Capacitive Touch Screen Research Articles

Design of a Detection System for Projected Capacitive Touch Screen Based on PSoC

Design of a Detection System for Projected Capacitive Touch Screen Based on PSoC

Piezoelectric vs. Capacitive Based Force Sensing in Capacitive Touch Panels

High sensitivity force sensing is a desirable function of capacitance touch screen panels. In this paper, we report on a dynamic force detection technique by utilizing piezoelectric materials. The force-voltage responsivities are investigated for four widely used stack-ups, with various panel thicknesses and touch locations. Based on the theoretical analysis and simulation results, the maximum responsivity and the signal-to-noise ratio are achieved at 0.42 V/N and 59.1 dB, respectively. The proposed technique implements force sensing successfully, enhancing the human–machine interactivity experience.

Fluorescent light energy harvesting using a capacitive touch screen

This Letter presents a fluorescent light energy harvesting method using a capacitive touch screen to charge a phone battery. The proposed idea utilises additional power circuitry, i.e., AC to DC and DC to DC converters to provide DC power to the load. Fluorescent light used in the experiment had a 29.56-V peak-to-peak voltage at 38 kHz frequency. Experimental measurements show that the fluorescent light energy harvesting system can generate 835 μW of power.

Design and Implementation of Tangible Interface Using Smart Puck System

In this paper, we propose a novel tangible interface system whose system does not use the expensive hardware is introduced. This proposed tangible interface is used on the table top capacitive multi touch-screen. The tangible interface apparatus which is called smart puck has sanguine arduino compatible board. The board has a Cds photo-sensing sensor and the EPP8266 WiFi module. The Cds sensor decodes the photometric PWM signals from the system and sends corresponding information to the system via TCP/IP. The system has a server called MT-Server to communicate with the smart pucks. The tangible interface shows reliable operation with fast response that is compatible to the expensive traditional devices in the market.

Self-assembled large scale metal alloy grid patterns as flexible transparent conductive layers.

The development of scalable synthesis techniques for optically transparent, electrically conductive coatings is in great demand due to the constantly increasing market price and limited resources of indium for indium tin oxide (ITO) materials currently applied in most of the optoelectronic devices. This work pioneers the scalable synthesis of transparent conductive films (TCFs) by exploiting the coffee-ring effect deposition coupled with reactive inkjet printing and subsequent chemical copper plating. Here we report two different promising alternatives to replace ITO, palladium-copper (PdCu) grid patterns and silver-copper (AgCu) fish scale like structures printed on flexible poly(ethylene terephthalate) (PET) substrates, achieving sheet resistance values as low as 8.1 and 4.9 Ω/sq, with corresponding optical transmittance of 79% and 65% at 500 nm, respectively. Both films show excellent adhesion and also preserve their structural integrity and good contact with the substrate for severe bending showing less than 4% decrease of conductivity even after 105 cycles. Transparent conductive films for capacitive touch screens and pixels of microscopic resistive electrodes are demonstrated.

Investigation the interaction between the pulsed ultraviolet laser beams and PEDOT:PSS/graphene composite films

This research aims to investigate the interaction between pulsed ultraviolet (UV) laser beams and transparent PEDOT:PSS/graphene composite films. The laser ablated microstructure on film surfaces provides the electrical isolation and prevents the electrical contact from each location for the projected capacitive touch screen. Before the laser processing, the surface roughness, microhardness, spectrum and cross-sectional view of PEDOT:PSS/graphene composite film were measured by an atomic force microscope, a nanoindenter, a spectrometer and a scanning electron microscope, respectively. The focused UV laser beam was irradiated along line patterns with an overlapping rate of 60% and the applied laser fluences much over the ablation thresholds of 1.27J/cm2 to 3.82J/cm2. The surface morphology, three-dimensional topography, and cross-sectional profile of isolated lines and electrode structures after laser microstructuring were measured by a confocal laser scanning microscope. By increasing the laser fluence from 1.27J/cm2 to 3.82J/cm2, the ablated line widths and depths increased from 12.17±0.24μm to 21±0.37μm and from 190±9nm to 227±15nm, respectively. Moreover, the ablated lines of microstructuring electrodes had a clear and regular ablated edge quality.

