Flexible and Transparent All-Graphene Circuits for Quaternary Digital Modulations

In modern communication system, modulation is a key function that embeds the baseband signal (information) into a carrier wave so that it can be successfully broadcasted through a medium such as air or cables. A flexible signal modulation scheme is hence essential to wide range of applications based on flexible electronics. Here we report a fully bendable all-graphene modulator circuit with the capability to encode a carrier signal with quaternary digital information for the first time. By exploiting the ambipolarity and the nonlinearity in a graphene transistor, we demonstrated two types of quaternary modulation schemes: 4-ary amplitude-shift keying (4-ASK) and quadrature phase-shift keying (QPSK). Remarkably, 4-ASK and QPSK can be realized with just 1 and 2 all-graphene transistors, respectively, representing a drastic reduction in circuit complexity when compared with conventional digital modulators. In addition, the circuit is not only flexible but also highly transparent (~95% transmittance) owing to their all-graphene design with every component (channel, interconnects, load resistor, and source/drain/gate electrodes) fabricated from graphene films. Taken together, these results represent a significant step toward achieving a high speed communication system that can be monolithically integrated on a flexible and transparent platform.Comment: 29 pages, 8 figures, 1 tabl

Stretchable Dual-Capacitor Multi-Sensor for Touch-Curvature-Pressure-Strain Sensing

We introduce a new type of multi-functional capacitive sensor that can sense several different external stimuli. It is fabricated only with polydimethylsiloxane (PDMS) films and silver nanowire electrodes by using selective oxygen plasma treatment method without photolithography and etching processes. Differently from the conventional single-capacitor multi-functional sensors, our new multifunctional sensor is composed of two vertically-stacked capacitors (dual-capacitor). The unique dual-capacitor structure can detect the type and strength of external stimuli including curvature, pressure, strain, and touch with clear distinction, and it can also detect the surface-normal directionality of curvature, pressure, and touch. Meanwhile, the conventional single-capacitor sensor has ambiguity in distinguishing curvature and pressure and it can detect only the strength of external stimulus. The type, directionality, and strength of external stimulus can be determined based on the relative capacitance changes of the two stacked capacitors. Additionally, the logical flow reflected on a tree structure with its branches reaching the direction and strength of the corresponding external stimulus unambiguously is devised. This logical flow can be readily implemented in the sensor driving circuit if the dual-capacitor sensor is commercialized actually in the future

Multifunctional graphene woven fabrics

Tailoring and assembling graphene into functional macrostructures with well-defined configuration are key for many promising applications. We report on a graphene-based woven fabric (GWF) prepared by interlacing two sets of graphene micron-ribbons where the ribbons pass each other essentially at right angles. By using a woven copper mesh as the template, the GWF grown from chemical vapour deposition retains the network configuration of the copper mesh. Embedded into polymer matrices, it has significant flexibility and strength gains compared with CVD grown graphene films. The GWFs display both good dimensional stability in both the warp and the weft directions and the combination of film transparency and conductivity could be optimized by tuning the ribbon packing density. The GWF creates a platform to integrate a large variety of applications, e.g., composites, strain sensors and solar cells, by taking advantages of the special structure and properties of graphene