Touch Sensitive Devices Research Articles

(Invited) Graphene-Based Materials for Sensing Applications

Graphene-related materials (GRM) such as graphene oxide (GO) and graphene quantum dots (GQDs) display advantageous characteristics with interest for building innovative biosensing platforms and even smart devices such as nano/micromotors for a myriad of uses including sensing. Quenching of the fluorescence induced by GO or photoluminescence of GQDs can easily operate in synergy with various other nanomaterials and platforms opening the way to several unprecedented biosensing strategies and unique nanomotor technologies. Taking advantage of GRMs we are developing simple, sensitive, selective and rapid biosensing platforms that include: a) GO – based microarray & laterals flow technologies taking advantages of high quenching efficiency of GO. A “turn ON by a pathogen” device will be shown as a highly sensitive detection system using plastics or paper/nanopaper substrates; b) GQDs–based sensors for contaminants detection based on the use of multifunctional composite materials that enable rapid, simple and sensitive platforms in connection to smartphone; c) electroluminescent-based approaches d) A water activated GO transfer technology using wax printed membranes for fast patterning of a touch sensitive device with interest for electronic devices including sensing as well as for a cost-efficient nanomotor building technology for several applications. This work is supported by EU (Graphene Flagship), CERCA Programme / Generalitat de Catalunya.

Multifunctional Conductive Paths Obtained by Laser Processing of Non-Conductive Carbon Nanotube/Polypropylene Composites.

Functional materials are promising candidates for application in structural health monitoring/self-healing composites, wearable systems (smart textiles), robotics, and next-generation electronics. Any improvement in these topics would be of great relevance to industry, environment, and global needs for energy sustainability. Taking into consideration all these aspects, low-cost fabrication of electrical functionalities on the outer surface of carbon-nanotube/polypropylene composites is presented in this paper. Electrical-responsive regions and conductive tracks, made of an accumulation layer of carbon nanotubes without the use of metals, have been obtained by the laser irradiation process, leading to confined polymer melting/vaporization with consequent local increase of the nanotube concentration over the electrical percolation threshold. Interestingly, by combining different investigation methods, including thermogravimetric analyses (TGA), X-ray diffraction (XRD) measurements, scanning electron and atomic force microscopies (SEM, AFM), and Raman spectroscopy, the electrical properties of multi-walled carbon nanotube/polypropylene (MWCNT/PP) composites have been elucidated to unfold their potentials under static and dynamic conditions. More interestingly, prototypes made of simple components and electronic circuits (resistor, touch-sensitive devices), where conventional components have been substituted by the carbon nanotube networks, are shown. The results contribute to enabling the direct integration of carbon conductive paths in conventional electronics and next-generation platforms for low-power electronics, sensors, and devices.

Rapid and Accumulated Modulation of Action-Effects on Action.

Auditory feedback to a keypress is used in many devices to facilitate the motor output. The timing of auditory feedback is known to have an impact on the motor output, yet it is not known if a keypress action can be modulated on-line by an auditory feedback or how quick an auditory feedback can influence an ongoing keypress. Furthermore, it is not clear if the prediction of auditory feedback already changes the early phase of a keypress action independent of sensory feedback, which would suggest that such prediction changes the motor plan. In the current study, participants pressed a touch-sensitive device with auditory feedback in a self-paced manner. The auditory feedback was given either after a short (60 msec) or long (160 msec) delay, and the delay was either predictable or not. Our results showed that the keypress peak force was modulated by the amount of auditory feedback delay even when the delay was unpredictable, thus demonstrating an on-line modulation effect. The latency of the on-line modulation was suggested to be as low as 70 msec, indicating a very fast sensory to motor mapping circuit in the brain. When the auditory feedback delay was predictable, a change in the very early phase of keypress motor output was found, suggesting that the prediction of sensory feedback is crucial to motor control. Therefore, even a simple keypress action contains rich motor dynamics, which depend on expected as well as on-line perceived sensory feedback.

