Touch Applications Research Articles

Highly Sensitive Soft Pressure Sensors for Wearable Applications Based on Composite Films with Curved 3D Carbon Nanotube Structures.

Soft pressure sensors based on 3D microstructures exhibit high sensitivity in the low-pressure range, which is crucial for various wearable and soft touch applications. However, it is still a challenge to manufacture soft pressure sensors with sufficient sensitivity under small mechanical stimuli for wearable applications. This work presents a novel strategy for extremely sensitive pressure sensors based on the composite film with local changes in curved 3D carbon nanotube (CNT) structure via expandable microspheres. The sensitivity is significantly enhanced by the synergetic effects of heterogeneous contact of the microdome structure and changes of percolation network within the curved 3D CNT structure. The finite-element method simulation is used to comprehend the relationships between the sensitivity and mechanical/electrical behavior of microdome structure under the applied pressure. The sensor shows an excellent sensitivity (571.64 kPa-1 ) with fast response time (85ms), great repeatability, and long-term stability. Using the developed sensor, a wireless wearable health monitoring system to avoid carpel tunnel syndrome is built, and a multi-array pressure sensor for realizing a variety of movements in real-time is demonstrated.

Synergistic effect of carbon nanotubes and carbon black as nanofillers of silicone rubber pressure sensors

Pressure sensors based on nitrogen-doped bamboo-shaped carbon nanotubes (N-BCNT) and carbon black (CB) as nanofillers, polyurethane foam (PU) as supporting substrate, and silicone rubber (SR) as a matrix were prepared. Dip coating was used to coat PU with 0.44 wt% nanofiller, including different mixing ratios of N-BCNT and CB (5:5; 6:4; 7:3; 8:2; 9:1). Then, the coated PU is impregnated in SR to fill the pores. Due to the higher aspect ratio of the N-BCNT, it contributes more to improving the electrical conductivity in the composites, while the CB fills the smaller gaps. The prepared sensors were tested in various applications, and it was found that the optimal mixing ratio of nanofillers was 7:3 N-BCNT:CB. Thus, a multifunctional pressure sensor has been developed successfully with excellent flexibility and good resilience, suitable for motion detection and finger touch applications. The pressure sensor showed high sensitivity, and the ability to detect a wide range of pressures. The sensor exhibited success in a range of applications, paving the way for its potential use in various fields in the future, such as wearable devices, prosthetics, robotic devices, and medical devices.

Crack-inducing Strain Sensor Array using Inkjet-Printed Silver Thin Film for Underplate and Off-centered Force Sensing Applications.

The change in resistance upon bending in metal films as thick as 1 mm used for underpanel force touch applications is limited by the low sensitivity, thus requiring high-performance readout circuitry. In this paper, we report inkjet-printed silver thin films having crack-inducing underlayers, which further increases the sensitivity of their resistance changes under deformation. This allows for detecting weak vertical forces even through the plates (force-receiving layer), such as 0.4 or 1.2 mm thick polyethylene terephthalate or 0.4 mm thick glass. The underplate sensors will detect a force level as low as 10 gf, which corresponds to the amount of force required for fingerprint recognition. Furthermore, such highly sensitive strain sensors can potentially solve the inaccuracy issue of wearable devices, which can occur when misplaced sensors detect relatively weak biosignals, such as heart rate and blood pressure. The sensor detects the accurate pulse patterns of the wrist artery even though it is off-centered from the artery by 6 mm or larger. The crack-based strain sensor and its usage as a hidden underplate force sensing device will create various wearable and user-machine interface applications.

