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Delhaye BP, Schiltz F, Crevecoeur F, Thonnard JL, Lefèvre P. Fast grip force adaptation to friction relies on localized fingerpad strains. SCIENCE ADVANCES 2024; 10:eadh9344. [PMID: 38232162 DOI: 10.1126/sciadv.adh9344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 12/18/2023] [Indexed: 01/19/2024]
Abstract
During object manipulation, humans adjust the grip force to friction, such that slippery objects are squeezed more firmly than sticky ones. This essential mechanism to keep a stable grasp relies on feedback from tactile afferents innervating the fingertips, that are sensitive to local skin strains. To test if this feedback originates from the skin-object interface, we asked participants to perform a grip-lift task with an instrumented object able to monitor skin strains at the contact through transparent plates of different frictions. We observed that, following an unbeknown change in plate across trials, participants adapted their grip force to friction. After switching from high to low friction, we found a significant increase in strain inside the contact arising ~100 ms before the modulation of grip force, suggesting that differences in strain patterns before lift-off are used by the nervous system to quickly adjust the force to the frictional properties of manipulated objects.
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Affiliation(s)
- Benoit P Delhaye
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Félicien Schiltz
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Frédéric Crevecoeur
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Jean-Louis Thonnard
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium
| | - Philippe Lefèvre
- Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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2
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Ziat M. Obituary: Vincent Hayward (1955-2023). Perception 2023; 52:752-756. [PMID: 37674444 DOI: 10.1177/03010066231198763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/08/2023]
Affiliation(s)
- Mounia Ziat
- Department of Information Design and Corporate Communication, Bentley University, Waltham, MA, USA
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3
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du Bois de Dunilac S, Córdova Bulens D, Lefèvre P, Redmond SJ, Delhaye BP. Biomechanics of the finger pad in response to torsion. J R Soc Interface 2023; 20:20220809. [PMID: 37073518 PMCID: PMC10113816 DOI: 10.1098/rsif.2022.0809] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 03/24/2023] [Indexed: 04/20/2023] Open
Abstract
Surface skin deformation of the finger pad during partial slippage at finger-object interfaces elicits firing of the tactile sensory afferents. A torque around the contact normal is often present during object manipulation, which can cause partial rotational slippage. Until now, studies of surface skin deformation have used stimuli sliding rectilinearly and tangentially to the skin. Here, we study surface skin dynamics under pure torsion of the right index finger of seven adult participants (four males). A custom robotic platform stimulated the finger pad with a flat clean glass surface, controlling the normal forces and rotation speeds applied while monitoring the contact interface using optical imaging. We tested normal forces between 0.5 N and 10 N at a fixed angular velocity of 20° s-1 and angular velocities between 5° s-1 and 100° s-1 at a fixed normal force of 2 N. We observe the characteristic pattern by which partial slips develop, starting at the periphery of the contact and propagating towards its centre, and the resulting surface strains. The 20-fold range of normal forces and angular velocities used highlights the effect of those parameters on the resulting torque and skin strains. Increasing normal force increases the contact area, the generated torque, strains and the twist angle required to reach full slip. On the other hand, increasing angular velocity causes more loss of contact at the periphery and higher strain rates (although it has no impact on resulting strains after the full rotation). We also discuss the surprisingly large inter-individual variability in skin biomechanics, notably observed in the twist angle the stimulus needs to rotate before reaching full slip.
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Affiliation(s)
- Sophie du Bois de Dunilac
- School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - David Córdova Bulens
- School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Philippe Lefèvre
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), and Institute of Neuroscience (IoNS), Université catholique de Louvain, 1348 Louvain-la-Neuve and 1200 Brussels, Belgium
| | - Stephen J. Redmond
- School of Electrical and Electronic Engineering, University College Dublin, Belfield, Dublin 4, Ireland
| | - Benoit P. Delhaye
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics (ICTEAM), and Institute of Neuroscience (IoNS), Université catholique de Louvain, 1348 Louvain-la-Neuve and 1200 Brussels, Belgium
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4
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Rezaei M, Nagi SS, Xu C, McIntyre S, Olausson H, Gerling GJ. Thin Films on the Skin, but not Frictional Agents, Attenuate the Percept of Pleasantness to Brushed Stimuli. ARXIV 2023:arXiv:2303.00049v1. [PMID: 36911281 PMCID: PMC10002820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 03/14/2023]
Abstract
Brushed stimuli are perceived as pleasant when stroked lightly on the skin surface of a touch receiver at certain velocities. While the relationship between brush velocity and pleasantness has been widely replicated, we do not understand how resultant skin movements - e.g., lateral stretch, stick-slip, normal indentation - drive us to form such judgments. In a series of psychophysical experiments, this work modulates skin movements by varying stimulus stiffness and employing various treatments. The stimuli include brushes of three levels of stiffness and an ungloved human finger. The skin's friction is modulated via non-hazardous chemicals and washing protocols, and the skin's thickness and lateral movement are modulated by thin sheets of adhesive film. The stimuli are hand-brushed at controlled forces and velocities. Human participants report perceived pleasantness per trial using ratio scaling. The results indicate that a brush's stiffness influenced pleasantness more than any skin treatment. Surprisingly, varying the skin's friction did not affect pleasantness. However, the application of a thin elastic film modulated pleasantness. Such barriers, though elastic and only 40 microns thick, inhibit the skin's tangential movement and disperse normal force. The finding that thin films modulate affective interactions has implications for wearable sensors and actuation devices.
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Affiliation(s)
- Merat Rezaei
- School of Engineering and Applied Science, at the University of Virginia, USA
| | - Saad S Nagi
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Chang Xu
- School of Engineering and Applied Science, at the University of Virginia, USA
| | - Sarah McIntyre
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Håkan Olausson
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Gregory J Gerling
- School of Engineering and Applied Science, at the University of Virginia, USA
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5
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Monnoyer J, Willemet L, Wiertlewski M. Rapid change of friction causes the illusion of touching a receding surface. J R Soc Interface 2023; 20:20220718. [PMID: 36751927 PMCID: PMC9905974 DOI: 10.1098/rsif.2022.0718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/09/2023] [Indexed: 02/09/2023] Open
Abstract
Shortly after touching an object, humans can tactually gauge the frictional resistance of a surface. The knowledge of surface friction is paramount to tactile perception and the motor control of grasp. While potent correlations between friction and participants' perceptual response have been found, the causal link between the friction of the surface, its evolution and its perceptual experience has yet to be demonstrated. Here, we leverage new experimental apparatus able to modify friction in real time, to show that participants can perceive sudden changes in friction when they are pressing on a surface. Surprisingly, only a reduction of the friction coefficient leads to a robust perception. High-speed imaging data indicate that the sensation is caused by a release of a latent elastic strain over a 20 ms timeframe after the activation of the friction-reduction device. This rapid change of frictional properties during initial contact is interpreted as a normal displacement of the surface, which paves the way for haptic surfaces that can produce illusions of interacting with mechanical buttons.
