Multi Stage based Time Series Analysis of User Activity on Touch Sensitive Surfaces in Highly Noise Susceptible Environments

This article proposes a multistage framework for time series analysis of user activity on touch sensitive surfaces in noisy environments. Here multiple methods are put together in multi stage framework; including moving average, moving median, linear regression, kernel density estimation, partial differential equations and Kalman filter. The proposed three stage filter consisting of partial differential equation based denoising, Kalman filter and moving average method provides ~25% better noise reduction than other methods according to Mean Squared Error (MSE) criterion in highly noise susceptible environments. Apart from synthetic data, we also obtained real world data like hand writing, finger/stylus drags etc. on touch screens in the presence of high noise such as unauthorized charger noise or display noise and validated our algorithms. Furthermore, the proposed algorithm performs qualitatively better than the existing solutions for touch panels of the high end hand held devices available in the consumer electronics market qualitatively.Comment: 9 pages (including 9 figures and 3 tables); International Journal of Computer Applications (published

Reduction of Common Mode Noise and Global Multivalued Offset in Touch Screen Systems by Correlated Double Sampling

Touch-based interactivity has become an important function in displays. This paper reports on the signal processing of touch signals in which touch interactivity is processed as an image, and correlated double sampling (CDS) algorithm is applied for both common-mode noise reduction and global multivalued offset cancellation. Based on experimental results, we achieved a boost in SNR of 7.6 dB. The processed signal reduces detection errors and power consumption of the system

Reduction of Noise Spikes in Touch Screen Systems by Low Pass Spatial Filtering

This paper reports on a low-pass spatial filtering technique for reduction of noise spikes in capacitive touch screen panels. Filter bandwidth is adjusted by dynamically evaluating attenuation of signal and noise spikes. Based on the experimental results, we boost the signal-to-noise ratio by 15.6 dB and attenuate noise spikes by 19.25 dB. The processed signal yields higher detection accuracy and lower power consumption

A Multi-functional Touch Panel for Multi-Dimensional Sensing in Interactive Displays

This thesis presents a flexible graphene/polyvinylidene difluoride (PVDF)/graphene sandwich for three-dimensional touch interactivity. Here, an x-y plane touch is sensed using graphene capacitive elements, while force sensing in the z-direction is by a piezoelectric PVDF/graphene sandwich. By employing different frequency bands for the capacitive- and force-induced electrical signals, the two stimuli are detected simultaneously, achieving three-dimensional touch sensing. Static force sensing and elimination of propagated stress are achieved by augmenting the transient piezo output with the capacitive touch, thus overcoming the intrinsic inability of the piezoelectric material in detecting non-transient force signals and avoiding force touch mis-registration by propagated stress. As a capacitive signal is important for force touch interpretation, optimization algorithms have been developed and implemented. With correlated double sampling (CDS) and spatial low-pass filtering (SLPF) based techniques, the signal-to-noise ratio (SNR) of the capacitive touch signal is boosted by 15.6 dB, indicating improved detection accuracy. In terms of the readout speed, fixed pattern and random pattern related down-sampling techniques are applied, giving rise to reductions in both readout time (11.3 ms) and power consumption (8.79 mW).China Scholarship Counci

Silver Nanowire Transparent Electrodes for Soft Optoelectronic and Electronic Devices

