Influence of medical gloves on fingerpad friction and feel

Friction experiments were carried out sliding a fingerpad, in both a bare state and with a latex glove donned, across a force plate to determine friction levels for different contact surface conditions (dry/wet; steel/glass). Donning a glove was found to increase the friction in dry conditions, but reduce it in wet conditions. A range of vibration frequencies were found to occur during sliding and the pronounced stick-slip behaviour for a bare finger sliding on wet glass was not found to occur when a latex glove was donned. These frequencies, along with those measured in a previous study, were used to inform the design of a tactile vibration perception study utilising a vibrating platform to replicate the sensation of finger sliding. The use of gloves was found to reduce the amplitude threshold at which participants were able to perceive vibrations. This effect was more extreme for double glove use, compared to single glove use. Glove donning also reduced the ability of participants to perceive differences in the frequency of vibrations. These findings have implications for surgeons' ability to carry out tactile explorations and the protocol described in this paper can be used for future studies on the effect of glove use on feel

Toward tactilely transparent gloves: Collocated slip sensing and vibrotactile actuation

Tactile information plays a critical role in the human ability to manipulate objects with one\u27s hands. Many environments require the use of protective gloves that diminish essential tactile feedback. Under these circumstances, seemingly simple tasks such as picking up an object can become very difficult. This paper introduces the SlipGlove, a novel device that uses an advanced sensing and actuation system to return this vital tactile information to the user. Our SlipGlove prototypes focus on providing tactile cues associated with slip between the glove and a contact surface. Relative motion is sensed using optical mouse sensors embedded in the glove\u27s surface. This information is conveyed to the wearer via miniature vibration motors placed inside the glove against the wearer\u27s skin. The collocation of slip sensing and tactile feedback creates a system that is natural and intuitive to use. We report results from a human subject study demonstrating that the SlipGlove allows the wearer to approach the capabilities of bare skin in detecting and reacting to fingertip slip. Users of the SlipGlove also had significantly faster and more consistent reaction to fingertip slip when compared to a traditional glove design. The SlipGlove technology allows us to enhance human perception when interacting with real environments and move toward the goal of a tactilely transparent glove

Complexity, rate, and scale in sliding friction dynamics between a finger and textured surface.

Sliding friction between the skin and a touched surface is highly complex, but lies at the heart of our ability to discriminate surface texture through touch. Prior research has elucidated neural mechanisms of tactile texture perception, but our understanding of the nonlinear dynamics of frictional sliding between the finger and textured surfaces, with which the neural signals that encode texture originate, is incomplete. To address this, we compared measurements from human fingertips sliding against textured counter surfaces with predictions of numerical simulations of a model finger that resembled a real finger, with similar geometry, tissue heterogeneity, hyperelasticity, and interfacial adhesion. Modeled and measured forces exhibited similar complex, nonlinear sliding friction dynamics, force fluctuations, and prominent regularities related to the surface geometry. We comparatively analysed measured and simulated forces patterns in matched conditions using linear and nonlinear methods, including recurrence analysis. The model had greatest predictive power for faster sliding and for surface textures with length scales greater than about one millimeter. This could be attributed to the the tendency of sliding at slower speeds, or on finer surfaces, to complexly engage fine features of skin or surface, such as fingerprints or surface asperities. The results elucidate the dynamical forces felt during tactile exploration and highlight the challenges involved in the biological perception of surface texture via touch

Haptics: Science, Technology, Applications

This open access book constitutes the proceedings of the 13th International Conference on Human Haptic Sensing and Touch Enabled Computer Applications, EuroHaptics 2022, held in Hamburg, Germany, in May 2022. The 36 regular papers included in this book were carefully reviewed and selected from 129 submissions. They were organized in topical sections as follows: haptic science; haptic technology; and haptic applications

Artificial Roughness Encoding with a Bio-inspired MEMS- based Tactile Sensor Array

A compliant 2×2 tactile sensor array was developed and investigated for roughness encoding. State of the art cross shape 3D MEMS sensors were integrated with polymeric packaging providing in total 16 sensitive elements to external mechanical stimuli in an area of about 20 mm2, similarly to the SA1 innervation density in humans. Experimental analysis of the bio-inspired tactile sensor array was performed by using ridged surfaces, with spatial periods from 2.6 mm to 4.1 mm, which were indented with regulated 1N normal force and stroked at constant sliding velocity from 15 mm/s to 48 mm/s. A repeatable and expected frequency shift of the sensor outputs depending on the applied stimulus and on its scanning velocity was observed between 3.66 Hz and 18.46 Hz with an overall maximum error of 1.7%. The tactile sensor could also perform contact imaging during static stimulus indentation. The experiments demonstrated the suitability of this approach for the design of a roughness encoding tactile sensor for an artificial fingerpad