Hardening the Security of Multi-Access Edge Computing through Bio-Inspired VM Introspection

The extreme bandwidth and performance of 5G mobile networks changes the way we develop and utilize digital services. Within a few years, 5G will not only touch technology and applications, but dramatically change the economy, our society and individual life. One of the emerging technologies that enables the evolution to 5G by bringing cloud capabilities near to the end users is Edge Computing or also known as Multi-Access Edge Computing (MEC) that will become pertinent towards the evolution of 5G. This evolution also entails growth in the threat landscape and increase privacy in concerns at different application areas, hence security and privacy plays a central role in the evolution towards 5G. Since MEC application instantiated in the virtualized infrastructure, in this paper we present a distributed application that aims to constantly introspect multiple virtual machines (VMs) in order to detect malicious activities based on their anomalous behavior. Once suspicious processes detected, our IDS in real-time notifies system administrator about the potential threat. Developed software is able to detect keyloggers, rootkits, trojans, process hiding and other intrusion artifacts via agent-less operation, by operating remotely or directly from the host machine. Remote memory introspection means no software to install, no notice to malware to evacuate or destroy data. Experimental results of remote VMI on more than 50 different malicious code demonstrate average anomaly detection rate close to 97%. We have established wide testbed environment connecting networks of two universities Kyushu Institute of Technology and The City College of New York through secure GRE tunnel. Conducted experiments on this testbed deliver high response time of the proposed system.

Spatio-Temporal Encoding Improves Neuromorphic Tactile Texture Classification

With the increase in interest in the deployment of robots in unstructured environments to work alongside humans, the development of human-like sense of touch for robots becomes important. In this work, we implement a multi-channel neuromorphic tactile system that encodes contact episodes as discrete spike events that mimic the behavior of slow adapting mechanoreceptors. We study the impact of information pooling across artificial mechanoreceptors on classification performance of spatially non-uniform naturalistic textures. We encoded the spatio-temporal activation patterns of mechanoreceptors through gray-level co-occurrence matrix computed from time-varying mean spiking rate-based tactile response volume. We found that this approach greatly improved texture classification in comparison to the use of individual mechanoreceptor response alone. In addition, the performance was also more robust to changes in sliding velocity. The importance of exploiting precise spatial and temporal correlations between sensory channels is evident from the fact that on either removal of precise temporal information or altering of spatial structure of response pattern, a significant performance drop was observed. This study thus demonstrates the superiority of population coding approaches that can exploit the precise spatio-temporal information encoded in activation patterns of mechanoreceptor populations. It, therefore, makes an advance in the direction of development of bio-inspired tactile systems required for realistic touch applications in robotics and prostheses.

A 200-μW Interface for High-Resolution Eddy-Current Displacement Sensors

This article presents a low-power eddy-current sensor interface for touch applications. It is based on a bang-bang digital phase-locked loop (DPLL) that converts the displacement of a metal target into digital information. The PLL consists of a digitally controlled oscillator (DCO) built around a sensing coil and a capacitive DAC, a comparator-based bang-bang phase/frequency detector (PFD), and a digital loop filter (DLF). The PLL locks the DCO to a reference frequency, making its digital input a direct representation of the sensing coil inductance. To compensate for the coil inductance tolerances, the DCO's center frequency can be trimmed by a second capacitive DAC. This approach obviates the need for a reference coil. When combined with a 5-mm-diameter sensing coil located 500 μm from a metal target, the interface achieves a displacement resolution of 6.7 nm (rms) in a 3-kHz bandwidth. It consumes 200 μW from a 1.8-V power supply, which represents the best-reported tradeoff between power consumption, bandwidth, and resolution.

Two‐dimensional long‐period fiber grating sensor for touch applications

AbstractIn this study we present a two‐dimensional force sensor based on a single long‐period fiber grating (LPG) to be applied to robotic manipulators grasping control. The measuring force is applied to the fiber transverse section and this lateral compression induces birefringence on the fiber, which splits the LPG resonant dip into two. We track these dips using polarized controlled light and process the LPG spectra using artificial neural networks to determine the force intensity and direction. Finally, our single sensor proposal for 2D forces measurement can estimate an applied force with 0.2148 N and 5.977 deg. error.

An Extremely Inexpensive, Simple, and Flexible Carbon Fiber Electrode for Tunable Elastomeric Piezo-Resistive Sensors and Devices Realized by LSTM RNN.