ADAPTABLE MULTI-TOUCH TECHNOLOGY SYSTEM FOR TOUCH SENSITIVE DEVICES

The touch sensing technology that has paved way for a user friendly interaction with the components has become a more prominent option in the recent days due to its capability of providing a direct communication by just one touch and its compatibility with the users of all age and different level of skills. The touch technology can be single or multi and supported by variety of technologies, such as resistive, capacitive, acoustic and infrared. Among all the technologies the capacitive sensor are widely opted as they possess a low hysteresis, good repeatability and faster response time. The paper also puts forward adaptable multi-touch technology system for the touch sensitive devices, by proposing a flexible capacitive touch sensor to make touch sensitive devices more users friendly with the a highest degree of sensitivity to the touch and satisfactory performance for a broader range of applications with the heightened durability.

Laser-induced erasable patterns in a N* liquid crystal on an iron doped lithium niobate surface.

A chiral nematic (N*) liquid crystal (LC) was hybridized with a z-cut iron doped lithium niobate (Fe:LN) substrate and exposed with a focused continuous wave diode laser beam. The N* LC layer was confined with a cover glass to provide a homogeneous LC layer thickness. Two distinct kinds of test cells were investigated, one with an uncoated glass covering slip and one with an indium tin oxide (ITO) coated cover glass. Photo generated electric fields (generated in the Fe:LN) resulted in a localized defect formation and textural transitions in the N* LC. Due to field confinement, the field induced responses were more localized in samples with ITO coated cover glasses. By scanning the laser beam on programmed trajectories, formation of persistent patterns could be achieved in the N* LC layer. Polarized optical microscopy of the exposed samples revealed that these patterns consisted of adjacent circular Frank-Pryce defects. Exposure with a slightly defocused laser beam could be applied selectively to erase these patterns. Thus, a promising method is reported to generate reconfigurable patterns, photonic motives, and touch sensitive devices in a hybridized N* LC with micron accuracy.

On-Skin Interaction Using Body Landmarks

The human skin is a promising surface for input to computing devices but differs fundamentally from existing touch-sensitive devices. The authors propose the use of skin landmarks, which offer unique tactile and visual cues, to enhance body-based user interfaces.

Online Urdu Handwriting Recognition System Using Geometric Invariant Features

Online touch sensitive devices facilitate users by providing an easy way for inputting online handwritten text. Many useful applications are developed for other cursive script language and are practically used in different fields like banking, commerce, academics, administration and education etc. There are also some systems proposed for online Urdu handwriting recognition but either they have low accuracy rates or high constraints on user while writing. Online Urdu handwriting recognition is a difficult task due to its cursive property and writing complexity. The proposed system tries to recognize Urdu characters and words by using geometric features i.e. cosine angles of trajectory, discrete fourier transform of trajectory, inflection points, self-intersections, convex hull, radial feature, grid (orthogonal and perspective), and retina feature. The proposed system is font, rotation, scale and shift invariant due to geometric invariant features. Before feature extraction low pass filtering and resampling is applied on each input stroke trajectory to remove noise caused by input device and hand movement. After feature extraction linear support vector machine is used for training and testing which gives up to 97% classification accuracy on test data. In recognition phase the proposed system gives a very low false rejection rate.

Water Activated Graphene Oxide Transfer Using Wax Printed Membranes for Fast Patterning of a Touch Sensitive Device.

We demonstrate a graphene oxide printing technology using wax printed membranes for the fast patterning and water activation transfer using pressure based mechanisms. The wax printed membranes have 50 μm resolution, longtime stability and infinite shaping capability. The use of these membranes complemented with the vacuum filtration of graphene oxide provides the control over the thickness. Our demonstration provides a solvent free methodology for printing graphene oxide devices in all shapes and all substrates using the roll-to-roll automatized mechanism present in the wax printing machine. Graphene oxide was transferred over a wide variety of substrates as textile or PET in between others. Finally, we developed a touch switch sensing device integrated in a LED electronic circuit.

