Search Results (25)

In-cell touch and display integrated panels, along with their integrated readout systems, are widely adopted in mobile devices for their cost-effectiveness and compact design. This paper proposes an analog Gaussian-shaped filter and a current mode compensation technique for dot-matrix Touch Screen Panel (TSP) readout systems. Specifically, this article presents a noise management strategy for both intrinsic and external noise, offering simulation guidelines for determining intrinsic circuit noise levels in relation to scan time and enhancing external noise immunity through the Gaussian-shaped filter response. The system achieved an intrinsic SNR of 66 dB with a 200 kHz TSP driving frequency and a 160 μs scan time, while the 4-bit quantized Gaussian coefficients filter provided 33 dB noise suppression for out-of-band noise. The compensation error in the dot-matrix capacitance compensation was measured at 1.24 pF, which corresponds to a 0.078% deviation. The simulated power consumption of the proposed readout system is 24 mW, with a layout area of 1.017 mm² for the 10-channel readout front-end. Full article

Owing to their physical and chemical properties and stimuli-responsive nature, gels and hydrogels play vital roles in diverse application fields. The three-dimensional polymeric network structure of hydrogels is considered an alternative to many materials, such as conductors, ordinary films, constituent components of machines and robots, etc. The most recent applications of gels are in different devices like sensors, actuators, flexible screens, touch panels, flexible storage, solar cells, batteries, and electronic skin. This review article addresses the devices where gels are used, the progress of research, the working mechanisms of hydrogels in those devices, and future prospects. Preparation methods are also important for obtaining a suitable hydrogel. This review discusses different methods of hydrogel preparation from the respective raw materials. Moreover, the mechanism by which gels act as a part of electronic devices is described. Full article

Many advanced technologies have been employed in high-performance active matrix displays, including liquid crystal displays, organic light-emitting diode displays, and micro-light-emitting diode displays. On the other side, there exists a strong demand for cost reduction, and it is one of the low-cost schemes for integrating the driver circuit in a panel based on thin-film transistor technologies. This paper reviews the overall concept, operation principles, and various circuit approaches in shift registers for scanning pulse generation. In addition, it deals with the implementation of additional functionalities in gate drivers to support pixel compensation, multi-line driving, in-cell capacitive touch screen, pixel sensing, and adaptive scanning region control. Full article

This study aims to synthesize and implement a robust fractional order PD (RFOPD) controller to increase the speed at which defects in automated touch panel inspection systems (ATPISs) are detected. A three-dimensional orthogonal stage (TDOS) driven by BLDC servo motors moves the inspection pen (IP) vertically and horizontally. The dynamic equation relating the BLDC servo motor input to the tip motion is established. A touch position identification (TPI) system is used to locate the touch point rapidly. An RFOPD controller is used to actuate the BLDC servo motors and move the TDOS rapidly and accurately in three dimensions. This method displaces the IP to any specified position and shows user-defined inspection trajectories on the touch screens. The gain-phase margin tester (GPMT) and stability equation methods are exploited to schedule the RFOPD controller gain settings and to maintain the specific safety margins for the controlled system. The simulation studies show that the proposed RFOPD controller exhibits better tracking and disturbance rejection responses than a conventional PID controller. The robustness of the RFOPD-controlled ATPIS, considering unmodeled uncertainties and friction-induced disturbances, is verified through simulation and experimental studies. Several user-defined inspection patterns are used to verify performance, and the experimental results show that the proposed RFOPD controller is effective. Full article

This paper presents a fully-differential touch screen panel (TSP) self-capacitance sensing (SCS) system with a self-capacitance mismatch calibration technique. Due to the self-capacitance mismatch of TSP, the analog front-end (AFE) of the receiver (RX) circuit suffers from dynamic range degradation and gain limitations, which lead to the signal-to-noise ratio (SNR) loss for the TSP SCS system. The proposed calibration introduces the difference in input resistance and the driving amplifier’s strength between the fully-differential input. Thus, the mismatch effect is efficiently relieved in terms of area and power consumption. The proposed calibration restores the SNR by $19.54$ dB even under the worst self-capacitance mismatch case. Full article

This paper investigates the usability of touch screens used in mass production road vehicles. Our goal is to provide a detailed comparison of conventional physical buttons and capacitive touch screens taking the human factor into account. The pilot test focuses on a specific Non-driving Related Task (NDRT): the control of the on-board climate system using a touch screen panel versus rotating knobs and push buttons. Psychological parameters, functionality, usability and, the ergonomics of In-Vehicle Information Systems (IVIS) were evaluated using a specific questionnaire, a system usability scale (SUS), workload assessment (NASA-TLX), and a physiological sensor system. The measurements are based on a wearable eye-tracker that provides fixation points of the driver’s gaze in order to detect distraction. The closed road used for the naturalistic driving study was provided by the ZalaZONE Test Track, Zalaegerszeg, Hungary. Objective and subjective results of the pilot study indicate that the control of touch screen panels causes higher visual, manual, and cognitive distraction than the use of physical buttons. The statistical analysis demonstrated that conventional techniques need to be complemented in order to better represent human behavior differences. Full article

