Flexible Displays Research Articles

Ultralong sodium alginate-based room temperature phosphorescence materials with advantages of color tunability, flexibility and facile large-area fabrication

Organic room temperature phosphorescence (RTP) has promising applications in diverse fields, whereas a formidable challenge remains in the development of flexible organic RTP materials, especially environmentally friendly RTP materials. In this work, natural polymer sodium alginate (SA)-based RTP materials have been facilely developed by doping phenylboronic acid (PBA) and its derivatives into SA matrices. 4-carboxyphenylboric acid doped system SA-CPBA exhibits the best RTP performance with an ultralong phosphorescence lifetime of up to 231 ms. Interestingly, SA-CPBA shows excitation-dependent phosphorescence color tunability by water vapor fumigation and heating, and the afterglow color change has good reversibility upon alternating treatment of water vapor fumigation and heating. Amazingly, flexible and transparent RTP films are obtained through adding a certain amount of glycerol (G) into SA-CPBA matrices, and SA-CPBA-G also possesses excellent excitation-dependent phosphorescence color tunability. Furthermore, the flexible SA-CPBA-G film can be conveniently fabricated on a large area. These excellent features enable the prepared SA-based RTP materials to be successfully applied in the fields of flexible display and information encryption. This work provides a guideline for the preparation of environmentally friendly flexible polymer-based color-tunable RTP materials and expands the application range of SA-based materials to the field of flexible displays.

Exploiting Physical Referent Features as Input for Multidimensional Data Selection in Augmented Reality

Embedding data into the physical environment using augmented reality (AR) is a practical approach for data visualization as it offers a large and flexible display space on or around the physical referent, i.e. the physical object to which the data is related. Yet current interaction in such context is often performed using cumbersome dedicated devices, tiring mid-air gestures or awkward on-body input. In this paper, we investigate the use of the physical referent itself as a support for input interaction with an embedded space-time cube (STC) representation. Hence, we first identify the most promising mappings between the physical features of the referent (edges, faces, corners) and the STC dimensions. Then, we design three data selection techniques using the physical referent and compare them to mid-air gestures when performing selection tasks on the STC. Overall, our work demonstrates that using the physical referent to support input interaction with embedded data representations is an efficient and comfortable approach for data selection in standing and sitting situations.

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.

Development of a hyperbranched oxazolidinone dynamic omniphobic liquid-like coating with high hardness and flexibility

Dynamic omniphobic liquid-like anti-fouling coatings have a wide range of applications. However, designing dynamic omniphobic liquid coatings that are highly hard, flexible, and low-cost remains a challenge. In this study, low-cost hyperbranched epoxy resin (HEBP), hexamethylene diisocyanate trimer (HDIT), and mono-hydroxyl-terminated poly(dimethysilxane) (HO-PDMS) were used as polymer matrix. Through a copolymerization reaction, a highly cross-linked rigid oxazolidinone structure (OX) and liquid-like molecular coating were obtained. Meanwhile, this unique design endowed the coating with ultra-high hardness (8H), exceptional flexibility, extremely high transparency, and dynamic omniphobic anti-fouling properties. Moreover, the layer can withstand cycles of friction or bending and exhibits excellent chemical barrier properties. Overall, this coating can be easily prepared on a large scale and has broad application prospects in different fields such as solar panels, outdoor public facilities, and flexible display screens.

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 %.

Organic molecules with dual triplet‐harvesting channels enable efficient X‐ray scintillation and imaging

AbstractOrganic scintillators have recently gained considerable attentions in X‐ray detection for their potential applications in biomedical radiograph and security inspection. However, the weak X‐ray absorption and/or inefficient exciton utilization have limited the development and commercialization of organic scintillators. Currently, high‐performance X‐ray organic scintillators are scarce and organic scintillators with dual triplet‐harvesting channels have not been explored before. Here, we develop several proof‐of‐concept sulfone‐based organic molecules, C1–C7, using different alkoxy chains to manipulate molecular packing mode. These materials exhibit dual triplet‐harvesting channels of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) in aggregated state. Inspiringly, these molecules display distinct radioluminescence under the X‐ray stimulation. Among them, C6 behaves the highest light yield of 16,558 photons MeV−1. Moreover, clear X‐ray images are demonstrated in both aggregated state and single‐molecule level. High spatial resolutions of 15.0 and 10.6 line pairs per millimeter (lp mm−1) are achieved for rigid and flexible scintillator screens, exceeding most reported organic and conventional inorganic scintillators. These results highlight the great potential of organic molecules with TADF and RTP nature for efficient X‐ray scintillation and imaging.