Here, we describe the utility of a carbon fiber (CF) electrode that is inexpensive, simple, and flexible and can be embedded with elastomeric nanocomposite piezo-resistive sensors fabricated from silicone rubber (Ecoflex) blended with carbon nanotubes (CNTs) and various wt % of silicone thinner to tune the sensitivity and softness range. The performance of the CF electrode was evaluated on the basis of piezo-resistive responses from the sensors subjected to dynamic sinusoidal compressive strains at different levels and frequencies. The responses were positive-pressure effects with rate-dependent asymmetric nonlinear hysteresis characteristics. Developing a mathematical model to describe the rate-dependent asymmetric nonlinear hysteresis behavior is technically impossible; therefore, we employed artificial intelligence-based hysteresis modeling, long short-term memory recurrent neural network, to describe the hysteresis nonlinearity. The debonding strength of the CF electrode was determined in the pull-off testing and was found to be much higher than that of a copper wire electrode. The debonding mechanism was further elucidated via an in situ resistance profile. The importance of a robust conductive interface between a CF electrode and a nanocomposite was experimentally demonstrated. It was found that the inherent piezo-resistance of the CF was negligible compared with the piezo-resistance of the sensor; therefore, the signals from the sensor were free of interference. We believe CF-embedded tunable piezo-resistive sensors could be used in biomedical devices, artificial e-skins, robotic touch applications, and flexible keyboards where the required stretchability of the electrode can be introduced via an appropriate geometrical design.

Frequency Hopping and Parallel Driving With Random Delay Especially Suitable for the Charger Noise Problem in Mutual-Capacitive Touch Applications

Charger noise can cause inaccurate touch points and fake touch points to appear; this can cause a device to behave incorrectly. The intensity of charger noise could be much larger than the intensities of the original touch signals. Furthermore, the frequency of charger noise varies for each different charger. Therefore, industry experts have identified charger noise as the most difficult problem in capacitive touch applications. The demand for a solution to this problem has become crucial for the mobile market. In this paper, we prove that a particular combination of frequency hopping and repeated integration is an effective method to handle this problem. In addition, we propose an efficient discrete Fourier transform-based algorithm to select an effective sensing frequency. We propose parallel driving with random delay to enhance the signal-to-noise ratio (SNR). We show an efficient hardware–software co-design that facilitates the application of our methods in touch ICs. The experimental results show that our methods can increase SNR by over 45 dB and can find an effective sensing frequency fast and dynamically.

The Collection in a New Light – Towards Visual Exploration and Navigation of Academic Library Resources

The current experience of using digital libraries is bereft of many of the distinct qualities of exploring and handling items in the physical library space. The main question addressed in this paper is how to bridge the gap between the highly visual experience of browsing physical libraries, and the comparatively impoverished digital library environments. Creating effective applications integrating digital content in physical library spaces requires careful strategies with respect to user experience, content selection, and connections to real-world collections and events. We show collection-centric, event-centric and integrative approaches to creating touch-based applications, and demonstrate how usage data from touch applications can be used for optimization, as well as for inspiration for new applications.

Capacitive touch sensor

PurposeThe purpose of this paper is to analyse the possibilities of mechanical switch replacement by capacitive film touch sensor in applications requiring high reliability and short response time. Advantage of replacing mechanical switch by capacitive touch sensor is no mechanical wear and possible implementation of sensor in application where the switch could not be used or where the flexibility of the sensor substrate is required. The aim of this work is to develop a capacitive touch sensor with the advantage of maximum mechanical resistance, short response time and high sensitivity.Design/methodology/approachBased on various possible sensors layouts, the authors realized 18 different (14 self-capacitance and four mutual capacitance) topologies of capacitive sensor for touch applications. Three different technologies – PCB, LTCC and polymer technology – were used to characterize sensor’s behaviour. For precise characterization of different layouts realized on various substrates, the authors used integrated circuit FDC2214 capacitance-to-digital converter.FindingsSensing range of the capacitive touch (proximity) sensor is affected by the per cent of area covered by the sensor, and it does not depend on topology of sensor. The highest sensing range offers PCB technology. Flexible substrates can be used as proper substituent to rigid PCB.Originality/valueThe novelty of this work lies in finding the touch capacitive sensors that allow shorter switching times compared to standard mechanical switches.

