposite double network hydrogel as biosensor and actuator.

Multi-stimuli- responsive mechanical strong stretchable hydrogel has grabbed extensive attention in recent years. Here, a novel stretchable conductive biocompatible near-infrared light(NIR)-/thermal-/pH-/ionic concentration- responsive carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/poly(N-isopropylacrylamide)(PNIPAm) nanocomposite double network hydrogel was fabricated through a simple one-pot in situ free radical polymerization, which is initiated by ultraviolet (UV) light and using N-(3-dimethylaminopropyl)-N-ethylcarbodiimidehydrochloride (EDC) and N,N'-bis(acryloyl)cystamine (BAC) as cross-linkers respectively, instead of toxic organic molecules. When the concentration of CMCTs, GO, EDC and BAC is 22.50, 0.103, 7.50 and 0.467 mg/mL respectively, the obtained hydrogel sample owns the highest tensile strength of 1046 kPa at failure strain of 1286% and a corresponding compressive stress of 2.37 MPa at deformation of 90%. Besides, these hydrogels have an obvious pH-/thermal-/ionic concentration-responsive properties depending on the concentration of the above mentioned factors, and their good conductive property makes them as candidate material for healthcare biosensors. Finally, we attempt to design a novel thermal-/NIR-responsive double network structure bilayer hydrogel, which has the potential use as remote actuator in dangerous places in the future.