Tough, Adhesive, Self-Healable, and Transparent Ionically Conductive Zwitterionic Nanocomposite Hydrogels as Skin Strain Sensors

Abstract

It is desired to create skin strain sensors composed of multifunctional conductive hydrogels with excellent toughness and adhesion properties to sustain cyclic loadings during use and facilitate the electrical signal transmission. Herein, we prepared transparent, compliant, and adhesive zwitterionic nanocomposite hydrogels with excellent mechanical properties. The incorporated zwitterionic polymers can form interchain dipole–dipole associations to offer additional physical cross-linking of the network. The hydrogels show a high fracture elongation up to 2000%, a fracture strength up to 0.27 MPa, and a fracture toughness up to 2.45 MJ/m3. Moreover, the reversible physical interaction imparts the hydrogels with rapid self-healing ability without any stimuli. The hydrogels are adhesive to many surfaces including polyelectrolyte hydrogels, skin, glasses, silicone rubbers, and nitrile rubbers. The presence of abundant zwitterionic groups facilitates ionic conductivity in the hydrogels. The combination of these properties enables the hydrogels to act as strain sensors with high sensitivity (gauge factor = 1.8). The strategy to design the tough, adhesive, self-healable, and conductive hydrogels as skin strain sensors by the zwitterionic nanocomposite hydrogels is promising for practical applications.

Flourishing Self‐Healing Surface Materials: Recent Progresses and Challenges

“…f) Stress–strain curves of the as‐prepared and self‐healed hydrogel with different healing time. c–f) Reproduced with permission . Copyright 2019, American Chemical Society.…”

“…The zwitterionic fusion and reconstructed microgel assemblies occurring at interface facilitated the self‐healing as depicted in the Figure 9b, and its self‐healable and biocompatible hydrogel properties offer a promising platform for biomedical applications of cell scaffolds, drug release, and wound healing. Besides, Fu et al reported a different type of zwitterionic nanocomposite hydrogel with tough, adhesive, self‐healable, and transparent performances which interchange dipole–dipole associations in existing zwitterionic polymer for reversible physical cross‐linking interactions at interface, thereby developing rapid self‐healing ability as shown in Figure 9c–f. According to the mechanical fracture strength, the healing efficiency of reversible physical cross‐linked zwitterionic was up to 74%.…”

Dual-Enzyme Crosslinking and Post-polymerization for Printing of Polysaccharide-Polymer Hydrogel

“…Hydrogels with three-dimensional networks have received wide attention due to their successful applications in tissue engineering (Yue et al, 2015;Mohamad et al, 2018;Qu et al, 2018Qu et al, , 2019Edri et al, 2019;Feng et al, 2019), biocatalysis (Diaz et al, 2010), biosensor (Wang et al, 2019), cell culture (Lou et al, 2017;Luo et al, 2019), drug delivery (Gao et al, 2018;Xu et al, 2019), biomedicines (Liow et al, 2017), wound healing (Ahmed et al, 2017), and 3D printing (Censi et al, 2011;Pataky et al, 2012;Malda et al, 2013;Li et al, 2015;Loebel et al, 2017;Lin et al, 2019). In general, hydrogels formed by natural polysaccharides are suitable for 3D printing and encapsulating biomolecules.…”

Tough and recoverable triple‐network hydrogels based on multiple pairs of toughing mechanisms with excellent ionic conductivity as stable strain sensors

“…With the development of tough hydrogels, ionic conductive hydrogels with enhanced mechanical properties and other healable functions were developed by doping salt (e.g., NaCl and LiCl) in the current tough hydrogels or the salt ions also participate in physical crosslinking . Another approach is using the polyelectrolyte which contain a lot of charge groups to facilitate the ion conduction . Suo and co‐workers developed highly stretchable, tough alginate/PAM hybrid DN hydrogels with alginate network ionically crosslinked by various multivalent cations (e.g., Ca 2+ , Fe 3+ , and Al 3+ ) .…”