Fabrication and Characterization of Piezoelectric Paper Based Device for Touch and Force Sensing Applications

A piezoelectric based touch sensitive device has been successfully fabricated by screen printing silver (Ag) and polyvinylidene fluoride (PVDF) inks as conductive and piezoelectric materials, respectively, on paper substrate. X-ray diffraction (XRD) analysis was performed to verify the formation of β-phase crystals in the PVDF layer during the curing process. Voltages, as high as 0.22 V, were observed for human finger touch tests and a sensitivity of 0.3 V/N was obtained when varying forces ranging from 0.2 N to 1.4 N, in steps of 0.2 N, were applied on the printed device. The piezoelectric-voltage analysis demonstrated that the printed device can be used for both touch and force sensing applications.

Exploring and modeling unimanual object manipulation on multi-touch displays

Touch-sensitive devices are becoming increasingly wide-spread, and consequently gestural interfaces have become familiar to the public. Despite the fact that many gestures require frequently dragging, pinching, spreading, and rotating the finger-tips, there currently does not exist a human performance model describing this interaction. In this paper, a novel user performance model is derived for virtual object manipulation on touch-sensitive displays, which involves simultaneous translation, rotation, and scaling of the object. Two controlled experiments with dual-finger unimanual manipulations were conducted to validate the new model. The results indicate that the model fits the experimental data well (with R2 and R values above 0.9), and performs the best among several alternative models. Moreover, based on the analysis of the empirical data, the simultaneity nature of manipulation in the task is explored and several design implications are provided.

Optimistic Programming of Touch Interaction

Touch-sensitive surfaces have become a predominant input medium for computing devices. In particular, multitouch capability of these devices has given rise to developing rich interaction vocabularies for “real” direct manipulation of user interfaces. However, the richness and flexibility of touch interaction often comes with significant complexity for programming these behaviors. Particularly, finger touches, though intuitive, are imprecise and lead to ambiguity. Touch input often involves coordinated movements of multiple fingers as opposed to the single pointer of a traditional WIMP interface. It is challenging in not only detecting the intended motion carried out by these fingers but also in determining the target objects being manipulated due to multiple focus points. Currently, developers often need to build touch behaviors by dealing with raw touch events that is effort consuming and error-prone. In this article, we present Touch, a tool that allows developers to easily specify their desired touch behaviors by demonstrating them live on a touch-sensitive device or selecting them from a list of common behaviors. Developers can then integrate these touch behaviors into their application as resources and via an API exposed by our runtime framework. The integrated tool support enables developers to think and program optimistically about how these touch interactions should behave, without worrying about underlying complexity and technical details in detecting target behaviors and invoking application logic. We discuss the design of several novel inference algorithms that underlie these tool supports and evaluate them against a multitouch dataset that we collected from end users. We also demonstrate the usefulness of our system via an example application.

A model of scrolling on touch-sensitive displays

Scrolling interaction is a common and frequent activity allowing users to browse content that is initially off-screen. With the increasing popularity of touch-sensitive devices, gesture-based scrolling interactions (e.g., finger panning and flicking) have become an important element in our daily interaction vocabulary. However, there are currently no comprehensive user performance models for scrolling tasks on touch displays. This paper presents an empirical study of user performance in scrolling tasks on touch displays. In addition to three geometrical movement parameters—scrolling distance, display window size, and target width, we also investigate two other factors that could affect the performance, i.e., scrolling modes—panning and flicking, and feedback techniques—with and without distance feedback. We derive a quantitative model based on four formal assumptions that abstract the real-world scrolling tasks, which are drawn from the analysis and observations of user scrolling actions. The results of a control experiment reveal that our model generalizes well for direct-touch scrolling tasks, accommodating different movement parameters, scrolling modes and feedback techniques. Also, the supporting blocks of the model, the four basic assumptions and three important mathematical components, are validated by the experimental data. In-depth comparisons with existing models of similar tasks indicate that our model performs the best under different measurement criteria. Our work provides a theoretical foundation for modeling sophisticated scrolling actions, as well as offers insights into designing scrolling techniques for next-generation touch input devices.