Robust integrated shift register circuit over clock noises for in‐cell touch applications

AbstractThis paper proposes an integrated shift register circuit for an in‐cell touch panel that is robust over clock noises. It is composed of 10 thin film transistors and 1 capacitor, and the time division driving method is adopted to prevent the negative effect of display signals on the touch sensing. Two pre‐charging nodes are employed for reducing the uniformity degradation of gate pulses over time. In particular, the proposed circuit connects a drain of the first pre‐charging node's pull‐up thin film transistor (TFT) to the positive supply voltage instead of clock signals. This facilitates to lower coupling noises as well as to clock power consumption. The simulation program with an integrated circuit emphasis is conducted for the proposed circuit with low temperature poly‐silicon TFTs. The positive threshold voltage that shifts up to 12 V at the first pre‐charging pull‐up TFT can be compensated for without the uniformity degradation of gate pulses. For a 60‐Hz full‐HD display with a 120‐Hz reporting rate of touches, the clock power consumption of the proposed gate driver circuit is estimated as 7.13 mW with 160 stages of shift registers. In addition, the noise level at the first pre‐charging node is lowered to −28.95 dB compared with 2.37 dB of the previous circuit.

Highly Transparent, Stretchable, and Self-Healing Ionic-Skin Triboelectric Nanogenerators for Energy Harvesting and Touch Applications.

Recently developed triboelectric nanogenerators (TENGs) act as a promising power source for self-powered electronic devices. However, the majority of TENGs are fabricated using metallic electrodes and cannot achieve high stretchability and transparency, simultaneously. Here, slime-based ionic conductors are used as transparent current-collecting layers of TENG, thus significantly enhancing their energy generation, stretchability, transparency, and instilling self-healing characteristics. This is the first demonstration of using an ionic conductor as the current collector in a mechanical energy harvester. The resulting ionic-skin TENG (IS-TENG) has a transparency of 92% transmittance, and its energy-harvesting performance is 12 times higher than that of the silver-based electronic current collectors. In addition, they are capable of enduring a uniaxial strain up to 700%, giving the highest performance compared to all other transparent and stretchable mechanical-energy harvesters. Additionally, this is the first demonstration of an autonomously self-healing TENG that can recover its performance even after 300 times of complete bifurcation. The IS-TENG represents the first prototype of a highly deformable and transparent power source that is able to autonomously self-heal quickly and repeatedly at room temperature, and thus can be used as a power supply for digital watches, touch sensors, artificial intelligence, and biointegrated electronics.

Revisit of Thermoplastic EPDM/PP Dynamic Vulcanizates

A comprehensive survey of the available literature showed that in the last few decades, there has been a growing interest in the use of thermoplastic vulcanizates (TPVs). TPVs are the second largest group of soft thermoplastic elastomers (TPEs) after styrene-based block copolymers, and offer a wide range of potential and proven applications, including in mechanical rubber goods, under-the-hood applications in the automotive field, industrial hose applications, electrical applications, consumer goods, and soft touch applications. Over the last two decades, TPVs have shown a strong and steady market growth (~12% per year). Commercialized TPVs are commonly based on blends of ethylene propylene diene monomer (EPDM) rubber and polypropylene (PP), and to a lesser extent on combinations of butyl or nitrile rubber with PP. EPDM/PP TPVs are characterized by finely dispersed crosslinked EPDM rubber particles (particles size varying between 0.5 and 2.0 μm) distributed in a continuous thermoplastic PP matrix. If the rubber particles of such a blend are small enough and if they are vulcanized well enough, then the properties of the blend are generally improved. This review article introduces various topics and aspects relevant to EPDM/PP TPVs. The development of TPVs, the use of various types of crosslinking systems and co-agents as crosslinking agents for PP/EPDM blends, the morphology and rheology of TPVs, and their typical end-use applications are also reviewed.

