Active Matrix Array Research Articles

Monolithically integrated high-density vertical organic electrochemical transistor arrays and complementary circuits.

Organic electrochemical transistors (OECTs) can be used to create biosensors, wearable devices and neuromorphic systems. However, restrictions in the micro- and nanopatterning of organic semiconductors, as well as topological irregularities, often limit their use in monolithically integrated circuits. Here we show that the micropatterning of organic semiconductors by electron-beam exposure can be used to create high-density (up to around 7.2 million OECTs per cm2) and mechanically flexible vertical OECT arrays and circuits. The energetic electrons convert the semiconductor exposed area to an electronic insulator while retaining ionic conductivity and topological continuity with the redox-active unexposed areas essential for monolithic integration. The resulting p- and n-type vertical OECT active-matrix arrays exhibit transconductances of 0.08-1.7 S, transient times of less than 100 μs and stable switching properties of more than 100,000 cycles. We also fabricate vertically stacked complementary logic circuits, including NOT, NAND and NOR gates.

Active-Matrix Array Based on Thin-Film Transistors Using Emerging Materials for Application: From Lab to Industry

The active-matrix technology incorporates a transistor to exert precise control over each pixel within a pixel array, eliminating the issue of crosstalk between neighboring pixels that is prevalent in the passive-matrix approach. Consequently, the active-matrix method facilitates the realization of high-resolution arrays, and this inherent advantage has propelled its widespread adoption, not only in display applications but also in diverse sensor arrays from lab to industry. In this comprehensive review, we delve into instances of active-matrix arrays utilizing thin-film transistors (TFTs) that leverage emerging materials such as organic semiconductors, metal oxide semiconductors, two-dimensional materials, and carbon nanotubes (CNTs). Our examination encompasses a broad classification of active-matrix research into two main categories: (i) displays and (ii) sensors. We not only assess the performance of TFTs based on emerging materials within the active-matrix framework, but also explore the evolving trends and directions in active-matrix-based displays and sensors.

3차원 집적 유연 인쇄 전자: 집적 회로, 메모리, 센서

Printing technologies have received a lot of attention and expectations for producing flexible and wearable electronics. However, the low transistor density of the printed devices has been a major obstacle to commercialization. In this review, a three-dimensional (3D) integration of organic flexible and printed electronics is described. First, layout-to-bitmap conversion and design rules for printed transistors, arrays, and integrated circuits are introduced. Then, printed 3D transistors, digital integrated circuits, and memories are described. Finally, 3D integration of printed active-matrix arrays and sensors is highlighted. This approach is a breakthrough technology that not only reduces the area occupied by a single transistor, memory, and sensor, but also increases the efficiency of routing, effectively reducing the area of the entire devices. In addition, monolithic 3D integration through the printing can stack transistor, memory, and sensor by simply repeating the additive process.

Multimodal Characterization of Cardiac Organoids Using Integrations of Pressure-Sensitive Transistor Arrays with Three-Dimensional Liquid Metal Electrodes.

Herein, we present an unconventional method for multimodal characterization of three-dimensional cardiac organoids. This method can monitor and control the mechanophysiological parameters of organoids within a single device. In this method, local pressure distributions of human-induced pluripotent stem-cell-derived cardiac organoids are visualized spatiotemporally by an active-matrix array of pressure-sensitive transistors. This array is integrated with three-dimensional electrodes formed by the high-resolution printing of liquid metal. These liquid-metal electrodes are inserted inside an organoid to form the intraorganoid interface for simultaneous electrophysiological recording and stimulation. The low mechanical modulus and low impedance of the liquid-metal electrodes are compatible with organoids’ soft biological tissue, which enables stable electric pacing at low thresholds. In contrast to conventional electrophysiological methods, this measurement of a cardiac organoid’s beating pressures enabled simultaneous treatment of electrical therapeutics using a single device without any interference between the pressure signals and electrical pulses from pacing electrodes, even in wet organoid conditions.

