Printed 5-V organic operational amplifiers for various signal processing

The important concept of printable functional materials is about to cause a paradigm shift that we will be able to fabricate electronic devices by printing methods in air at room temperature. One of the promising applications of the printed electronics is a disposable electronic patch sensing system which can monitor the health conditions without any restraint. Operational amplifiers (OPAs) are an essential component for such sensing system, since an OPA enables a wide variety of signal processing. Here we demonstrate printed OPAs based on complementary organic semiconductor technology. They can be operated with a standard safe power source of 5 V with a minimal power consumption of 150 nW, and used as amplifiers, a variety of mathematical operators, signal converters, and oscillators. The printed micropower organic OPAs with the low voltage operation and the high versatility will open up the disposable electronic patch sensing system in near future

Thermal Stability of a Fully Printed Ultra-Thin Organic Pre-Amplifier Circuit Meant for on-Skin applications

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Temperature Correction of Printed Na+, K+, and pH Sensors with PEDOT:PSS‐Based Thermistors toward Wearable Sweat Sensing

Abstract Temperature correction for sensors is a critical aspect of ensuring accurate measurements in wearable devices, because skin and sweat temperatures vary between 20 and 40 °C depending on individual and time. Here, this study reports on the temperature dependence and correction techniques of printed Na+, K+, and pH sensors toward wearable applications. The ion sensor array is fabricated using a cost‐effective printing method. To enable temperature correction, a printed thermistor of crosslinked poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is monolithically integrated with the ion sensor array on a flexible plastic substrate. Temperature dependence of the potential response of the printed ion sensors exhibits a linear behavior with a slope of 1–2 mV °C−1 in the physiological skin temperature range of 20–40 °C. Applying temperature correction to the ion sensors, the maximum relative errors are reduced from 60% to 7.8% for the Na+ sensors and from 76% to 14.6% for the K+ sensors, while the maximum absolute error is reduced from 0.88 to 0.19 for the pH sensors, indicating the critical importance of temperature correction as a technology for wearable printed ion sensors

Detection of 1,5-anhydroglucitol as a Biomarker for Diabetes Using an Organic Field-Effect Transistor-Based Biosensor

Sensor devices that can be fabricated on a flexible plastic film produced at a low cost using inkjet-printing technology are suitable for point-of-care applications. An organic field-effect transistor (OFET)-based biosensor can function as a potentiometric electrochemical sensor. To investigate the usefulness of an OFET-based biosensor, we demonstrated the detection of 1,5-anhydroglucitol (1,5-AG) and glucose, which are monosaccharides used as biomarkers of diabetes. An OFET-based biosensor combined with a Prussian blue (PB) electrode, modified with glucose oxidase (GOx) or pyranose oxidase (POx), was utilized for the detection of the monosaccharides. When the GOx- or POx-PB electrode was immersed in glucose solution at the determined concentration, shifts in the low-voltage direction of transfer characteristic curves of the OFET were observed to be dependent on the glucose concentrations in the range of 0–10 mM. For 1,5-AG, the curve shifts were observed only with the POx-PB electrode. Detection of glucose and 1,5-AG was achieved in a substrate-specific manner of the enzymes on the printed OFET-biosensor. Although further improvements are required in the detection concentration range, the plastic-filmOFET-biosensors will enable the measurement of not only diabetes biomarkers but also various other biomarkers

Charge Carrier Distribution in Low-Voltage Dual-Gate Organic Thin-Film Transistors

Dual-gate organic thin-film transistors (DGOTFTs), which exhibit better electrical properties, in terms of on-current and subthreshold slope than those of single-gate organic thin-film transistors (OTFTs) are promising devices for high-performance and robust organic electronics. Electrical behaviors of high-voltage (>10 V) DGOTFTs have been studied: however, the performance analysis in low-voltage DGOTFTs has not been reported because fabrication of low-voltage DGOTFTs is generally challenging. In this study, we successfully fabricated low-voltage (<5 V) DGOTFTs by employing thin parylene film as gate dielectrics and visualized the charge carrier distributions in low-voltage DGOTFTs by a simulation that is based on finite element method (FEM). The simulation results indicated that the dual-gate system produces a dual-channel and has excellent control of charge carrier density in the organic semiconducting layer, which leads to the better switching characteristics than the single-gate devices