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Affiliation(s)
- Jocelyn Monnoyer
- Aix-Marseille University, CNRS, ISM, Marseille, France
- Stellantis, Human Factors Group, Velizy, France
| | - Laurence Willemet
- Cognitive Robotics Department, Delft University of Technology, Delft, The Netherlands
| | - Michaël Wiertlewski
- Cognitive Robotics Department, Delft University of Technology, Delft, The Netherlands
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6
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Ryan CP, Ciotti S, Cosentino L, Ernst MO, Lacquaniti F, Moscatelli A. Masking Vibrations and Contact Force Affect the Discrimination of Slip Motion Speed in Touch. IEEE TRANSACTIONS ON HAPTICS 2022; 15:693-704. [PMID: 36149999 DOI: 10.1109/toh.2022.3209072] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Multiple cues contribute to the discrimination of slip motion speed by touch. In our previous article, we demonstrated that masking vibrations at various frequencies impaired the discrimination of speed. In this article, we extended the previous results to evaluate this phenomenon on a smooth glass surface, and for different values of contact force and duration of the masking stimulus. Speed discrimination was significantly impaired by masking vibrations at high but not at low contact force. Furthermore, a short pulse of masking vibrations at motion onset produced a similar effect as the long masking stimulus, delivered throughout slip motion duration. This last result suggests that mechanical events at motion onset provide important cues to the discrimination of speed.
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7
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Serhat G, Vardar Y, Kuchenbecker KJ. Contact evolution of dry and hydrated fingertips at initial touch. PLoS One 2022; 17:e0269722. [PMID: 35830372 PMCID: PMC9278764 DOI: 10.1371/journal.pone.0269722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 05/26/2022] [Indexed: 11/19/2022] Open
Abstract
Pressing the fingertips into surfaces causes skin deformations that enable humans to grip objects and sense their physical properties. This process involves intricate finger geometry, non-uniform tissue properties, and moisture, complicating the underlying contact mechanics. Here we explore the initial contact evolution of dry and hydrated fingers to isolate the roles of governing physical factors. Two participants gradually pressed an index finger on a glass surface under three moisture conditions: dry, water-hydrated, and glycerin-hydrated. Gross and real contact area were optically measured over time, revealing that glycerin hydration produced strikingly higher real contact area, while gross contact area was similar for all conditions. To elucidate the causes for this phenomenon, we investigated the combined effects of tissue elasticity, skin-surface friction, and fingerprint ridges on contact area using simulation. Our analyses show the dominant influence of elastic modulus over friction and an unusual contact phenomenon, which we call friction-induced hinging.
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Affiliation(s)
- Gokhan Serhat
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
- * E-mail:
| | - Yasemin Vardar
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
- Department of Cognitive Robotics, Delft University of Technology, Delft, CD, The Netherlands
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Shao Y, Dou H, Tao P, Jiang R, Fan Y, Jiang Y, Zhao J, Zhang Z, Yue T, Gorb SN, Ren L. Precise Controlling of Friction and Adhesion on Reprogrammable Shape Memory Micropillars. ACS APPLIED MATERIALS & INTERFACES 2022; 14:17995-18003. [PMID: 35389609 DOI: 10.1021/acsami.2c03589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Microstructured surfaces with stimuli-responsive performances have aroused great attention in recent years, but it still remains a significant challenge to endow surfaces with precisely controlled morphological changes in microstructures, so as to get the precise control of regional properties (e.g., friction, adhesion). Herein, a kind of carbonyl iron particle-doped shape memory polyurethane micropillar with precisely controllable morphological changes is realized, upon remote near-infrared light (NIR) irradiation. Owing to the reversible transition of micropillars between bent and upright states, the micro-structured surface exhibits precisely controllable low-to-high friction transitions, together with the changes of friction coefficient ranging from ∼0.8 to ∼1.2. Hence, the changes of the surface friction even within an extremely small area can be precisely targeted, under local NIR laser irradiation. Moreover, the water droplet adhesion force of the surface can be reversibly switched between ∼160 and ∼760 μN, demonstrating the application potential in precisely controllable wettability. These features indicate that the smart stimuli-responsive micropillar arrays would be amenable to a variety of applications that require remote, selective, and on-demand responses, such as a refreshable Braille display system, micro-particle motion control, lab-on-a-chip, and microfluidics.
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Affiliation(s)
- Yanlong Shao
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Haixu Dou
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Peng Tao
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Rujian Jiang
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Yong Fan
- College of Chemistry, Jilin University, Changchun 130022, China
| | - Yue Jiang
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Jie Zhao
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Zhihui Zhang
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Tailin Yue
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
| | - Stanislav N Gorb
- Department of Functional Morphology and Biomechanics, Kiel University, Kiel 24118, Germany
| | - Luquan Ren
- Key Laboratory of Bionic Engineering, Ministry of Education, College of Biological and Agricultural Engineering, Jilin University, Changchun 130022, China
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9
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Torres DA, Vezzoli E, Lemaire-Semail B, Adams M, Giraud-Audine C, Giraud F, Amberg M. Mechanisms of Friction Reduction in Longitudinal Ultrasonic Surface Haptic Devices With Non-Collinear Vibrations and Finger Displacement. IEEE TRANSACTIONS ON HAPTICS 2022; 15:8-13. [PMID: 34982693 DOI: 10.1109/toh.2021.3140003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Friction reduction using ultrasonic longitudinal surface vibration can modify the user perception of the touched surface and induce the perception of textured materials. In the current paper, the mechanisms of friction reduction using longitudinal vibration are analyzed at different finger exploration velocities and directions over a plate. The development of a non-Coulombic adhesion theory based on experimental results is evaluated as a possible explanation for friction reduction with vibrations that are non-collinear with the finger displacement. Comparison with experimental data shows that the model adequately describes the reduction in friction, although it is less accurate for low finger velocities and depends on motion direction.
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10
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Abstract
Humans have the remarkable ability to manipulate a large variety of objects, regardless of how fragile, heavy, or slippery they are. To correctly scale the grip forces, the nervous system gauges the slipperiness of the surface. This information is present at the instant we first touch an object, even before any lateral force develops. However, how friction could be estimated without slippage only from the fingertip skin deformation is not understood, either in neuroscience or engineering disciplines. This study demonstrates that a radial tensile strain of the skin is involved in the perception of slipperiness during this initial contact. These findings can inform the design of advanced tactile sensors for robotics or prosthetics and for improving haptic human–machine interactions. Humans efficiently estimate the grip force necessary to lift a variety of objects, including slippery ones. The regulation of grip force starts with the initial contact and takes into account the surface properties, such as friction. This estimation of the frictional strength has been shown to depend critically on cutaneous information. However, the physical and perceptual mechanism that provides such early tactile information remains elusive. In this study, we developed a friction-modulation apparatus to elucidate the effects of the frictional properties of objects during initial contact. We found a correlation between participants’ conscious perception of friction and radial strain patterns of skin deformation. The results provide insights into the tactile cues made available by contact mechanics to the sensorimotor regulation of grip, as well as to the conscious perception of the frictional properties of an object.
