Display Devices Research Articles

Characterization of Thin AlN/Ag/AlN-Reflector Stacks on Glass Substrates for MEMS Applications

Thin metal layers such as silver (Ag) are being utilized for various optical and plasmonic applications as well as for electrical purposes, e.g., as transparent electrodes in display devices or solar cells. This paper focuses on optical MEMS applications such as the Fabry–Pérot interferometer (FPI). Within such filters, reflector materials such as distributed Bragg reflectors (DBRs) or subwavelength gratings (SWGs) have been widely used so far, whereas metallic thin films (MTFs) were limited in application due to their comparatively higher absorption. In this paper, thin sputtered Ag layers with thicknesses of 20, 40 and 60 nm on glass substrates have been investigated, and it is shown that the absorption is very low in the visible spectral range (VIS) and increases only in near-infrared (NIR) with increasing wavelength. Thus, we consider Ag-thin layers to be an interesting reflector material at least for the VIS range, which can be easily fabricated and integrated. However, Ag is not inert and stable when exposed to the atmosphere. Hence, it needs a passivation material. For this purpose, AlN has been chosen in this contribution, which can be deposited by sputtering as well. In this contribution, we have chosen thin AlN layers for this purpose, which can also be deposited by sputtering. Thus, various AlN/Ag/AlN-reflector stacks were created and patterned by lift-off technology preferably. The fabricated reflectors were characterized with respect to adhesion, stress, cohesion, homogeneity, and most importantly, their optical properties. It was found that the thickness of the AlN can be used to adjust the reflectance–transmittance ratio in the VIS range, and influences the adsorption in the NIR range as well. Based on the measured values of the reflectors with 40 nm Ag, an exemplary transmission filter characteristics has been predicted for a wavelength range from 400 to 800 nm. Both the maximum transmittance and the full width at half maximum (FWHM) can be tuned by variation of the AlN thickness from 20 to 60 nm.

Research of aging test on high Tg colorless polyimide

AbstractFor the past few years, colorless polyimide (CPI) has been drawn much attention for its application in transparent electronics. The high temperature (even to 450°C) process of the preparation of organic light‐emitting diode display (OLED) device may have huge challenges on the properties of CPI, so we designed a series of aging test experiments to study the influence of test temperature and atmosphere on the high transparency percentages (Tr%) of CPI films with structure of Glass/SiO2/CPI/SiO2. As the aging temperature increased from 430 to 450°C and then to 470°C, the Tr% of the film decreased significantly. Comparing with the sample without aging, the transmission losses were 0.22%, 1.42%, and 4.82% for the films aging with 430, 450, and 470°C in N2 atmosphere, respectively. Additionally, aging in nitrogen resulted in less Tr% loss (1.22%) compared with air (1.42%). This research offers insights into how to maintain the high Tr% of CPI films during high‐temperature processing. Furthermore, it supports the development of more durable and reliable CPI‐based components for OLED displays and other transparent electronic devices. This can lead to advancements in the performance of these devices, potentially extending their lifespan and broadening their range of applications.

Electroless deposition of high-uniformity nickel microbumps with ultrahigh resolution of 8 μm pitch for monolithic Micro-LED display

Micro-light-emitting diode (Micro-LED) displays have attracted growing attention due to their unsurpassed properties that satisfy the requirements of reality/virtual reality (AR/VR) displays. A crucial procedure of monolithic integration technology in high-density microdisplays is the interconnection process, which is intimately associated with the quality of the display device. Microfluidic electroless interconnection (MELI), an innovative low-temperature and pressure-free chip-stacking approach that eliminates the warpage-induced issues and cracking damage of the chip caused by thermo-compression bonding (TCB), holds great promise as a technology for establishing interconnections between the CMOS driver and Micro-LED. However, the requirement for the consistency of the microbump arrays and the risk of creating bridges is significantly intensified with smaller gaps in stacked chips, which restricts the application range of MELI to high-density interconnects. This paper analyzes the feasibility of further lowering the stand-off height of stacked chips in ultrafine pitch interconnects by optimizing the bump preparation process. The plasma modification time and surfactant concentration during the bump preparation process have been investigated. The result indicated that microbump arrays with a uniformity of less than 3% could be successfully manufactured by employing a 7-min plasma treatment and incorporating optimal surfactants, which catalyzes the implementation of the subsequent vertical interconnection process and eventually enhances yields of Micro-LEDs.

