Ultra-stretchable and conductive polyacrylamide/carboxymethyl chitosan composite hydrogels with low modulus and fast self-recoverability as flexible strain sensors

• Published in: International journal of biological macromolecules 2023-12, Vol.253, p.127146-127146, Article 127146
• Main Authors: Ding, Hongyao, Liu, Jie, Huo, Peixian, Ding, Rongjian, Shen, Xiaodong, Mao, Hongli, Wen, Yuefang, Li, Hui, Wu, Zi Liang
• Format: Article
• Language: English
• Subjects: Carboxymethyl chitosan; Flexible sensors; Stretchable hydrogel
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2023.127146

There is a great demand for the fabrication of soft electronics using hydrogels due to their biomimetic structures and good flexibility. However, conventional hydrogels have poor mechanical properties, which restricts their applications as stretchable sensors. Herein, a facile one-step strategy is proposed to fabricate tough and conductive hydrogels by making use of the graftability of carboxymethyl chitosan without extra conductive matter and crosslinking agent. The obtained polyacrylamide/carboxymethyl chitosan composite hydrogels possess outstanding transmittance and excellent mechanical performances, with tensile breaking stress of 630 kPa, breaking strain of 4560 %, toughness of 8490 kJ/m3. These hydrogels have low modulus of 5–20 kPa, fast recoverability after unloading, high conductivity of ~0.85 S/m without the addition of other conductive substances and good biocompatibility. The ionic conductivity of the gels originates from the counterions of carboxymethyl chitosan, affording the hydrogels as resistive-type sensors. The resultant hydrogel sensors demonstrate a broad strain window (0.12–1500 %), excellent linear response, high sensitivity with the gauge factor reaching 11.72, and great durability, capable of monitoring diverse human motions. This work provides a new strategy to develop stretchable conductive hydrogels with promising applications in the fields of artificial intelligence and flexible electronics. •A novel hydrogel is developed based on the idea of semi-interpenetrating network.•The hydrogels exhibit high tensile stress and toughness.•The hydrogels display low modulus, fast self-recoverability and high conductivity.•The hydrogel has a high sensitive in monitoring human motions.