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11
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Peng Y, Serfass CM, Kawazoe A, Shao Y, Gutierrez K, Hill CN, Santos VJ, Visell Y, Hsiao LC. Elastohydrodynamic friction of robotic and human fingers on soft micropatterned substrates. NATURE MATERIALS 2021; 20:1707-1711. [PMID: 33927390 DOI: 10.1038/s41563-021-00990-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 03/18/2021] [Indexed: 05/10/2023]
Abstract
Frictional sliding between patterned surfaces is of fundamental and practical importance in the haptic engineering of soft materials. In emerging applications such as remote surgery and soft robotics, thin fluid films between solid surfaces lead to a multiphysics coupling between solid deformation and fluid dissipation. Here, we report a scaling law that governs the peak friction values of elastohydrodynamic lubrication on patterned surfaces. These peaks, absent in smooth tribopairs, arise due to a separation of length scales in the lubricant flow. The framework is generated by varying the geometry, elasticity and fluid properties of soft tribopairs and measuring the lubricated friction with a triborheometer. The model correctly predicts the elastohydrodynamic lubrication friction of a bioinspired robotic fingertip and human fingers. Its broad applicability can inform the future design of robotic hands or grippers in realistic conditions, and open up new ways of encoding friction into haptic signals.
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Affiliation(s)
- Yunhu Peng
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher M Serfass
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Anzu Kawazoe
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Yitian Shao
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Kenneth Gutierrez
- Department of Mechanical and Aerospace Engineering, University of California-Los Angeles, Los Angeles, CA, USA
| | - Catherine N Hill
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Veronica J Santos
- Department of Mechanical and Aerospace Engineering, University of California-Los Angeles, Los Angeles, CA, USA
| | - Yon Visell
- Department of Electrical and Computer Engineering, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Lilian C Hsiao
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA.
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12
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Attractive forces slow contact formation between deformable bodies underwater. Proc Natl Acad Sci U S A 2021; 118:2104975118. [PMID: 34615709 DOI: 10.1073/pnas.2104975118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2021] [Indexed: 11/18/2022] Open
Abstract
Thermodynamics tells us to expect underwater contact between two hydrophobic surfaces to result in stronger adhesion compared to two hydrophilic surfaces. However, the presence of water changes not only energetics but also the dynamic process of reaching a final state, which couples solid deformation and liquid evacuation. These dynamics can create challenges for achieving strong underwater adhesion/friction, which affects diverse fields including soft robotics, biolocomotion, and tire traction. Closer investigation, requiring sufficiently precise resolution of film evacuation while simultaneously controlling surface wettability, has been lacking. We perform high-resolution in situ frustrated total internal reflection imaging to track underwater contact evolution between soft-elastic hemispheres of varying stiffness and smooth-hard surfaces of varying wettability. Surprisingly, we find the exponential rate of water evacuation from hydrophobic-hydrophobic (adhesive) contact is three orders of magnitude lower than that from hydrophobic-hydrophilic (nonadhesive) contact. The trend of decreasing rate with decreasing wettability of glass sharply changes about a point where thermodynamic adhesion crosses zero, suggesting a transition in mode of evacuation, which is illuminated by three-dimensional spatiotemporal height maps. Adhesive contact is characterized by the early localization of sealed puddles, whereas nonadhesive contact remains smooth, with film-wise evacuation from one central puddle. Measurements with a human thumb and alternatively hydrophobic/hydrophilic glass surface demonstrate practical consequences of the same dynamics: adhesive interactions cause instability in valleys and lead to a state of more trapped water and less intimate solid-solid contact. These findings offer interpretation of patterned texture seen in underwater biolocomotive adaptations as well as insight toward technological implementation.
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13
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Ghasemi H, Yazdani H, Fini EH, Mansourpanah Y. Interactions of SARS-CoV-2 with inanimate surfaces in built and transportation environments. SUSTAINABLE CITIES AND SOCIETY 2021; 72:103031. [PMID: 36570725 PMCID: PMC9761300 DOI: 10.1016/j.scs.2021.103031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 05/13/2021] [Accepted: 05/16/2021] [Indexed: 05/11/2023]
Abstract
Understanding the interactions and transmission of pathogens with/via inanimate surfaces common in the built environment and public transport vehicles is critical to promoting sustainable and resilient urban development. Here, molecular dynamics (MD) simulations are used to study the adhesion of SARS-CoV-2 (the causative agent of COVID-19) to some of these surfaces at different temperatures (same for surfaces and ambiance) ranging from -23 to 60 °C. Surfaces simulated are aluminum, copper, copper oxide, polyethylene (PE), and silicon dioxide (SiO2). Steered MD (SMD) simulations are also used to investigate the transfer of the virus from PE and SiO2 when a contaminated surface is touched. The virus shows the lowest and highest adhesions to PE and SiO2, respectively (20 vs 534 eV). Influence of temperature is not found to be noticeable. Using simulated water molecules to represent moisture on the skin, SMD simulations show that water molecules can lift the virus from the PE surface but damage the virus when lifting it from the the SiO2 surface. The results suggest that the PE surface is a more favorable surface to transmit the virus than the other surfaces simulated in this study. The results are compared with those reported in a few experimental studies.
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Affiliation(s)
- Hamid Ghasemi
- Department of Civil and Environmental Engineering, Howard University, 2300 Sixth St NW #1026, Washington, DC 20059, USA
| | - Hessam Yazdani
- Department of Civil and Environmental Engineering, Howard University, 2300 Sixth St NW #1026, Washington, DC 20059, USA
| | - Elham H Fini
- School of Sustainable Engineering and the Built Environment, Arizona State University, 660 S. College Avenue, Tempe, AZ 85287, USA
| | - Yaghoub Mansourpanah
- Membrane Research Laboratory, Lorestan University, Khorramabad, 68137-17133, Iran
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14
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15
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Daunizeau T, Gueorguiev D, Haliyo S, Hayward V. Phononic Crystals Applied to Localised Surface Haptics. IEEE TRANSACTIONS ON HAPTICS 2021; 14:668-674. [PMID: 33844631 DOI: 10.1109/toh.2021.3072566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Metamaterials are solid lattices with periodicities commensurate with desired wavelengths. Their geometric features can endow the bulk material with unusual properties, such as inter alia, negative indices of refraction or unique absorbing qualities. Mesoscale metamaterials and phononic crystals can be designed to cause the occurence of band gaps in the ultrasonic domain. These localised phenomena induce fixed boundary conditions that correspond to acoustic mirrors which, in turn, can be used to establish waveguides in thin plates. Ultrasonic lubrication has been successfully applied to create haptic interfaces that operate by modulating the apparent friction of a surface. In this article, we demonstrate that phononic crystals can be designed to localise the modulation of friction in specific portions of the surface of a thin plate, opening novel possibilities for the design of surface haptic interfaces.