Chiral monomer template for designing Low-Driving-Field blue phase liquid crystals

Blue phase liquid crystals (BPLC) are known to be useful for various non-trivial applications due to their nanoscale self-assembled cubic crystalline structures. Even though the BPLC exhibits an efficient optically isotropic phase due to the double helical confinement of liquid crystal (LC) molecules within a few hundred-nanometer range, this hinders the orientation of LC molecules along the applied field direction. Consequently, the BPLC demands larger driving fields to operate, degrading the device’s performance in real-world applications. In this context, we provide a chiral monomer template for BPLC that decreases the driving field by 52 % while the electro-optical responses remain unaffected. Furthermore, our approach provides higher thermal stability, with a broader BPLC phase range (42 °C), including near ambient temperature. As this approach potentially overcomes the fundamental challenges of BPLC, the proposed system could be useful for next-generation display devices.

Multimodal human-computer interaction for virtual reality

Virtual reality (VR) is an interactive simulation environment based on computer technology that enables users to immerse themselves in a virtual world. With the continuous advancement of technology, VR has shown great potential in various fields. This article aims to review the application of VR in different fields and its impact on society. First, this paper introduces VR's basic principles and technical characteristics. VR systems are usually composed of head-mounted display devices, trackers, joysticks, etc., enabling users to experience immersive virtual environments by simulating real-world perception and interaction. Secondly, this paper discusses the application of VR in the field of education. VR technology can provide an immersive learning experience, enabling students to personally participate in the course content, greatly enhancing the effect of learning. At the same time, VR can also simulate experimental scenes, train operational skills, etc., to provide students with more abundant and practical learning resources. Then, this paper introduces the application of VR in the medical field. VR can be used for rehabilitation training of patients, psychological treatment, and other aspects, effectively improving the quality and effect of medical services. In addition, this paper also discusses the application of VR in entertainment, tourism, and other fields. VR technology can bring users immersive gaming experience, virtual tourism, etc., and inject new vitality into the entertainment industry. In tourism, VR can provide tourists with an immersive sightseeing experience, so they can feel the distant scenery at home.

Self-Healing Hydrogel Bioelectronics.

Hydrogels have emerged as powerful building blocks to develop various soft bioelectronics because of their tissue-like mechanical properties, superior bio-compatibility, the ability to conduct both electrons and ions, and multiple stimuli-responsiveness. However, hydrogels are vulnerable to mechanical damage, which limits their usage in developing durable hydrogel-based bioelectronics. Self-healing hydrogels aim to endow bioelectronics with the property of repairing specific functions after mechanical failure, thus improving their durability, reliability, and longevity. This review discusses recent advances in self-healing hydrogels, from the self-healing mechanisms, material chemistry, and strategies for multiple properties improvement of hydrogel materials, to the design, fabrication, and applications of various hydrogel-based bioelectronics, including wearable physical and biochemical sensors, supercapacitors, flexible display devices, triboelectric nanogenerators (TENGs), implantable bioelectronics, etc. Furthermore, the persisting challenges hampering the development of self-healing hydrogel bioelectronics and their prospects are proposed. This review is expected to expedite the research and applications of self-healing hydrogels for various self-healing bioelectronics.

Inkjet-Printed Dielectric Layer for the Enhancement of Electrowetting Display Devices.

