Electrotactile Display Research Articles

Imperceptible liquid metal based tattoo for Human-Machine interface on hairy skin

Biopotential signals recorded by skin surface electrodes reflect the state of the body and corresponding organ functions. These signals are commonly utilized in clinical diagnosis, health monitoring, sports training, and human–computer interaction. However, the utilization of conventional electrodes on hairy skin causes a number of issues, including suboptimal skin compliance, obstructed sweat secretion and impaired tactile perception, making it difficult to obtain long-term and high-fidelity biopotential recordings. Here, we propose an imperceptible spray-on electrode tattoo (SE-tattoo) with sweat-permeability, high adhesiveness, high conductivity, and fast curing ability (<20 s). The water-based conductive ink is sprayed directly on the hairy skin to form a conformable conductive tattoo that neither affects nor is affected by the skin hair. We demonstrate it for heart health monitoring, sports training, electro-tactile display and close-loop teleoperation control. The SE-tattoo offers a reliable and versatile solution to biopotential recordings and serves as a promising platform for bidirectional human–machine interaction.One-Sentence Summary: Imperceptible sweat-permeable SE-tattoo enables high-fidelity biopotential recordings for bidirectional human–machine interaction.

Orientation of tactile attention on the surface of the tongue.

The tongue is an incredibly complex sensory organ, yet little is known about its tactile capacities compared to the hands. In particular, the tongue receives almost no visual input during development and so may be calibrated differently compared to other tactile senses for spatial tasks. Using a cueing task, via an electro-tactile display, we examined how a tactile cue (to the tongue) or an auditory cue can affect the orientation of attention to electro-tactile targets presented to one of four regions on the tongue. We observed that response accuracy was generally low for the same modality condition, especially at the back of the tongue. This implies that spatial localization ability is diminished either because the tongue is less calibrated by the visual modality or because of its position and orientation inside the body. However, when cues were provided cross-modally, target identification at the back of the tongue seemed to improve. Our findings suggest that, while the brain relies on a general mechanism for spatial (and tactile) attention, the surface of the tongue may not have clear access to these representations of space when solely provided via electro-tactile feedback but can be directed by other sensory modalities. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A Braille Reading System Based on Electrotactile Display With Flexible Electrode Array

Due to visual impairment and lack of social attention, the reading problem of the blind has not been well resolved. Many existing Braille reading devices still have many problems and are not accepted by the public. This paper developed a portable Braille reading system based on electrotactile display technology. The proposed system is composed of a six-channel electrotactile stimulator, a flexible electrode array for Braille display and a graphical user interface (GUI) for monitoring and control. Based on the flexibility of the system, two Braille reading strategies have been designed: spatial mode and sequential mode. The system was preliminary tested by six sighted subjects. The results showed that subjects were able to recognize Braille characters with more than 80&#x0025; accuracy within less than 10 seconds for the initial use. Compared to existing Braille reading systems, this system is portable, wearable and flexible in control.

Electrotactile display composed of two-dimensionally and densely distributed microneedle electrodes

The present paper describes a thin and flexible electrotactile display having an array of microneedle electrodes that present tactile sensation on the forearm in a two-dimensional manner at low voltages. Tactile displays elicit tactile sensation by artificially stimulating tactile receptors. Electrotactile displays stimulate tactile receptors electrically and can be designed to be thin, light, and flexible, and therefore wearable. We developed an electrotactile display having microneedle electrodes that penetrate the high-impedance stratum corneum, thereby decreasing the threshold voltage to provide tactile sensation. Stimulation at a point and in a line was successfully demonstrated in our prior work. In this paper, we demonstrate an electrotactile display that can present tactile sensation in a plane with two-dimensionally distributed microneedle electrodes. The display is expected to increase the variety of tactile sensation and the amount of available information. We conducted experiments to determine the optimal gap between the microneedles to efficiently present a plane-like sensation. When the gap is too large, the subjects do not perceive a plane-like tactile sensation but only point-like stimulations at the electrodes, whereas the small gap leads to difficulties in manufacturing. A gap of 3mm was experimentally found to be optimal. Using the manufactured electrotactile display, smooth/rough sensation in a plane was successfully presented on the forearm.

