Large-area (64 × 64 array) inkjet-printed high-performance metal oxide bilayer heterojunction thin film transistors and n-metal-oxide-semiconductor (NMOS) inverters

It is a big challenge to construct large-scale,high-resolution and high-performance inkjet-printed metal oxide thin film transistor (TFT) arrays with independent gates for the new printed displays.Here,a self-confined inkjet printing technology has been developed to construct large-area (64 × 64 array),high-resolution and high-performance metal oxide bilayer (In2O3/IGZO) heterojunctionTFTs with independent bottom gates on transparent glass substrates.Inkjet printing In2O3 dot arrays with the diameters from 55 to 70 μm and the thickness of ～10 nm were firstly deposited on UV/ozone treated AIOx dielectric layers,and then IGZO dots were selectively printed on the top of In2O3 dots by self-confined technology to form In2O3/IGZO heterojunction channels.When the inkjet-printed IO layers treated by UV/ozone for more than 30 min or oxygen plasma for 5 min prior to print IGZO thin films,the mobility of the resulting printed In2O3/IGZO heterojunction TFTs are correspondingly enhanced to be 18.80 and 28.44 cm2 V-1 s-1 with excellent on/off ratios (＞108) and negligible hysteresis.Furthermore,the printed N-Metal-Oxide-Semiconductor (NMOS) inverter consisted of an In2O3/IGZO TFT and an IGZO TFT has been demonstrated,which show excellent performance with the voltage gain up to 112.The strategy demonstrated here can be considered as general approaches to realize a new generation of high-performance printed logic gates,circuits and display driving circuits.     

High-resolution inkjet-printed organic thin film transistor array with commercially applicable source-drain electrode process

High-resolution inkjet printing of an organic thin film transistor (OTFT) array for mass-production is still regarded as an immature technology due to the difficulty in controlling the dimension of pattern and registry with other layers in commercial large-scale substrates. Especially, in the case of on organic gate insulator (OGI) in an inkjet-printed OTFT array, it is impossible to use plasma pre-treatment of the OGI for the hydrophobicity required for high-resolution inkjet printing of an organic semiconductor (OSC) due to its non-selectivity between organic layers, both inside and outside the channel area. A novel and commercially applicable process of the source-drain (SD) electrode prior to inkjet printing of the OSC in the bottom contact structure not only allowed a selective plasma treatment for high-resolution inkjet printing of OSC on OGI without the extra photolithographic process, but also protected the channel interface from the harmful outcomes of wet or plasma processes. This method enabled uniform electrical characteristics of more than 300 thousand pixels of an OTFT array for a backplane. Based on these results, a 5.7 inch electrophoretic display (EPD), with a high resolution of 140 dots per inch (DPI), on a plastic substrate was successfully demonstrated.     

Demonstration of inkjet-printed silver nanoparticle microstrip lines on alumina for RF power modules

The paper shows the application of direct inkjet printing on alumina for fast-prototyping of high frequency circuits, adopting inks based on polymer–silver nanocomposite. Modeling, design, fabrication and experimental characterization of different microwave testing structures is presented and discussed. The integration of soldered surface mount devices and ground connections through wrap-around is successfully exploited. A 4 W power amplifier operating in the 0.7–1 GHz band (35% fractional bandwidth), is designed, fabricated and characterized, demonstrating the feasibility of the adopted approach.     

Inkjet deposition of a hole-transporting small molecule to realize a hybrid solution-evaporation green top-emitting OLED

The QUPD molecule has been deposited by inkjet printing as a hole-transport layer in top-emitting green OLEDs. A systematic study of the QUPD-based ink formulation has been done and different solvent mixtures have been investigated, in order to find the best composition (QUPD in toluene/IPA/anisole, 8/1/1 v/v/v) leading to the best film forming properties. Spin-coated PEDOT-PSS has been used as hole injecting layer. Subsequent layers have been deposited by vacuum sublimation. The resulting hybrid, solution-sublimation, OLEDs have been encapsulated by atomic layer deposition using Al₂O₃ material. In order to overcome the issue related to the thickness control of the organic layers deposited from solution, second order cavity length OLEDs have been fabricated by modifying the n-doped electron transport layer thickness. In that case, the relative OLED efficiency variation (10.5%) due to the thickness variation is far less compared to first order cavity length (34%) allowing a better reproducibility of the OLED fabrication. In the end, high efficiency (18 lm/W) green OLEDs of two different sizes, 0.44 cm² and 4 cm², have been fabricated, using an inkjet printed QUPD layer as hole transporting layer.     

Control of on-demand nanoliter drop volume and jetting velocity in piezoelectric inkjet printing

Consistent dosages placed with high accuracy onto the substrate are critical for drop-on-demand (DoD) inkjet printing to be adopted in additive manufacturing and device characterization. Practically, the consistency of drop volume and drop jetting velocity is subject to process uncertainties, such as fluctuations of applied pressure and variations in printheads, for which open-loop approaches are unable to compensate. In this work, a stochastic process model of the relation between two control parameters of a firing waveform and two output features, drop volume and drop jetting velocity, is developed from standard printhead calibration data. An image-based control strategy based on a projection-based one-step-ahead Kalman estimator for model parameters estimation is proposed to regulate the drop volume and the drop jetting velocity. The effectiveness of the proposed control strategy is experimentally validated for three inks with broad properties. By including input boundary layers, an order of magnitude improvement in reducing drop volume and jetting velocity variations is also experimentally demonstrated.     