Rapid detection of E. coli cells in urine samples using a self-capacitance touchscreen device.

Escherichia coli is one of the main causes of urinary tract infections (UTIs). E. coli is commonly detected from urine using standard culture method. However, the urine sampling and analysis required for these methods can be costly, time consuming (requires 24 to 48 hours) and labor-intensive. This work proposes a capacitive touch screen sensor concept as possible alternative device for rapid detection of E. coli in urine samples. E. coli solutions prepared at different concentrations and urine samples (with spiked and nor spike E. coli) obtained from healthy women participants, have been analyzed using a capacitance evaluation kit. It has been demonstrated in this study that the use of this evaluation kit provides a low-cost and simple alternative system for detecting E. coli present in urine. Several experimental tests were performed to determine the optimal testing volume, the sensitivity of the sensor, limit of detection and repeatability. The optimal testing volume was 80 microliters and the analytical sensitivity was 17 counts per picofarad (pF). The lowest detectable concentration is around 3.98 × 10(5) CFU/ml. The repeatability (r) was found to be 7.2 or 6.2 % (in r%). The capacitive touch sensor gave promising results that could be used to design and realize a portable diagnostic device for early-stage detection of UTIs.

74.1L: Late‐News Paper: Force‐Sensing Touch screens

We present breakthrough touchscreens having dual capacitive and force‐sensing technologies. NDT's screen‐printed force‐sensing module is attached directly under the capacitive touchscreens, thus providing high sensitivity, fine spatial resolution and scalability to bigger display sizes. This is in contrast to present force‐sensing displays with capacitive plates or force‐sensing resistors on the display periphery.

Low-Power Touch-Sensing Circuit With Reduced Scanning Algorithm for Touch Screen Panels on Mobile Devices

Touch screen panel (TSP) technology has dramatically enhanced the connectivity between man and machine, in particular within mobile consumer electronics where mobility is a key design criterion. This paper introduces a novel charge-sensing technique derived from the behavioral characteristics of a mutual capacitive touch screen panel. The approach is based on a reduced scan algorithm whereby both the target and its surroundings form the node and the selection process is conducted in two phases. In the first phase, the introduction of a charge on the TSP is sensed, while the second phase evaluates when the touch event occurs on the TSP. The proposed algorithm reduces the number of sensing nodes activated during the waiting period by observing the behavior of a single row within the charge sensing array, as opposed to the more conventional approach in which all TSP nodes are scanned. As a result, power consumption is reduced by 60% during the sensing phase, while the dynamic sensing range is increased by a factor of 38% for a complete two-stage sensing cycle.

Concurrent Driving Method with Fast Scan Rate for Large Mutual Capacitance Touch Screens

A novel touch screen control technique is introduced, which scans each frame in two steps of concurrent multichannel driving and differential sensing. The proposed technique substantially increases the scan rate and reduces the ambient noise effectively. It is also extended to a multichip architecture to support excessively large touch screens with great scan rate improvement. The proposed method has been implemented using 0.18 μm CMOS TowerJazz process and tested with FPGA and AFE board connecting a 23-inch touch screen. Experimental results show a scan rate improvement of up to 23.8 times and an SNR improvement of 24.6 dB over the conventional method.

Healable capacitive touch screen sensors based on transparent composite electrodes comprising silver nanowires and a furan/maleimide diels-alder cycloaddition polymer.