Bio-impedance identification of fingertip skin for enhancement of electro-tactile-based preference

Research in rehabilitation engineering has shown that electrodes can produce tactile sensations with appropriate electrical signals to stimulate the multiple tactile receptors located under the fingertip skin. Numerous equivalent skin–electrode interfaces have been modeled to characterize the electrical properties of the skin; however, the values of these circuit models are continually changing, due both to the nonlinearity associated with human fingertip skin and to individual user differences. As a result, electrical stimulation that is suitable in terms of current or voltage level for tactile sensations cannot be guaranteed for every user. An identification method is then necessary for characterizing the parameters of the skin–electrode interface circuit model so as to improve rendering consistency and comfort for every user regardless of skin condition. In this paper, we introduce a custom-built electro-tactile display terminal, and then using this display terminal for data collection, we present an online identification scheme for determining the bio-impedance parameters of the well-known Cole–Cole circuit model for the skin–electrode interface. For this, a modified Kalman least squares iterative approach is used that relies on measuring only one-port square wave stimulation voltages. The repeatability and reliability of the identification scheme are tested by identifying the resistor–capacitor (RC) load bio-impedance networks of different users with both a dry and slightly damp index fingertip over multiple identification trials. Additionally, because of the inevitable variation in the parameters over multiple measurements, the repeatability of multiple calculated RC models (dry and wet) is further evaluated. The significance of our work is that it greatly improves the tactile rendering performance of electrical stimulation (electro-tactile) systems and will benefit the development of electro-tactile-based rehabilitative robotic devices and human–robot interfaces.

大面積電気触覚ディスプレイのための微小針電極アレイの開発

大面積電気触覚ディスプレイのための微小針電極アレイの開発

Information transfer using wearable thin electrotactile displays with microneedle electrodes

Tactile sensation is considered as a promising information transfer tool that can replace or compensate for sight and hearing information. In this study, we developed a sheet-type electrotactile display with microneedle electrodes. This flexible and thin display is suitable for wearable applications. It can present tactile sensation to the skin at a low voltage by penetrating the stratum corneum with microneedles. As a proof-of-concept experiment of transferring information via tactile sensation, we first tried to convey signals of two patterns using a single display. Next, we attempted to use multiple displays and experimentally investigated the spatial resolution of the tactile sensation on the forearm. Finally, 3-bit information was successfully transferred by three devices attached to the forearm.

Presentation of Various Tactile Sensations Using Micro-Needle Electrotactile Display.

Tactile displays provoke tactile sensations by artificially stimulating tactile receptors. While many types of tactile displays have been developed, electrotactile displays that exploit electric stimulation can be designed to be thin, light, flexible and thus, wearable. However, the high voltages required to stimulate tactile receptors and limited varieties of possible sensations pose problems. In our previous work, we developed an electrotactile display using a micro-needle electrode array that can drastically reduce the required voltage by penetrating through the high-impedance stratum corneum painlessly, but displaying various tactile sensations was still a challenge. In this work, we demonstrate presentation of tactile sensation of different roughness to the subjects, which is enabled by the arrangement of the electrodes; the needle electrodes are on the fingertip and the ground electrode is on the fingernail. With this arrangement, the display can stimulate the tactile receptors that are located not only in the shallow regions of the finger but also those in the deep regions. It was experimentally revealed that the required voltage was further reduced compared to previous devices and that the roughness presented by the display was controlled by the pulse frequency and the switching time, or the stimulation flow rate. The proposed electrotactile display is readily applicable as a new wearable haptic device for advanced information communication technology.

Micro-needle electro-tactile display.