The interaction between motion and texture in the sense of touch

Besides providing information on elementary properties of objects, like texture, roughness, and softness, the sense of touch is also important in building a representation of object movement and the movement of our hands. Neural and behavioral studies shed light on the mechanisms and limits of our sense of touch in the perception of texture and motion, and of its role in the control of movement of our hands. The interplay between the geometrical and mechanical properties of the touched objects, such as shape and texture, the movement of the hand exploring the object, and the motion felt by touch, will be discussed in this article. Interestingly, the interaction between motion and textures can generate perceptual illusions in touch. For example, the orientation and the spacing of the texture elements on a static surface induces the illusion of surface motion when we move our hand on it or can elicit the perception of a curved trajectory during sliding, straight hand movements. In this work we present a multiperspective view that encompasses both the perceptual and the motor aspects, as well as the response of peripheral and central nerve structures, to analyze and better understand the complex mechanisms underpinning the tactile representation of texture and motion. Such a better understanding of the spatiotemporal features of the tactile stimulus can reveal novel transdisciplinary applications in neuroscience and haptics

Towards a Technology-Based Assessment of Sensory-Motor Pathological States Through Tactile Illusions

Touch provides important information on the physical properties of external objects, and contributes to the sense of our hand position and displacement in perceptual tasks. Recent studies showed that the texture of the touched surface produced a bias on the perceived tactile motion, ultimately affecting the direction of hand motion in reaching tasks. Specifically, moving on a plate with parallel ridges, the hand motion deviates towards a direction opposite with respect to the one predicted by tactile flow mathematical model, i.e. perpendicular to the ridges. Here, we used this phenomenon to quantitatively assess an impairment in tactile channel. We asked healthy participants slide the hand on a plate with parallel ridges, either with bare fingertip or by wearing a glove. The glove condition simulated a dysfunction in tactile channel, as may occur in pathological conditions, for e.g. due to a neurological disease. Our hypothesis is that, wearing a glove, the systematic error induced by the texture orientation will be smaller because the information provided by the tactile channel is noisier. Results are in agreement with our hypothesis, and could open interesting perspectives towards a quantitative technology-based tool for the assessment of tactile impairment in pathological conditions

Modeling of frictional forces during bare-finger interactions with solid surfaces

Touching an object with our fingers yields frictional forces that allow us to perceive and explore its texture, shape, and other features, facilitating grasping and manipulation. While the relevance of dynamic frictional forces to sensory and motor function in the hand is well established, the way that they reflect the shape, features, and composition of touched objects is poorly understood. Haptic displays -electronic interfaces for stimulating the sense of touch- often aim to elicit the perceptual experience of touching real surfaces by delivering forces to the fingers that mimic those felt when touching real surfaces. However, the design and applications of such displays have been limited by the lack of knowledge about what forces are felt during real touch interactions. This represents a major gap in current knowledge about tactile function and haptic engineering. This dissertation addresses some aspects that would assist in their understanding. The goal of this research was to measure, characterize, and model frictional forces produced by a bare finger sliding over surfaces of multiple shapes. The major contributions of this work are (1) the design and development of a sensing system for capturing fingertip motion and forces during tactile exploration of real surfaces; (2) measurement and characterization of contact forces and the deformation of finger tissues during sliding over relief surfaces; (3) the development of a low order model of frictional force production based on surface specifications; (4) the analysis and modeling of contact geometry, interfacial mechanics, and their effects in frictional force production during tactile exploration of relief surfaces. This research aims to guide the design of algorithms for the haptic rendering of surface textures and shape. Such algorithms can be used to enhance human-machine interfaces, such as touch-screen displays, by (1) enabling users to feel surface characteristics also presented visually; (2) facilitating interaction with these devices; and (3) reducing the need for visual input to interact with them.Ph.D., Electrical Engineering -- Drexel University, 201

Characterizing and imaging gross and real finger contacts under dynamic loading

We describe an instrument intended to study finger contacts under tangential dynamic loading. This type of loading is relevant to the natural conditions when touch is used to discriminate and identify the properties of the surfaces of objects — it is also crucial during object manipulation. The system comprises a high performance tribometer able to accurately record in vivo the components of the interfacial forces when a finger interacts with arbitrary surfaces which is combined with a high-speed, high-definition imaging apparatus. Broadband skin excitation reproducing the dynamic contact loads previously identified can be effected while imaging the contact through a transparent window, thus closely approximating the condition when the skin interacts with a non-transparent surface during sliding. As a preliminary example of the type of phenomenon that can be identified with this apparatus, we show that traction in the range from 10 to 1000 Hz tends to decrease faster with excitation frequency for dry fingers than for moist fingers

FingerSlide: Investigating Passive Haptic Sliding As A Tacton Channel

The haptic sensation of sliding a surface under a probing finger can be used to convey surface information or coded data to the user. In this paper, we investigate users' ability to discern different sliding profiles based on the velocity and direction of sliding for use as haptic-tactons. We built FingerSlide, a novel haptic device which can position and control moving surfaces under a user's finger and used this to run two independent studies. The first study investigates if users can identify the direction of sliding at different velocities. The second study investigates if the users can distinguish a difference between two velocities. Our results show a faster response for higher velocities in the direction study and high error rates in identifying differences in the direction study. We discuss these results and infer design considerations for haptic devices that use the sliding effect to convey information