Multitouch Gesture-Based Authentication

This paper investigates multitouch gestures for user authentication on touch sensitive devices. A canonical set of 22 multitouch gestures was defined using characteristics of hand and finger movement. Then, a multitouch gesture matching algorithm robust to orientation and translation was developed. Two different studies were performed to evaluate the concept. First, a single session experiment was performed in order to explore feasibility of multitouch gestures for user authentication. Testing on the canonical set showed that the system could achieve good performance in terms of distinguishing between gestures performed by different users. In addition, the tests demonstrated a desirable alignment of usability and security as gestures that were more secure from a biometric point of view were rated as more desirable in terms of ease, pleasure, and excitement. Second, a study involving a three-session experiment was performed. Results indicate that biometric information gleaned from a short user-device interaction remains consistent across gaps of several days, though there is noticeable degradation of performance when the authentication is performed over multiple sessions. In addition, the study showed that user-defined gestures yield the highest recognition rate among all other gestures, whereas the use of multiple gestures in a sequence aids in boosting verification accuracy. In terms of memorability, the study showed that it is feasible for a user to recall user-defined gestural passwords and it is observed that the recall rate increases over time. It is also noticed that performing a user-defined gesture over a customized background image does result in higher verification performance. In terms of usability, the study shows that users did not have difficulty in performing multitouch gestures as they all rated each gesture as easy to perform.

GESTURE BASED TOUCHPAD SECURITY SYSTEM WITH DESIGN OF TOUCH SCREEN CONTROLLER

The purpose of the project is to present a new approach on the design of security systems by using a touch sensitive device. Security is a permanent concern in a variety of environments ranging from physical access restriction in home and industrial settings to information security in digital systems. Numeric passwords, fingerprint recognition, and many other techniques have been extensively implemented in the past but they present certain drawbacks. The proposed technique makes use of a touch device to recognize symbols as passwords and takes time into account to add a new dimension and prevent password theft. We implemented a prototype that demonstrates the capabilities of the proposed security approach by showing one direct application in physical access restriction systems.

The Forking Paths

The project The Forking Paths aims to create a set of interactive cinematographic narratives, within an applied research that seeks to transfer the spectator from an extradiegetic level to an intradiegetic level, creating a metalepsis. The intention is, above all, to analyze the possibilities of the spectator's identification as the main character, by the manipulation of the idea of time in Cinema. We aim to reach this proposal through the use of specific narrative resources, as well as through the possibility of choice between alternative image flows. The project The forking paths is intended to be available in different media and supports such as the Internet, touch sensitive screen devices and conventional cinemas.

Temporal weighting of interaural time and level differences carried by broadband noises

Localization of real sounds involves integrating acoustic spatial cues as they evolve over time. This study measured binaural sensitivity over time, in the form of temporal weighting functions (TWFs) for trains of of noise bursts. Each stimulus comprised sixteen 1-ms bursts of white noise, presented at an interval (ICI) of 2 or 5 ms. In separate conditions, noise samples were either repeated (“frozen”) or newly generated (“fresh”) across bursts. On each of many trials, listeners indicated the apparent lateral position of a stimulus along a horizontal scale displayed on a touch-sensitive device. Lateral positions varied across trials as interaural time (ITD) and level (ILD) differences ranged +/-500 µs ITD or +/-5 dB ILD. Interaural differences of individual bursts in each train received additional random variation (ranging +/-100 µs and +/-2 dB) to allow calculation of TWFs by multiple linear regression of normalized responses onto per-burst ITD and ILD values. Consistent with past studies, TWFs for “frozen” noise-burst trains demonstrated large ICI-dependent weights on the initial burst (“onset dominance”), elevated weights near offset, and lower weights for interior bursts. Flatter TWFs, smaller onset/offset weights, and greater interior weights were measured for “fresh” vs “frozen” noise burst trains. [Supported by R01 DC011548.]

