High-Performance Solid-State Supercapacitors Fabricated by Pencil Drawing and Polypyrrole Depositing on Paper Substrate

A solid-state powerful supercapacitor(SC) is fabricated with a substrate of Xerox paper. Its current collector based on a foldable electronic circuit is developed by simply pencil drawing. Thin graphite sheets on paper provide effective channels for electron transmission with a low resistance of 95 X sq-1. The conductive organic material of polypyrrole coated on thin graphite sheets acts as the electrode material of the device. The as-fabricated SC exhibits a high specific capacitance of 52.9 F cm-3at a scan rate of 1 m V s-1. An energy storage unit fabricated by three full-charged series SCs can drive a commercial light-emitting diode robustly. This work demonstrated a simple, versatile and costeffective method for paper-based devices.

Feature-preserving color pencil drawings from photographs

Color pencil drawing is well-loved due to its rich expressiveness.This paper proposes an approach for generating feature-preserving color pencil drawings from photographs.To mimic the tonal style of color pencil drawings,which are much lighter and have relatively lower saturation than photographs,we devise a lightness enhancement mapping and a saturation reduction mapping.The lightness mapping is a monotonically decreasing derivative function,which not only increases lightness but also preserves input photograph features.Color saturation is usually related to lightness,so we suppress the saturation dependent on lightness to yield a harmonious tone.Finally,two extremum operators are provided to generate a foreground-aware outline map in which the colors of the generated contours and the foreground object are consistent.Comprehensive experiments show that color pencil drawings generated by our method surpass existing methods in tone capture and feature preservation.

Paper-based all-solid-state flexible asymmetric micro-supercapacitors fabricated by a simple pencil drawing methodology

Flexible micro-scale energy storage devices as the key component to power the flexible miniaturized electronic devices are attracting extensive attention. In this study, interdigitated asymmetric all-solidstate flexible micro-supercapacitors（MSCs） were fabricated by a simple pencil drawing process followed by electrodepositing MnO_2 on one of the as-drawn graphite electrode as anode and the other as cathode.The as-prepared electrodes showed high areal specific capacitance of 220 μF/cm^2 at 2.5 μA/cm^2. The energy density and the corresponding power density of the resultant asymmetrical flexible MSCs were up to 110 μWh/cm^2 and 1.2 μW/cm^2, respectively. Furthermore, excellent cycling performance（91% retention of capacity after 1000 cycles） was achieved. The resultant devices also exhibited good electrochemical stability under bending conditions, demonstrating superior flexibility. This study provides a simple yet efficient methodology for designing and fabricating flexible supercapacitors applicable for portable and wearable electronics.