Electrowetting with a dielectric layer is commonly preferred in practical applications. However, its potential is often limited by factors like the properties of the dielectric layer and its breakdown, along with the complexity of the deposition method. Fortunately, advancements in 3D inkjet printing offer a more adaptable solution for making patterned functional layers. In this study, we used a negative photoresist (HN-1901) to create a new dielectric layer for an electrowetting display on a 3-inch ITO glass using a Dimatix DMP-2580 inkjet printer. The resulting devices performed better due to their enhanced resistance to dielectric breakdown. We meticulously investigated the physical properties of the photoresist material and printer settings to achieve optimal printing. We also controlled the uniformity of the dielectric layer by adjusting ink drop spacing. Compared to traditional electrowetting display devices, those with inkjet-printed dielectric layers showed significantly fewer defects like bubbles and electrode corrosion. They maintained an outstanding response time and breakdown resistance, operating at an open voltage of 20 V. Remarkably, these devices achieved faster response times of ton 22.3 ms and toff 14.2 ms, surpassing the performance of the standard device.

Energy transfer from Ce3+ to Eu3+ in the spinel structure of ZnAl2O4 phosphor for optoelectronic applications

Zinc aluminate (ZnAl2O4), with a spinel structure is known for its versatile applications as catalyst, ceramic material, and optoelectronic device. ZnAl2O4 is an excellent host for trivalent rare-earth ions such as Dy3+ , Tb3+, Eu3+ and Sm3+ has been extensively investigated for application in display devices. The focus of this work is on Ce3+ and Eu3+ co-dopants aiming to address issues such as multistage combustion synthesis routes, the formation of secondary phases, that often impact luminescence intensity. Through a systematic approach, we synthesized the ZnAl2O4 host with consistent cerium concentration and varying europium ions using one-step combustion synthesis route. The findings reveal that the synthesized material exhibits efficient energy transfer, mitigates concentration quenching and demonstrates favorable color chromaticity. The crystal structure analysis confirms phase purity and addresses concerns related to secondary phase formation. The simplified and cost-effective approach of one-step combustion synthesis method for synthesizing Ce3+ and Eu3+ co-doped ZnAl2O4 suggests that this phosphor has potential applications in ultraviolet photo-electronic technology and other opto-electronic devices.

Trajectory-based alignment for optical see-through HMD calibration

AbstractIn order to align the virtual and real content precisely through augmented reality devices, especially in optical see-through head-mounted displays (OST-HMD), it is necessary to calibrate the device before using it. However, most existing methods estimated the parameters via 3D-2D correspondences based on the 2D alignment, which is cumbersome, time-consuming, theoretically complex, and results in insufficient robustness. To alleviate this issue, in this paper, we propose an efficient and simple calibration method based on the principle of directly calculating the projection transformation between virtual space and the real world via 3D-3D alignment. The proposed method merely needs to record the motion trajectory of the cube-marker in the real and virtual world, and then calculate the transformation matrix between the virtual space and the real world by aligning the two trajectories in the observed view. There are two advantages associated with the proposed method. First, the operation is simple. Theoretically, the user only needs to perform four alignment operations for calibration without changing the rotation variation. Second, the trajectory can be easily distributed throughout the entire observation view, resulting in more robust calibration results. To validate the effectiveness of the proposed method, we conducted extensive experiments on our self-built optical see-through head-mounted display (OST-HMD) device. The experimental results show that the proposed method can achieve better calibration results than other calibration methods.

The podcast in the consumption agenda of Colombian digital users

The proliferation of smartphones as the hub of consumption through screen devices has created a fresh path for accessing information, entertainment, and musical content. The digital ecosystem is revitalizing sound, and users are venturing into narratives and alternative formats that grab their attention and shape a content regimen that defines their sonosphere. This study centers on assessing audience indicators in digital repositories via surveys and systematized focus groups that characterize podcast listeners in Colombia. The main objective is to evaluate the podcast’s reach, thematic interests and developmental structures. In order to identify gaps for the effective expansion and integration of sound in devices and channels where audio content is widely used, this study examines the impact of podcasts on the sound culture of Colombians. In order to identify gaps for the effective expansion and integration of sound in devices and channels where audio content is widely used, this study examines the impact of podcasts on the sound culture of Colombians. The study also profiles Colombian sound consumers through display devices in the current radio landscape. The podcast serves as a means of linking novel audiences with auditory communication, a triangulation of radio content, music, and podcasts which syncs with digital consumption trends and deviates from the simultaneous and drawn-out consumption of radio broadcasts.

