We present gas-permeable, ultrathin, and stretchable electrodes enabled by self-assembled porous substrates and conductive nanostructures. An efficient and scalable breath figure method is employed to introduce the porous skeleton, and then silver nanowires (AgNWs) are dip-coated and heat-pressed to offer electric conductivity. The resulting film has a transmittance of 61%, sheet resistance of 7.3 Ω/sq, and water vapor permeability of 23 mg cm–2 h–1. With AgNWs embedded below the surface of the polymer, the electrode exhibits excellent stability in the presence of sweat and after long-term wear. We demonstrate the promising potential of the electrode for wearable electronics in two representative applications: skin-mountable biopotential sensing for healthcare and textile-integrated touch sensing for human–machine interfaces. The electrode can form conformal contact with human skin, leading to low skin–electrode impedance and high-quality biopotential signals. In addition, the textile electrode can be used in a self-capacitance wireless touch sensing system.

PSS (5.2 eV) hole extraction layer. The modified Cu mesh electrodes show remarkable potential as a substitute of ITO/PET in the flexible OPV and OLED devices. The OPV cells constructed on our Cu mesh electrodes present a similar power conversion efficiency of 2.04% as those on ITO/PET electrodes. The flexible OLED prototype devices can achieve a brightness of 10 000 cd at an operation voltage of 8 V.

Although plenty of active materials could be used as supercapacitor electrodes, only limited ones have been engineered to construct transparent supercapacitors. Specially, it is a great challenge to make opaque metal oxides, which often own high energy density, into transparent films. Here, we demonstrate a novel approach to fabricate transparent MnO films for flexible transparent supercapacitors. By utilizing breath-figure polymer films with ordered pores as template, arrays of MnO islands were electrochemically deposited, with high light transmission. The thickness and interspace distance of MnO island arrays could be adjusted by tuning deposition time so that the capacitance and transparency of the electrodes are changed accordingly. Such island array structure can effectively eliminate the internal stress existing in the composite film to avoid cracks during bending operation. The assembled transparent supercapacitor shows a transmittance of 44% at 550 nm and can yield a high capacitance of 4.73 mF/cm at a current density of 50 μA/cm, demonstrating high flexibility and stability.

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Coating nickel onto copper nanowires (Cu NWs) by one-pot synthesis is an efficient approach to improving the oxidation resistance of the nanowires. Because Ni is much less conductive than Cu, it is of great importance to understand the relationship between the thickness of the Ni coating layer and the properties of NWs. Here we demonstrate one-pot synthesis of Cu-Ni core-shell NWs with a tunable Ni thickness by simply varying the Cu and Ni mole ratio in the precursor. We have observed that an increase in Ni thickness decreases the aspect ratio, surface smoothness and network conductivity of the resulting NWs. However, Cu-Ni NWs with a thicker Ni layer display higher oxidation temperature. The optimal Cu-Ni NWs, which were prepared using a Cu(2+)/Ni(2+) molar ratio of 1/1, have a Ni-layer thickness of about 10 nm and the onset oxidation temperature of 270 °C. The derived transparent conductive films present a transmittance of 76% and a sheet resistance of 300 Ω sq(-1). The flexible heater constructed from such high quality Cu-Ni NW films demonstrates effective performance in heating and defrosting.

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The efficient utilization of Ag NW by avoiding their aggregation and multi-layer stacking in their networks can improve the optical and electrical properties of the derived transparent conductive electrodes (TCEs).

developed in recent years. The stretchable conductors used in those sensors work via piezoresistive sensing mechanism, such as thin metal films (TMFs) deposited onto stretchable polymers [18][19][20] and some filler-type elastomers composed of carbon nanotubes, [16,17] graphene, [21,22] and metal nanowires. [14,[23][24][25][26][27][28] Particularly, TMFs strain sensors are feasible to be prepared in a large area by direct deposition approach, making it compatible with conventional Si-based processes and easy to integrate into external circuits and devices. However, the stiff feature of TMFs will lead to mechanical failure when stretched over their elongation limit, e.g., less than 1% for thin Cu films. [19] To resolve this problem, various structures with wavy, buckle, wrinkle, or network topography have been introduced to adapt mechanical deformation. [29][30][31][32][33] However, these strain sensors are operated only in uniaxial or biaxial stretching directions, [29] not suitable for the omnidirectional model, which is crucial for practical applications. For example, a strain sensor attached to the human body will inevitably suffer from multidimensional strain. Developing multidimensional TMFs-based strain sensor is highly demanded while still a challenge. It is noteworthy that metal mesh films are possibly stretched in all direction, taking a honeycomb metal mesh film as an example. A simulated polyethylene terephthalate (PET) mesh with a honeycomb structure that consists of regular hexagonal cells is depicted in Figure 1a. The ratio of pore size diameter D to the frame width W (D/W) is controlled to be 5/1 (Figure 1d). The experiments by stretching PET meshes show that the elongation degree along X-direction is higher than that on Y-direction (Figure 1b,c). The maximum elongation along X-direction (e max-x ) and Y-direction (e max-y ) (calculated from Equations E1 and E2 in the Supporting Information) are 41.2% (Figure 1e) and 15.2% (Figure 1f), respectively.The above simulation results demonstrate that a singledomain honeycomb metal mesh features an anisotropic elongation depending on the grid orientation, such as the metal grid transparent conductors fabricated by laser sintering of silver nanoparticle ink and laser ablation of copper film. [34,35] For structures fabricated by self-assembly process, such as the metal meshes prepared by breath-figure approach, are composed of multiple domains with various grid orientation due to the existence of line defects. [36,37] This merit results in isotropic characteristics, such as uniform conductivity and stretchability in a large area. In this work, we prepare a transparent, highly stretchable, and omnidirectional strain sensor using porous honeycomb-structured Ag mesh film that consists of multiple Thin metal films can be engineered to fabricate strain sensors by conquering their stiffness using wavy, buckle, or wrinkle topography. However, these structures usually operate in uniaxial or biaxial stretching directions, limiting their application in the omnidirecti...