Bioinspired Gradient Stretchable Aerogels for Ultrabroad‐Range‐Response Pressure‐Sensitive Wearable Electronics and High‐Efficient Separators

Abstract

Broad‐range‐response pressure‐sensitive wearable electronics are urgently needed but their preparation remains a challenge. Herein, we report unprecedented bioinspired wearable electronics based on stretchable and superelastic reduced graphene oxide/polyurethane nanocomposite aerogels with gradient porous structures by a sol‐gel/hot pressing/freeze casting/ambient pressure drying strategy. The gradient structure with a hot‐pressed layer promotes strain transfer and resistance variation under high pressures, leading to an ultrabroad detection range of 1 Pa–12.6 MPa, one of the broadest ranges ever reported. They can withstand 10 000 compression cycles under 1 MPa, which can't be achieved by traditional flexible pressure sensors. They can be applied for broad‐range‐response electronic skins and monitoring various physical signals/motions and ultrahigh pressures of automobile tires. Moreover, the gradient aerogels can be used as high‐efficient gradient separators for water purification.

Super-stretchable and negative-Poisson-ratio meta-aerogels

“…The maximum tensile strains of all the previously reported intrinsically stretchable aerogels were no higher than approximately 400%. [7,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Moreover, the stretchability of our aerogels were higher than those of the reported intrinsically stretchable foams and sponges based on inorganic building blocks [39] and various polymers including polydimethylsiloxane (PDMS) [40][41][42][43] , PU [44][45][46][47][48][49], poly(vinylidene fluoride) (PVDF) [50] , and polyacrylate [51] (Figure 3j and Table S5).…”

“…[37] As shown in the FTIR spectra (Figure S12g-i), the peaks of PUF1 and the rGO/PU aerogel at 2870, 1721, 1086, and 700 cm -1 corresponded to the stretching vibration of C-H, C=O, C-O, and inplane vibration of C-H, respectively. [5,20,22] These peaks were also observed in rGO/PPy/PUF1, rGO/PPy/PUF1-UHP, rGO/PPy/PU, and rGO/PPy/PU-UHP. The intensities of these peaks became weaker after the incorporation of rGO and PPy.…”

“…The Raman spectra of the rGO/polymer aerogels exhibited the D band at approximately 1327 cm -1 and G band at approximately 1580 cm -1 , corresponding to the characteristic bands of rGO, confirming the successful incorporation of rGO in the composite aerogels (Figure S12d-f). [22] For rGO/PPy/PUF1, rGO/PPy/PUF1-UHP, rGO/PPy/PU, and rGO/PPy/PU-UHP, there were two new bands at approximately 957 and 1055 cm -1 . The band at 957 cm -1 corresponded to the ring deformation vibration of PPy, while the band at 1055 cm -1 was attributed to the in-plane deformation of C-H and in-plane bending of N-H in PPy.…”

“…As presented in the XRD patterns (Figure S12a-c), PUF1 showed a broad peak at approximately 19.5°, corresponding to the carbon chains with regular interplanar spacing in PUF1, while MF exhibited no obvious characteristic peak. [22] The rGO/polymer aerogels (rGO/PPy/PUF1, rGO/PPy/PU, and rGO/MF) presented an obvious peak at approximately 21°, resulting from the synergistic effect of rGO and the polymers (PUF, PU, or MF) (Figure S12a-c). For the hot-pressed rGO/polymer aerogels, the intensity of this characteristic peak became higher, probably because rGO was further reduced during hot pressing.…”

“…[21] Besides, we have reported stretchable (~100% elongation at break) rGO/PU nanocomposite aerogels with a gradient porous structure for high-performance pressure-sensitive wearable electronics. [22] Some special porous microstructures such as lamellar and honeycomb-like structures possess excellent mechanical strength and can effectively reduce stress concentration and contribute to stress transfer, which may endow the resultant aerogels with deformability and stretchability. Carbon aerogels with a long-range lamellar multi-arch porous structure obtained by bidirectional freezing can achieve stretchability with a large tensile strain of 80%.…”