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16
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Rezaei M, Nagi SS, Xu C, McIntyre S, Olausson H, Gerling GJ. Thin Films on the Skin, but not Frictional Agents, Attenuate the Percept of Pleasantness to Brushed Stimuli. WORLD HAPTICS CONFERENCE. WORLD HAPTICS CONFERENCE 2021; 2021:49-54. [PMID: 35043106 PMCID: PMC8763324 DOI: 10.1109/whc49131.2021.9517259] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Brushed stimuli are perceived as pleasant when stroked lightly on the skin surface of a touch receiver at certain velocities. While the relationship between brush velocity and pleasantness has been widely replicated, we do not understand how resultant skin movements - e.g., lateral stretch, stick-slip, normal indentation - drive us to form such judgments. In a series of psychophysical experiments, this work modulates skin movements by varying stimulus stiffness and employing various treatments. The stimuli include brushes of three levels of stiffness and an ungloved human finger. The skin's friction is modulated via non-hazardous chemicals and washing protocols, and the skin's thickness and lateral movement are modulated by thin sheets of adhesive film. The stimuli are hand-brushed at controlled forces and velocities. Human participants report perceived pleasantness per trial using ratio scaling. The results indicate that a brush's stiffness influenced pleasantness more than any skin treatment. Surprisingly, varying the skin's friction did not affect pleasantness. However, the application of a thin elastic film modulated pleasantness. Such barriers, though elastic and only 40 microns thick, inhibit the skin's tangential movement and disperse normal force. The finding that thin films modulate affective interactions has implications for wearable sensors and actuation devices.
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Affiliation(s)
- Merat Rezaei
- School of Engineering and Applied Science, at the University of Virginia, USA
| | - Saad S Nagi
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Chang Xu
- School of Engineering and Applied Science, at the University of Virginia, USA
| | - Sarah McIntyre
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Håkan Olausson
- Center for Social and Affective Neuroscience (CSAN), Linköping University, Sweden
| | - Gregory J Gerling
- School of Engineering and Applied Science, at the University of Virginia, USA
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17
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Delhaye BP, Jarocka E, Barrea A, Thonnard JL, Edin B, Lefèvre P. High-resolution imaging of skin deformation shows that afferents from human fingertips signal slip onset. eLife 2021; 10:64679. [PMID: 33884951 PMCID: PMC8169108 DOI: 10.7554/elife.64679] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 04/13/2021] [Indexed: 01/27/2023] Open
Abstract
Human tactile afferents provide essential feedback for grasp stability during dexterous object manipulation. Interacting forces between an object and the fingers induce slip events that are thought to provide information about grasp stability. To gain insight into this phenomenon, we made a transparent surface slip against a fixed fingerpad while monitoring skin deformation at the contact. Using microneurography, we simultaneously recorded the activity of single tactile afferents innervating the fingertips. This unique combination allowed us to describe how afferents respond to slip events and to relate their responses to surface deformations taking place inside their receptive fields. We found that all afferents were sensitive to slip events, but fast-adapting type I (FA-I) afferents in particular faithfully encoded compressive strain rates resulting from those slips. Given the high density of FA-I afferents in fingerpads, they are well suited to detect incipient slips and to provide essential information for the control of grip force during manipulation. Each fingertip hosts thousands of nerve fibers that allow us to handle objects with great dexterity. These fibers relay the amount of friction between the skin and the item, and the brain uses this sensory feedback to adjust the grip as necessary. Yet, exactly how tactile nerve fibers encode information about friction remains largely unknown. Previous research has suggested that friction might not be recorded per se in nerve signals to the brain. Instead, fibers in the finger pad might be responding to localized ‘partial slips’ that indicate an impending loss of grip. Indeed, when lifting an object, fingertips are loaded with a tangential force that puts strain on the skin, resulting in subtle local deformations. Nerve fibers might be able to detect these skin changes, prompting the brain to adjust an insecure grip before entirely losing grasp of an object. However, technical challenges have made studying the way tactile nerve fibers respond to slippage and skin strain difficult. For the first time, Delhaye et al. have now investigated how these fibers respond to and encode information about the strain placed on fingertips as they are loaded tangentially. A custom-made imaging apparatus was paired with standard electrodes to record the activity of four different kinds of tactile nerve fibers in participants who had a fingertip placed against a plate of glass. The imaging focused on revealing changes in skin surface as tangential force was applied; the electrodes measured impulses from individual nerve fibers from the fingertip. While all the fibers responded during partial slips, fast-adapting type 1 nerves generated strong responses that signal a local loss of grip. Recordings showed that these fibers consistently encoded changes in the skin strain patterns, and were more sensitive to skin compressions related to slippage than to stretch. These results show how tactile nerve fibers encode the subtle skin compressions created when fingers handle objects. The methods developed by Delhaye et al. could further be used to explore the response properties of tactile nerve fibers, sensory feedback and grip.
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Affiliation(s)
- Benoit P Delhaye
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium.,Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Ewa Jarocka
- Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
| | - Allan Barrea
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium.,Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Jean-Louis Thonnard
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium.,Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
| | - Benoni Edin
- Department of Integrative Medical Biology, Umeå University, Umeå, Sweden
| | - Philippe Lefèvre
- Institute of Information and Communication Technologies, Electronics and Applied Mathematics, Université catholique de Louvain, Louvain-la-Neuve, Belgium.,Institute of Neuroscience, Université catholique de Louvain, Brussels, Belgium
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18
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Huloux N, Willemet L, Wiertlewski M. How to Measure the Area of Real Contact of Skin on Glass. IEEE TRANSACTIONS ON HAPTICS 2021; 14:235-241. [PMID: 33909571 DOI: 10.1109/toh.2021.3073747] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The contact between the fingertip and an object is formed by a collection of micro-scale junctions, which collectively constitute the real contact area. This real area of contact is only a fraction of the apparent area of contact and is directly linked to the frictional strength of the contact (i.e., the lateral force at which the finger starts sliding). As a consequence, a measure of this area of real contact can help probe into the mechanism behind the friction of skin on glass. In this article, we present two methods to measure the variations of contact area; one that improves upon a tried-and-true fingertip imaging technique to provide ground truth, and the other that relies on the absorption and reflection of acoustic energy. To achieve precise measurements, the ultrasonic method exploits a recently developed model of the interaction that incorporates the non-linearity of squeeze film levitation. The two methods are in good agreement ($\rho =0.94$) over a large range of normal forces and vibration amplitudes. Since the real area of contact fundamentally underlies fingertip friction, the methods described in the article have importance for studying human grasping, understanding friction perception, and controlling surface-haptic devices.