The importance of therapeutic touch in nursing

Nowadays nurses consider the energy interaction with the environment of patients during nursing care. Nursing care includes combination of physical, social, psychological and in additon spiritual aspects. Nightingale who define the effects of energetic healing environment, placed touch application was firmly in the center of nursing practice. Rogers, Watson and the other nursing theorists mentioned that energy studies represents a good example for professional approach to spiritual health nursing. Nurses use non-conventional energy therapies like therapeutic touch further anymore in many countries. Therapeutic touch is a supplementary technique which is used for a specific purpose and intent of the universal energy and affection that helps patient finding the balance and attaining health. Nurses can reduce the occurrence of emotions like fear and anxiety, providing strong therapeutic effects in patients by using effective contact. It is an incomplete form of communication if nurses touch the patients just for daily planned interventions, patient-nurse relationship will approach will strengthen more by using, the level-professional friendship that include acceptance, interest and support posts. This article written with the aim to describe the therapeutic touch applications, explain benefits and areas.

Manufacturing Yield for Multiple Lines Gold Bumping Processes With Asymmetric Tolerances

Development of touch display driver IC (TDDI) has enabled slimmer smartphone design by virtue of the integration of touch controller and display driver ICs (DDIs) into a single chip. TDDI plays an important role in touch integrated display panels. Compared to conventional DDI, TDDI requires more bonding pads for touch applications, thus increasing the usage of gold. The requirement to keep costs down forces manufacturers to look for ways to reduce the usage of gold. In order to reduce the usage of gold, gold bumping processes with asymmetric tolerances are considered, in which deviations from the target are less tolerable in lower specification limits than in upper specification limits. In addition, due to economies of scale considerations, gold bumping processes involving multiple manufacturing lines are commonly considered in Taiwan. However, no yield index has been developed for multiple-line gold bumping processes with asymmetric tolerances. In this paper, we propose a new yield index ${C}^{{\prime \prime M}}_{{pk}} $ and derive an approximate distribution of $\hat {{C}}^{{\prime \prime M}}_{ {pk}} $ . In addition, the lower confidence bounds and critical values are provided for the multiple-line gold bumping processes with asymmetric tolerances. For illustration purposes, a real-world application in a gold bumping factory which is located in the Science-Based Industrial Park in Hsinchu, Taiwan, is presented.

P‐134: A Spatial Light Modulator with a Two‐Dimensional Array of Liquid Crystal Bubbles

AbstractA spatial light modulator (SLM) modulates one of the properties (amplitude, phase, polarization) of an optical wavefront that may be electrical, optical or pressure sensitive. This SLM is formed via surface‐assisted assembly of a two‐dimensional array cholesteric liquid crystal bubbles in an electro‐optical cell. This SLM device serves as an input transducer enabling active or bistable processing operations to control of light transmission or scattering. This finding will be useful for optical display and touch applications.

16.3: Printed Touch Sensors Using Carbon NanoBud® Material

AbstractCarbon NanoBud® transparent conductive films and touch sensors were manufactured by aerosol synthesis, Direct Dry Printing® and laser ablation. Touch sensors with high contrast for outdoor readability, flexibility allowing folding, and sharpangle 3D‐formability are described. CNB™ film production has now started for high‐quality touch applications.

43.1: Invited Paper: Touch‐Technology Diversity in Commercial Applications

AbstractProjected capacitive (p‐cap) touch technology now dominates the consumer‐electronics touch market, but many different touch technologies still compete in the commercial touch applications. Why is this so? Will it continue? While p‐cap market share will continue to grow, this objective analysis supports the view that diverse requirements in commercial‐touch applications will maintain touch ‘biodiversity‘.

Touchware: a software-based technique for high-resolution multi-touch sensing devices

Finger pointing on touch screens is a very natural way of human computer interaction. However, for many capacitive touch sensing devices, it may suffer from the nature of direct input since the size of human fingers and the lack of sensing precision make absolute positioning on touch screen difficult, especially on multi–touch sensing devices. Even if high–resolution/precision multi–touch devices become popular in the market, the cost is high and the positioning algorithm is not a flexible module. In this paper, we present Touchware, a software–based technique to overcome these limitations with low cost and to provide support for the development of multi–touch applications for rich input modalities. We introduce the maxima–based clustering algorithm and weight–based geometric algorithm for accurate finger positioning and first–contact–based decision with sniper for ghost pattern elimination. We evaluated the performance and show how the techniques can be successfully used for single–touch and multi–touch applications.