Ultraviolet Light Debondable Optically Clear Adhesives for Flexible Displays through Efficient Visible-Light Curing.

With growing sustainability concerns, the need for products that facilitate easy disassembly and reuse has increased. Adhesives, initially designed for bonding, now face demands for selective removal, enabling rapid assembly-disassembly and efficient maintenance across industries. This need is particularly evident in the display industry, with the rise of foldable devices necessitating specialized adhesives. A novel optically clear adhesive (OCA) is presented for foldable display, featuring a unique UV-stimulated selective removal feature. This approach incorporates benzophenone derivatives into the polymer network, facilitating rapid debonding under UV irradiation. A key feature of this method is the adept use of visible-light-driven radical polymerization for OCA film fabrication. This method shows remarkable compatibility with various monomers and exhibits orthogonal reactivity to benzophenone, rendering it ideal for large-scale production. The resultant OCA not only has high transparency and balanced elasticity, along with excellent resistance to repeated folding, but it also exhibits significantly reduced adhesion when exposed to UV irradiation. By merging this customized formulation with strategically integrated UV-responsive elements, an effective solution is offered that enhances manufacturing efficiency and product reliability in the rapidly evolving field of sustainable electronics and displays. This research additionally contributes to eco-friendly device fabrication, aligning with emerging technology demands.

A novel portable flip-phone based visual behaviour assay for zebrafish

The optokinetic reflex (OKR) serves as a vital index for visual system development in early life, commonly observed within the first six months post-birth in humans. Zebrafish larvae offer a robust and convenient model for OKR studies due to their rapid development and manageable size. Existing OKR assays often involve cumbersome setups and offer limited portability. In this study, we present an innovative OKR assay that leverages the flexible screen of the Samsung Galaxy Z Flip to optimize setup and portability. We conducted paired slow-phase velocity measurements in 5-day post-fertilization (dpf) zebrafish larvae (n = 15), using both the novel flip-phone-based assay and a traditional liquid–crystal display (LCD) arena. Utilizing Bland–Altman plots, we assessed the agreement between the two methods. Both assays were efficacious in eliciting OKR, with eye movement analysis indicating high tracking precision in the flip-phone-based assay. No statistically significant difference was observed in slow-phase velocities between the two assays (p = 0.40). Our findings underscore the feasibility and non-inferiority of the flip-phone-based approach, offering streamlined assembly, enhanced portability, and the potential for cost-effective alternatives. This study contributes to the evolution of OKR assay methodologies, aligning them with emerging research paradigms.

Te4+-doped Cs2SnCl6 scintillator for flexible and efficient X-ray imaging screens

Cs2SnCl6:Te4+ vacancy-ordered double perovskite microcrystals were synthesized via a co-precipitation method and applied for high-resolution X-ray imaging as flexible scintillator screens.

High comprehensive properties of colorless transparent polyimide films derived from fluorine-containing and ether-containing dianhydride.

Fluorinated colorless transparent polyimide (CPI) films are crucial for flexible displays and wearable devices, but their development is limited by high costs and relatively low mechanical properties. In this study, a series of colorless transparent polyimide films was synthesized by incorporating the cost-effective ether-containing diamine, 4,4'-isopropylidenediphenoxy bis(phthalic anhydride) (BPADA), into commercially available 4,4'-(hexafluoroisopropyl)diphthalic anhydride (6FDA) and 2,2'-bis(trifluoromethyl)benzidine (TFMB). The comprehensive properties of the films were systematically investigated using a combination of experimental and numerical methods, including molecular dynamics (MD) simulations and density functional theory (DFT). This study focuses on exploring the influence of varying dianhydride ratios on the aforementioned properties. The incorporation of BPADA in the dianhydride significantly enhances the mechanical properties and flexibility of the film. When the ratio of ether anhydride to fluorine anhydride is 4 : 6 (CPI-4), the tensile strength is 135.3 MPa, and the elongation at break is 8.3%, which is 109.6% and 118.45% higher than that of the original film without ether anhydride. This research provides valuable insights for the future application of new polyimide materials in flexible display devices.

