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In this study, we propose a novel compensation scheme that utilizes variable reset voltage (VRV) to mitigate the flicker phenomenon observed in low temperature poly-Si and oxide (LTPO) active-matrix organic light emitting diode (AMOLED) displays at low frequencies. We have experimentally demonstrated that the flicker caused by luminance fluctuations at low frequencies is the result of interactions between the slow transient de-trapping of the oxide thin film transistor (TFT) and hysteresis of the driving TFT (D-TFT). Although slow transient de-trapping of the oxide TFT is difficult to be compensated, we have demonstrated that D-TFT hysteresis can be modulated by adjusting the gate in panel (GIP) timing and reset voltage. Accordingly, the luminance amplitude component at 1 Hz was significantly reduced from 0.201 cd/m 2 to 0.093 cd/m 2 by applying sequentially modulated VRV within the skip frame where image data were not updated. Consequently, the flicker phenomenon was improved at low driving frequencies below 10 Hz.

Low-temperature polycrystalline silicon and oxide (LTPO)-based pixel circuits are increasingly being adopted in medium-sized active-matrix organic light-emitting diode (AMOLED) displays due to their power-saving advantages. However, conventional pixel circuits originally developed for mobile displays face challenges when applied to larger panels, due to aggravated IR-drop and residual luminance at black levels. To address these issues, we propose a novel pixel circuit composed of nine thin-film transistors (TFTs) and one storage capacitor (C ST ). The proposed design compensates for luminance non-uniformity caused by IR-drop in the V DD line and ensures stable variable refresh rate (VRR) operation without requiring an additional compensation scheme, such as the on-bias voltage (OBV) used in conventional designs, which causes residual luminance in dark states. To validate the effectiveness of the proposed circuit, a 13-inch LTPO AMOLED panel was fabricated. Flicker was measured to be below − 50 dB at a 10 Hz refresh rate under both 140 nits and 6 nits conditions. In addition, luminance uniformity was significantly improved from 69% to 89% under the high luminance condition of 1,600 nits. These results demonstrate that the proposed pixel circuit achieves improved luminance uniformity and stable VRR performance.

This paper proposes a novel pixel circuit and driving scheme that adopts low-temperature polycrystalline silicon and oxide thin-film transistors (LTPO TFTs) for mobile devices using active-matrix organic light-emitting diode (AMOLED) displays. The proposed pixel circuit and driving scheme provide uniform luminance and render flicker invisible at variable refresh rates (VRRs) from 1 to 120 Hz. Using the proposed pixel circuit with extended compensation time (t COMP ) improves the luminance uniformity at a high-frame rate. The proposed driving scheme applies a voltage to the driving TFTs (D-TFTs) higher than the programmed data voltage during the skip frame. This reduces the flicker caused by the hysteresis of D-TFTs during low-frame rate driving. A 6.0-inch quad high-definition (QHD) LTPO-based AMOLED display was fabricated using the new pixel circuit and driving scheme. Experimental results of the proposed pixel circuit show that the standard deviation of luminance was reduced from 0.056 to 0.008 by extending t COMP from 2 to 8 µs. The flicker level was −51 dB, so there was no visual artifact during 1 Hz driving. A flicker-free LTPO-based AMOLED display with low power consumption is possible; driving can proceed in 1-120 Hz range.

This paper proposes a novel circuit called the Line-Selector Unit (LSU) that enhances conventional oxide thin-film-transistor (TFT) scan drivers. The LSU, consisting of four transistors, one capacitor, and three additional control signals, allows a traditional scan driver to generate scan signals only in the selected area. A 12-stage scan driver with the LSU was fabricated using oxide TFTs, and experimental results demonstrate that the LSU operates regardless of the position and size of the selected area. Moreover, the LSU does not experience voltage stress during conventional scan driving and enhances reliability by employing an optimized driving method that distributes positive voltage bias stress during selective-scan driving. In addition, the LSU consumes only 0.1% of the total scan driver power consumption, making it a highly compatible and energy-efficient solution for low-power display applications.