In situ diagnosis and simultaneous treatment of cardiac diseases using a single-device platform

The in situ diagnosis of cardiac activities with simultaneous therapeutic electrical stimulation of the heart is key to preventing cardiac arrhythmia. Here, we present an unconventional single-device platform that enables in situ monitoring even in a wet condition and control of beating heart motions without interferences to the recording signal. This platform consists of the active-matrix array of pressure-sensitive transistors for detecting cardiac beatings, biocompatible, low-impedance electrodes for cardiac stimulations, and an alginate-based hydrogel adhesive for attaching this platform conformally to the epicardium. In contrast to conventional electrophysiological sensing using electrodes, the pressure-sensitive transistors measured mechanophysiological characteristics by monitoring the spatiotemporal distributions of cardiac pressures during heart beating motions. In vivo tests show mechanophysiological readings having good correlation with electrocardiography and negligible interference with the electrical artifacts caused during cardiac stimulations. This platform can therapeutically synchronize the rhythm of abnormal heartbeats through efficient pacing of cardiac arrhythmia.

Active-Matrix Pixelated-LED Control System for Automotive Headlamps

This paper presents a driving circuitry system for high-resolution, pixelated-LED automotive headlamps. The system consists of an array of pixel drivers, and a row/column driver suitable for an active-matrix array configuration with the individual dimming control capabilities on each pixelated-LED. An asynchronous serial communication protocol is introduced to minimize the number of data transmission interface signals between the row/column driver and pixel drivers. The proposed pixel driver is designed to drive each pixelated-LED with constant current and pulse width modulation (PWM). It contains a memory cell for dimming data, and a sample-and-hold driver stage to minimize the static power consumption of the pixel driver. The proposed system has been fabricated by using a 0.18-μm CMOS process. The test chip includes a 2 × 16 pixel array with an embedded row/column driver. The functional operation has been verified with an 8 × 16 LED array system prototype.

Printable inks and deformable electronic array devices.

Deformable printed electronic array devices are expected to revolutionize next-generation electronics. However, although remarkable technological advances in printable inks and deformable electronic array devices have recently been achieved, technical challenges remain to commercialize these technologies. In this review article a brief introduction to printing methods highlighting significant research studies on ink formation for conductors, semiconductors, and insulators is provided, and the structural design and successful printing strategies of deformable electronic array devices are described. Successful device demonstrations are presented in the applications of passive- and active-matrix array devices. Finally, perspectives and technological challenges to be achieved are pointed out to print practically available deformable devices.

3D Heterogeneous Device Arrays for Multiplexed Sensing Platforms Using Transfer of Perovskites.

Despite recent substantial advances in perovskite materials, their 3D integration capability for next-generation electronic devices is limited owing to their inherent vulnerability to heat and moisture with degradation of their remarkable optoelectronic properties during fabrication processing. Herein, a facile method to transfer the patterns of perovskites to planar or nonplanar surfaces using a removable polymer is reported. After fabricating perovskite devices on this removable polymer film, the conformal attachment of this film on target surfaces can place the entire devices on various substrates by removing this sacrificial film. This transfer method enables the formation of a perovskite image sensor array on a soft contact lens, and in vivo tests using rabbits demonstrate its wearability. Furthermore, 3D heterogeneous integration of a perovskite photodetector array with an active-matrix array of pressure-sensitive silicon transistors using this transfer method demonstrates the formation of a multiplexed sensing platform detecting distributions of light and tactile pressure simultaneously.

Mechanoluminescent, Air-Dielectric MoS2 Transistors as Active-Matrix Pressure Sensors for Wide Detection Ranges from Footsteps to Cellular Motions.