School of Energy and Chemical Engineering (Energy Engineering)Recently, with an increasing importance of human-machine interface along with the rapid growth of Internet of Things (IoT), various flexible and stretchable electronic and optoelectronic devices have been developed for the wide range of multifunctional and wearable applications such as touch screen panels, organic solar cells, organic light-emitting diodes, thin-film loudspeakers, microphones, interactive displays, and electronic skins. High mechanical flexibility/stretchability, optical transparency, and electrical conductivity are the critical properties that transparent conductive electrodes (TCEs) should possess for the realization of high-performance flexible/stretchable electronics and optoelectronics. While indium tin oxide (ITO) has been widely used in commercial TCEs, the further development and application of ITO have been limited by the high cost and inherent brittleness of the material. One promising alternative to ITO as a TCE material is silver nanowire (AgNW) networks having good flexibility and stretchability, which can provide lower sheet resistance (Rs) and higher optical transmittance (T) than other TCE candidates such as carbon nanotubes, graphene, and conducting polymers. Moreover, AgNW networks can be readily prepared by low-cost solution-based process, enabling the mass production of next-generation optoelectronic and electronic applications. The integration of AgNW networks with the flexible/stretchable substrates can provide powerful platforms to realize highly stable and high-performance soft optoelectronic and electronic devices with the superior transparency and stable supply of electrical conductivity during mechanical deformations. This thesis covers our recent studies about flexible/stretchable AgNW TCEs and their applications in various soft optoelectronic and functional electronic devices. First, chapter 1 introduces research trends in flexible/stretchable transparent electrodes and several issues of AgNW networks that should be carefully considered for their future soft optoelectronic and electronic device applications. In chapter 2, we demonstrated a simple and efficient assembly strategy for the large-area, highly cross-aligned AgNW arrays for TCE applications through a modified bar-coating assembly. As opposed to conventional solvent-evaporation-induced assemblies, which are slow and produce nonuniform conductive networks, our modified bar-coating strategy enables fast, efficient, and uniform alignment of AgNWs in a large-area by simply dragging the Meyer rod over the AgNW solution on the target substrates. For the potential applications, we demonstrated large-scale, flexible, and transparent resistive-type touch screens and force-sensitive mechanochromic touch screens using cross-aligned AgNW transparent electrodes which exhibited highly uniform and precise touch sensing performance across the entire region. In chapter 3, we introduced ultrathin, transparent, and conductive hybrid nanomembranes (NMs) with nanoscale thickness, consisting of the orthogonal AgNW arrays embedded in a polymer matrix. Here, we present a skin-attachable NM loudspeaker and wearable transparent NM microphone, which can emit thermoacoustic sound and can provide excellent acoustic sensing capabilities. In chapter 4, solution-processable, high-performance flexible alternating-current electroluminescent (ACEL) devices are developed based on high-k nanodielectrics and cross-aligned AgNW transparent electrodes. The solution-processed La-doped barium titanate (BTO:La) nanocuboids are fabricated as high dielectric constant nanodielectrics, which can enhance the dielectric constant of an ACEL devices, enabling the fabrication of high-performance flexible ACEL devices with a lower operating voltage as well as higher brightness. In chapter 5, we fabricated transparent, flexible, and self-healable thermoacoustic loudspeakers based on AgNW/poly(urethane-hindered urea) (PUHU) conductive electrodes. Our self-healable AgNW/PUHU electrodes exhibit a great self-healing property for the surface damages by means of the dynamic reconstruction of reversible bulky urea bonds in PUHU. In chapter 6, synesthetic bimodal generation of sound and color is demonstrated by stretchable sound-in-display devices consisting of strain-insensitive stretchable AgNW electrodes and field-induced inorganic EL phosphor emissive layers. The stretchable sound-in-display devices show highly robust and reliable EL and sound generating performances that can be repeatedly stretched and released without severe performance degradation because of the use of strain-insensitive AgNW electrodes. Finally, in chapter 7, we summarize this thesis along with the future perspective of flexible/stretchable transparent electrodes that should be considered for next-generation soft electronic and optoelectronic device applications. In this thesis, studies on flexible/stretchable AgNW transparent electrodes and their device applications could be further expanded for diverse soft and wearable optoelectronic and electronic applications such as wearable sensors, healthcare monitoring devices, and human-machine interfaces with better convenience, appearance, and reusability.ope

From wearable towards epidermal computing : soft wearable devices for rich interaction on the skin

