Hybrid Piezoresistive 2D MoS2/PEGDA/PANI Covalent Hydrogels for Wearable Strain Sensors

The continuous research on electronics, biocompatible materials and nanomaterials has led to the design of a new generation of wearable devices that can be employed in direct contact with the body of the user, which is attractive for real-time, non-invasive health monitoring 1 . For the satisfaction of such requirements, hydrogel-based conductive devices are often proposed as promising candidates for these applications, thanks to their softness, flexibility, and biocompatibility. Here we report the synthesis of conductive hybrid hydrogels containing two-dimensional (2D) MoS 2 . The nanoflakes are integrated in the polymeric matrix creating an anisotropic structure, which helps to generate mismatch stress for a strain sensing under a certain stimulus 2 , thus allowing the gel to give an electrical response to pressure. 2D MoS 2 nanoflakes were produced via top-down chemical exfoliation 3 and were incorporated in the hydrogel through a covalent grafting to the polymeric building blocks by exploiting the prior surface functionalization of the flakes 4 . The conductivity of the hydrogels was increased with the further incorporation of in-situ polyaniline (PANI), which is a widely used material in biomedical applications as a biocompatible conductive polymer 5 . The as-obtained hydrogels are characterized through a combination of techniques, whereas their electromechanical properties are investigated via a home-made setup to prove that compression causes an increase in current due to the piezoresistive properties introduced with the incorporation of 2D MoS 2 and PANI. 1 Xie, J. et al. J Electrochem Soc 2020 , 167 , 037541. 2 Zhang, D. et al. J Mater Chem B 2020 , 8 , 3171–3191. 3 Acerce, M. et al. Nat Nanotechnol 2015 , 10 , 313–318. 4 Knirsch, K. C. et al. ACS Nano 2015 , 9 , 6018–6030. 5 Humpolicek, P. et al. J. Synth Met 2012 , 162 , 722–727.