3D integration of printed organic dual-gate FETs on a flexible substrate

The direct printing of organic thin-film transistors(TFTs) gives us a facile and fast route to fabrication of freeform electronicapplications on a flexible substrate. However, despite the significantimprovement in the performances of organic semiconductors, electronics industrystill has not adopted the printed organic TFTs for manufacturing electronic applications.The low resolution, large feature size, and variation of inkjet printing havelimited the implementation of organic integrated circuits with reasonabletransistor densities and uniformity. To overcome these problems, we have developeda robust inkjet design rule optimized for high-yield circuit patterning, and fabricatea three-dimensional (3D) printed dual-gate (DG) organic TFT where n- and p-typeTFTs are stacked in transistor-on-transistor manner halving the transistor footprint. In this work, all the functional layers including electrodes andsemiconductors are fully printed except a parylene dielectric that is formed bychemical vapor deposition. The design rule has been developed via a systematic study on the influenceof inkjet printing parameters such as substrate temperature, drop spacing) on theminimum width, smoothness, and reproducibility of vertically or horizontally printedmetal lines. The stacked DG TFTs showed average carrier mobilities of around 0.2and 0.7 cm2V-1s-1 for the n-type and p-type, respectively,showing exceptional uniformity and long-term stability at 5 V operation voltage.We successfully demonstrated 7-stage ring-oscillator on a flexible PEN film withthe maximum frequency of 200 Hz and a gate delay of 340 ms. Our 3D printing approach providesa path for achieving high transistor density, high yield, high uniformity, andlong-term stability, which are critical for the realization of printed organic electronicsapplications.1

Three-dimensional monolithic integration in flexible printed organic transistors

The scalability of printable integrated circuits is lagging far behind that of conventional silicon-based technologies. Here, Kwon et al. show a three-dimensional integration approach by stacking printeddual-gate organic transistors on plastic foils with a density of 60 transistors per centimeter square

3D integration of printed organic dual-gate FETs on a flexible substrate

The direct printing of organic thin-film transistors(TFTs) gives us a facile and fast route to fabrication of freeform electronicapplications on a flexible substrate. However, despite the significantimprovement in the performances of organic semiconductors, electronics industrystill has not adopted the printed organic TFTs for manufacturing electronic applications.The low resolution, large feature size, and variation of inkjet printing havelimited the implementation of organic integrated circuits with reasonabletransistor densities and uniformity. To overcome these problems, we have developeda robust inkjet design rule optimized for high-yield circuit patterning, and fabricatea three-dimensional (3D) printed dual-gate (DG) organic TFT where n- and p-typeTFTs are stacked in transistor-on-transistor manner halving the transistor footprint. In this work, all the functional layers including electrodes andsemiconductors are fully printed except a parylene dielectric that is formed bychemical vapor deposition. The design rule has been developed via a systematic study on the influenceof inkjet printing parameters such as substrate temperature, drop spacing) on theminimum width, smoothness, and reproducibility of vertically or horizontally printedmetal lines. The stacked DG TFTs showed average carrier mobilities of around 0.2and 0.7 cm2V-1s-1 for the n-type and p-type, respectively,showing exceptional uniformity and long-term stability at 5 V operation voltage.We successfully demonstrated 7-stage ring-oscillator on a flexible PEN film withthe maximum frequency of 200 Hz and a gate delay of 340 ms. Our 3D printing approach providesa path for achieving high transistor density, high yield, high uniformity, andlong-term stability, which are critical for the realization of printed organic electronicsapplications.

Printed Organic Complementary Inverter with Single SAM Process Using a p-type D-A Polymer Semiconductor

The demonstration of the complementary integrated circuit using printing processes is indispensable for realizing electronic devices using organic thin film transistors. Although complementary integrated circuits have advantages such as low power consumption and a wide output voltage range, complementary integrated circuits fabricated by the printing method have problems regarding driving voltage and performance. Studies on fabrication processes of electronic circuits for printing technology, including optimization and simplification, are also important research topics. In this study, the fabrication process of the printed complementary integrated circuit was simplified by applying a p-type donor-acceptor (D-A) polymer semiconductor, which is not strongly affected by the electrode work function. An inverter circuit and the ring oscillator circuit were demonstrated using this process. The fabricated ring oscillator array showed excellent performance, with low voltage operation and low performance variation