As the demand for flexible organic light-emitting diodes (OLEDs) grows beyond that for rigid OLEDs, various elements of OLEDs, such as thin-film transistors, electrodes, thin-film encapsulations (TFEs), and touch screen panels, have been developed to overcome OLEDs’ physical and chemical limitations through material and structural design. In particular, TFEs, which protect OLEDs from the external environment, including reactive gases, heat, sunlight, dust, and particles, have technical difficulties to be solved. This review covers various encapsulation technologies that have been developed with the advent of atomic layer deposition (ALD) technology for highly reliable OLEDs, in which solutions to existing technical difficulties in flexible encapsulations are proposed. However, as the conventional encapsulation technologies did not show technological differentiation because researchers have focused only on improving their barrier performance by increasing their thickness and the number of pairs, OLEDs are inevitably vulnerable to environmental degradation induced by ultraviolet (UV) light, heat, and barrier film corrosion. Therefore, research on multi-functional encapsulation technology customized for display applications has been conducted. Many research groups have created functional TFEs by applying nanolaminates, optical Bragg mirrors, and interfacial engineering between layers. As transparent, wearable, and stretchable OLEDs will be actively commercialized beyond flexible OLEDs in the future, customized encapsulation considering the characteristics of the display will be a key technology that guarantees the reliability of the display and accelerates the realization of advanced displays. Full article

This paper presents a front-end architecture for touch screen panel (TSP) readout in a TSP-integrated, ultrathin flexible display to mitigate severe display noise interference, which is an uncommon mode caused by the large panel load of the TSP in the flexible display. The differential sensing method with multireference TSP channels minimized an imbalance of the phase and amplitude of the coupled-display noise interference. In addition, cascaded time-discrete bandpass sampling was employed to enhance the touch sensitivity in the sensing block. Moreover, a rated front-end block could be reconfigured to a differential or single-ended sensing structure, which reused the prefilter capacitors in the differential sensing for offset cancellation in reference capacitance sensing. To further improve the sensitivity, programmable postfiltering was employed on the reference TSP channels. Subsequently, the proposed front-end was implemented in a 350 nm process, wherein it achieved a SNR of 50.5 dB with a scan rate of 200 Hz and attenuated aggravated display noise interference by more than 6.84 dB as compared to the conventional differential sensing method. The designed chip occupied an area of 4.8 mm² and consumed 17.6 mW from a 3 V supply. Full article

This paper proposes a low-computing-complexity touch signal detection method and analog front-end (AFE) circuits based on cross-correlation technology for large mutual capacitance touch screen panels (TSPs). To solve the traditional touch signal detection method problem of lots of invalid data being sampled and processed in a large-size TSP, the proposed method only samples and processes the signals around the touch points rather than full-screen data to decrease the computing complexity and analog–digital convertor (ADC) acquisition number. Compared with the traditional method, the proposed touch points search algorithm complexity decreases from MN to M + nN where M, N, and n are the number of RX channels, TX channels, and touch points, respectively. The maximum ADC acquisition number of the proposed method decreases from MN to 18n. Based on the proposed touch signal detection method, the AFE circuits are designed by a 0.11 μm process. The proposed dual cross-correlation AFE achieves detection of the weak touch signal submerged in the large display panel noise. The average channel area and power consumption are decreased to 0.015 mm² and 0.227 mW, respectively. The maximum frame rate is 384.6 Hz with 10 touch points. The proposed cross-correlation AFE achieves a high frame rate while reducing the die area and power consumption. Full article

This paper presents a mutual capacitance touch readout IC architecture for 120 Hz high-refresh-rate AMOLED displays. In high-refresh-rate AMOLED panels, whole pixels in a horizontal line should be updated without any time-sharing with each other, leading to an amplified display noise on touch screen panel (TSP) electrodes. The proposed system architecture mitigates severe display noise by synchronizing the driving for the TSP and AMOLED pixel circuits. The proposed differential sensing technique, which is based on noise suppression in reference to mutual capacitance channels, minimizes common-mode display noise. In the front-end circuit, intrinsic circuit offset is cancelled by a chopping scheme, which correlates to the phase of the driving signals in the TSP driver and operating clocks of the front-end. Operating at a 120 Hz scan-rate, it reduces display noise by more than 11.6 dB when compared with the conventional single-ended TSP sensing method. With a built-in 130-nm CMOS, a prototype IC occupies an area of 8.02 mm² while consuming 6.4-mW power from a 3.3 V analog voltage supply. Full article