Research on Modeling and Motion Optimization for an Underactuated Bionic Scorpion Robot Arm.

Flexible screen possessing a high-contrast ratio to accomplish high-definition display can be attributed to the accuracy of polarizer assembly. Different from the existing polarizer attached onto a flexible screen, resulting in low-accuracy and nonalignment attaching behaviors, a unique approach of underactuated bionic scorpion robot arms can be developed to explore the stable capture and accurate alignment motion operations. Overall structure design and D-H kinematic simulation of bionic scorpion robot arm can be conducted to analyze virtual three-key typical motions. Motion optimization of structural parameters and corresponding motion workspaces verification can be adopted to evaluate motion range and ability. Experiments can be utilized to verify the rationality of theoretical modeling and optimization simulation of bionic scorpion robot arm. Experimental results illustrate that it is evident to demonstrate that the motion behaviors of bionic scorpion robot arm can be verified to be consistent with three key states of virtual theoretical motions. The key joints possessing minor errors may also be utilized to illustrate the relatively excellent dynamic motions existing in bionic scorpion robot arm. Further, advancing the stable motion behaviors of bionic scorpion robot arm may solve the problems of low-accuracy and misalignment polarizer attachments.

Achieving 9% EQE in light-emitting electrochemical cells via a TADF-sensitized fluorescence strategy.

Light-emitting electrochemical cells (LECs) are appealing for cost-effective, large-area emission applications; however, their luminescence efficiency is significantly limited by exciton annihilation caused by high concentration polarons. Here, we present thermally activated delayed fluorescence (TADF) sensitized fluorescence LECs (TSF-LECs) that achieve a record 9% EQE. The TADF sensitizers with rapid reverse intersystem crossing (RISC) rates can effectively convert triplet excitons to singlet excitons in LECs, thereby establishing a more efficient overall energy transfer pathway. Importantly, magneto-electroluminescence measurements indicate that the additional RISC route in TSF-LECs significantly suppresses the annihilation of triplet excitons and thus reduces exciton loss under high concentration polaron conditions. Compared to LECs without a sensitizer, TSF-LECs exhibit improved EQE and luminance, extended operational lifetimes, and suppressed efficiency roll-off. A flexible display prototype based on TSF-LECs was further fabricated, capable of stably displaying high-brightness preset patterns for extended periods. The exploration of the exciton dynamics in high concentration polaron environments offers valuable insights for future developments in high-efficiency LEC technology.

Fraunhofer FEP: Innovative roll-to-roll plasma process for graphene layers / TNO develops first method for fully circular electronics / drupa 2024: “Record number of deals signed” / IDEEL project: Industry-relevant scaling of laser drying processes for lithium-ion batteries within reach / FlexEnable achieves “historic breakthrough“ in flexible display technology / “The most powerful organic photovoltaic system in Germany to date”

Fraunhofer FEP: Innovative roll-to-roll plasma process for graphene layers / TNO develops first method for fully circular electronics / drupa 2024: “Record number of deals signed” / IDEEL project: Industry-relevant scaling of laser drying processes for lithium-ion batteries within reach / FlexEnable achieves “historic breakthrough“ in flexible display technology / “The most powerful organic photovoltaic system in Germany to date”

Analysis of Flexible Screen Bending Strain Measurement Based on Digital Image Correlation (Invited)

Analysis of Flexible Screen Bending Strain Measurement Based on Digital Image Correlation (Invited)

Simulation study on frictional resistance and influencing factors of flexible screen pipe tripping into horizontal wellbore

Simulation study on frictional resistance and influencing factors of flexible screen pipe tripping into horizontal wellbore

Simulation study on frictional resistance and influencing factors of flexible screen pipe tripping into horizontal wellbore

Simulation study on frictional resistance and influencing factors of flexible screen pipe tripping into horizontal wellbore

Electroluminescence, Mechanoluminescence, and Triboelectric from Superior Multimode Systems Based on Flexible Hydrogels for Human Motion Sensing