Human skin provides a large, always available, and easy to access real-estate for interaction. Recent advances in new materials, electronics, and human-computer interaction have led to the emergence of electronic devices that reside directly on the user's skin. These conformal devices, referred to as Epidermal Devices, have mechanical properties compatible with human skin: they are very thin, often thinner than human hair; they elastically deform when the body is moving, and stretch with the user's skin. Firstly, this thesis provides a conceptual understanding of Epidermal Devices in the HCI literature. We compare and contrast them with other technical approaches that enable novel on-skin interactions. Then, through a multi-disciplinary analysis of Epidermal Devices, we identify the design goals and challenges that need to be addressed for advancing this emerging research area in HCI. Following this, our fundamental empirical research investigated how epidermal devices of different rigidity levels affect passive and active tactile perception. Generally, a correlation was found between the device rigidity and tactile sensitivity thresholds as well as roughness discrimination ability. Based on these findings, we derive design recommendations for realizing epidermal devices. Secondly, this thesis contributes novel Epidermal Devices that enable rich on-body interaction. SkinMarks contributes to the fabrication and design of novel Epidermal Devices that are highly skin-conformal and enable touch, squeeze, and bend sensing with co-located visual output. These devices can be deployed on highly challenging body locations, enabling novel interaction techniques and expanding the design space of on-body interaction. Multi-Touch Skin enables high-resolution multi-touch input on the body. We present the first non-rectangular and high-resolution multi-touch sensor overlays for use on skin and introduce a design tool that generates such sensors in custom shapes and sizes. Empirical results from two technical evaluations confirm that the sensor achieves a high signal-to-noise ratio on the body under various grounding conditions and has a high spatial accuracy even when subjected to strong deformations. Thirdly, Epidermal Devices are in contact with the skin, they offer opportunities for sensing rich physiological signals from the body. To leverage this unique property, this thesis presents rapid fabrication and computational design techniques for realizing Multi-Modal Epidermal Devices that can measure multiple physiological signals from the human body. Devices fabricated through these techniques can measure ECG (Electrocardiogram), EMG (Electromyogram), and EDA (Electro-Dermal Activity). We also contribute a computational design and optimization method based on underlying human anatomical models to create optimized device designs that provide an optimal trade-off between physiological signal acquisition capability and device size. The graphical tool allows for easily specifying design preferences and to visually analyze the generated designs in real-time, enabling designer-in-the-loop optimization. Experimental results show high quantitative agreement between the prediction of the optimizer and experimentally collected physiological data. Finally, taking a multi-disciplinary perspective, we outline the roadmap for future research in this area by highlighting the next important steps, opportunities, and challenges. Taken together, this thesis contributes towards a holistic understanding of Epidermal Devices}: it provides an empirical and conceptual understanding as well as technical insights through contributions in DIY (Do-It-Yourself), rapid fabrication, and computational design techniques.Die menschliche Haut bietet eine große, stets verfügbare und leicht zugängliche Fläche für Interaktion. Jüngste Fortschritte in den Bereichen Materialwissenschaft, Elektronik und Mensch-Computer-Interaktion (Human-Computer-Interaction, HCI) [so that you can later use the Englisch abbreviation] haben zur Entwicklung elektronischer Geräte geführt, die sich direkt auf der Haut des Benutzers befinden. Diese sogenannten Epidermisgeräte haben mechanische Eigenschaften, die mit der menschlichen Haut kompatibel sind: Sie sind sehr dünn, oft dünner als ein menschliches Haar; sie verformen sich elastisch, wenn sich der Körper bewegt, und dehnen sich mit der Haut des Benutzers. Diese Thesis bietet, erstens, ein konzeptionelles Verständnis von Epidermisgeräten in der HCI-Literatur. Wir vergleichen sie mit anderen technischen Ansätzen, die neuartige Interaktionen auf der Haut ermöglichen. Dann identifizieren wir durch eine multidisziplinäre Analyse von Epidermisgeräten die Designziele und Herausforderungen, die angegangen werden müssen, um diesen aufstrebenden Forschungsbereich voranzubringen. Im Anschluss daran untersuchten wir in unserer empirischen Grundlagenforschung, wie epidermale Geräte unterschiedlicher Steifigkeit die passive und aktive taktile Wahrnehmung beeinflussen. Im Allgemeinen wurde eine Korrelation zwischen der Steifigkeit des Geräts und den taktilen Empfindlichkeitsschwellen sowie der Fähigkeit zur Rauheitsunterscheidung festgestellt. Basierend auf diesen Ergebnissen leiten wir Designempfehlungen für die Realisierung epidermaler Geräte ab. Zweitens trägt diese Thesis zu neuartigen Epidermisgeräten bei, die eine reichhaltige Interaktion am Körper ermöglichen. SkinMarks trägt zur Herstellung und zum Design neuartiger Epidermisgeräte bei, die hochgradig an die Haut angepasst sind und Berührungs-, Quetsch- und Biegesensoren mit gleichzeitiger visueller Ausgabe ermöglichen. Diese Geräte können an sehr schwierigen Körperstellen eingesetzt werden, ermöglichen neuartige Interaktionstechniken und erweitern den Designraum für die Interaktion am Körper. Multi-Touch Skin ermöglicht hochauflösende Multi-Touch-Eingaben am Körper. Wir präsentieren die ersten nicht-rechteckigen und hochauflösenden Multi-Touch-Sensor-Overlays zur Verwendung auf der Haut und stellen ein Design-Tool vor, das solche Sensoren in benutzerdefinierten Formen und Größen erzeugt. Empirische Ergebnisse aus zwei technischen Evaluierungen bestätigen, dass der Sensor auf dem Körper unter verschiedenen Bedingungen ein hohes Signal-Rausch-Verhältnis erreicht und eine hohe räumliche Auflösung aufweist, selbst wenn er starken Verformungen ausgesetzt ist. Drittens, da Epidermisgeräte in Kontakt mit der Haut stehen, bieten sie die Möglichkeit, reichhaltige physiologische Signale des Körpers zu erfassen. Um diese einzigartige Eigenschaft zu nutzen, werden in dieser Arbeit Techniken zur schnellen Herstellung und zum computergestützten Design von multimodalen Epidermisgeräten vorgestellt, die mehrere physiologische Signale des menschlichen Körpers messen können. Die mit diesen Techniken hergestellten Geräte können EKG (Elektrokardiogramm), EMG (Elektromyogramm) und EDA (elektrodermale Aktivität) messen. Darüber hinaus stellen wir eine computergestützte Design- und Optimierungsmethode vor, die auf den zugrunde liegenden anatomischen Modellen des Menschen basiert, um optimierte Gerätedesigns zu erstellen. Diese Designs bieten einen optimalen Kompromiss zwischen der Fähigkeit zur Erfassung physiologischer Signale und der Größe des Geräts. Das grafische Tool ermöglicht die einfache Festlegung von Designpräferenzen und die visuelle Analyse der generierten Designs in Echtzeit, was eine Optimierung durch den Designer im laufenden Betrieb ermöglicht. Experimentelle Ergebnisse zeigen eine hohe quantitative Übereinstimmung zwischen den Vorhersagen des Optimierers und den experimentell erfassten physiologischen Daten. Schließlich skizzieren wir aus einer multidisziplinären Perspektive einen Fahrplan für zukünftige Forschung in diesem Bereich, indem wir die nächsten wichtigen Schritte, Möglichkeiten und Herausforderungen hervorheben. Insgesamt trägt diese Arbeit zu einem ganzheitlichen Verständnis von Epidermisgeräten bei: Sie liefert ein empirisches und konzeptionelles Verständnis sowie technische Einblicke durch Beiträge zu DIY (Do-It-Yourself), schneller Fertigung und computergestützten Entwurfstechniken