Adjusting Fitts’ Paradigm for Small Touch-Sensitive Input Device with Large Group of Users

Fitts’ paradigm is a classic theory to describe the relationship between movement time, distance and accuracy for rapid aimed movement. Generally speaking, it describes the Speed-Accuracy Tradeoff (SAT) along task condition as well as along users. A controlled factorial experiment is conducted for small touch-sensitive input device to observe SAT relationship within task condition and large number of users. Fitts’ paradigm did not successfully model the SAT relationship, due to ambiguous definition of accuracy index and lack of variables to reflect subject bias. Fitts’ paradigm was adjusted by revising accuracy index appropriate for direct finger input, and by introducing a trajectory variable to keep track of the subject bias. It raised the model fit (R2) from 0.523 to 0.833 for a model of task condition.

Three-Dimensional Touch Interface for Medical Education

We present the technical principle and evaluation of a multimodal virtual reality (VR) system for medical education, called a touch simulator. This touch simulator comes with an innovative three-dimensional (3-D) touch sensitive input device. The device comprises a six-axis force-torque sensor connected to a tangible object representing the shape of an anatomical structure. Information related to the point of contact is recorded by the sensor, processed, and audiovisually displayed. The touch simulator provides a high level of user-friendliness and fidelity compared to other purely graphically oriented simulation environments. In this paper, the touch simulator has been realized as an interactive neuroanatomical training simulator. The user can visualize and manipulate graphical information of the brain surface or different cross-sectional slices by a finger-touch on a brain-like shaped tangible object. We evaluated the system by theoretical derivations, experiments, and subjective questionnaires. In the theoretical analysis, we could show that the contact point estimation error mainly depends on the accuracy and the noise of the sensor, the amount and direction of the applied force, and the geometry of the tangible object. The theoretical results could be validated by experiments: applying a normal force of 10 N on a 120 mm x 120 mm x 120 mm cube causes a maximum error of 2.5 +/- 0.7 mm. This error becomes smaller when increasing the contact force. Based on the survey results, the touch simulator may be a useful tool for assisting medical schools in the visualization of brain image data and the study of neuroanatomy.

Psychopharmacological studies in rats responding at touch-sensitive devices.

A multiple choice serial reaction time task was used to investigate visual attention in rats. The intelligence panel consisted of a transparent touch-sensitive device, placed directly in front of a video monitor. Amphetamine (0.2-1.6 mg/kg IP) increased errors of omission and decreased latency to respond, but had no effect on accuracy. The 5-HT agonist quipazine (0.6-2.4 mg/kg IP) increased errors of omission, but did not affect other parameters. ICV administration of hemicholinium-3 (1-4 micrograms) had no effect upon performance. Thus, psychopharmacological manipulations can reliably alter performance in the touch window box, suggesting potential new avenues for rat cognitive testing.

STIMULUS CONTROL IN THE USE OF LANDMARKS BY PIGEONS IN A TOUCH‐SCREEN TASK

Pigeons were tested in a search task on the surface of a monitor on which their responses were registered by a touch-sensitive device. A graphic landmark array was presented consisting of a square outline (the frame) and a colored "landmark." The unmarked goal, pecks at which produced reward, was located near the center of one edge of the frame, and the landmark was near it. The entire array was displaced without rotation on the monitor from trial to trial. On occasional no-reward tests, the following manipulations were made to the landmark array: (a) either the frame or the landmark was removed; (2) either one edge of the frame or the landmark was shifted; and (3) two landmarks were presented with or without the frame present. On these two-landmark tests, the frame, when present, defined which was the "correct" landmark. When the frame was absent, the "correct" landmark was arbitrarily determined. Results showed that pecks of 2 pigeons were controlled almost solely by the landmark, pecks of 3 were controlled primarily by the landmark but the frame could distinguish the correct landmark, and 1 bird's behavior was controlled primarily by the frame. Stimulus control in this search task is thus selective and differs across individuals. Comparisons to other search tasks and to other stimulus control experiments are made.