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) MoS2. 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 MoS2 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 MoS2 and PANI.<br/><br/>[1] Xie, J. et al. J Electrochem Soc 2020, 167, 037541.<br/>[2] Zhang, D. et al. J Mater Chem B 2020, 8, 3171–3191.<br/>[3] Acerce, M. et al. Nat Nanotechnol 2015, 10, 313–318.<br/>[4] Knirsch, K. C. et al. ACS Nano 2015, 9, 6018–6030.<br/>[5] Humpolicek, P. et al. J. Synth Met 2012, 162, 722–727.