A healable transparent capacitive touch screen sensor has been fabricated based on a healable silver nanowire-polymer composite electrode. The composite electrode features a layer of silver nanowire percolation network embedded into the surface layer of a polymer substrate comprising an ultrathin soldering polymer layer to confine the nanowires to the surface of a healable Diels-Alder cycloaddition copolymer and to attain low contact resistance between the nanowires. The composite electrode has a figure-of-merit sheet resistance of 18 Ω/sq with 80% transmittance at 550 nm. A surface crack cut on the conductive surface with 18 Ω is healed by heating at 100 °C, and the sheet resistance recovers to 21 Ω in 6 min. A healable touch screen sensor with an array of 8×8 capacitive sensing points is prepared by stacking two composite films patterned with 8 rows and 8 columns of coupling electrodes at 90° angle. After deliberate damage, the coupling electrodes recover touch sensing function upon heating at 80 °C for 30 s. A capacitive touch screen based on Arduino is demonstrated capable of performing quick recovery from malfunction caused by a razor blade cutting. After four cycles of cutting and healing, the sensor array remains functional.

Front‐end Δ C / C 0 capacitive interface based on negative impedance converter

A simple design methodology of the capacitive front-end readout electronics, based on the negative impedance converter, is presented. The concept uses a parallel connection of positive and inverted-negative value capacitors, that allows removing the constant part C0 from the sensor gain transfer function. The circuit enables integration of an accurate and very sensitive capacitance-to-voltage converter with ordinary discrete operational amplifiers. This is required in experimental scientific instrumentation as well as in the integrated CMOS interface of capacitive microelectromechanical systems (MEMSs) and touchscreens. Circuit description, noise considerations and measured results are presented.

Algorithm for improving SNR using high voltage and differential Manchester code for capacitive touch screen panel

An algorithm for a capacitive touch screen panel that can make the sum of the signal into `0' for the use of high voltage is presented. The differential Manchester code is combined with the Walsh-Hadamard code to generate an input coded signal. Owing to the property of the differential Manchester code, the Moore-Penrose pseudoinverse matrix is employed to decode-mutual capacitance from the received signal. As only the variation between the un-touch and touch condition is detected at the receiver, a high-voltage input coded signal is used. Unlike a normal touch system, the decoded sensing capacitance in the proposed algorithm does not have an absolute value. Positive decoded capacitance is the un-touch condition and negative decoded capacitance is the touch condition. The simulated signal-to-noise ratio (SNR) of the proposed algorithm is 27.9 dB, which is 8.26 dB higher than SNR in not return to zero (NRZ).

A 45-dB, 150-Hz, and 18-mW Touch Controller for On-Cell Capacitive TSP Systems

A touch controller is proposed for on-cell capacitive touch screen panel systems, which adopts a newly proposed peaking noise detector and low-frequency rejection filters. Implemented in a 0.35-μmCMOS, the proposed touch controller with 3.3-V drive signal shows the maximum signal-to-noise ratio and scan rate of 45 dB and 150 Hz, respectively, while consuming 18 mW from a 3.3-V supply.

Efficient Multi-Touch Detection Algorithm for Large Touch Screen Panels

Large mutual capacitance touch screen panels (TSP) are susceptible to display and ambient noise. This paper presents a multi-touch detection algorithm using an efficient noise compensation technique for large mutual capacitance TSPs. The sources of noise are presented and analyzed. The algorithm includes the steps to overcome each source of noise. The algorithm begins with a calibration technique to overcome the TSP mutual capacitance variation. The algorithm also overcomes the shadow effect of a hand close to TSP and mutual capacitance variation by dynamic threshold calculations. Time and space filters are also used to filter out ambient noise. The experimental results were used to determine the system parameters to achieve the best performance.