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19
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Nam S, Kuchenbecker KJ. Optimizing a Viscoelastic Finite Element Model to Represent the Dry, Natural, and Moist Human Finger Pressing on Glass. IEEE TRANSACTIONS ON HAPTICS 2021; 14:303-309. [PMID: 33945487 DOI: 10.1109/toh.2021.3077549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
When a fingerpad presses into a hard surface, the development of the contact area depends on the pressing force and speed. Importantly, it also varies with the finger's moisture, presumably because hydration changes the tissue's material properties. Therefore, we collected data from one finger repeatedly pressing a glass plate under three moisture conditions, and we constructed a finite element model that we optimized to simulate the same three scenarios. We controlled the moisture of the subject's finger to be dry, natural, or moist and recorded 15 pressing trials in each condition. The measurements include normal force over time plus finger-contact images that are processed to yield gross contact area. We defined the axially symmetric 3D model's lumped parameters to include an SLS-Kelvin model (spring in series with parallel spring and damper) for the bulk tissue, plus an elastic epidermal layer. Particle swarm optimization was used to find the parameter values that cause the simulation to best match the trials recorded in each moisture condition. The results show that the softness of the bulk tissue reduces as the finger becomes more hydrated. The epidermis of the moist finger model is softest, while the natural finger model has the highest viscosity.
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20
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Vardar Y, Kuchenbecker KJ. Finger motion and contact by a second finger influence the tactile perception of electrovibration. J R Soc Interface 2021; 18:20200783. [PMID: 33784888 PMCID: PMC8086864 DOI: 10.1098/rsif.2020.0783] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Electrovibration holds great potential for creating vivid and realistic haptic sensations on touchscreens. Ideally, a designer should be able to control what users feel independent of the number of fingers they use, the movements they make, and how hard they press. We sought to understand the perception and physics of such interactions by determining the smallest 125 Hz electrovibration voltage that 15 participants could reliably feel when performing four different touch interactions at two normal forces. The results proved for the first time that both finger motion and contact by a second finger significantly affect what the user feels. At a given voltage, a single moving finger experiences much larger fluctuating electrovibration forces than a single stationary finger, making electrovibration much easier to feel during interactions involving finger movement. Indeed, only about 30% of participants could detect the stimulus without motion. Part of this difference comes from the fact that relative motion greatly increases the electrical impedance between a finger and the screen, as shown via detailed measurements from one individual. By contrast, threshold-level electrovibration did not significantly affect the coefficient of kinetic friction in any conditions. These findings help lay the groundwork for delivering consistent haptic feedback via electrovibration.
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Affiliation(s)
- Yasemin Vardar
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany.,Department of Cognitive Robotics, Faculty of Mechanical, Maritime and Materials Engineering (3mE), Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Katherine J Kuchenbecker
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569 Stuttgart, Germany
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21
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Xu C, Wang Y, Gerling GJ. An elasticity-curvature illusion decouples cutaneous and proprioceptive cues in active exploration of soft objects. PLoS Comput Biol 2021; 17:e1008848. [PMID: 33750948 PMCID: PMC8016306 DOI: 10.1371/journal.pcbi.1008848] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 04/01/2021] [Accepted: 03/03/2021] [Indexed: 11/18/2022] Open
Abstract
Our sense of touch helps us encounter the richness of our natural world. Across a myriad of contexts and repetitions, we have learned to deploy certain exploratory movements in order to elicit perceptual cues that are salient and efficient. The task of identifying optimal exploration strategies and somatosensory cues that underlie our softness perception remains relevant and incomplete. Leveraging psychophysical evaluations combined with computational finite element modeling of skin contact mechanics, we investigate an illusion phenomenon in exploring softness; where small-compliant and large-stiff spheres are indiscriminable. By modulating contact interactions at the finger pad, we find this elasticity-curvature illusion is observable in passive touch, when the finger is constrained to be stationary and only cutaneous responses from mechanosensitive afferents are perceptible. However, these spheres become readily discriminable when explored volitionally with musculoskeletal proprioception available. We subsequently exploit this phenomenon to dissociate relative contributions from cutaneous and proprioceptive signals in encoding our percept of material softness. Our findings shed light on how we volitionally explore soft objects, i.e., by controlling surface contact force to optimally elicit and integrate proprioceptive inputs amidst indiscriminable cutaneous contact cues. Moreover, in passive touch, e.g., for touch-enabled displays grounded to the finger, we find those spheres are discriminable when rates of change in cutaneous contact are varied between the stimuli, to supplant proprioceptive feedback.
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Affiliation(s)
- Chang Xu
- School of Engineering and Applied Science, University of Virginia, Charlottesville, Virginia, United States of America
| | - Yuxiang Wang
- School of Engineering and Applied Science, University of Virginia, Charlottesville, Virginia, United States of America
| | - Gregory J. Gerling
- School of Engineering and Applied Science, University of Virginia, Charlottesville, Virginia, United States of America
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22
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A review of the neurobiomechanical processes underlying secure gripping in object manipulation. Neurosci Biobehav Rev 2021; 123:286-300. [PMID: 33497782 DOI: 10.1016/j.neubiorev.2021.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 01/05/2021] [Accepted: 01/11/2021] [Indexed: 11/24/2022]
Abstract
O'SHEA, H. and S. J. Redmond. A review of the neurobiomechanical processes underlying secure gripping in object manipulation. NEUROSCI BIOBEHAV REV 286-300, 2021. Humans display skilful control over the objects they manipulate, so much so that biomimetic systems have yet to emulate this remarkable behaviour. Two key control processes are assumed to facilitate such dexterity: predictive cognitive-motor processes that guide manipulation procedures by anticipating action outcomes; and reactive sensorimotor processes that provide important error-based information for movement adaptation. Notwithstanding increased interdisciplinary research interest in object manipulation behaviour, the complexity of the perceptual-sensorimotor-cognitive processes involved and the theoretical divide regarding the fundamentality of control mean that the essential mechanisms underlying manipulative action remain undetermined. In this paper, following a detailed discussion of the theoretical and empirical bases for understanding human dexterous movement, we emphasise the role of tactile-related sensory events in secure object handling, and consider the contribution of certain biophysical and biomechanical phenomena. We aim to provide an integrated account of the current state-of-art in skilled human-object interaction that bridges the literature in neuroscience, cognitive psychology, and biophysics. We also propose novel directions for future research exploration in this area.
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23
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Abstract
Fingerprints are unique to primates and koalas but what advantages do these features of our hands and feet provide us compared with the smooth pads of carnivorans, e.g., feline or ursine species? It has been argued that the epidermal ridges on finger pads decrease friction when in contact with smooth surfaces, promote interlocking with rough surfaces, channel excess water, prevent blistering, and enhance tactile sensitivity. Here, we found that they were at the origin of a moisture-regulating mechanism, which ensures an optimal hydration of the keratin layer of the skin for maximizing the friction and reducing the probability of catastrophic slip due to the hydrodynamic formation of a fluid layer. When in contact with impermeable surfaces, the occlusion of the sweat from the pores in the ridges promotes plasticization of the skin, dramatically increasing friction. Occlusion and external moisture could cause an excess of water that would defeat the natural hydration balance. However, we have demonstrated using femtosecond laser-based polarization-tunable terahertz wave spectroscopic imaging and infrared optical coherence tomography that the moisture regulation may be explained by a combination of a microfluidic capillary evaporation mechanism and a sweat pore blocking mechanism. This results in maintaining an optimal amount of moisture in the furrows that maximizes the friction irrespective of whether a finger pad is initially wet or dry. Thus, abundant low-flow sweat glands and epidermal furrows have provided primates with the evolutionary advantage in dry and wet conditions of manipulative and locomotive abilities not available to other animals.
