Multi‐Network Poly(β‐cyclodextrin)/PVA/Gelatin/Carbon Nanotubes Composite Hydrogels Constructed by Multiple Dynamic Crosslinking as Flexible Electronic Devices

Abstract

Multifunctional hydrogels with good stretchability and self-healing properties have attracted considerable attention in the field of flexible electronic devices. However, hydrogels constructed by traditional chemical crosslinking usually have poor mechanical properties and lack self-healing, adhesion, and biocompatibility, which cannot meet the requirements of flexible wearable devices. This work introduced multiple dynamic crosslinking, including borate ester bond, Schiff-base, and host-guest interaction, into polymer networks to fabricate triple-network gelatin/polyvinyl alcohol/carbon nanotube composite hydrogels with good self-healing ability (healing efficiency of 95.0%), mechanical strength (54.6 kPa), stretchability (778%), biocompatibility, conductivity, adhesion, and remodeling properties. Carbon nanotubes can serve as the filler to improve the electrical conductivity of the triple-network hydrogels. The resulting hydrogel can be made into a strain sensor with high strain sensitivity (gauge factor up to 16.0). More importantly, the strain sensor can be used to monitor various human and organ movements. Owing to its good self-healing ability, the self-healed hydrogel sensor also can detect human movements with almost the same electrical signal strength as the original one. This study gives novel insights for the design of multifunctional self-healing hydrogels that have great potential in various application fields such as electronic skins, soft robots, and wearable devices.

Ultrastretchable Composite Organohydrogels with Dual Cross-Links Enabling Multimodal Sensing

“…The first stage (<300% strain) follows GF = 4.9 ( R 2 = 0.988) (inset graph in Figure b), and the second one (300–2500% strain) follows GF = 11.9 ( R 2 = 0.998). The two-stage evolution has also been reported on some other conductive composite organohydrogels, which is attributed to the nonlinear alterations of the deformation of ion channels . In brief, the connections between neighboring MXene nanosheets are not easily broken up when the sensor suffers a small strain, leading to a low-level GF value.…”

“…For plastic, glass, rubber, ceramic, and gristle, the formation of hydrogen bonds at the interfaces accounts for the adhesion. For the metallic materials, the occurrence of coordination bonds between PAM and metal is also included in the adhesion mechanism . The adhesive strengths range in a normal level of PAM-based hydrogels or organohydrogels, which are strong enough to ensure the mechanical stability of the sensor device …”

“…The twostage evolution has also been reported on some other conductive composite organohydrogels, 59 which is attributed to the nonlinear alterations of the deformation of ion channels. 57 In brief, the connections between neighboring MXene nanosheets are not easily broken up when the sensor suffers a small strain, leading to a low-level GF value. As the nanosheet−nanosheet distances are larger enough with an increased strain level, it is hard for the free electrons to hop the barrier.…”

Sustainable Macromolecular Materials in Flexible Electronics

“…[254] Thanks to its high flexibility and adhesion force, it can be applied to many kinds of surfaces and can be used in motion detection and health monitoring applications by easily adhering to human skin (Figure 8c). [171,172] In the polymerization step, crosslinks are established with the contribution of polyvinyl alcohol (PVA), taking the mechanical properties and resistive sensitivity one step further. Due to its flexibility, gelatin, which is also evaluated in the literature as an electroactive material, will be preferred more frequently in the coming years owing to its mechanical strength.…”

Multifunctional Double-Network Self-Healable Hydrogel and Its Application to Highly Reliable Strain Sensors

“…These characteristics have recently triggered numerous investigations to develop DNHs, through an eco-friendly and low-cost synthetic process for use in various electronics-related applications, including conducting and resisting materials, electrodes, or sensors with particular functionalities and stimulus-responsive properties. − Tsai et al fabricated a double-network hydrogel using PVA, agarose, borax, zinc oxide (ZnO), and poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) . Using the latter as a sensing layer, they fabricated a self-powered, self-healing, and wearable ultraviolet (UV) photodetector.…”