Microflotronics: A Flexible, Transparent, Pressure‐Sensitive Microfluidic Film

There is an increasing demand for sensitive, flexible, and low‐cost pressure sensing solutions for health monitoring, wearable sensing, robotic and prosthetic applications. Here, the first flexible and pressure‐sensitive microfluidic film is reported, referred to as a microflotronic, with high transparency and seamless integratability with the state‐of‐the‐art microelectronics. The microflotronic film represents the initial effort to utilize a continuous microfluidic layer as the sensing elements for large‐area dynamic pressure mapping applications, and meanwhile an ultrahigh sensitivity of 0.45 kPa−1 has been achieved in a compact, flexible, and transparent packaging. The response time of the device is in the millisecond range, which is at least an order of magnitude faster than that of its conventional flexible solid‐state counterparts. In addition, the fabrication process of the device is fully compatible with the industrial‐scale manufacturing of capacitive touchscreen devices and liquid‐crystal displays. The overall device packaging can be as thin as 200 μm with an optical transparency greater than 80%. Several practical applications were successfully demonstrated, including surface topology mapping and dynamic blood pressure monitoring. The microflotronic devices offer an alternative approach to the solid‐state pressure sensors, by offering an unprecedented sensitivity and ultrafast response time in a completely transparent, flexible and adaptive platform.

Development of a high-resolution RGBW flexible display using a white organic light-emitting diode with microcavity structure and that of a side-roll touch panel

In this study, white organic electroluminescent devices with microcavity structures were developed. A flexible high-resolution active-matrix organic light-emitting diode display with low power consumption using red, green, blue, and white sub-pixels formed by a color-filter method was fabricated. In addition, a side-roll touch display was developed in combination with a capacitive flexible touch screen.

A Methodology for Evaluating Accuracy of Capacitive Touch Sensing Grid Patterns

In recent years, there has been significant increase in research conducted in the field of capacitive touch technology. Capacitive touch screen technology, both in consumer electronics (for example, smartphones, MP3 players, etc.) and in wall mount displays (for example, ATM kiosks) seem to be omnipresent in the future. This paper discusses the physical design of the self-capacitive grid patterns used in current smartphones and the interpolation algorithms used to determine the position of the touch. The main aim of this paper is to simulate and test different touch screen patterns other than the widely used diamond shaped grid design and to provide a methodology for the accuracy comparison of sensor patterns. The paper deals with self-capacitance and presents results based on simulations for various sensor patterns.

A capacitive touch screen sensor for detection of urinary tract infections in portable biomedical devices.

Incidence of urinary tract infections (UTIs) is the second highest among all infections; thus, there is a high demand for bacteriuria detection. Escherichia coli are the main cause of UTIs, with microscopy methods and urine culture being the detection standard of these bacteria. However, the urine sampling and analysis required for these methods can be both time-consuming and complex. This work proposes a capacitive touch screen sensor (CTSS) concept as feasible alternative for a portable UTI detection device. Finite element method (FEM) simulations were conducted with a CTSS model. An exponential response of the model to increasing amounts of E. coli and liquid samples was observed. A measurable capacitance change due to E. coli presence and a tangible difference in the response given to urine and water samples were also detected. Preliminary experimental studies were also conducted on a commercial CTSS using liquid solutions with increasing amounts of dissolved ions. The CTSS was capable of distinguishing different volumes of liquids, also giving an exponential response. Furthermore, the CTSS gave higher responses to solutions with a superior amount of ions. Urine samples gave the top response among tested liquids. Thus, the CTSS showed the capability to differentiate solutions by their ionic content.

An alternative method for smartphone input using AR markers

Abstract As smartphones came into wide use recently, it has become increasingly popular not only among young people, but among middle-aged people as well. Most smartphones adopt capacitive full touch screen, so touch commands are made by fingers unlike the PDAs in the past that use touch pens. In this case, a significant portion of the smartphone's screen is blocked by the finger so it is impossible to see the screens around the finger touching the screen; this causes difficulties in making precise inputs. To solve this problem, this research proposes a method of using simple AR markers to improve the interface of smartphones. A marker is placed in front of the smartphone camera. Then, the camera image of the marker is analyzed to determine the position of the marker as the position of the mouse cursor. This method can enable click, double-click, drag-and-drop used in PCs as well as touch, slide, long-touch-input in smartphones. Through this research, smartphone inputs can be made more precise and simple, and show the possibility of the application of a new concept of smartphone interface.