Thin, ultra-flexible devices that can be manufactured in a process that covers a large area will be essential to realizing low-cost, wearable electronic applications including foldable displays and medical sensors. The printing technology will be instrumental in fabricating these novel electronic devices and circuits; however, attaining fully printed devices on ultra-flexible films in large areas has typically been a challenge. Here we report on fully printed organic thin-film transistor devices and circuits fabricated on 1-mm-thick parylene-C films with high field-effect mobility (1.0 cm 2 V À 1 s À 1 ) and fast operating speeds (about 1 ms) at low operating voltages. The devices were extremely light (2 g m À 2 ) and exhibited excellent mechanical stability. The devices remained operational even under 50% compressive strain without significant changes in their performance. These results represent significant progress in the fabrication of fully printed organic thin-film transistor devices and circuits for use in unobtrusive electronic applications such as wearable sensors.

, takeo Shiba, takao nishikawa & Shizuo tokito * facile fabrication and high ambient stability are strongly desired for the practical application of temperautre sensor in real-time wearable healthcare. Herein, a fully printed flexible temperature sensor based on cross-linked poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was developed. By introducing the crosslinker of (3-glycidyloxypropyl)trimethoxysilane (GOPS) and the fluorinated polymer passivation (CYTOP), significant enhancements in humidity stability and temperature sensitivity of PEDOT:PSS based film were achieved. The prepared sensor exhibited excellent stability in environmental humidity ranged from 30% RH to 80% RH, and high sensitivity of −0.77% °C −1 for temperature sensing between 25 °C and 50 °C. Moreover, a wireless temperature sensing platform was obtained by integrating the printed sensor to a printed flexible hybrid circuit, which performed a stable real-time healthcare monitoring. Body temperature is an essential vital parameter reflecting the physiological activities. Monitoring of body temperature provides insight into human health conditions, such as cardiovascular condition, wound healing, pulmonological diagnostics, and syndromes prediction 1-4. Therefore, the flexible temperature sensor is highly desired to realize personal healthcare devices, which enable real-time monitoring of an individual's health state 5,6. Many efforts have been made to develop flexible temperature sensors, which mainly contain three types: pyroelectric detectors 7,8 , resistive temperature detectors (RTDs) 9,10 , and thermistors 11. Among them, the thermistor which relies on the thermo-resistive effect of sensing material is widely used, due to its simple device structure, fast response, and wide sensing range 12,13. Various thermistor materials have been developed and investigated, including composites of conductive filler with polymer, and temperature sensing conductive materials such as silver nanowire (AgNW) 14,15 , carbon nanotubes (CNTs) 16 , reduced graphene oxide (rGO) 17,18 , and poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) 19,20. However, most of these studies focused on improving the sensitivity and mechanical performance of temperature sensors, while their ambient stability, especially humidity stability, has rarely been considered. Additionally, the development of wearable temperature sensors via simple fabrication still a big challenge. Since the use of wearable devices inevitably exposed to ambient humidity, it is of great interest to develop a facile fabricated humidity-resistant temperature sensor. In contrast to its counterparts, PEDOT:PSS has been proven as a promising candidate for the wearable temperature sensor, not only owing to its outstanding mechanical properties and turntable electrical characteristics, but also the superior in simple, patternable, and high reproducible fabrication, such as printing 21,22. However, as a water-soluble polymer, the resistance of PEDOT:PSS also be easily affecte...

The field-effect mobility of a liquid-crystalline semiconducting polymer, poly(2,5-bis(3-hexadecylthiophene-2-yl)thieno[3,2-b]thiophene) (PB16TTT), has depended significantly on the surface energies of self-assembled monolayers (SAMs) formed on insulating layers. Using a SAM with fluoroalkyl groups, with a low surface energy of 13.3 mN/m, the mobility of PB16TTT reached as high as 1 cm2/V s. These results indicate that an edge-on orientation of the polymer chains progresses more favorably on the surfaces with low surface energies via the liquid-crystalline phase.

Printing fully solution-processed organic electronic devices may potentially revolutionize production of flexible electronics for various applications. However, difficulties in forming thin, flat, uniform films through printing techniques have been responsible for poor device performance and low yields. Here, we report on fully solution-processed organic thin-film transistor (TFT) arrays with greatly improved performance and yields, achieved by layering solution-processable materials such as silver nanoparticle inks, organic semiconductors, and insulating polymers on thin plastic films. A treatment layer improves carrier injection between the source/drain electrodes and the semiconducting layer and dramatically reduces contact resistance. Furthermore, an organic semiconductor with large-crystal grains results in TFT devices with shorter channel lengths and higher field-effect mobilities. We obtained mobilities of over 1.2 cm2 V−1 s−1 in TFT devices with channel lengths shorter than 20 μm. By combining these fabrication techniques, we built highly uniform organic TFT arrays with average mobility levels as high as 0.80 cm2 V−1 s−1 and ideal threshold voltages of 0 V. These results represent major progress in the fabrication of fully solution-processed organic TFT device arrays.

Ultrathin electronic circuits that can be manufactured by using conventional printing technologies are key elements necessary to realize wearable health sensors and next-generation flexible electronic devices. Due to their low level of power consumption, complementary (CMOS) circuits using both types of semiconductors can be easily employed in wireless devices. Here, we describe ultrathin CMOS logic circuits, for which not only the source/drain electrodes but also the semiconductor layers were printed. Both p-type and n-type organic thin film transistor devices were employed in a D-flip flop circuit in the newly developed stacked structure and exhibited excellent electrical characteristics, including good carrier mobilities of 0.34 and 0.21 cm2 V−1 sec−1, and threshold voltages of nearly 0 V with low operating voltages. These printed organic CMOS D-flip flop circuits exhibit operating frequencies of 75 Hz and demonstrate great potential for flexible and printed electronics technology, particularly for wearable sensor applications with wireless connectivity.