Ultrahigh‐Water‐Content, Superelastic, and Shape‐Memory Nanofiber‐Assembled Hydrogels Exhibiting Pressure‐Responsive Conductivity

Abstract

High-water-content hydrogels that are both mechanically robust and conductive could have wide applications in fields ranging from bioengineering and electronic devices to medicine; however, creating such materials has proven to be extremely challenging. This study presents a scalable methodology to prepare superelastic, cellular-structured nanofibrous hydrogels (NFHs) by combining alginate and flexible SiO nanofibers. This approach causes naturally abundant and sustainable alginate to assemble into 3D elastic bulk NFHs with tunable water content and desirable shapes on a large scale. The resultant NFHs exhibit the integrated properties of ultrahigh water content (99.8 wt%), complete recovery from 80% strain, zero Poisson's ratio, shape-memory behavior, injectability, and elastic-responsive conductivity, which can detect dynamic pressure in a wide range (>50 Pa) with robust sensitivity (0.24 kPa ) and durability (100 cycles). The fabrication of such fascinating materials may provide new insights into the design and development of multifunctional hydrogels for various applications.

Bioinspired Nanocomposite Hydrogels with Highly Ordered Structures

“…A recent work reported the fabrication of high-water-content and superelastic nanofibrous hydrogels with ordered cellular structures that contain sustainable alginate and electrospun nanofibers that were fabricated by using a freezing-induced strategy (Figure 6a). [95] Owing to the synergistic effects between ordered nanofibrous architectures and hydrogel networks, materials with a Poisson's ratio of zero, shape-memory behavior, injectability, elastic-responsive conductivity, and pressure-sensitive properties can be realized. Meanwhile, this strategy has been utilized to fabricate ordered architectures with 2D nanomaterials.…”

“…Reproduced with permission. [95] Copyright 2017, Wiley-VCH. b) Schematic illustration of the process of fabricating nanocomposite hydrogels with ordered macroporous structures by using a freeze-casting strategy.…”

“…• Time/energy-consuming during freezing [94][95][96][97][98] Self-assembly Nanoparticles (0D) Nanotubes (1D) Nanosheets (2D) Nanolamellae (2D)…”

Nanofiber‐Based Hydrogels: Controllable Synthesis and Multifunctional Applications

“…Recently, novel porous nanofiber‐assembled hydrogels (NFHs) with ultrahigh water‐holding capacity, superelasticity, and excellent shape‐memory properties, have been successfully synthesized by freeze‐drying method . The fabrication process mainly consists of four major components: electrospun flexible SiO 2 nanofibers, hydrogel precursor of alginate, crosslinker of metallic cations, and water.…”

“…Recently, different types of fiber‐enhanced hydrogels have been prepared via taking various fibrous materials as reinforcements, such as traditional fabrics, 3D‐printed microfiber frames, and novel nanofibers . Among those fibrous reinforcements, nanofibers can not only enhance the mechanical strength through increasing the stress dissipation along the interfaces between nanofibers and hydrogels, the network structure formed by the nanofibers can also greatly improve the performance and expand new application areas of hydrogel materials, which owe to the properties of large length–diameter ratio, high specific surface area, high porosity, unique chemical/physical and mechanical characteristic of nanofibers . Based on the rapid progress in nanotechnology and materials science, unremitting efforts have focused on the structure and composition design for achieving advanced nanofiber‐based hydrogels (NFHGs) with high mechanical strength and multifunctional application performance.…”