Entering the Next Dimension: A Review of 3D User Interfaces for Virtual Reality

In the last decade, the use of virtual reality (VR) technologies has been increasing, as head-mounted display devices, such as the Meta Quest series, have become commercially accessible to everyday consumers. There are plenty of software applications developed for VR, ranging from games to serious training. Despite the fast-growing emergence of novel and natural gesture-based interface components, traditional windows, icons, menus, and pointer user interfaces still remain popular in these implementations. Therefore, navigating and interacting within 3-dimensional environments can still be challenging in virtual reality. This body of work will serve as a reference to the literature survey on 3-dimensional user interfaces and their implementations, and categorize them to reiterate a set of design recommendations for implementing 3-dimensional user interfaces in virtual reality. While questions revolve around the need for a 3-dimensional user interface if a 2-dimensional user interface suffices, we cannot ignore the capabilities and benefits offered when utilising 3-dimensional space. Unlike other work, this work proposes a novel metaphor-guided quadrant model to delineate the 3-dimensional user interface problem in an end-to-end manner. To achieve this, over 30 unique articles selected using a meta-analyses methodology were reviewed. The result highlights the dimensional semantics of the inputs and dimensional outcomes of the virtual targets. Notable reiterated design recommendations would match devices to interaction and then to the tasks in 3-dimensional environments, reducing the degrees of freedom, imposing constraints when possible, and not implementing one single best interaction technique. The results of this survey will be beneficial for virtual reality simulation designers or researchers attempting to determine the appropriate model when developing user interfaces for virtual reality content.

Pelatihan Pembuatan Pembangkit Listrik Energi Baru Terbarukan di SMK Negeri 7 Kota Pontianak

Indonesia has enormous potential for new renewable energy (EBT), but it has not been followed up with optimal utilization and energy saving behavior is still very low in everyday life. The introduction of EBT-based learning media in the form of solar power plants (PLTS), hydroelectric power plants (PLTA) and wind power plants (PLTB) is the technology that is most easily applied to all groups in various sectors, especially in the education sector. Utilization of PLTS, PLTA and PLTB technology requires human resources (HR) who have the competence to manage it. So this Community Service Activity (PKM) program proposes training in creating an EBT power plant at SMK Negri 7 Pontianak as a means to support human resources in understanding energy conservation and the use of EBT. The learning media consists of a PLTS display with a photovoltaic system, a PLTA display with a mini turbine connected to a dynamo and a PLTB display which utilizes the power of wind gusts to rotate a turbine which is then connected directly to a generator so that each display device produces electrical energy. Methods for carrying out activities include implementation and socialization of learning media. From the results of the presentation and training on making EBT power plants, students and teachers were enthusiastic about hearing and gaining new understanding and skills regarding the use of EBT technology in the form of learning media.

Fully Enclosed Composite Micro/Nano‐Package for High‐Quality Micro‐LED Display Pixels and In Situ Nanoimprint Technology

AbstractMicro/mini‐light emitting diode (LED) arrays are regarded as the most promising next generation of display devices. However, the inherent Lambertian radiation of LED chips results in a significant pixel crosstalk. To improve the display quality, high‐quality micro/mini‐LED display pixels with fully enclosed composite micro/nano‐packages and in situ nanoimprint technology are proposed and demonstrated in this work. The nanoimprint template is designed as a composite structure comprising an intermediate sandwich cavity array and thin‐bottom nanostructure layer. Contact is maintained between the template and LED chips array substrate. By vacuuming the sealed sandwich cavities, the thin‐bottom nanostructure layer is deformed to drive the upward protrusion of the liquid optical polymer. Moreover, the nanocavities on the thin nanostructure layer are fully filled by the polymer, forming a composite micro/nano‐package. The characteristics of the composite micro/nano‐package, such as the aperture and protrusion height, can be flexibly adjusted by changing the template structure or process parameters. A 6 × 8 array LED chips display device enclosed by a composite micro/nanopackage is developed. The divergence angle of the single LED chip decreases to 72° from the original 138°, the light‐extraction efficiency increases18.4%, and the luminescence spectrum and current‐voltage characteristics changes only minimally.