Design of Touch Screen Controller IC for Transparent Fingerprint Sensor

Department of Electrical EngineeringA design of system architecture and analog-front-end (AFE) with high SNR and high frame rate for mutual capacitive touch screen with multiple electrodes is presented. Firstly, a differential continuous-mode parallel operation architecture (DCPA) is proposed for large-sized TSP. The proposed architecture achieves a high product of signal-to-noise ratio (SNR) and frame rate, which is a requirement of ROIC for large-sized TSP. DCPA is accomplished by using the proposed differential sensing method with a parallel architecture in a continuous-mode. A continuous-type differential charge amplifier removes the common-mode noise component, and reduces the self-noise by the band-pass filtering effect of the continuous-mode charge amplifier. In addition, the differential parallel architecture cancels the timing skew problem caused by the continuous-mode parallel operation and effectively enhances the power spectrum density of the signal. The proposed ROIC was fabricated using a 0.18-um CMOS process and occupied an active area of 1.25 mm2. The proposed system achieved a 72 dB SNR and 240 Hz frame rate with a 32 channel TX by 10 channel RX mutual capacitive TSP. Moreover, the proposed differential-parallel architecture demonstrated higher immunity to lamp noise and display noise. The proposed system consumed 42.5 mW with a 3.3-V supply. Secondly, readout IC (ROIC) with a differential coded multiple signaling method (DCMS) is proposed to detect an atto-farad capacitance difference for fingerprint recognition in fingerprint TSP. A readout IC with high SNR and fast frame rate are required in the fingerprint recognition. However, the capacitance difference by the ridge and valley of the fingerprint is very small, so that the signal-to-noise ratio is very low. In addition, it takes long time to scan whole fingerprint TSP with multiple electrodes. A fully differential architecture with differential signaling is proposed to detect the low capacitance difference in fingerprint TSP. The internal noise generated is minimized by 2nd fully differential operational amplifier and external noise is eliminated by a lock-in sensing structure. In addition, DCMS reduces an AC offset and enhances a higher product of SNR and frame rate in multiple channels. The proposed architectures can distinguish a 50-atto-farad which is a capacitance difference resulted from the ridges and valley of the finger under the 0.3T glass. The total scan time for 42 ?? 42 fingerprint TSP is less than 21 ms and the power consumption is below 20 mW at 3.3 V supply voltage. IC has been fabricated using a 0.18 ??m standard CMOS process.ope

