With the emergence of human interface technology, the development of new applications based on stretchable electronics such as conformal biosensors and rollable displays are required. However, the difficulty in developing semiconducting materials with high stretchability required for such applications has restricted the range of applications of stretchable electronics. Here, we present stretchable, printable, and transparent transistors composed of monolithically patterned graphene films. This material offers excellent mechanical, electrical, and optical properties, capable of use as semiconducting channels as well as the source/drain electrodes. Such monolithic graphene transistors show hole and electron mobilities of 1188 ± 136 and 422 ± 52 cm(2)/(V s), respectively, with stable operation at stretching up to 5% even after 1000 or more cycles.

As an atomically thin material with low surface energy, graphene is an excellent candidate for reducing adhesion and friction when coated on various surfaces. Here, we demonstrate the superior adhesion and frictional characteristics of graphene films which were grown on Cu and Ni metal catalysts by chemical vapor deposition and transferred onto the SiO(2)/Si substrate. The graphene films effectively reduced the adhesion and friction forces, and multilayer graphene films that were a few nanometers thick had low coefficients of friction comparable to that of bulk graphite.

A high-performance low-voltage graphene field-effect transistor (FET) array was fabricated on a flexible polymer substrate using solution-processable, high-capacitance ion gel gate dielectrics. The high capacitance of the ion gel, which originated from the formation of an electric double layer under the application of a gate voltage, yielded a high on-current and low voltage operation below 3 V. The graphene FETs fabricated on the plastic substrates showed a hole and electron mobility of 203 ( 57 and 91 ( 50 cm 2 /(V · s), respectively, at a drain bias of -1 V. Moreover, ion gel gated graphene FETs on the plastic substrates exhibited remarkably good mechanical flexibility. This method represents a significant step in the application of graphene to flexible and stretchable electronics.KEYWORDS Graphene, ion gel, flexible electronics, field effect transistor, low-voltage operation G raphene has attracted attention for a range of electronic applications, such as displays, solar cells, and sensors owing to its exceptional electronic and optoelectronic properties. [1][2][3][4] Recent developments in the large area synthesis of high-quality graphene films has created new pathways for the application of graphene to highfrequency devices. [5][6][7] There are two general approaches for fabricating graphene devices over large areas: one that employs graphene grown directly on SiC wafers 8 and another that transfers graphene films synthesized on metal layers to other useful substrates. 9,10 The latter approach is attractive because of the special attributes of graphene films, such as flexible/stretchable device fabrication and the possibility of fabrication over large areas. This approach has produced device arrays on rigid insulating wafers and is scalable to a wafer size. 9 Although several studies have reported graphene field-effect transistors (FETs) on a plastic substrate, 11 there are still significant challenges in fabricating large scale, flexible graphene FETs.Exploring graphene for flexible electronics requires solution-processable, high-capacitance gate dielectrics that can form at low temperature with a good interface with the graphene films transferred to plastic sheets. Although several high-k inorganic dielectrics, such as HfO 2 , Al 2 O 3 , and ZrO 2 , have been applied to the fabrication of graphene FETs, they cannot be available for flexible devices based on plastic substrates due to their high growth temperature. 8,12,13 This paper reports a promising method for fabricating a low-voltage operating graphene FET array on plastic substrates using an ion gel as the gate dielectric. The ion gel consists of a room temperature ionic liquid and gelating triblock copolymer, which exhibits an extremely high capacitance of 5.17 µF/cm 2 . [14][15][16] The high capacitance of the ion gel gate dielectrics in the graphene FETs provides both high on-current and low voltage operation. Furthermore, ion gel gated graphene FETs fabricated on plastic substrates show very good mechanical flexibility.Before the fabric...