AbstractFlexible sensors have attracted extensive research interest due to their great application potential in biodetection, flexible display, and wearable devices. However, they still have a lot of room for improvement in terms of luminous color, flexibility, and self‐powered systems. A wearable, antifreeze, and discoloration sensing system based on electroluminescence, mechanoluminescence, and tribo‐power generation is developed in this paper. Triboelectric nanogenerator systems can harvest biomechanical energy from hand clapping and knee/elbow bending to generate real‐time electrical signals. The use of dielectric materials reduces the initial voltage and frequency of light‐emitting devices, enabling them to be driven by Triboelectric nanogenerators. At the same time, the device can produce red, blue, white, and other multicolor light. In addition, the system can produce an optical signal output due to external mechanical stimulation. As a result, the sensor system is simple to manufacture and unique to operate, proving its potential applications in areas such as cold‐resistant displays, wearable optoelectronics, soft robotics, and electronic skin.

Direct coating of transparent and wear-resistant polysilsesquioxane on ultra-thin glass for flexible cover windows

This study presents a wear-resistant and anti-fragile ultra-thin glass (UTG) as a flexible cover window. Direct coating of ladder-like polysilsesquioxane (PSQ) onto UTG was introduced to achieve flexibility and protective properties at the same time. In contrast, conventional lamination-based protective films for UTG compromise surface hardness and wear resistance because of using the soft adhesive. The resulting cover window demonstrated pencil hardness of 8H and 1000 cycles of abrasion resistance with 91 % of optical transmittance. Pen and ball drop test results also revealed impact resistance of PSQ-coated UTG improved dramatically compared to the bare UTG. Lastly, a rigorous 200,000-fold test at 3R inward and 6R outward bending verifies the outstanding folding cycle reliability, making it suitable for innovative protective layers for the flexible display industry.

Metal Halide Nanocrystals@Silica Aerogel Composite with Enhanced Dispersion Stability and Light Output for Efficient X-Ray Imaging in Harsh Environment.

Metal halide nanocrystals (MHNCs) embedded in a polymer matrix as flexible X-ray detector screens is an effective strategy with the advantages of low cost, facile preparation, and large area flexibility. However, MHNCs easily aggregate during preparation, recombination, under mechanical force, storage, or high operating temperature. Meanwhile, it shows an unmatched refractive index with polymer, resulting in low light yield. The related stability and properties of the device remain a huge unrevealed challenge. Herein, a composite screen (CZBM@AG-PS) by integrating MHNCs (Cs2ZnBr4: Mn2+ as an example) into silica aerogel (AG) and embedded in polystyrene (PS) is successfully developed. Further characterization points to the high porosity AG template that can effectively improve the dispersion of MHNCs in polymer detector screens, essentially decreasing nonradiative transition, Rayleigh scattering, and performance aging induced by aggregation in harsh environments. Furthermore, the higher light output and lower optical crosstalk are also achieved by a novel light propagation path based on the MHNCs/AG and AG/PS interfaces. Finally, the optimized CZBM@AG-PS screen shows much enhanced light yield, spatial resolution, and temperature stability. Significantly, the strategy is proven universal by the performance tests of other MHNCs embedded composite films for ultra-stable and efficient X-ray imaging.

PopTouch: A Submillimeter Thick Dynamically Reconfigured Haptic Interface with Pressable Buttons.

The interactions with touchscreens rely heavily on vision: The virtual buttons and virtual sliders on a touchscreen provide no mechanical sense of the object they seek to represent. This work presents PopTouch: a 500µm thick flexible haptic display that creates pressable physical buttons on demand. PopTouch can be mounted directly on touchscreens or any other smooth surface, flat, or curved. The buttons of PopTouch are independently controlled hydraulically amplified electrostatic zipping taxels (tactile pixels) that generate 1.5mm of out of plane displacement. When pressed by the user, the buttons provide intuitive mechanical feedback thanks to a snap-through characteristic in their force-displacement profile. The snap-through threshold can be as high as 4 N, and is tuned by design and actuation parameters. This work presents two versions of PopTouch: a transparent PopTouch for integration on Touchscreens with built-in touch sensing, such as smartphones and a sensorized PopTouch, with embedded thin-film piezoelectric sensors on each taxel, for integration on substrates without built-in touch sensing, such as a steering wheel. PopTouch adds static and vibrating button-like haptics to any device thanks to its thin profile, flexibility, low power consumption (6mW per button), rapid refresh rate (2Hz), and freely configured array format.