Tactile pressure sensors as flexible bioelectronic devices have been regarded as the key component for recently emerging applications in electronic skins, health-monitoring devices, or human-machine interfaces. However, their narrow range of sensible pressure and their difficulty in forming high integrations represent major limitations for various potential applications. Herein, we report fully integrated, active-matrix arrays of pressure-sensitive MoS2 transistors with mechanoluminescent layers and air dielectrics for wide detectable range from footsteps to cellular motions. The inclusion of mechanoluminescent materials as well as air spaces can increase the sensitivity significantly over entire pressure regimes. In addition, the high integration capability of these active-matrix sensory circuitries can enhance their spatial resolution to the level sufficient to analyze the pressure distribution in a single cardiomyocyte. We envision that these wide-range pressure sensors will provide a new strategy toward next-generation electronics at biomachine interfaces to monitor various mechanical and biological phenomena at single-cell resolution.

2D Dielectrophoresis using an active matrix array made by thin‐film‐transistor technology

New types of devices made using thin‐film‐transistor (TFT) technology were used in this article for dielectrophoresis purpose with microbeads, yeast cells, and HepG2 cells. That technology allows obtaining centimeter size transparent substrates covered with a large and dense array of 100 µm microelectrodes individually controllable. The purpose of these devices is the development of platforms for various applications on cells and cells culture, like manipulation, sensing, monitoring, or stimulation on the same device. Dielectrophoresis is one of the applications and is a key target for precise patterning and 2D displacement of cells on the device. In this article, 2D results of dielectrophoresis with microbeads and yeast cells and device programming are described. Then, application to mammal HepG2 liver cells shows the possibility of cells patterning with such devices. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Flexible IGZO TFT SPICE Model and Design of Active Strain-Compensation Circuits for Bendable Active Matrix Arrays

The detailed measurement and characterization of strain-induced performance variations in flexible InGaZnO thin-film transistors (IGZO TFTs) resulted in a SPICE TFT model able to simulate tensile and compressive bending. This model was used to evaluate a new concept, namely, the active compensation of strain-induced performance variations in pixel driving circuits for bendable active matrix arrays. The designed circuits can compensate the mobility and threshold voltage shifts in IGZO TFTs induced by bending. In a single TFT, a drain current of 1mA varies by $83~\mu \text{A}$ per percent of mechanical strain. The most effective compensation circuit design, comprising one additional TFT and two resistors, reduces the driving current variation to $1.1~\mu \text{A}$ per percent of strain. The compensation circuit requires no additional control signals and increases the power consumption by only $235~\mu \text{W}$ (corresponds to 4.7%). Finally, switching operation is possible for frequencies up to 200 kHz. This opens a way toward the fabrication of flexible displays with constant brightness even when bent.

A High-Performance Optical Memory Array Based on Inhomogeneity of Organic Semiconductors.

Organic optical memory devices keep attracting intensive interests for diverse optoelectronic applications including optical sensors and memories. Here, flexible nonvolatile optical memory devices are developed based on the bis[1]benzothieno[2,3-d;2',3'-d']naphtho[2,3-b;6,7-b']dithiophene (BBTNDT) organic field-effect transistors with charge trapping centers induced by the inhomogeneity (nanosprouts) of the organic thin film. The devices exhibit average mobility as high as 7.7 cm2 V-1 s-1 , photoresponsivity of 433 A W-1 , and long retention time for more than 6 h with a current ratio larger than 106 . Compared with the standard floating gate memory transistors, the BBTNDT devices can reduce the fabrication complexity, cost, and time. Based on the reasonable performance of the single device on a rigid substrate, the optical memory transistor is further scaled up to a 16 × 16 active matrix array on a flexible substrate with operating voltage less than 3 V, and it is used to map out 2D optical images. The findings reveal the potentials of utilizing [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivatives as organic semiconductors for high-performance optical memory transistors with a facile structure. A detailed study on the charge trapping mechanism in the derivatives of BTBT materials is also provided, which is closely related to the nanosprouts formed inside the organic active layer.

Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges

Integrated electronic circuitries with pressure sensors have been extensively researched as a key component for emerging electronics applications such as electronic skins and health-monitoring devices. Although existing pressure sensors display high sensitivities, they can only be used for specific purposes due to the narrow range of detectable pressure (under tens of kPa) and the difficulty of forming highly integrated arrays. However, it is essential to develop tactile pressure sensors with a wide pressure range in order to use them for diverse application areas including medical diagnosis, robotics or automotive electronics. Here we report an unconventional approach for fabricating fully integrated active-matrix arrays of pressure-sensitive graphene transistors with air-dielectric layers simply formed by folding two opposing panels. Furthermore, this realizes a wide tactile pressure sensing range from 250 Pa to ∼3 MPa. Additionally, fabrication of pressure sensor arrays and transparent pressure sensors are demonstrated, suggesting their substantial promise as next-generation electronics.

High performance organic transistor active-matrix driver developed on paper substrate.

The fabrication of electronic circuits on unconventional substrates largely broadens their application areas. For example, green electronics achieved through utilization of biodegradable or recyclable substrates, can mitigate the solid waste problems that arise at the end of their lifespan. Here, we combine screen-printing, high precision laser drilling and thermal evaporation, to fabricate organic field effect transistor (OFET) active-matrix (AM) arrays onto standard printer paper. The devices show a mobility and on/off ratio as high as 0.56 cm2V−1s−1 and 109 respectively. Small electrode overlap gives rise to a cut-off frequency of 39 kHz, which supports that our AM array is suitable for novel practical applications. We demonstrate an 8 × 8 AM light emitting diode (LED) driver with programmable scanning and information display functions. The AM array structure has excellent potential for scaling up.

Application of Flexible OLED Display Technology for Electro-Optical Stimulation and/or Silencing of Neural Activity

This paper presents a new biophotonic application for large-area, high-resolution, flexible organic light-emitting diode (OLED) display technology currently used to manufacture low-cost color flexible displays on plastic substrates. The new concept uses a fully addressable high resolution flexible OLED pixel array on a thin, mechanically compliant biocompatible plastic substrate to selectively stimulate and/or silence small groups of neurons on either the cortical surface or, alternatively, within the deep brain. Optical measurements from a 455 nm blue flexible OLED test structure demonstrated the ability to emit 1 mW/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of instantaneous light intensity using a 13 V, 20 Hz pulse, which meets the minimum reported intensity at ~ 450 nm to induce optical stimulation in genetically modified neural tissue. Biocompatibility was successfully demonstrated by the ability to grow human epithelial cells on the surface of a full TFT process flow plastic flexible display substrate. Additionally, a new active matrix array display architecture was designed to support pulsed mode OLED operation. These preliminary results demonstrate the initial viability of extending flexible plastic substrate OLED display technology to the development of large-area, high-resolution emissive active matrix arrays for chronic optogenetic applications.

P‐10: Oxide TFT Fabrication by Nano‐Rheology Printing for Display Application

AbstractA nano‐rheology printing method was used to fabricate oxide thin‐film transistors (TFTs). This method utilizes the rheological properties of oxide precursor gels that are imprinted at an elevated temperature. TFTs designed for an active matrix array were successfully developed with high alignment accuracy, and the operation of its transistors was confirmed.

Fabrication and performance of a 64 × 5 element 1.5D active matrix array transducer for medical imaging

Compared to 1D phased array probes with a fixed focus in elevation, multi-row arrays can significantly improved the slice thickness throughout image by expanding aperture and dynamic focusing in elevation. This paper describes the design and measurement of a 64×5 element 1.5D ultrasonic transducer that enables dynamic focusing and apodization in the elevation direction. We manufactured a transducer with an aperture size of 24mm×16mm using a widely used piezoelectric ceramic (PZT-5H) as the piezoelectric vibrator. The measured center frequency and −6dB fractional bandwidth of the 1.5D transducer were 3MHz and 79%, respectively. A two-way insertion loss of −58dB was obtained at the average center frequency. We carried out a sound field simulation and measured the actual transmitting (one-way) sound field data by using a hydrophone. In this way the sound beam profile in elevation direction was obtained, showing the −6dB slice thickness measured was about 2mm throughout the whole range of interest (from near to far field). This provided a much greater focal depth and much better imaging resolution in the elevation direction than can be achieved by using 1D probe.

