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Manganese dioxide (MnO2) has emerged as one of the most promising pseudo-capacitive materials with ultra-high theoretical specific capacitance in the energy storage field. Unfortunately, poor electrical conductivity and unfavorable cycling stability greatly impede its application as an excellent electrode material. In this paper, manganese dioxide (MnO2) nanoparticles with well-controlled morphology and density are deposited on the surface of three-dimensional porous carbon nanotube sponge (CNTS) through a controllable electrochemical deposition method. The conductive and flexible CNTS skeleton greatly enhances the conductivity of a MnO2-composed electrode and dramatically improves the cycling stability. The ratio of the pseudo-capacitive contribution to the electrochemical double-layer capacitive contribution can be tuned by MnO2 deposition time. The CNTS@MnO2 composite electrode and assembled symmetric flexible solid-state supercapacitor (FSSC) device using the CNTS@MnO2 composite as electrodes achieved superior volumetric capacitances of up to 4.62 F·cm–3 (at 10 mA·cm–3) and 3.72 F·cm–3 (at 5 mA·cm–3), respectively. Meanwhile, the capacitance preservation remained around 100% after 10,000 rapid charge–discharge cycles. Moreover, the salt-induced Hofmeister effect further increased the tensile strength of the CNTS@MnO2@PVA composite-based FSSC device to as high as 2.02 MPa (with an elongation at the break of 354%), which is almost two times tougher than the initial. Considering the excellent electrochemical and mechanical properties as well as environmental friendliness, our CNTS@MnO2 hybrids have a feasible application prospect in flexible, wearable, and implantable electronic devices.

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Spider silks, mainly constructed of spidroin, have received extensive attention for their excellent mechanical properties, slow biodegradability, and high biocompatibility. However, due to uncontrollable protein-folding processes, the structural transition of spidroin, especially when composited with other functional materials under confinement, is insufficiently understood. Herein, we report a pressure-induced conformational transition process of the spidroin which is confined within carbon nanotube (CNT) sponge matrixes. The structural transition of spidroin from α-helix to β-sheet can be induced by a very small hydrostatic pressure (several megapascals) and recover easily through a subsequent solvent vapor annealing process in an ambient atmosphere. Therefore, the spidroin/CNT sponge exhibits reversible vapor-/pressure-sensitive "shape-memory" behavior with the recovery efficiency close to 100%. Our observation reveals a crucial mechanism for the conformational transition of spidroin under confinement, which paves the way toward the fabrication of spider silk-based products with superior performances.

Natural spider silks with striking performances achieve extensive investigations. Nonetheless, a lack of consensus over the mechanism of the natural spinning hinders the development of artificial spinning methods where the regenerated spider silks generally show poor performances compared with the natural fibers. As is known, the Plateau–Rayleigh instability tends to break solution column into droplets and is considered a main challenge during fiber‐spinning. Here in this study, by harnessing the viscoelastic properties of the regenerated spidroin dope solution via organic salt–zinc acetate (ZA), this outcome can be avoided, and dry‐spinning of long and mechanically robust regenerated spider silk ribbons can be successfully realized. The as‐obtained dry‐spun spider silk ribbons show an enhanced modulus up to 14 ± 4 GPa and a toughness of ≈51 ± 9 MJ m−3 after the post‐stretching treatment, which is even better than that of the pristine spider silk fibers. This facile and flexible strategy enriches the spinning methodologies which bypass the bottleneck of precisely mimicking the complex natural environment of the glands in spiders, shining a light to the spider‐silk‐based textile industrial applications.