Haptic feedback is strongly demanded for high-precision robot-assisted surgery and teleoperation. The haptic feedback consists of force and tactile feedback, however tactile feedback has been little studied and the size and weight of the system poses challenges for practical applications. In this paper we propose a sheet-type wearable electro-tactile display which provides tactile sensations to the user as the feedback at a low voltage and power consumption. The display possesses needle-shaped electrodes, which can penetrate through the high-impedance stratum corneum. We developed the fabrication process and, as the first step, we investigated the tactile sensation that can be created to the fingertip by the display. Rough and smooth surfaces were successfully presented to the user. Then, we characterized the tactile display when used on the forearm, in particular, with respect to the spatial resolution. These tactile displays can be used to inform the user of the surface property of the parts of interest, such as tumor tissues, and to guide him in the manipulation of surgery robots.

Material Roughness Modulation via Electrotactile Augmentation.

Tactile exploration of a material's texture using a bare finger pad is a daily human activity. However, modern tactile displays do not allow users to experience the natural sensations of a material when artificial sensations are presented. We propose an electrotactile augmentation technique capable of superimposing vibrotactile sensations in a finger pad, thereby allowing the texture modulation of real materials. Users attach two stimulus electrodes to the middle phalanx of a finger and a grounded electrode at the base of the finger in order to evoke nerve activity. This paper evaluates the proposed electrotactile augmentation for roughness modulation of real materials. First, we introduce the principle of the electrotactile display, which presents artificial sensations at the finger pad. We then confirm that the perceived frequency of mechanical vibration at the finger pad can be shifted using electrotactile augmentation. Finally, we discuss a user study, wherein participants rated the roughness of real materials explored using the proposed system. Experimental results indicate that fine- and macro-roughness perceptions of real materials can be altered using electrotactile augmentation.

Electrotactile display using microfabricated micro-needle array

This paper describes an electrotactile display with micro-needle electrodes. The electrotactile display can produce tactile sensations by stimulating tactile receptors using an electric current. Micro-needle electrodes can drastically decrease the threshold voltage required to stimulate tactile receptors by penetrating the stratum corneum, which has a higher impedance than the dermis. In addition, the optimized length of the needle allows us to stimulate tactile receptors painlessly. In the present study, we developed a process for fabricating a micro-needle array in which the length and tip radius can be controlled using electrochemical etching. A micro-needle array was successfully fabricated to form an electrotactile display. In addition, we experimentally determined the suitable shape of the micro-needle electrodes for electrotactile display applications. When the tip radius of the needle is too small, the impedance between the finger and micro-needles becomes large due to the small contact area. On the other hand, when the tip radius is too large, the needle cannot penetrate the skin surface and the impedance is not sufficiently small. The experiments verified the superiority of needle electrode devices to flat electrode devices with respect to the threshold voltage at each frequency.

1A1-L05 微小針を用いた薄型電気触覚ディスプレイ

In this paper we experimentally demonstrate a sheet-type micro-needle electro-tactile display. It is thin and flexible enough to be easily attached to our body and can create tactile stimulation at low voltage. We developed the fabrication processes and then, investigated the minimum voltages to stimulate tactile receptors. We consider that when we have more displays on the body, more information can be transferred to the user. We attached the displays to the forearm and experimentally deduced the maximum number of the displays when the user can discriminate the stimulation from each display. In addition, we investigated infection caused by the insertion of the needle using a swab test. No bacteria were found on the display after 3 hours of insertion test.

1P2-X05 圧力分布に基づく電気刺激パターンの変調による弾性感の提示(触覚と力覚(2))

We have developed a system composed of an electro-tactile display and distributed pressure sensor underneath. The pressure sensor detects finger pressure distribution, and the electro-tactile display presents tactile sensation in accordance with the pressure distribution, so that local "force-feedback" is achieved at each electrode. In this paper, we utilized this system to express softness feeling. The tactile stimulation is presented just at the edge of the finger contact area so that it enhances expansion and shrinking of contact area when the users press and release their fingers. Experimental result revealed that proposed algorithm surely increases subjective softness.

