Characteristics of the indium tin oxide (ITO) thin films fabricated by a direct printing method were investigated. For the direct printing, 30 mass% ITO ink was formulated by dispersing ITO nanoparticles of less than 10 nm in diameter into alcohol based solvent with additives. Then, the ITO ink was printed onto a glass substrate, which was followed by the heat treatment at 350, 400, 500 and 600°C to fabricate the sintered films. Then, cross-section of sintered film was observed. As a result, the ITO thin film showed porous nanostructure. Also, sheet resistance of the ITO thin film decreased with increasing heating temperature. The decrease of the resistance was attributed to the improvement of carrier concentration in the ITO thin film. In the meanwhile, the optical transmittance increased in proportional to the heating temperature. In case of the ITO thin film heated at 600°C, the improved characteristics of the electrical resistance and the optical transmittance were achieved as 2.19×103 Ω/sq and 78.6%, respectively.
A UV curable, healable polymer was synthesized, and hybridized with silver nanowires to afford a pressure-sensitive e-skin capable of irradiation-induced healing.
Lightweight, low-cost, eco-friendly, and mechanically flexible Ti3C2Tx (MXene) electrodes require for paper electronics. We develop a highly durable and conductive traditional Korean paper (Hanji) covered with MXene for Hanji-based paper electronics. The effective networking of MXene on the cellulose structure of Hanji leads to a highly conductive and flexible Hanji which acts as a multi-functional paper for Hanji-based paper electronics. Owing to the synergetic combination of Hanji and MXene, the as-prepared Hanji/MXene exhibits a low sheet resistance of 0.62 Ohm square-1, and outstanding mechanical stability without breaking the Hanji fibers. To further evaluate the potential of our Hanji/MXene composite, its performance in electromagnetic interference (EMI) shielding, interconnectors, heaters, supercapacitors, and temperature sensor applications is investigated. Shielding and heater paper samples employing Hanji/MXene-based electrodes show an EMI shielding efficiency (EMI SE) of 43.3 dB and saturation temperature of 76 °C at a low voltage of 3 V. Moreover, the Hanji/MXene-based supercapacitors exhibit a capacitance of 139.6 mF cm-2 at a current density of 1 mA cm-2. Furthermore, the Hanji/MXene-based temperature sensors exhibit an effective sensing performance over a wide temperature range. Overall, the successful operation of Hanji-based EMI shielding devices, interconnectors, heaters, supercapacitors, and temperature sensors indicates that Hanji/MXene serves as a promising conductive paper substrate for multi-functional paper electronics.
Abstract This paper presents the successful fabrication of a transparent electrode comprising a sandwich structure of silicone/Ag nanowires (AgNWs)/silicone equipped with Diels–Alder (DA) adducts as crosslinkers to realise highly stable stretchability. Because of the reversible DA reaction, the crosslinked silicone successfully bonds with the silicone overcoat, which should completely seal the electrode. Thus, any surrounding liquid cannot leak through the interfaces among the constituents. Furthermore, the nanowires are protected by the silicone cover when they are stressed by mechanical loads such as bending, folding and stretching. After delicate optimisation of the layered silicone/AgNW/silicone sandwich structure, a stretchable transparent electrode which can withstand 1000 cycles of 50% stretching–releasing with an exceptionally high stability and reversibility was fabricated. This structure can be used as a transparent strain sensor; it possesses a strong piezoresistivity with a gauge factor greater than 11.
Abstract A typical capacitive mechanical sensor implemented using a layer of soft dielectric polymer sandwiched between two flexible electrodes, where the capacitance is formed, suffers from unintended buckling instability upon repeated stretch‐and‐release owing to different mechanical characteristics of constituent materials and unstable interfaces. Here, a stretchable, healable, and transparent strain/pressure‐sensitive capacitor is successfully fabricated by hybridizing Ag nanowires (AgNWs) with a polydimethylsiloxane containing maleimide‐derived Diels–Alder (DA) adducts as reversible crosslinkers. AgNWs formed on the surface of the cured polymer sheet are impregnated under the surface of the film by utilizing the vaporized solvent‐assisted retro‐DA reaction. Two identical films with fully impregnated AgNWs under the polymer surface are subjected to lamination with the insulated areas facing each other to implement a sandwich‐structure with a centering dielectric layer. Owing to the retro‐DA and reversible crosslinking during heating, two films in contact are fully integrated as if the architecture is originally made of a single film. The sensitivity to pressure under the stretching condition increases by about 320% compared to that without stretching.
The high interest sparked by the foldable smartphones recently released on the market is gradually shifting to the next generation of flexible electronic devices, such as electronic skins in the form of stretchable thin films. To develop such devices, good mechanical flexibility of all components (including the substrate, electrode, and encapsulant) is critical. Various technologies have been developed to enhance the flexibility of these components; however, progress in developing interconnection methods for flexible and stretchable devices has been limited. Here, we developed an ultrafast photoinduced interconnection method that does not require any adhesive or surface treatment. This method is based on heating metal nanostructures using intense pulsed light (IPL) and the reversible cross-linking of polymers. First, we synthesized a stretchable, transparent, and free-standing polymer substrate that can be reversibly cross-linked, and then Ag nanowire (AgNW) networks were formed on its surface. This electrode was irradiated with IPL, which locally heated the AgNWs, followed by decomposition of the polymer via the retro-Diels-Alder reaction and recross-linking. Independently fabricated AgNW/polymer films were layered and irradiated three times with IPL to form a bonded sample with excellent joint quality and no increase in electrical resistance compared to a single electrode. Furthermore, the interconnected electrodes were stretchable and optically transparent. Even when more than 200% strain was applied in a peel test, no breakage at the joint was observed. This allowed us to successfully produce a stretchable, transparent, and bending-insensitive pressure sensor for various applications such as motion detectors or pressure sensor arrays.
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