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24
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Affiliation(s)
- Subramanian Sundaram
- Biological Design Center, Boston University, Boston, MA, USA
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
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25
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Moscatelli A, Nimbi FM, Ciotti S, Jannini EA. Haptic and Somesthetic Communication in Sexual Medicine. Sex Med Rev 2020; 9:267-279. [PMID: 32690471 DOI: 10.1016/j.sxmr.2020.02.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 02/05/2020] [Accepted: 02/09/2020] [Indexed: 11/24/2022]
Abstract
INTRODUCTION The word "haptics" refers to sensory inputs arising from receptors in the skin and in the musculoskeletal system, particularly crucial in sexual economy. Haptic stimuli provide information about mechanical properties of touched objects and about the position and motion of the body. An important area in this field is the development of robotic interfaces for communication through the "haptic channel," which typically requires a collaboration between engineers, neuroscientists, and psychologists. Many aspects of human sexuality, such as arousal and intercourse, can be considered from a haptic perspective. OBJECTIVES To review the current literature on haptics and somatosensation, and discuss potential applications of haptic interfaces in sexual medicine. METHODS Articles for this review were collected based on the results of a bibliographic search of relevant papers in Cochrane Library, Google Scholar, Web of Science, Scopus, and EBSCO. The search terms used, including asterisks, were "haptic∗," "somatosensor∗," "sexual∗," and related terms describing the role of touch, technology, and sexuality. Additional terms included "interface∗," "touch," and "sex∗." RESULTS We have provided a functional and anatomical description of the somatosensory system in humans, with special focus on neural structures involved in affective and erotic touch. One interesting topic is the development of haptic interfaces, which are specialized robots generating mechanical signals that stimulate our somatosensory system. We provided an overview on haptic interfaces and evaluated the role of haptics in sexual medicine. CONCLUSION Haptics and studies on the neuroscience of the somatosensory system are expected to provide useful insights for sexual medicine and novel tools for sexual dysfunction. In the future, crosstalk between sexology and haptics may produce a novel generation of user-friendly haptic devices generating a higher level of realism and presence in providing stimuli. Moscatelli A, Nimbi FM, Ciotti S, et al. Haptic and Somesthetic Communication in Sexual Medicine. J Sex Med 2021;9:267-279.
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Affiliation(s)
- Alessandro Moscatelli
- Course of Physiology, Department of Systems Medicine and Center of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy; Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Filippo M Nimbi
- Course of Psychosexology, Department of Dynamic and Clinical Psychology, Sapienza University of Rome, Rome, Italy
| | - Simone Ciotti
- Course of Physiology, Department of Systems Medicine and Center of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy; Laboratory of Neuromotor Physiology, IRCCS Fondazione Santa Lucia, Rome, Italy
| | - Emmanuele A Jannini
- Chair of Endocrinology & Medical Sexology (ENDOSEX), Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.
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26
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Introduction of a New In-Situ Measurement System for the Study of Touch-Feel Relevant Surface Properties. Polymers (Basel) 2020; 12:polym12061380. [PMID: 32575513 PMCID: PMC7361978 DOI: 10.3390/polym12061380] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 06/09/2020] [Accepted: 06/16/2020] [Indexed: 12/13/2022] Open
Abstract
The touch-feel sensation of product surfaces arouses growing interest in various industry branches. To entangle the underlying physical and material parameters responsible for a specific touch-feel sensation, a new measurement system has been developed. This system aims to record the prime physical interaction parameters at a time, which is considered a necessary prerequisite for a successful physical description of the haptic sensation. The measurement setup enables one to measure the dynamic coefficient of friction, the macroscopic contact area of smooth and rough surfaces, the angle enclosed between the human finger and the soft-touch surfaces and the vibrations induced in the human finger during relative motion at a time. To validate the measurement stand, a test series has been conducted on two soft-touch surfaces of different roughness. While the individual results agree well with the literature, their combination revealed new insights. Finally, the investigation of the haptics of polymer coatings with the presented measuring system should facilitate the design of surfaces with tailor-made touch-feel properties.
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27
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Nam S, Vardar Y, Gueorguiev D, Kuchenbecker KJ. Physical Variables Underlying Tactile Stickiness During Fingerpad Detachment. Front Neurosci 2020; 14:235. [PMID: 32372893 PMCID: PMC7177046 DOI: 10.3389/fnins.2020.00235] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 03/03/2020] [Indexed: 11/26/2022] Open
Abstract
One may notice a relatively wide range of tactile sensations even when touching the same hard, flat surface in similar ways. Little is known about the reasons for this variability, so we decided to investigate how the perceptual intensity of light stickiness relates to the physical interaction between the skin and the surface. We conducted a psychophysical experiment in which nine participants actively pressed their finger on a flat glass plate with a normal force close to 1.5 N and detached it after a few seconds. A custom-designed apparatus recorded the contact force vector and the finger contact area during each interaction as well as pre- and post-trial finger moisture. After detaching their finger, participants judged the stickiness of the glass using a nine-point scale. We explored how sixteen physical variables derived from the recorded data correlate with each other and with the stickiness judgments of each participant. These analyses indicate that stickiness perception mainly depends on the pre-detachment pressing duration, the time taken for the finger to detach, and the impulse in the normal direction after the normal force changes sign; finger-surface adhesion seems to build with pressing time, causing a larger normal impulse during detachment and thus a more intense stickiness sensation. We additionally found a strong between-subjects correlation between maximum real contact area and peak pull-off force, as well as between finger moisture and impulse.
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Affiliation(s)
- Saekwang Nam
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Yasemin Vardar
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - David Gueorguiev
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Katherine J Kuchenbecker
- Haptic Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
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28
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Li B, Hauser S, Gerling GJ. Identifying 3-D spatiotemporal skin deformation cues evoked in interacting with compliant elastic surfaces. IEEE HAPTICS SYMPOSIUM : [PROCEEDINGS]. IEEE HAPTICS SYMPOSIUM 2020; 2020:35-40. [PMID: 34458383 PMCID: PMC8395532 DOI: 10.1109/haptics45997.2020.ras.hap20.22.5a9b38d8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We regularly touch soft, compliant fruits and tissues. To help us discriminate them, we rely upon cues embedded in spatial and temporal deformation of finger pad skin. However, we do not yet understand, in touching objects of various compliance, how such patterns evolve over time, and drive perception. Using a 3-D stereo imaging technique in passive touch, we develop metrics for quantifying skin deformation, across compliance, displacement, and time. The metrics map 2-D estimates of terminal contact area to 3-D metrics that represent spatial and temporal changes in penetration depth, surface curvature, and force. To do this, clouds of thousands of 3-D points are reduced in dimensionality into stacks of ellipses, to be more readily comparable between participants and trials. To evaluate the robustness of the derived 3-D metrics, human subjects experiments are performed with stimulus pairs varying in compliance and discriminability. The results indicate that metrics such as penetration depth and surface curvature can distinguish compliances earlier, at less displacement. Observed also are distinct modes of skin deformation, for contact with stiffer objects, versus softer objects that approach the skin's compliance. These observations of the skin's deformation may guide the design and control of haptic actuation.
