Biological muscles generally possess well-aligned muscle fibers and thus excellent strength and toughness. Inspired by their microstructure, tough wood hydrogels with a preserved unique alignment of cellulose fibers, mechanical anisotropy, and desirable flexibility were developed by introducing chemically and ionically cross-linked poly(acrylic acid) (PAA) into the abundant pores of delignified wood. PAA chains well infiltrated the parallelly aligned cellulose fibers of wood and formed a layer-by-layer network structure, resulting in strong, elastic tangential, and radial wood hydrogel slices. The tangential slices had a high compressive strength of 1.73 MPa and a maximum strain at fracture of 69.4%, while those of the radial slices were 0.6 MPa and 47.0%. After sandwiching the radial and tangential hydrogel slices with reduced graphene oxide (rGO) film electrodes into capacitive pressure sensors (CPSs), the tangential CPS displayed the most desired, gradient sensitivity values in the whole stress range. Additionally, the wrinkling treatment of the rGO electrode greatly improved the capacitance responsiveness toward pressure. The real-time sensing stress values of our tangential CPS during monitoring practical human activities were calculated in the range of 0.1−1.3 MPa, demonstrating the achievement of ultrafast, highly sensitive, and wide-stress-range detection for potential applications in human−machine interfaces.
Since
highly stretchable hydrogels have demonstrated their promising
applications in flexible tactile sensors and wearable devices, the
current challenge has been imposed on stretchable and multifunctional
electronics. Here, we report a multifunctional sensor composed of
a liquid metal (LM) nanodroplet-adhered self-assembled polymeric network,
anionic carboxymethylcellulose (CMC), and cationic polyacrylamide
(PAAm). The synergistic effect, zeta potential reduction, by CMC and
macromolecules enveloped by LM contributes to the stabilization of
the ternary system during preparation and, thus, the homogenization
of the products. By engineering and optimizing the ternary hybrid
hydrogels, excellent extensibility (tensile strain near 300%), readily
reversible hysteresis loops, and accessible deformability (low modulus
of 104 Pa) are afforded. The fabricated sensor exhibits
a high tensile strain gauge factor of around 0.7 and a high compressive
stress sensitivity of up to 0.12 kPa–1, a fast response
time below 125 ms, and a high stability and precision in usage. In
a series of practical scenarios, the assembled sensor displays distinguished
abilities to monitor bodily motions, record electrocardiograms, authenticate
handwriting, discern temperature, and infer materials, making them
highly promising for multifunctional intelligent soft sensing.
Elastic polyion hydrogels (EPIH) as pressure sensors require to be microstructurally modified or micropatterned to improve the sensitivity of the parallel-plate sensing configurations. In this work, we designed a novel...
Taking inspiration and utilizing materials directly from nature, a simple and green strategy to fabricate biomass-based highly sensitive flexible tactile sensors was developed. The capacitive sensing devices were constructed by...
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