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Millisecond-scale temporal spiking patterns encode sensory information in the periphery, but their role in the neocortex remains controversial. The sense of touch provides a window into temporal coding because tactile neurons often exhibit precise, repeatable, and informative temporal spiking patterns. In the somatosensory cortex (S1), responses to skin vibrations exhibit phase locking that faithfully carries information about vibratory frequency. However, the respective roles of spike timing and rate in frequency coding are confounded because vibratory frequency shapes both the timing and rates of responses. To disentangle the contributions of these two neural features, we measured S1 responses as rhesus macaques performed frequency discrimination tasks in which differences in frequency were accompanied by orthogonal variations in amplitude. We assessed the degree to which the strength and timing of responses could account for animal performance. First, we showed that animals can discriminate frequency, but their performance is biased by amplitude variations. Second, rate-based representations of frequency are susceptible to changes in amplitude but in ways that are inconsistent with the animals’ behavioral biases, calling into question a rate-based neural code for frequency. In contrast, timing-based representations are highly informative about frequency but impervious to changes in amplitude, which is also inconsistent with the animals’ behavior. We account for the animals’ behavior with a model wherein frequency coding relies on a temporal code, but frequency judgments are biased by perceived magnitude. We conclude that information about vibratory frequency is not encoded in S1 firing rates but primarily in temporal patterning on millisecond timescales. [ABSTRACT FROM AUTHOR]

Humans rely on their fingers to sense and interact with external environment. Understanding the tribological behavior between finger skin and object surface is crucial for various fields, including tactile perception, product appearance design, and electronic skin research. Quantitatively describing finger frictional behavior is always challenging, given the complex structure of the finger. In this study, the texture and sliding direction dependence of finger skin friction was quantified based on explicit mathematic models. The proposed double-layer model of finger skin effectively described the nonlinear elastic response of skin and predicted the scaling-law of effective elastic modulus with contact radius. Additionally, the skin friction model on textured surface considering adhesion and deformation factors was established. It revealed that adhesive term dominated finger friction behavior in daily life, and suggested that object texture size mainly influenced friction-induced vibrations rather than the average friction force. Combined with digital image correlation (DIC) technique, the effect of sliding direction on finger friction was analyzed. It was found that the anisotropy in finger friction was governed by the finger's ratchet pawl structure, which also contributes to enhanced stick-slip vibrations in the distal sliding direction. The proposed friction models can offer valuable insights into the underlying mechanism of skin friction under various operating conditions, and can provide quantitative guidance for effectively encoding friction into haptics. [ABSTRACT FROM AUTHOR]

Our mental representation of our body depends on integrating various sensory modalities, such as tactile information. In tactile distance estimation (TDE) tasks, participants must estimate the distance between two tactile tips applied to their skin. This measure of tactile perception has been linked to body representation assessments. Studies in individuals with fibromyalgia (FM), a chronic widespread pain syndrome, suggest the presence of body representation distortions and tactile alterations, but TDE has never been examined in this population. Twenty participants with FM and 24 pain-free controls performed a TDE task on three Body regions (upper limb, trunk, lower limb), in which they manually estimated the interstimuli distance on a tablet. TDE error, the absolute difference between the estimation and the interstimuli distance, was not different between the Groups, on any Body region. Drawings of their body as they felt it revealed clear and frequent distortions of body representation in the group with FM, compared to negligible perturbations in controls. This contrast between distorted body drawings and unaltered TDE suggests a preserved integration of tactile information but an altered integration of this information with other sensory modalities to generate a precise and accurate body representation. Future research should investigate the relative contribution of each sensory information and prior knowledge about the body in body representation in individuals with FM to shed light on the observed distortions. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to elucidate whether an external reference frame contributes to tactile localization in blindfolded healthy humans. In a session, the right forearm was passively moved until the elbow finally reached to the target angle, and participants reached the left index finger to the right middle fingertip. The locus of the right middle fingertip indicated by the participants deviated in the direction of the elbow extension when vibration was provided to the biceps brachii muscle during the passive movement. This finding indicates that proprioception contributes to the identification of the spatial coordinate of the specific body part in an external reference frame. In another session, the tactile stimulus was provided to the dorsal of the right hand during the passive movement, and the participants reached the left index finger to the spatial locus at which the tactile stimulus was provided. Vibration to the biceps brachii muscle did not change the perceived locus of the tactile stimulus indicated by the left index finger. This finding indicates that an external reference frame does not contribute to tactile localization during the passive movement. Humans may estimate the spatial coordinate of the tactile stimulus based on the time between the movement onset and the time at which the tactile stimulus is provided. [ABSTRACT FROM AUTHOR]

Highlights Fully organic and passive tactile sensors are developed via mimicking the sensing behavior of natural sensory cells. Controllable polarizability of conjugated polymers is adopted for the first time to construct passive tactile sensors. Machine learning-assisted surface texture detection, material property recognition, as well as shape/profile perception are realized with the tactile sensors.