利用喷墨打印技术制备的类神经气体传感器

利用喷墨打印技术沉积生物高分子溶液的方法,打印出金的梳状微电极的阵列图形,并采用NaX型沸石分子筛作为敏感膜,研制了探测神经类毒气沙林的相似物DMMP气体的阻抗型传感器。电极图形使用简单的绘图软件autoCAD画出,通过简单改进过的办公用喷墨打印机在金衬底上打印一层自组装膜的阻挡层,经过湿法刻蚀后得到了梳状微电极阵列。将制得的传感器对1ppm(即1×10-6)DMMP气体进行检测,测得在0.01Hz处,其电阻的相对变化值为10.7%。与传统MEMS工艺相比较,喷墨打印方法制备传感器具有工艺步骤简化,成本低,可在柔性等不同材料上制作等优点,有着广泛的应用前景。     

Drop‐on‐Demand Inkjet Printing of Thermally Tunable Liquid Crystal Microlenses

In this letter, the authors demonstrate Drop‐on‐Demand printing of variable focus, polarization‐independent, liquid crystal (LC) microlenses. By carefully selecting the surface treatment applied to a glass substrate, the authors are able to deposit droplets with a well‐defined curvature and contact angle, which result in micron‐sized lenses with focal lengths on the order of 300–900 µm. Observations with an optical polarizing microscope confirm the homeotopic alignment of the LC director in the droplets, which is in accordance with the polarization independent focal length. Results show that microlenses of different focal lengths can be fabricated by depositing successive droplets onto the same location on the substrate, which can then be used to build up programmable and arbitrary arrays of microlenses of various lens sizes and focal lengths. Finally, the authors utilize the thermal dependency of the order parameter of the LC to demonstrate facile tuning of the focal length. This technique has the potential to offer a low‐cost solution to the production of variable focus, arbitrary, microlens arrays.

     

High-performance zirconia ceramic additively manufactured via NanoParticle Jetting

Additive manufacturing has received tremendous attention in the manufacturing and materials industry in the past three decades. Zirconia-based advanced ceramics have been the subject of substantial interest related to structural and functional ceramics. NanoParticle Jetting (NPJ), a novel material jetting process for selectively depositing nanoparticles, is capable of fabricating dense zirconia components with a highlydetailed surface, precisely controllable shrinkage, and remarkable mechanical properties. The use of NPJ greatly improves the 3D printing process and increases the printing accuracy. An investigation into the performance of NPJ-printed ceramic components evaluated the physical and mechanical properties and microstructure. The experimental results suggested that the NPJ-fabricated ZrO₂ cuboids exhibited a high relative density of 99.5%, a glossy surface with minimum roughness of 0.33 μm, a general linear shrinkage factor of 17.47%, acceptable hardness of 12.43 ± 0.09 GPa, outstanding fracture toughness of 7.52 ± 0.34 MPa m^1/2, comparable flexural strength of 699 ± 104 MPa, dense grain distribution of the microstructure, and representative features of the fracture. Subsequently, the exclusive printing scheme that achieved these favorable properties was analyzed. The innovative NanoParticle Jetting? system was shown to have significant potential for additive manufacturing.     

喷墨打印机关键技术研究

喷墨打印技术是一种快速发展的高质量图像输出技术,在非接触打印技术领域占有重要地位。惠普、佳能和爱普生三个公司几乎占领了整个喷墨打印机市场,每个公司都有各自独特的核心技术。从喷墨打印机的基本技术指标出发,对爱普生喷墨打印机的关键技术进行了介绍,着重探讨了爱普生公司相比其它喷墨打印机生产厂家的优势所在。     

Radical polymers improve the metal-semiconductor interface in organic field-effect transistors

Modifying the organic-metal interface in organic field-effect transistors (OFETs) is a critical means by which to improve device performance; however, to date, all of the interfacial modifying layers utilized in these systems have been closed-shell in nature. Here, we introduce open-shell oxidation-reduction-active (redox-active) macromolecules, namely radical polymers, in order to serve as interfacial modifiers in pentacene-based OFETs. Through careful selection of the chemistry of the specific radical polymer, poly(2,2,6,6-tetramethylpiperidine-1-oxyl methacrylate) (PTMA), the charge transport energy level of the interfacial modifying layer was tuned to provide facile charge injection and extraction between the pentacene active layer and the gold source and drain electrodes of the OFET. The inclusion of this radical polymer interlayer, which was deposited in through straightforward inkjet printing, led to bottom-contact, bottom-gate OFETs with significantly increased mobility and ON/OFF current ratios relative to OFETs without the PTMA interlayer. The underlying mechanism for this improvement in device performance is explained in terms of the charge transport capability at the organic-metal interface and with respect to the pentacene grain growth on the radical polymer. Thus, this effort presents a new, open-shell-based class of materials for interfacial modifying materials, and describes the underlying physics behind the practical operation of these materials.