Mussel-Inspired Cellulose Nanocomposite Tough Hydrogels with Synergistic Self-Healing, Adhesive, and Strain-Sensitive Properties

Abstract

The remarkable progress in efforts to prepare conductive self-healing hydrogels mimicking human skin's functions has been witnessed in recent years. However, it remains a great challenge to develop an integrated conductive gel combining excellent self-healing and mechanical properties, which is derived from their inherent compromise between the dynamic cross-links for healing and steady cross-links for mechanical strength. In this work, we design a tough, self-healing, and self-adhesive ionic gel by constructing synergistic multiple coordination bonds among tannic acid-coated cellulose nanocrystals (TA@CNCs), poly(acrylic acid) chains, and metal ions in a covalent polymer network. The incorporated TA@CNC acts as a dynamic connected bridge in the hierarchically porous network mediated by multiple coordination bonds, endowing the ionic gels the superior mechanical performance. Reversible nature of dynamic coordination interactions leads to excellent recovery property as well as reliable mechanical and electrical self-healing property without any assistance of external stimuli. Intriguingly, the ionic gels display durable and repeatable adhesiveness ascribed to the presence of catechol groups from the incorporated tannic acid, which can be adhered directly on human skin without inflammatory response and residual. Additionally, the ionic gels with a great strain sensitivity can be employed as flexible strain sensors to monitor and distinguish both large motions (e.g., joints bending) and subtle motions (e.g., pulse and breath), which enable us to analyze the data on the user interface of smart phone via programmable wireless transmission. This work provides a new prospect for the design of the biocompatible cellulose-based hydrogels with stretchable, self-adhesive, self-healing, and strain-sensitive properties for potential applications in wearable electronic sensors and healthcare monitoring.

Super‐Stretchable Zinc–Air Batteries Based on an Alkaline‐Tolerant Dual‐Network Hydrogel Electrolyte

“…The peaks at around 1160 and 1023 cm −1 are attributed to asymmetric stretching vibration of COC glycoside and CO stretching in the COH stretching, respectively, [30][31][32][33][34] while the peak at 895 cm −1 is related to COC bridge. The peaks at around 1160 and 1023 cm −1 are attributed to asymmetric stretching vibration of COC glycoside and CO stretching in the COH stretching, respectively, [30][31][32][33][34] while the peak at 895 cm −1 is related to COC bridge.…”

Poly(acrylic acid)‐chitosan @ tannic acid double‐network self‐healing hydrogel based on ionic coordination

“…The presence of coordination bonds can be examined using UV‐Vis spectroscopy and the hypothesis about possible coordination modes was proposed. As shown in Figure E, PAA and PAA‐CS@TA solutions do not have significant absorbance in the range of 350 to 800 nm, while PAA‐CS@TA‐Al 3+ , CS@TA‐Al 3+ , and PAA‐Al 3+ demonstrated distinct absorption peaks around 460 nm . UV spectra suggest the formation of coordination bonds, confirming that the coordination bonds not only exist in CS@TA (metal‐phenol coordination).…”

Inorganic Salts Induce Thermally Reversible and Anti‐Freezing Cellulose Hydrogels

“…There is acrossover of G' and G'' for the three gels in the heating and cooling cycle.T his is the sol-gel transition temperature which is defined as T gel .F or the heating process, the T gel is 69, 71, and 70 8 8Cf or Gel-0, Gel-water,a nd Gelglycerol, respectively. [18] Thephysical cross-links of hydrogen bonding and the crystalline domains are broken and rebuilt during the thermal cycle.R e-establishment of equilibrium is achieved at the cooling process.F or Gel-0 T gel = 68 8 8C, while for Gel-water and Gel-glycerol T gel = 45 and 65 8 8C, respectively,i nt he cooling cycle.T hese results demonstrate the thermally induced transformation of the three gels,w hich endows the hydrogels with remoldability and 3D-printing ability.T he formation of the gel structure is induced by the strong self-aggregation of cellulose and temperature can influence the balance of the hydrogel.…”