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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A push-mode piezo inkjet equivalent circuit model enhanced by diaphragm displacement measurements

This paper reports on ways to better predict droplet ejection velocity of push-mode piezo inkjet technology by upgrading the conventional equivalent circuit model. Calculation results from the traditional model imply that the driving pulse width conditions without ink ejection only periodically exist in the pull-push piezo driving mode. However, ink ejection is actually observed under any pulse width condition. The displacement of the diaphragm with respect to the piezo element input voltage waveform was measured with a highly accurate capacitive displacement gauge to correct for the difference between the actual measurements and calculations. The equivalent circuit model was then modified so that the measured diaphragm residual oscillations could be expressed. We presumed that an actual inkjet printhead contains an effective spring oscillation component, effective actuator mass, and damping component larger than that used in conventional equivalent circuit model calculations. We demonstrated that the difference between the calculated results and actual measurements could be reduced. Modifications to equivalent circuit model are based on the addition of an effective mechanical spring oscillation component having the same function as the ink chamber compliance, an increase in actuator inertance corresponding to the mass of the actuator, and an effective resistance element expressing a damped oscillation

Mechanical Fatigue Behavior of Flexible Printed Organic Thin-Film Transistors under Applied Strain

We report on the mechanical fatigue behavior of printed, organic, thin-film transistors (OTFTs) based on a polymer semiconductor, investigated by repeatedly applying strain to the flexible OTFT devices and assessing their electrical characteristics after 60,000 bending cycles. As part of our investigation, we established that the rates of reduction in source/drain currents in the OTFT device depended on bending directions. Our improved understanding of the mechanical fatigue behavior of the flexible printed OTFT devices provides valuable insights into their employment in practical flexible electronics applications

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

3D Organic Transistors and Circuits Fabricated by Inkjet-Printing

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3D Complementary Organic Field-Effect Transistors and Logic Circuits Fabricated by Inkjet-Printing

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A Flexible 3D Organic Preamplifier for a Lactate Sensor

Organic transistors are promising platforms for wearable biosensors. However, the strategies to improve signal amplification have yet to be determined, particularly regarding biosensors that generate very weak signals. In this study, an organic voltage amplifier is presented for a lactate sensor on flexible plastic foil. The preamplifier is based on a 3D complementary inverter, which is achieved by vertically stacking complementary transistors with a shared gate between them. The shared gate is extended and functionalized with a lactate oxidase enzyme to detect lactate. The sensing device successfully detects the lactate concentration in the human sweat range (20-60 mm) with high sensitivity (6.82 mV mm(-1)) due to high gain of its amplification. The 3D integration process is cost-effective as it is solution-processable and doubles the number of transistors per unit area. The device presented in this study would pave the way for the development of high-gain noninvasive sweat lactate sensors that can be wearable