Some animals, such as the chameleon and cephalopod, have the remarkable capability to change their skin colour. This unique characteristic has long inspired scientists to develop materials and devices to mimic such a function. However, it requires the complex integration of stretchability, colour-changing and tactile sensing. Here we show an all-solution processed chameleon-inspired stretchable electronic skin (e-skin), in which the e-skin colour can easily be controlled through varying the applied pressure along with the applied pressure duration. As such, the e-skin's colour change can also be in turn utilized to distinguish the pressure applied. The integration of the stretchable, highly tunable resistive pressure sensor and the fully stretchable organic electrochromic device enables the demonstration of a stretchable electrochromically active e-skin with tactile-sensing control. This system will have wide range applications such as interactive wearable devices, artificial prosthetics and smart robots.

Sensing the force digitally Our skin provides us with a flexible waterproof barrier, but it also contains a sensor array that feels the world around us. This array provides feedback and helps us to avoid a hot object or increase the strength of our grip on an object that may be slipping away. Tee et al. describe an approach to simulate the mechanoreceptors of human skin, using pressure-sensitive foils and printed ring oscillators (see the Perspective by Anikeeva and Koppes). The sensor successfully converted pressure into a digital response in a pressure range comparable to that found in a human grip. Science , this issue p. 313 ; see also p. 274

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Porous graphitic carbon is essential for many applications such as energy storage devices, catalysts, and sorbents. However, current graphitic carbons are limited by low conductivity, low surface area, and ineffective pore structure. Here we report a scalable synthesis of porous graphitic carbons using a conjugated polymeric molecular framework as precursor. The multivalent cross-linker and rigid conjugated framework help to maintain micro- and mesoporous structures, while promoting graphitization during carbonization and chemical activation. The above unique design results in a class of highly graphitic carbons at temperature as low as 800 °C with record-high surface area (4073 m2 g–1), large pore volume (2.26 cm–3), and hierarchical pore architecture. Such carbons simultaneously exhibit electrical conductivity >3 times more than activated carbons, very high electrochemical activity at high mass loading, and high stability, as demonstrated by supercapacitors and lithium–sulfur batteries with excellent performance. Moreover, the synthesis can be readily tuned to make a broad range of graphitic carbons with desired structures and compositions for many applications.

Two ultrastable luminescent covalent organic frameworks (COFs), PyTA‐BC and PyTA‐BC‐Ph, are synthesized through polycondensations of 4,4′,4″,4′″‐pyrene‐1,3,6,8‐tetrayl)tetraaniline (PyTA‐4NH2) with two carbazole‐based derivatives having different degrees of conjugation. The PyTA‐BC and PyTA‐BC‐Ph COFs exhibit ultrahigh thermal stabilities (up to 421 °C), excellent crystallinity, and high Brunauer–Emmett–Teller surface areas (up to 1445 m2 g−1). These COFs display strong fluorescence emissions in various solvents, with their emission maxima gradually red‐shifting upon increasing the polarity of the solvent (solvatochromism). Upon exposure to HCl, they respond very rapidly and sensitively in terms of changing their colors and fluorescence emission maxima. In the presence of a sacrificial electron donor, these COFs mediate the highly efficient photocatalytic evolution of H2 from water. In the absence of a noble metal cocatalyst, the COFs and ascorbic acid provide a photocatalytic H2 production of up to 1183 µmol g−1 h−1 (λ ≥ 420 nm); this value is the highest reported to date for a COF. Such COFs appear to be potentially useful as chemosensors for the naked‐eye and sensitive spectroscopic detection of HCl and as cocatalysts for the sustainable photocatalytic production of H2 from water.