Immersive haptic simulation for training nurses in emergency medical procedures

AbstractThe use of haptic simulation for emergency procedures in nursing training presents a viable, versatile and affordable alternative to traditional mannequin environments. In this paper, an evaluation is performed in a virtual environment with a head-mounted display and haptic devices, and also with a mannequin. We focus on a chest decompression, a life-saving invasive procedure used for trauma-associated cardiopulmonary resuscitation (and other causes) that every emergency physician and/or nurse needs to master. Participants’ heart rate and blood pressure were monitored to measure their stress level. In addition, the NASA Task Load Index questionnaire was used. The results show the approved usability of the VR environment and that it provides a higher level of immersion compared to the mannequin, with no statistically significant difference in terms of cognitive load, although the use of VR is perceived as a more difficult task. We can conclude that the use of haptic-enabled virtual reality simulators has the potential to provide an experience as stressful as the real one while training in a safe and controlled environment.

The Heterogeneous Packaging of A 3 × 3 Mini‐LED Array for Smart Contact Lens Display Applications

For the needs of augmented reality (AR), virtual reality (VR) and mixed reality (MR), smart contact lenses (SCL) have become an important platform as a display source in the future consumer market. Accordingly, this paper demonstrates a display device based on contact lenses. This device integrates a 3 × 3 Mini‐LED display array, a micro antenna, and a driver and transmission chip and is packaged in a smart contact lens made of hydroxyethyl methacrylate (HEMA). It is note that in order to simultaneously meet the goals of wearing comfort, biocompatibility, wireless energy transmission and adjustable display functions, the final package thickness needs to be less than 200 μm. Here, we use heterogeneous packaging technology to connect the driver and transmission chip and the Mini‐LED display array with metal wires on the flexible substrate, and use metal wires on the same conductive layer to design the antenna required for wireless energy transmission. In order to complete the above functions, we use 920 MHz RFID technology as the energy source for wireless energy transmission. When the antenna of the RFID reader is 2 cm away from the smart contact lens, the designed receiving chip can receive 100 μW of energy. After converting this energy to DC 3 V, it can drive Mini‐LED with a current of about 30 μA, and the mini‐LED display array can be instantly controlled to display different contents by transmitting display commands through the RFID protocol. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Colorless Polyamide–Imide films with tunable coefficient of thermal expansion and their application in flexible display devices

In a previous study, our group reported the fabrication of a series of colorless polyamide–imide (PAI) films (named TFDB-DABPO-TPC-6FDA) with good thermal stability. To further improve their properties, herein, the effect of adding blocks in molecules on the performance of polyimide (PI) films was studied. By changing the order and amount of the four reactants added each time, seven PAIs with different structures and block lengths were obtained. Their glass transition temperatures (Tg) ranged from 359 °C to 368 °C, and their transmittance at 430 nm (T430) was 82.7%–85.1 %. Importantly, the coefficient of thermal expansion (CTE) of these seven PAIs decreased almost linearly from 31.1 to 18.5 ppm/K, making it possible to fabricate PI films with a desired CTE value for specific applications. Furthermore, the PAI-6-T film, which had the longest polyamide block and the best overall performance (Tg = 362 °C, CTE = 18.5 ppm/K, T430 = 83.1 %, tensile strength = 179.4 MPa, dielectric constant (Dk) = 2.53, and dielectric loss (Df) = 0.0088 at 10 GHz) was used as a substrate to fabricate a flexible printed circuit board (FPCB) and an organic light-emitting diode (OLED). Mechanical–electrical test shows that Ag was firmly bonded with the PAI-6-T film, and the resistance of FPCB@PAI-6-T only increased by 14.8 % after 150,000 folding tests. The flexible OLED@PAI-6-T exhibited pure green emission, a turn-on voltage of 3.0 V, a luminance of 1000 cd/m2 at 6 V, a current efficiency of 1.31 cd/A, and an external quantum efficiency of 0.44 %.