With the development of brain-computer interface industry, large amounts of related applications have entered people’s vision. BCI applications based on steady-state visual evoked potentials (SSVEP) are widely used because they do not require pre-training and have high information transmission rates. However, in the actual use of SSVEP stimulus paradigm, the subjects will produce visual fatigue with the use, and fatigue will affect the transmission efficiency. In this experiment, an experimental environment consisting of two paradigm stimulus frequencies (7.5 Hz, 15 Hz), three resolutions (800 × 600, 1280 × 720, 1920 × 1080) and three refresh rates (120 Hz, 240 Hz, 360 Hz) is set up. The Likert scale is used to collect subjective fatigue and preference scores, and the EEG acquisition system and eye tracker are used to collect objective data. Using the proposed information entropy-CRITIC algorithm to combine subjective and objective indicators, a fatigue assessment system (display screen fitness-DSF) is innovated to score different experimental environments. The higher the DSF score, the better the visual experience. The results show that when using the 7.5 Hz SSVEP paradigm, the combination of 360 Hz and 1920 × 1080 can bring the best visual experience. When using the 15 Hz SSVEP paradigm, the combination of 240 Hz and 1280 × 720 is the best. DSF provides powerful help for hardware and software selection guidance and vision protection when using SSVEP-based BCI applications.

Purpose Additive manufacturing (AM) has been one of the most highlighted processes of the last few years. AM prints complex parts and items from 3D files regarding different materials, such as polymers. Moreover, there are different AM techniques available for polymers, such as selective laser sintering. In the SLS technology, polyamides 11 and 12 lead 88% of the market. These materials are high-cost and use an average of 50% of virgin material at each printing. It is possible to use lower rates of virgin material, but at least 30% is recommended. Low rates of virgin material decrease mechanical properties. Design/methodology/approach This study aims to evaluate the influence on the mechanical properties of the percentage of reused PA12 in parts manufactured by the SLS process. The specimens of PA12 were manufactured with a percentage of virgin/reused polymer of 50/50, 40/60, 30/70, 20/80 and 10/90. We considered three distinct printing directions to compare the mechanical properties of the specimens: horizontal, perpendicular and vertical. Findings The results showed that when the percentage of reused material increases, the tensile strength limit (TSL), flexural strength limit and Shore D hardness decrease. Another aspect visualized was the fragile behavior presented in the vertical specimens. In addition, DSC analysis indicated a 2% reduction of crystallinity. Scanning electron microscopy images revealed spherical voids and unfused particles of PA12 at the fracture of tensile test specimens. The material thermal history and unfused particles could decrease the material properties. Originality/value We observed that the mechanical properties, such as the TSL, flexural strength limit and hardness, decrease as the percentage of reused material increases. In addition, the process presented a printing-direction dependence, where the vertical direction presented as the more brittle between the ones used.

The refresh rate is one of the important parameters of visual presentation devices, and assessing the effect of the refresh rate of a device on motion perception has always been an important direction in the field of visual research. This study examined the effect of the refresh rate of a device on the motion perception response at different stimulation frequencies and provided an objective visual electrophysiological assessment method for the correct selection of display parameters in a visual perception experiment. In this study, a flicker-free steady-state motion visual stimulation with continuous scanning frequency and different forms (sinusoidal or triangular) was presented on a low-latency LCD monitor at different refresh rates. Seventeen participants were asked to observe the visual stimulation without head movement or eye movement, and the effect of the refresh rate was assessed by analyzing the changes in the intensity of their visual evoked potentials. The results demonstrated that an increased refresh rate significantly improved the intensity of motion visual evoked potentials at stimulation frequency ranges of 7 Hz-28 Hz, and there was a significant interaction between the refresh rate and motion frequency. Furthermore, the increased refresh rate also had the potential to enhance the ability to perceive similar motion. Therefore, we recommended using a refresh rate of at least 120 Hz in motion visual perception experiments to ensure a better stimulation effect. If the motion frequency or velocity is high, a refresh rate of ≥240 Hz is also recommended.

