A simple strategy is developed to fabricate ultrasensitive and flexible pressure sensors via constructing a sandwich-like graphene based porous structure.

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Hydrogels have been attracting much attention on account of their soft and wet nature but inherently poor and unbalanced mechanical performance severely limits their applications. Herein, we reported a strategy to fabricate polyacrylamide/ chitosan/montmorillonite nanocomposite hydrogels by simultaneously introducing lamellar montmorillonite and chitosan microcrystalline structure via a facile and universal two-step method composed of in situ free radical polymerization and alkali treatment . The incorporation of two-dimensional nanoclay and chitosan microcrystalline structure into polyacrylamide network synergistically facilitated the formation of robust and uniform polymer architecture through physical interactions and thus significantly improved the mechanical behavior. As a result, the satisfactory mechanical properties of the optimal nanocomposite hydrogels were achieved at a relative high water content (80 wt %), including a superior tensile strength of 1.91 MPa, high tensile strain of 1005%, and exceptionally great toughness of 14.16 MJ•m −3 , respectively. Furthermore, they also possessed excellent compressive properties assessed from cyclic tests. On the basis of the structural evolution observation and analysis, a possible strengthening mechanism for enhanced mechanical properties was discussed and proposed. This high-performance nanocomposite hydrogel shows great potential as a promising candidate for structural or load-bearing materials.

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Advanced organic vapor sensors that simultaneously have high sensitivity, fast response, and good reproducibility are required. Herein, flexible, robust, and conductive vapor-grown carbon fibers (VGCFs)-filled polydimethylsiloxane (PDMS) porous composites (VGCFs/PDMS sponge (CPS)) with multilevel pores and thin, rough, and hollows wall were prepared based on the sacrificial template method and a simple dip-spin-coating process. The optimized material showed outstanding mechanical elasticity and durability, good electrical conductivity and hydrophobicity, as well as excellent acid and alkali tolerance. Additionally, CPS exhibited good reproducible sensing behavior, with a high sensitivity of ~1.5 × 105 s−1 for both static and flowing organic vapor, which was not affected in cases such as 20% squeezing deformation or environment humidity distraction (20~60% RH). Interestingly, both the reproducibility and sensitivity of CPS were better than those of film-shaped VGCFs/PDMS (CP), which has a thickness of two hundred microns. Therefore, the contradiction between the reproducibility and high sensitivity was well-solved here. The above excellent performance could be ascribed to the unique porous structures and the rough, thin, hollow wall of CPS, providing various gas channels and large contact areas for organic vapor penetration and diffusion. This work paves a new way for developing advanced vapor sensors by optimizing and tailoring the pore structure.