Electronic skin (e-skin) presents a network of mechanically flexible sensors that can conformally wrap irregular surfaces and spatially map and quantify various stimuli 1-12 . Previous works on e-skin have focused on the optimization of pressure sensors interfaced with an electronic readout, whereas user interfaces based on a human-readable output were not explored. Here, we report the first user-interactive e-skin that not only spatially maps the applied pressure but also provides an instantaneous visual response through a built-in active-matrix organic light-emitting diode display with red, green and blue pixels. In this system, organic light-emitting diodes (OLEDs) are turned on locally where the surface is touched, and the intensity of the emitted light quantifies the magnitude of the applied pressure. This work represents a system-on-plastic 4,13-17 demonstration where three distinct electronic componentsthin-film transistor, pressure sensor and OLED arrays-are monolithically integrated over large areas on a single plastic substrate. The reported e-skin may find a wide range of applications in interactive input/control devices, smart wallpapers, robotics and medical/health monitoring devices.Although both passive 6,8,12 and active-matrix 1,2,5,9 designs can be used for enabling the predicted user-interactive e-skins, the active-matrix design is advantageous as it minimizes signal crosstalk and thereby offers better spatial resolution and contrast, and a faster response. In the active-matrix backplane circuitry, each pixel is controlled by a thin-film transistor (TFT) that acts as a switch for addressing either current-or voltage-driven devices. Here, we incorporate the active-matrix design into the e-skin by using semiconductor-enriched nanotubes 18 as the channel material of the TFTs. Carbon nanotube networks are proven to be a promising material platform for high-performance TFTs (refs 9,17,19-21) with high current drives needed for switching OLEDs (ref. 22). A schematic structure of a pixel of the user-interactive e-skin with an integrated TFT, OLED and pressure sensor is depicted in Fig. 1a. Each pixel in the active-matrix consists of a nanotube TFT with the drain connected to the anode of an OLED. The OLED uses a simple bilayer structure 23 and the colour of the emitted light is controlled by using different emissive layer materials (details in the Methods). In this work, red, green, blue and yellow colours are demonstrated. On top of the OLEDs, a pressure-sensitive rubber 1,5,24,25 (PSR) is laminated, which is in electrical contact with the cathode (that is, top contact) of the OLED at each pixel. The top surface of the PSR is coated with a conductive silver ink to act as the ground contact. Here, the conductivity of the PSR increases by an applied pressure 1,5,24,25 in the underlying OLED turning on. As illustrated in Fig. 1b, the single-pixel circuitry is integrated into an active-matrix array. The resulting system-on-plastic provides a touch user interface, allowing the pressure profile to be...

No abstract

Polymer light‐emitting devices are fabricated using single‐walled carbon nanotube‐polymer composite electrodes as both the electron and hole injection electrodes. The devices are metal‐free and can be linearly stretched up to 45% strain. This represents a proof‐of‐concept, highly stretchable semiconductor device wherein every part of the device is intrinsically stretchable.

Shape-memory polymer light-emitting diodes (PLEDs) using a new silver nanowire/polymer electrode are reported. The electrode can be stretched by up to 16% with only a small increase in sheet resistance. Large deformation shape change and recovery of the PLEDs to various bistable curvatures result in minimal loss of electroluminescence performance.

Fully printed transistors are a key component of ubiquitous flexible electronics. In this work, the advantages of an inverse gravure printing technique and the solution processing of semiconductor-enriched single-walled carbon nanotubes (SWNTs) are combined to fabricate fully printed thin-film transistors on mechanically flexible substrates. The fully printed transistors are configured in a top-gate device geometry and utilize silver metal electrodes and an inorganic/organic high-κ (~17) gate dielectric. The devices exhibit excellent performance for a fully printed process, with mobility and on/off current ratio of up to ~9 cm(2)/(V s) and 10(5), respectively. Extreme bendability is observed, without measurable change in the electrical performance down to a small radius of curvature of 1 mm. Given the high performance of the transistors, our high-throughput printing process serves as an enabling nanomanufacturing scheme for a wide range of large-area electronic applications based on carbon nanotube networks.

Direct conversion of light into mechanical work, known as the photomechanical effect, is an emerging field of research, largely driven by the development of novel molecular and polymeric material systems. However, the fundamental impediment is that the previously explored materials and structures do not simultaneously offer fast and wavelength-selective response, reversible actuation, low-cost fabrication and large deflection. Here, we demonstrate highly versatile photoactuators, oscillators and motors based on polymer/single-walled carbon nanotube bilayers that meet all the above requirements. By utilizing nanotubes with different chirality distributions, chromatic actuators that are responsive to selected wavelength ranges are achieved. The bilayer structures are further configured as smart 'curtains' and light-driven motors, demonstrating two examples of envisioned applications.

No abstract

Organometal halide perovskite and poly(ethylene oxide) composite thin films are studied. Single-layer light-emitting diodes using the composite thin film sandwiched between indium tin oxide and indium-gallium eutectic alloy exhibit a low turn-on voltage and high brightness because of the ionic conductivity of the composite film and the formation of a p-i-n homojunction.