Controlled doping rates of graphene oxide in aluminum for high electrical performance and oxygen reduction reaction

The brush coating method allows the advantage of being able to produce thin films simply and quickly. This study introduces a method for thin-film production by brushing a solution containing graphene doped in Al2O3 using the sol–gel method. Graphene oxide (GO) is suitable for semiconductors with bandgap values of about 1.7 eV at room temperature, and the characteristics of the thin films were analyzed according to the doping ratio. First, X-ray photoelectron spectroscopy measurements were obtained to analyze the chemical composition of the thin-film surface. Since graphene is a carbon isomer, the characteristic of oxygen vacancies was confirmed by the increasing C–C bond intensity with increasing GO doping concentration. In addition, Raman analysis was performed to analyze the concentration of molecular groups of compounds for defects in graphene. Thereafter, through atomic force microscopy measurements, as the graphene doping ratio increased, the average roughness increased from 1.785 to 33.67, the residual DC voltage also increased by about 48.42 %, and the polar anchoring energy also increased by about 16.33 %. In addition, response-time–transmittance measurements were performed to measure the electro-optical properties of the thin film, and excellent Vth and stable response speed were obtained. Additionally, the validity of the results was supported through bandgap analysis. Finally, the degree of alignment of liquid–crystal molecules on the film surface was confirmed by polarized optical microscopy and pretilt angle measurements, and the suitability of the thin film for display devices was shown via transmittance measurements. As a result, GO:Al2O3 hybrid thin film is an excellent candidate for use as an alignment film for solar energy, secondary batteries, and next-generation liquid crystal displays.

Near eye display based on multiplexed retinal projections for robust compensation of eye pupil variance.

Among various specifications of near eye display (NED) devices, a compact formfactor is essential for comfortable user experience but also the hardest one to accomplish due to the slowest progresses. A pinhole/pinlight array based light-field (LF) technique is considered as one of the candidates to achieve that goal without thicker and heavier refractive optics. Despite those promising advantages, however, there are critical issues, such as dark spots and contrast distortion, which degrade the image quality because of the vulnerability of the LF retinal image when the observer's eye pupil size changes. Regardless of previous attempts to overcome those artifacts, it was impossible to resolve both issues due to their trade-off relation. In this paper, in order to resolve them simultaneously, we propose a concept of multiplexed retinal projections to integrate the LF retinal image through rotating transitions of refined and modulated elemental images for robust compensation of eye pupil variance with improved conservation of contrast distribution. Experimental demonstrations and quantitative analysis are also provided to verify the principle.

High-performance nano-scale InSnO transistors

Nanoscale short-channel oxide thin film transistors (TFTs) have attracted widespread research interest due to their potential applications in advanced display and memory devices. In this work, we fabricate 10 μm channel length indium-tin-oxide (ITO) TFTs and analyze the uniformity and repeatability of ITO TFTs at the long channel range. Then we fabricate ITO TFTs with a series of channel lengths ranging from 10 μm to 150 nm and through an optimized process we finally fabricate 130 nm channel length high-performance ITO TFTs with an on-state current of 93 (μA/μm), a subthreshold swing of 102 (mV decade–1), and on/off ratio over 107 at a drain voltage of 3 V.

Polymer-stabilized blue phase liquid crystal devices with ultra-low hysteresis and driving stability

Hysteresis is a critical factor that plays a significant role in determining the electro-optical performance of display devices, especially in polymer-stabilized blue phase liquid crystal devices (PSBPLCDs). The presence of hysteresis limits the accuracy of device operation and affects its long-term stability. To address this challenge, we have employed a few short-chain monofunctional methacrylate monomers at an appropriate concentration to form microscale network holes in PSBPLCDs. These PSBPLCDs with microscale network holes show low hysteresis (<0.5 %) for networks with non-smooth surfaces and even ultra-low hysteresis (∼0.02 %) for networks with smooth surfaces. The PSBPLCDs exhibit a wide temperature range exceeding 85 °C and have similar response times to that of conventional PSBPLCDs. Moreover, these PSBPLCDs have a low hysteresis and small residual birefringence even after undergoing 2,000,000 driving cycles. These research results are significant in determining the appropriate selection of monofunctional monomers for the design and development of PSBPLCDs.