1A2-R04 電気触覚ディスプレイ用微小針電極アレイの開発(VRとインタフェース)

This paper describes electro tactile display with micro-needle electrodes that stimulate tactile receptors using electric stimulation. Electro tactile displays can be thin and flexible, however, the high electric impedance of the stratum corneum requires high voltage to stimulate the tactile receptors. In our device, we use needles as electrodes and the needle length was designed to have approximately the same length as the stratum corneum so as not to injure nerve area. This device allowed subjects to feel tactile sensation with lower voltage than a flat electrode array with good repeatability. In addition, the tactile sensation was created in the vicinity of the needles, i.e., tactile display with a high spatial resolution was achieved.

Electrotactile Display with Real-Time Impedance Feedback Using Pulse Width Modulation.

An electrotactile display is a tactile interface composed of skin surface electrodes. The use of such a device is limited by the variability of the elicited sensation. One possible solution to this problem is to monitor skin electrical impedance. Previous studies revealed a correlation between impedance and threshold, but did not construct real-time feedback loops. In this study, an electrotactile display was constructed using a 1.45 μs feedback loop. Real-time pulse width modulation was proposed, and the relationship between skin resistance and absolute threshold was measured to find a function for determining a suitable pulse width from skin resistance. An evaluation experiment revealed that the proposed algorithm suppressed spatial variation and reduced temporal change.

Guest Editorial for Special Section on Consumer Electronics

THE number of daily human computer interactions with consumer devices is increasing at a staggering rate. Just considering text messaging in the United States alone, more than a trillion text messages have been sent in the last year (CTIA Semi-Annual survey October 2011). The fundamental means of interacting with our digital environment are through video, audio, and haptics, and the sense of touch is paramount in how we enter information into the device. As a result, haptics in consumer electronics has been a topic of growing importance in the publications of not only the haptics community, but also those of the IEEE Consumer Electronics Society. For two years now, the International Conference on Consumer Electronics (ICCE) has adopted haptics to the tracks on human computer interfaces. This resulted in a joint call for papers for both the journal and the ICCE, leading to this special section. Touch screens are the predominant interface today, and are driving consumer haptic adoption. Given the immense number of interactions with digital devices, it is critical to make those interactions intuitive and natural to use, and to maximize the channels available to us for interaction, such as using haptics in different ways to convey information back to the user. Both of these areas will be addressed by the five papers in this special section. The first generations of haptic-enabled consumer devices, and the majority on the market today, have been primarily based on electromagnetic motors that create whole device vibration. This, however, is only the beginning when considering the range of haptic experiences that are possible. High fidelity haptics, using piezo actuators and electroactive polymers, are currently being launched in the market and will be an important step in advancing the user experience by taking advantage of the broader range of experiences that can be rendered. Future devices will go beyond even that by providing directional cues via vibrotactile travelling waves, creating the feel of real world textures, and enabling new haptic experiences such as skin stretch, variable friction, or even small or large scale deformation. One of the keys to widespread commercial success of haptics in consumer devices is in developing the entire ecosystem for this multidisciplinary field. This includes making advancements in the understanding of human haptic perception, the base enabling technologie such as actuators, amplifiers, and rendering methods, as well as the software development and design tools, all culminating in the way that haptics is used in the end application. The first four papers in this special section are directed at the base enabling technologies such as electrotactile displays, vibrotactile travelling waves, and providing multimodal direction cues for mobile devices, while the last paper focuses on how haptics is used in the interface. The first paper, “Electrotactile Feedback for Handheld Devices with Touch Screen and Simulation of Roughness, by M. Ercan Altinsoy and Sebastian Merchel, introduces a novel electrotactile display integrated into a mobile device touchscreen. They apply the technology to rendering of virtual textures on the touchscreen and demonstrate that the electrotactile display is capable of controlling the perceived roughness of textures via two psychophysical experiments. This work expands the benefits of the electrotactile display that has some integration advantages over the more common vibrotactile approach. The next two papers have a common theme, a vibrotactile flow (or wave), that can be produced by two vibrotactile actuators to deliver the sensation of a moving vibration on a plane. The second paper, “Vibrotactile Rendering for a Traveling Vibrotactile Wave Based on a Haptic Processor,” by Sang-Youn Kim and Jeong Cheol Kim, is particularly relevant to this special section as they present an electronic chip that includes the function of vibrotactile wave generation and is ready for adoption in consumer mobile devices. The third paper, “Smooth Vibrotactile Flow Generation Using Two Piezoelectric Actuators,” by Jeonggoo Kang, Jongsuh Lee, Heewon Kim, Kwangsu Cho, Semyung Wang, and Jeha Ryu, advances the technology for vibrotactile waves by using two wideband piezoelectric actuators. They propose a frequency-sweeping algorithm that can modulate the resonance position on a plate and demonstrate that the algorithm can improve the quality of vibrotactile flow perception. These two papers further elevate the possibility of using the vibrotactile flow technology in commercial handheld devices. In the fourth paper, “Mobile Navigation Using Haptic, Audio, and Visual Direction Cues with a Handheld Test Platform,” Rebecca L. Koslover, Brian T. Gleeson, Joshua T. de Bever, and William R. Provancher develop a multimodal 4 IEEE TRANSACTIONS ON HAPTICS, VOL. 5, NO. 1, JANUARY-MARCH 2012