Aligned Silver Nanowire Networks as Transparent Electrodes for High-Performance Optoelectronics and Electronic Devices

Department of Energy EngineeringFlexible transparent electrode is an essential component for several kinds of electronic and optoelectronic applications, such as organic solar cells (OSCs), perovskite solar cells (PSCs), organic light-emitting diodes (OLEDs), touch sensors, and electronic skins (E-skins). Although conventional indium tin oxide (ITO) has been widely used in commercial transparent electrodes, it still shows a limitation in the fabrication of flexible transparent electrodes for applications in flexible/wearable electronic devices because of their inherent brittleness. Among various alternatives of ITO, silver nanowire (AgNW) network has been considered as promising conductive nano-material due to their high electrical conductivity, excellent transmittance, and mechanical flexibility that can be readily deposited by cost-effective and large-scale solution process. However, random AgNW networks prepared by solution processing have several drawbacks, such as high junction resistance between nanowires (NWs), low transmittance, haze issues, and rough surface morphologies, resulting in a degradation of the device performance. Electrical and optical properties of random AgNW networks can be strongly affected by controlling NW density, electrical current path, and junction resistance related to conductive percolated networks. Therefore, manipulating the assembled structure of AgNW network can provide powerful platforms to realize ideal flexible transparent electrodes with high electrical conductivity, superior transmittance, and smooth surface morphologies for achieving high-performance electronic and optoelectronic device. In this thesis, we introduce aligned AgNW transparent electrodes and their applications in flexible optoelectronic and functional electronic devices. Firstly, Chapter 1 introduces the research tends in transparent electrodes and several issues of AgNW networks that should be carefully considered in the fabrication for their potential device applications. In chapter 2, we demonstrate the capillary printing technique to make highly aligned AgNW network to fabricate high-performance transparent electrodes for improving device efficiency of optoelectronic devices including OSCs and OLEDs. In Chapter 3, we demonstrate the fabrication of nanoparticle (NP)-enhanced plasmonic AgNW electrode for high-performance optoelectronic devices in which the NP-NW hybrid plasmonic system generates gap plasmonic coupling which induces a large electric field enhancement, resulting in an improvement of the device efficiency in both OSC and OLED devices. In Chapter 4, we demonstrate the fabrication of ultrathin and flexible perovskite solar cell foils with orthogonal AgNW electrodes, which exhibits high power-per-weight performance as well as a conformal contact capability to curvilinear surface. In Chapter 5, we introduce a large-scale assembly technique to uniformly align AgNW arrays for the fabrication of large area transparent electrodes, where cross-aligned AgNW network shows better electrical and optical properties as well as large-scale uniformity than random AgNW network. For the proof of the concept demonstration, we fabricated a flexible force-sensitive touch screen panel integrated with a mechanochromic polymer film. Finally, we introduce a transparent and conductive nano-membrane (NM) incorporated with orthogonal AgNW arrays in Chapter 6, which exhibits enhanced electrical and mechanical properties than pure polymeric NMs. To show the unique properties of these hybrid NMs for potential device applications, we demonstrate skin-attachable thermoacoustic-based NM loudspeaker and wearable NM microphone, both of which show much improved device performances compared to conventional thin film-based devices. In this thesis, studies on aligned AgNW transparent electrodes and their device applications could be further expanded for diverse flexible and wearable optoelectronic and electronic applications, such as conformal wearable sensors, healthcare monitoring devices, and wearable plasmonic devices.clos