Among the various applications of carbon nanotubes (CNTs) that have been investigated since the discovery of their exceptional potential in the electronic field, great interest has been directed towards the creation of carbon-based materials capable of replacing Indium Tin Oxide (ITO) as a transparent electrode. Such transparent conductive films find application in touch panels, LCD screens, OLED displays, photovoltaic cells, and many others. This review presents a collection of techniques that have been proposed during the last decade for the modeling of carbon nanotube-based materials by means of equivalent electrical networks. These networks represent the electrical properties of CNT-based conductive thin films in a way that can be easily included in circuit simulators for the simulation-assisted design of the different devices under static and dynamic conditions. Full article

It is important to operate devices with control panels and touch screens assisted by haptic feedback in mobile environments such as driving automobiles and electric power wheelchairs. A lot of consideration is needed to give accurate haptic feedback, especially, presenting clear touch feedback to the elderly and people with reduced sensation is a very critical issue from healthcare and safety perspectives. In this study, we aimed to identify the perceptual characteristics for the frequency and direction of haptic vibration on the touch screen with vehicle-driving vibration and to propose an efficient haptic system based on these characteristics. As a result, we demonstrated that the detection threshold shift decreased at frequencies above 210 Hz due to the contact pressure during active touch, but the detection threshold shift increased at below 210 Hz. We found that the detection thresholds were 0.30–0.45 gpeak with similar sensitivity in the 80–270 Hz range. The haptic system implemented by reflecting the experimental results achieved characteristics suitable for use scenarios in automobiles. Ultimately, it could provide practical guidelines for the development of touch screens to give accurate touch feedback in the real-world environment. Full article

The multiple frequency driving method (MFDM) capacitive touch system (CTS), which drives transmit (TX) electrodes in parallel, has been developed to improve the touch-sensitivity of large touch screens at high speed. However, when driving multiple TX electrodes at the same time, TX signals are merged through the touch panel, which results in increasing the peak-to-average power ratio (PAPR) of combined signals. Due to the high PAPR, the signal is distorted out of the power amplifier’s linear range, causing a touch malfunction. The MFDM CTS can avoid this problem by reducing the drive voltage or partially driving the TX electrodes in parallel. However, these methods cause a significant performance drop with respect to signal-to-noise ratio (SNR) in the MFDM systems. This paper proposes a stack method which reduces PAPR effectively without the performance degradation of MFDM and achieves real-time touch sensitivity in large display panels. The proposed method allocates a suitable phase for each TX electrode to reduce the peak power of combined signals. Instead of investigating all of the phases for the total number of TX electrodes, the optimal phase is estimated from the highest frequency to the lowest one and fixed one by one, which can reduce the required time to find a suitable phase considerably. As a result, it enables high-speed sensing of multi-touch on a large touch screen and effectively reduces PAPR to secure high signal-to-noise-ratio (SNR). Through experiments, it was verified that the proposed method in this paper has an SNR of 39.36 dB, achieving a gain of 19.35 and 5.98 dB compared to the existing touch system method and the algorithm used in the communication system, respectively. Full article

Acrylic pressure-sensitive adhesives (PSAs) are used as fixatives between layers of a display. PSAs’ function is an important factor that determines the performance of the display. Of the various display types available, the touch screen panel (TSP) of smart devices is firmly related to the relative permittivity of the elementals. Therefore, adjusting the relative permittivity of the PSA is indispensable for driving the TSP. Accordingly, selected acrylic pre-polymers were polymerized and the pre-polymer was blended and cross-linked with monomers with different chemical structure to adjust the relative permittivity. The monomers were hexametyldisiloxane (HMDS), N-vinylcaprolactam (NVC), tert-butyl acrylate (TBA), and isooctadecyl acrylate (ISTA). The gel fraction and transmittance as a function of the monomers show a similar result to the pure acrylic PSA. However, the gel fraction value decreased to about 90% and the transmittance decreased to about 85%, due to the immiscibility between nonpolar HMDS and acrylic PSA. On the other hand, the adhesion properties were improved when NVC was added because of the polarity of the nitrogen group. In addition, the relative permittivity of the PSA decreased regardless of the monomer chosen. There was, however, a difference in the optimal content of each monomer, and NVC decreased from 4 phr content to about 3.4 in reducing relative permittivity. Through the above results, it was confirmed that NVC having a nitrogen group is most advantageous in lowering adhesion properties and relative permittivity, and necessitates further research based on the findings. Full article