Design Considerations of an Amorphous Silicon Demultiplexer

This paper deals with the optimization of amorphous silicon gate driver circuits for active matrix array applications. It is based on static and dynamic models for hydrogenated amorphous silicon thin-film transistor operations. The models are extended to investigate amorphous silicon demultiplexer functionality. The proposed circuit is an improvement of an earlier published architecture. The circuit performance is discussed and demonstrated to be more reliable. It is shown that the response of the demultiplexer in terms of charging/discharging time is improved, the feed-through is reduced and the optimization of the circuit response is a reliable trade-off between stability and speed. This may contribute to overcome amorphous silicon technology shortcomings. DOI: http://dx.doi.org/10.5755/j01.eee.19.8.5397

SU‐C‐220‐05: Investigation of Novel, Focused, Segmented Scintillator Geometries for High DQE Megavoltage Active Matrix Imagers

Purpose: Megavoltage active matrix, flat‐panel imagers (AMFPIs) have become ubiquitous in modern radiotherapy environments. However, their imaging performance is severely constrained by very low DQE (∼1%). While significant performance improvements have been demonstrated through introduction of thick, precision‐machined matrices of optically‐ isolated crystalline detector elements, the benefits are constrained by geometric beam divergence. It is therefore of interest to examine the potential performance of focused, segmented scintillator geometries specifically designed to circumvent DQE losses caused by divergence. Methods: The potential detection efficiency and DQE performance of hypothetical detector geometries was examined by means of Monte Carlo simulation of radiation transport. The choice of geometries examined was governed by considerations including: maximization of DQE through geometrically focused elements; manufacturability of the focused matrix; and feasibility of the underlying active matrix of indirect detection imaging pixels. Calculations were performed for a variety of candidate scintillator materials up to 6 cm thick. Results: The most promising detector geometries identified in the study consisted of matrices of scintillator elements located along the surface of a plane, as well as along the surface of a spherical cap. For cap detectors, elements arranged in a warped‐rectangular matrix, concentric rings, and a geodesic are of interest — and geometries employing a single element shape are particularly favored, although at the cost of fill factor. While focused planar detectors would be compatible with conventional AMFPI arrays, cap detectors would involve active matrix arrays in the shape of an approximately spherically curved surface created through cut and bend techniques. Overall, depending upon detector geometry, scintillator material and scintillator thickness, calculations indicate that DQE improvements of up to a factor of ∼50 are conceivable. Conclusions: This initial theoretical study suggests that the promise of very high DQE performance from thick, segmented scintillators could be realized through novel, focused detector geometries. Work supported by NIH grant R01‐CA051397

Modelling the imaging performance and low contrast detectability in digital mammography

A digital x-ray mammography is a modern method for the early detection of breast cancer. The quality of a mammography image depends on various factors, the detector structure and performance being of primary importance. The aim of this work was to develop an analytical model simulating the imaging performance of a new commercially available digital mammography detector. This was achieved within the framework of the linear cascaded systems (LCS) theory. System analysis has allowed the estimation of important image quality metrics such as the Modulation Transfer Function (MTF), the Noise Power Spectrum (NPS) and the Detective Quantum Efficiency (DQE). The detector was an indirect detection system consisting of a large area, 100μm thick, CsI:TI scintillator coupled to an active matrix array of amorphous silicon (a-Si:H) photodiodes combined with thin film transistors (TFT). Pixel size was 100μm, while the active pixel dimension was 70μm. MTF and DQE data were calculated for air kerma conditions of 25, 53, 67 μGy using a 28 kVp Mo-Mo x-ray spectrum. The theoretical results were compared with published experimental data. The deviation between the theoretical and experimental MTF curves was less than 4%, while the DQE differences were found at an acceptable level. The model was also used to estimate system's capability to detect low contrast objects in the breast. It was estimated that, in the breast gland, low contrast structures larger than 1.4mm can be adequately identified by the above system.