New generation of interactive platforms based on novel printed smart materials

Programa doutoral em Engenharia Eletrónica e de Computadores (área de Instrumentação e Microssistemas Eletrónicos)The last decade was marked by the computer-paradigm changing with other digital devices suddenly becoming available to the general public, such as tablets and smartphones. A shift in perspective from computer to materials as the centerpiece of digital interaction is leading to a diversification of interaction contexts, objects and applications, recurring to intuitive commands and dynamic content that can proportionate more interesting and satisfying experiences. In parallel, polymer-based sensors and actuators, and their integration in different substrates or devices is an area of increasing scientific and technological interest, which current state of the art starts to permit the use of smart sensors and actuators embodied within the objects seamlessly. Electronics is no longer a rigid board with plenty of chips. New technological advances and perspectives now turned into printed electronics in polymers, textiles or paper. We are assisting to the actual scaling down of computational power into everyday use objects, a fusion of the computer with the material. Interactivity is being transposed to objects erstwhile inanimate. In this work, strain and deformation sensors and actuators were developed recurring to functional polymer composites with metallic and carbonaceous nanoparticles (NPs) inks, leading to capacitive, piezoresistive and piezoelectric effects, envisioning the creation of tangible user interfaces (TUIs). Based on smart polymer substrates such as polyvinylidene fluoride (PVDF) or polyethylene terephthalate (PET), among others, prototypes were prepared using piezoelectric and dielectric technologies. Piezoresistive prototypes were prepared with resistive inks and restive functional polymers. Materials were printed by screen printing, inkjet printing and doctor blade coating. Finally, a case study of the integration of the different materials and technologies developed is presented in a book-form factor.A última década foi marcada por uma alteração do paradigma de computador pelo súbito aparecimento dos tablets e smartphones para o público geral. A alteração de perspetiva do computador para os materiais como parte central de interação digital levou a uma diversificação dos contextos de interação, objetos e aplicações, recorrendo a comandos intuitivos e conteúdos dinâmicos capazes de tornarem a experiência mais interessante e satisfatória. Em simultâneo, sensores e atuadores de base polimérica, e a sua integração em diferentes substratos ou dispositivos é uma área de crescente interesse científico e tecnológico, e o atual estado da arte começa a permitir o uso de sensores e atuadores inteligentes perfeitamente integrados nos objetos. Eletrónica já não é sinónimo de placas rígidas cheias de componentes. Novas perspetivas e avanços tecnológicos transformaram-se em eletrónica impressa em polímeros, têxteis ou papel. Neste momento estamos a assistir à redução da computação a objetos do dia a dia, uma fusão do computador com a matéria. A interatividade está a ser transposta para objetos outrora inanimados. Neste trabalho foram desenvolvidos atuadores e sensores e de pressão e de deformação com recurso a compostos poliméricos funcionais com tintas com nanopartículas (NPs) metálicas ou de base carbónica, recorrendo aos efeitos capacitivo, piezoresistivo e piezoelétrico, com vista à criação de interfaces de usuário tangíveis (TUIs). Usando substratos poliméricos inteligentes tais como fluoreto de polivinilideno (PVDF) ou politereftalato de etileno (PET), entre outos, foi possível a preparação de protótipos de tecnologia piezoelétrica ou dielétrica. Os protótipos de tecnologia piezoresistiva foram feitos com tintas resistivas e polímeros funcionais resistivos. Os materiais foram impressos por serigrafia, jato de tinta, impressão por aerossol e revestimento de lâmina doctor blade. Para terminar, é apresentado um caso de estudo da integração dos diferentes materiais e tecnologias desenvolvidos sob o formato de um livro.This project was supported by FCT – Fundação para a Ciência e a Tecnologia, within the doctorate grant with reference SFRH/BD/110622/2015, by POCH – Programa Operacional Capital Humano, and by EU – European Union