Poly(acrylic acid)/Dipeptide Double-Network Hydrogel to Achieve a Highly Stretchable Strain Sensor

Flexible and stretchable strain sensors can be applied for human health monitoring and disease diagnoses via the output of multiple biophysical signals. However, it is still a challenge to fabricate short-peptide-based strain sensors. Here, we prepared a novel polymer-dipeptide double-network hydrogel with excellent stretchability, responsiveness, and stability. The poly(acrylic acid) (PAA) gel, by cross-linking, maintains mechanical and flexible properties, and the fluorenyl methoxycarbonyl-diphenylalanine (Fmoc-FF) network, by non-covalent interactions, is helpful for energy dissipation. With increasing tensile or compression strains, the PAA/Fmoc-FF hydrogel exhibited a high mechanical strength and fast recovery. Moreover, as the presence of KCl improves the electronic conductivity, the hybrid gel exhibited a cyclic strain-stress performance, which is the foundation of a strain sensor. Based on that, its application as a motion sensor was demonstrated by monitoring the movements of human joints, such as the forefinger, wrist, elbow, and knee. Consequently, the hybrid polymer-peptide gel could be an ideal candidate for wearable sensors in the future.Keywords:strain sensor;double-network hydrogel;dipeptide;poly(acrylic acid)