Electrotactile Feedback for Handheld Devices with Touch Screen and Simulation of Roughness.

We present a novel electrotactile display that can be integrated into current handheld devices with touch screens. In this display, tactile information is presented to the fingertip of the user by transmitting small currents through electrodes. Experiments were conducted to investigate the perception of simulated textures using this electrotactile display technique. One fundamental feature of texture, which is the focus of this study, is roughness. The aim of the first experiment was to investigate the relationship between electrotactile stimulation parameters such as current and pulse frequency and the perception of roughness. An increase in the current magnitude resulted in an increase in perceived roughness. The aim of the second experiment was to investigate parameter combinations of electrotactile stimuli can be used to simulate textures. Subjects adjusted the intensity and frequency of the current stimuli until the simulated textures were perceived as being equal to reference textures such as sandpapers of varying grit numbers and grooved woods with varying groove widths. Subjects tended to find an electrotactile stimulus with a high current magnitude and a low pulse frequency more suitable to represent rough surfaces. They tended to find just-perceptible current magnitudes suitable for very smooth surfaces and did not show a preference for any frequency.

Development of A Spatially Transparent Electrotactile Display and Application to Hand Tool Navigation

Development of A Spatially Transparent Electrotactile Display and Application to Hand Tool Navigation

Design of a Wearable Fingertip Haptic Braille Device

Existing technologies and devices have facilitated the interaction of the blind or visually impaired (BVI) with their surroundings. However, reading remains an area where the potential of these technologies is not fully utilized. This work presents preliminary studies for the design of a finger-wearable E-Braille device that will allow the BVI to read electronic documents as they would read any document in Braille. The proposed device is wearable on a single finger on of the distal and middle phalanges (dorsal side). The main elements of the device are electrotactile display and force sensor. The electrotactile display is an electric board containing a matrix of electrodes that sends current to the fingertip for stimulating the touch feeling of a particular Braille character. By sending a sequence of Braille characters to this board, information can be sent to the user of the device through the generated electrotactile feeling. The force sensor is used in a feedback control loop to maintain steady contact pressure between the fingertip and the display board throughout the reading process. The entire finger-wearable E-Braille tactile display device is composed of a housing that can be customized to individual users, a miniature dc motor, mechanical components, and main elements. The initial testing of the proposed device is underway. Preliminary results indicate that the device can provide tactile sensation similar to that of reading a Braille document. The initial assessment of the device usability is underway.

Transmission System of Spatially Distributed Tactile Information using Finger-shaped GelForce and Electrotactile Display

Transmission System of Spatially Distributed Tactile Information using Finger-shaped GelForce and Electrotactile Display