Highly Flexible, Self-Bonding, Self-Healing, and Conductive Soft Pressure Sensors Based on Dicarboxylic Cellulose Nanofiber Hydrogels

Abstract

Conductive hydrogels have gained a great deal of interest in the flexible electronics industry because of their remarkable inherent properties. However, a significant challenge remains for balancing hydrogel's conductivity, self-healing, and strength properties. Herein, double network ionic hydrogels were fabricated by concurrently introducing borax into dicarboxylic cellulose nanofiber (DCNFs) and polyacrylamide (PAM) hydrogels. The incorporation of borax provided a superabsorbent feature to the PAM/DCNF hydrogels (without borax) with the equilibrium water absorption rate increased from 552 to 1800% after 42 h. The compressive strength of the prepared hydrogel was 935 kPa compared to 132 kPa for the PAM hydrogel, with high cycling stability (stable after 1000 compression cycles with 50% strain). The hydrogel pressure sensor had a very sensitive response (gauge factor = 1.36) in the strain range from 10 to 80%, which made it possible to detect mechanical motion accurately and reliably. The developed hydrogels with high-performance, environmentally friendly properties are promising for use in future artificial skin and human−machine interface applications.

Recyclable Ionic Conductive Hydrogels Based on Autonomous Polymerization of α-Lipoic Acid for Flexible Wearable Electronic Sensors

“…The gauge factor (GF) of a strain sensor was defined as the slope of the relative change in the resistance–strain curve, which could be expressed mathematically by eq : GF = Δ R R 0 ε where Δ R is the change in resistance, R 0 is the resistance at initial strain, and ε is the applied strain.…”

Preparation and performance analysis of CNC/GO/CNTs/PVA/SA-Ca2+ conductive hydrogels

“…Among all physical interactions, hydrogen bonding is of great interest due to its prevalence in all living organisms, and it plays a crucial role in building and stabilizing the three-dimensional structure of biological macromolecules. 6 However, hydrogen bonding-based hydrogels are usually unstable to heat and solvents, and to address this challenge, 7 the introduction of certain chemical crosslinks into physical hydrogels to form stable chemical networks is an ideal strategy to improve the stability of physical hydrogels. 8 At present, cellulose nanocrystals, 9 multi-walled carbon nanotubes, 10 and graphene oxide 11 have been widely mentioned to improve the mechanical properties of hydrogels.…”