there are only a few reports of stretchable polymer electronics. [8,9] Due to high crystallinity and rigid polymer backbone, semiconducting polymers typically exhibit high tensile moduli and a high degree of brittleness, leading to rapid degradation of electrical properties during stretching. [10][11][12] In this regard, maintaining both the charge transport properties and ductility is a challenge for developing polymers for novel stretchable electronic applications. [13,14] π-conjugated polymers, such as polythiophene or donor-acceptor polymers, show high backbone coplanarity and crystalline packing due to their rigid polymer chains and strong π-π interaction. [15] Nevertheless, the presence of large fractions of interconnected crystalline domains in the solid state, a lack of significant chain folding and/or coiling, and high glass transition temperatures contribute to the high tensile moduli of polymer films and make these films too rigid to release the applied stress. In contrast, for polymer thin films containing properly engineered crystalline and amorphous regions, such as polyurethane and elastic polypropylene, the applied stress is preferentially dissipated in the relatively softer amorphous regions. Similar to other reported semicrystallineThe design of polymer semiconductors possessing high charge transport performance, coupled with good ductility, remains a challenge. Understanding the distribution and behavior of both crystalline domains and amorphous regions in conjugated polymer films, upon an applied stress, shall provide general guiding principles to design stretchable organic semiconductors. Structure-property relationships (especially in both side chain and backbone engineering) are investigated for a series of poly(tetrathienoacene-diketopyrrolopyrrole) polymers. It is observed that the fused thiophene diketopyrrolopyrrole-based polymer, when incorporated with branched side chains and an additional thiophene spacer in the backbone, exhibits improved mechanical endurance and, in addition, does not show crack propagation until 40%strain. Furthermore, this polymer exhibits a hole mobility of 0.1 cm 2 V −1 s −1 even at 100% strain or after recovered from strain, which reveals prominent continuity and viscoelasticity of the polymer thin film. It is also observed that the molecular packing orientations (either edge-on or face-on) significantly affect the mechanical compliance of the polymer films. The improved stretchability of the polymers is attributed to both the presence of soft amorphous regions and the intrinsic packing arrangement of its crystalline domains.Recently, polymer-based electronics have shown significant progress in terms of flexibility as well as bendability. [1][2][3][4][5][6][7] However,

By mimicking natural photosynthesis, generating hydrogen through visible-light-driven splitting of water would be an almost ideal process for converting abundant solar energy into a usable fuel in an environmentally friendly and high-energy-density manner. In a search for efficient photocatalysts that mimic such a function, here we describe a series of cycloplatinated polymer dots (Pdots), in which the platinum complex unit is presynthesized as a comonomer and then covalently linked to a conjugated polymer backbone through Suzuki–Miyaura cross-coupling polymerization. On the basis of our design strategy, the hydrogen evolution rate (HER) of the cycloplatinated Pdots can be enhanced by 12 times in comparison to that of pristine Pdots under otherwise identical conditions. In comparison to the Pt-complex-blended counterpart Pdots, the HER of cycloplatinated Pdots is over 2 times higher than that of physically blended Pdots. Furthermore, enhancement of the photocatalytic reaction time with high eventual hydrogen production and low efficiency rolloff are observed by utilizing the cycloplatinated Pdots as photocatalysts. On the basis of their performance, our cyclometallic Pdot systems appear to be alternative types of promising photocatalysts for visible-light-driven hydrogen evolution.

Due to the lack of a bandgap, applications of graphene require special device structures and engineering strategies to enable semiconducting characteristics at room temperature. To this end, graphene-based vertical field-effect transistors (VFETs) are emerging as one of the most promising candidates. Previous work attributed the current modulation primarily to gate-modulated graphene-semiconductor Schottky barrier. Here, we report the first experimental evidence that the partially screened field effect and selective carrier injection through graphene dominate the electronic transport at the organic semiconductor/graphene heterointerface. The new mechanistic insight allows us to rationally design graphene VFETs. Flexible organic/graphene VFETs with bending radius <1 mm and the output current per unit layout area equivalent to that of the best oxide planar FETs can be achieved. We suggest driving organic light emitting diodes with such VFETs as a promising application.