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Affiliation(s)
- Bingxu Li
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904 USA
| | - Steven Hauser
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904 USA
| | - Gregory J Gerling
- School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904 USA
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29
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Dhong C, Miller R, Root NB, Gupta S, Kayser LV, Carpenter CW, Loh KJ, Ramachandran VS, Lipomi DJ. Role of indentation depth and contact area on human perception of softness for haptic interfaces. SCIENCE ADVANCES 2019; 5:eaaw8845. [PMID: 31497646 PMCID: PMC6716960 DOI: 10.1126/sciadv.aaw8845] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 07/23/2019] [Indexed: 05/22/2023]
Abstract
In engineering, the "softness" of an object, as measured by an indenter, manifests as two measurable parameters: (i) indentation depth and (ii) contact area. For humans, softness is not well defined, although it is believed that perception depends on the same two parameters. Decoupling their relative contributions, however, has not been straightforward because most bulk-"off-the-shelf"-materials exhibit the same ratio between the indentation depth and contact area. Here, we decoupled indentation depth and contact area by fabricating elastomeric slabs with precise thicknesses and microstructured surfaces. Human subject experiments using two-alternative forced-choice and magnitude estimation tests showed that the indentation depth and contact area contributed independently to perceived softness. We found an explicit relationship between the perceived softness of an object and its geometric properties. Using this approach, it is possible to design objects for human interaction with a desired level of perceived softness.
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Affiliation(s)
- Charles Dhong
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, CA 92093-0448, USA
| | - Rachel Miller
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, CA 92093-0448, USA
| | - Nicholas B. Root
- Department of Psychology, University of California, San Diego, 9500 Gilman Drive, Mail Code 0109, La Jolla, CA 92093-0109, USA
| | - Sumit Gupta
- Department of Structural Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92003-0085, USA
| | - Laure V. Kayser
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, CA 92093-0448, USA
| | - Cody W. Carpenter
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, CA 92093-0448, USA
| | - Kenneth J. Loh
- Department of Structural Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92003-0085, USA
| | - Vilayanur S. Ramachandran
- Department of Psychology, University of California, San Diego, 9500 Gilman Drive, Mail Code 0109, La Jolla, CA 92093-0109, USA
| | - Darren J. Lipomi
- Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, CA 92093-0448, USA
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30
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Moscatelli A, Scotto CR, Ernst MO. Illusory changes in the perceived speed of motion derived from proprioception and touch. J Neurophysiol 2019; 122:1555-1565. [PMID: 31314634 DOI: 10.1152/jn.00719.2018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
In vision, the perceived velocity of a moving stimulus differs depending on whether we pursue it with the eyes or not: A stimulus moving across the retina with the eyes stationary is perceived as being faster compared with a stimulus of the same physical speed that the observer pursues with the eyes, while its retinal motion is zero. This effect is known as the Aubert-Fleischl phenomenon. Here, we describe an analog phenomenon in touch. We asked participants to estimate the speed of a moving stimulus either from tactile motion only (i.e., motion across the skin), while keeping the hand world stationary, or from kinesthesia only by tracking the stimulus with a guided arm movement, such that the tactile motion on the finger was zero (i.e., only finger motion but no movement across the skin). Participants overestimated the velocity of the stimulus determined from tactile motion compared with kinesthesia in analogy with the visual Aubert-Fleischl phenomenon. In two follow-up experiments, we manipulated the stimulus noise by changing the texture of the touched surface. Similarly to the visual phenomenon, this significantly affected the strength of the illusion. This study supports the hypothesis of shared computations for motion processing between vision and touch.NEW & NOTEWORTHY In vision, the perceived velocity of a moving stimulus is different depending on whether we pursue it with the eyes or not, an effect known as the Aubert-Fleischl phenomenon. We describe an analog phenomenon in touch. We asked participants to estimate the speed of a moving stimulus either from tactile motion or by pursuing it with the hand. Participants overestimated the stimulus velocity measured from tactile motion compared with kinesthesia, in analogy with the visual Aubert-Fleischl phenomenon.
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Affiliation(s)
- Alessandro Moscatelli
- Department of Systems Medicine and Centre of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy.,Laboratory of Neuromotor Physiology, IRCCS Santa Lucia Foundation, Rome, Italy.,Cognitive Interaction Technology-Cluster of Excellence, Bielefeld University, Bielefeld, Germany
| | - Cecile R Scotto
- Centre de Recherches sur la Cognition et l'Apprentissage, Université de Poitiers-Université de Tours-Centre National de la Recherche Scientifique, Poitiers, France.,Cognitive Interaction Technology-Cluster of Excellence, Bielefeld University, Bielefeld, Germany
| | - Marc O Ernst
- Applied Cognitive Psychology, Ulm University, Ulm, Germany.,Cognitive Interaction Technology-Cluster of Excellence, Bielefeld University, Bielefeld, Germany
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31
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Kikegawa K, Kuhara R, Kwon J, Sakamoto M, Tsuchiya R, Nagatani N, Nonomura Y. Physical origin of a complicated tactile sensation: ' shittori feel'. ROYAL SOCIETY OPEN SCIENCE 2019; 6:190039. [PMID: 31417711 PMCID: PMC6689606 DOI: 10.1098/rsos.190039] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Accepted: 06/10/2019] [Indexed: 05/22/2023]
Abstract
Shittori feel is defined as a texture that is moderately moisturized; however, many people experience 'shittori feel' when they touch a dry solid material containing little liquid. Here, shittori feel was evaluated for 12 materials. We found that the highest score of shittori feel was achieved by powders. Multiple regression analysis showed that shittori feel is a complex sense of moist and smooth feels. We analysed the relationship between the physical properties and the moist/smooth feels to show how subjects felt certain feels simultaneously. The moist and smooth feels are related to the surface roughness and friction characteristics of the materials. The moist and smooth feels can be perceived when the finger starts to move on the material surface and when the finger moves and rubs the material surface, respectively.