Smart electronic textiles with electronic functions like displaying can provide transformative opportunities for wearable devices that traditional rigid devices are hard to realize. A general strategy of enabling textiles to display is weaving light-emitting fibers into textiles and designing control circuits. However, it remains challenging for the current electronic textiles to display full-color images and videos. Here, we demonstrate a large-area integrated electronic textile system (with a size of 72 cm × 50 cm) by weaving light-emitting diode (LED) fibers, touch-sensing fibers and polyester fibers, which could display full-color images (with a gamut of 117.6% NTSC) and continuous videos (with a refresh rate of 11.7 Hz) by designing low-voltage supply mode and parallelly transmitting circuits. After integration of touch-sensing fibers, such textile system could achieve various touch display and interactive functions like smart phones or computers, including hand input of text, hand painting, computing and playing games. The stability and durability of textile system withstanding 5000 bending cycles was also demonstrated for wearable applications. The integrated electronic textile system shows similar flexibility and breathability with regular textiles, which is promising to serve as new human-machine interface to change the way in which people interact with electronics.

Low-refresh-rate driving is an effective way to reduce the power consumption of active-matrix organic light-emitting diode (AMOLED) displays. However, in conventional low-temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) pixel circuits, leakage current through switching TFTs can disturb the stored gate voltage of the driving TFT during the long emission period. This causes the time-dependent variation in driving current and visible flicker. In this study, a novel pixel circuit for leakage suppression in low-refresh-rate driving is presented. Bias aging was first applied to reduce the leakage current of the LTPS TFT, and a device model was then built from the characteristics measured at 60 °C. Based on this model, the leakage-induced instability of a conventional 7T1C pixel circuit was analyzed. To suppress this effect, a new 8T1C pixel circuit was proposed. The key idea is to reduce the source–drain voltage of the leakage-sensitive switching TFT during the emission period by raising the initial line potential to a level close to the storage node potential. Simulation results show that the proposed circuit greatly reduces the time-dependent variation in both the driving TFT gate voltage and the driving current compared with the conventional 7T1C circuit. Perceptual evaluation based on human visual sensitivity also confirms stable low-refresh-rate operation down to 20 Hz over the practical gray range. These results show that the proposed circuit is an effective solution for moderate low-refresh-rate operation without relying on low-temperature polycrystalline silicon and oxide (LTPO) technology.

This study investigated novel driving scheme for low-temperature polycrystalline silicon and oxide (LTPO) active-matrix organic light-emitting diode (AMOLED) displays under variable refresh rate (VRR) driving conditions with aim of reducing the brightness instability (i.e., flicker and luminance variation) for seamless performance. The mechanisms underlying brightness fluctuations in displays were examined, focusing on frequency-dependent differences in gate-inpanel (GIP) operations. Notably, our study revealed additional factors within the GIP operation that cause LTPO flicker and VRR performance, in addition to previously identified factors of thin-film transistor hysteresis and OLED charging. Consequently, variable GIP voltage driving method that reduced these issues and enhanced display performance was proposed. The proposed method could minimize brightness fluctuations to levels imperceptible to users and facilitate performance improvement through driving options in peripheral circuits without modifying panel design and is applicable across various applications utilizing LTPO OLED technology. Its driving scheme was validated through simulation and measurement of luminance variation during frequency transition using 6.0-inch LTPO-applied AMOLED displays. The experimental results indicated a decrease in luminance difference from 14.2% to 1.5%, particularly at extremely low brightness level of 0.2 nit. The luminance distortion decreased from 7 to less than 1, which is a just noticeable color difference (JNCD).