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Affiliation(s)
- Kana Kikegawa
- Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan
| | - Rieko Kuhara
- Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan
| | - Jinhwan Kwon
- Department of Informatics, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Maki Sakamoto
- Department of Informatics, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan
| | - Reiichiro Tsuchiya
- Daito Kasei Kogyo, Co., Ltd, 1-6-28 Akagawa, Asahi, Osaka 535-0005, Japan
| | - Noboru Nagatani
- Daito Kasei Kogyo, Co., Ltd, 1-6-28 Akagawa, Asahi, Osaka 535-0005, Japan
| | - Yoshimune Nonomura
- Department of Biochemical Engineering, Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan
- Author for correspondence: Yoshimune Nonomura e-mail:
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Gueorguiev D, Vezzoli E, Sednaoui T, Grisoni L, Lemaire-Semail B. The Perception of Ultrasonic Square Reductions of Friction With Variable Sharpness and Duration. IEEE TRANSACTIONS ON HAPTICS 2019; 12:179-188. [PMID: 30676978 DOI: 10.1109/toh.2019.2894412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The human perception of square ultrasonic modulation of the finger-surface friction was investigated during active tactile exploration by using short frictional cues of varying duration and sharpness. In a first experiment, we asked participants to discriminate the transition time and duration of short square ultrasonic reductions of friction. They proved very sensitive to discriminate millisecond differences in these two parameters with the average psychophysical thresholds being 2.3-2.4 ms for both parameters. A second experiment focused on the perception of square friction reductions with variable transition times and durations. We found that for durations of the stimulation larger than 90 ms, participants often perceived three or four edges when only two stimulations were presented while they consistently felt two edges for signals shorter than 50 ms. A subsequent analysis of the contact forces induced by these ultrasonic stimulations during slow and fast active exploration showed that two identical consecutive ultrasonic pulses can induce significantly different frictional dynamics especially during fast motion of the finger. These results confirm the human sensitivity to transient frictional cues and suggest that the human perception of square reductions of friction can depend on their sharpness and duration as well as on the speed of exploration.
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Contact mechanics between the human finger and a touchscreen under electroadhesion. Proc Natl Acad Sci U S A 2018; 115:12668-12673. [PMID: 30482858 DOI: 10.1073/pnas.1811750115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The understanding and control of human skin contact against technological substrates is the key aspect behind the design of several electromechanical devices. Among these, surface haptic displays that modulate the friction between the human finger and touch surface are emerging as user interfaces. One such modulation can be achieved by applying an alternating voltage to the conducting layer of a capacitive touchscreen to control electroadhesion between its surface and the finger pad. However, the nature of the contact interactions between the fingertip and the touchscreen under electroadhesion and the effects of confined material properties, such as layering and inelastic deformation of the stratum corneum, on the friction force are not completely understood yet. Here, we use a mean field theory based on multiscale contact mechanics to investigate the effect of electroadhesion on sliding friction and the dependency of the finger-touchscreen interaction on the applied voltage and other physical parameters. We present experimental results on how the friction between a finger and a touchscreen depends on the electrostatic attraction between them. The proposed model is successfully validated against full-scale (but computationally demanding) contact mechanics simulations and the experimental data. Our study shows that electroadhesion causes an increase in the real contact area at the microscopic level, leading to an increase in the electrovibrating tangential frictional force. We find that it should be possible to further augment the friction force, and thus the human tactile sensing, by using a thinner insulating film on the touchscreen than used in current devices.
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Complexity, rate, and scale in sliding friction dynamics between a finger and textured surface. Sci Rep 2018; 8:13710. [PMID: 30209322 PMCID: PMC6135846 DOI: 10.1038/s41598-018-31818-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/23/2018] [Indexed: 11/24/2022] Open
Abstract
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.
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Hauser SC, Gerling GJ. Imaging the 3-D Deformation of the Finger Pad When Interacting with Compliant Materials. IEEE HAPTICS SYMPOSIUM : [PROCEEDINGS]. IEEE HAPTICS SYMPOSIUM 2018; 2018:7-13. [PMID: 31080839 DOI: 10.1109/haptics.2018.8357145] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We need to understand the physics of how the skin of the finger pad deforms, and their tie to perception, to accurately reproduce a sense of compliance, or 'softness,' in tactile displays. Contact interactions with compliant materials are distinct from those with rigid surfaces where the skin flattens completely. To capture unique patterns in skin deformation over a range of compliances, we developed a stereo imaging technique to visualize the skin through optically clear stimuli. Accompanying algorithms serve to locate and track points marked with ink on the skin, correct for light refraction through stimuli, and estimate aspects of contact between skin and stimulus surfaces. The method achieves a 3-D spatial resolution of 60-120 microns and temporal resolution of 30 frames per second. With human subjects, we measured the skin's deformation over a range of compliances (61-266 kPa), displacements (0-4 mm), and velocities (1- 15 mm/s). The results indicate that the method can differentiate patterns of skin deformation between compliances, as defined by metrics including surface penetration depth, retention of geometric shape, and force per gross contact area. Observations of biomechanical cues of this sort are key to understanding the perceptual encoding of compliance.
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Affiliation(s)
- Steven C Hauser
- Departments of Systems and Information Engineering and Biomedical Engineering at the University of Virginia, USA
| | - Gregory J Gerling
- Departments of Systems and Information Engineering and Biomedical Engineering at the University of Virginia, USA
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Janko M, Wiertlewski M, Visell Y. Contact geometry and mechanics predict friction forces during tactile surface exploration. Sci Rep 2018; 8:4868. [PMID: 29559728 PMCID: PMC5861050 DOI: 10.1038/s41598-018-23150-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 03/02/2018] [Indexed: 11/23/2022] Open
Abstract
When we touch an object, complex frictional forces are produced, aiding us in perceiving surface features that help to identify the object at hand, and also facilitating grasping and manipulation. However, even during controlled tactile exploration, sliding friction forces fluctuate greatly, and it is unclear how they relate to the surface topography or mechanics of contact with the finger. We investigated the sliding contact between the finger and different relief surfaces, using high-speed video and force measurements. Informed by these experiments, we developed a friction force model that accounts for surface shape and contact mechanical effects, and is able to predict sliding friction forces for different surfaces and exploration speeds. We also observed that local regions of disconnection between the finger and surface develop near high relief features, due to the stiffness of the finger tissues. Every tested surface had regions that were never contacted by the finger; we refer to these as “tactile blind spots”. The results elucidate friction force production during tactile exploration, may aid efforts to connect sensory and motor function of the hand to properties of touched objects, and provide crucial knowledge to inform the rendering of realistic experiences of touch contact in virtual reality.
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Affiliation(s)
- Marco Janko
- Drexel University, Department of Electrical and Computer Engineering, Philadelphia, 19104, USA
| | | | - Yon Visell
- University of California, Department of Electrical and Computer Engineering, Media Arts & Technology Program, and Department of Mechanical Engineering, Santa Barbara, California, 93106, USA.
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Ball P. Material witness: Get a grip. NATURE MATERIALS 2017; 16:1057. [PMID: 29066826 DOI: 10.1038/nmat5022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
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