Abstract Digital technologies, such as virtual or augmented reality, can potentially support neurocognitive functions of the aging populations worldwide and complement existing intervention methods. However, aging-related declines in the frontal-parietal network and dopaminergic modulation which progress gradually across the later periods of the adult lifespan may affect the processing of multisensory congruence and expectancy based contextual plausibility. We assessed hemodynamic brain responses while middle-aged and old adults experienced car-riding virtual-reality scenarios where the plausibility of vibrotactile stimulations was manipulated by delivering stimulus intensities that were either congruent or incongruent with the digitalized audio-visual contexts of the respective scenarios. Relative to previous findings observed in young adults, although highly plausible vibrotactile stimulations confirming with contextual expectations also elicited higher brain hemodynamic responses in middle-aged and old adults, this effect was limited to virtual scenarios with extreme expectancy violations. Moreover, individual differences in plausibility-related frontal activity did not correlate with plausibility violation costs in the sensorimotor cortex, indicating less systematic frontal context-based sensory filtering in older ages. These findings have practical implications for advancing digital technologies to support aging societies.

Human fingers possess stable high sensitivity and a wide range of tactile perception, attributed to the gradient microstructure and the interlocking collagen fiber on the skin's surface. However, challenges persist in achieving simultaneous enhancement of multiple functionalities in artificial skin. Inspired by the unique structure of the skin, a two‐step process involving ion diffusion‐induced and strong‐weak topological crosslinking is synergistically employed to fabricate a bilayer gradient hydrogel. Zn2+ initially diffuses to induce the formation of weak bonds, imparting elasticity. Subsequently, Fe3+/Zn2+ diffusion constructs a strong‐weak topologically crosslinked network, enhancing the toughness of the gel while reducing the brittleness associated with robust bonds. Due to its distinctive design, the gel employs an adaptive energy dissipation strategy subjected to large and small stress, ensuring high sensitivity (3.31 kPa−1, 0–2 kPa), wide sensing range (0.4–40.6 kPa), and exceptional stability (500 cycles). This flexible approach enables programmable design in three dimensions, including ion diffusion type, direction, and shape. This gel can detect the gentle brushing of feathers and human body movements. It utilizes significant differences generated by magnitudes of stress to perform binary information encryption. This study introduces a novel strategy for preparing skin‐like gels, offering promising potential for expanding their applications in complex scenarios. [ABSTRACT FROM AUTHOR]

Somatosensory tactile experience is a key aspect of our interaction with the environment. It is involved in object manipulation, in the planning and control of actions and, in its affective components, in the relationships with other individuals. It is also a foundational component of body awareness. An intriguing aspect of sensory perception in general and tactile perception in particular is the way in which stimulation comes to consciousness. Indeed, although being aware of something seems a rather self-evident and monolithic aspect of our mental states, sensory awareness may be in fact modulated by many different processes that impact on the mere stimulation of the skin, including the way in which we perceive our bodies as belonging to us. In this review, we first took into consideration the pathological conditions of absence of phenomenal experience of touch, in the presence of implicit processing, as initial models for understanding the neural bases of conscious tactile experience. Subsequently, we discussed cases of tactile illusions both in normal subjects and in brain-damaged patients which help to understand which high-order processes impact tactile awareness. Finally, we discussed the observations reported in the review in light of some influential models of touch and body representation. [ABSTRACT FROM AUTHOR]

Due to the excellent maneuverability and obstacle crossing of legged robots, it is possible for an autonomous legged wall-climbing robots to replace manual inspection of ship exterior panels. However, when the magnetic adsorption legged wall-climbing robot steps on the convex point or convex line of the wall, or even when the robot missteps, the robot is likely to detach from the ferromagnetic wall. Therefore, this paper proposes a tactile sensor for the legged magnetic adsorption wall-climbing robot to detect the magnetic adsorption state and improve the safety of the autonomous crawling of the robot. The tactile sensor mainly comprises a three-dimensional (3D)-printed shell, a tactile slider, and three isometric sensing units, with an optimized geometry. The experiment shows that the triboelectric tactile sensor can monitor the sliding depth of the tactile slider and control the light-emitting device (LED) signal light. In addition, in the demonstration experiment of detecting the adsorption state of the robot's foot, the triboelectric tactile sensor has strong adaptability to various ferromagnetic wall surfaces. Finally, this study establishes a robot gait control system to verify the feedback control ability of the triboelectric tactile sensor. The results show that the robot equipped with the triboelectric tactile sensor can recognize the dangerous area on the crawling wall and autonomously avoid the risk. Therefore, the proposed triboelectric tactile sensor has great potential in realizing the tactile sensing ability of robots and enhancing the safety and intelligent inspection of ultra-large vessels. [ABSTRACT FROM AUTHOR]

Digital technologies, such as virtual or augmented reality, can potentially support neurocognitive functions of the aging populations worldwide and complement existing intervention methods. However, aging-related declines in the frontal-parietal network and dopaminergic modulation which progress gradually across the later periods of the adult lifespan may affect the processing of multisensory congruence and expectancy based contextual plausibility. We assessed hemodynamic brain responses while middle-aged and old adults experienced car-riding virtual-reality scenarios where the plausibility of vibrotactile stimulations was manipulated by delivering stimulus intensities that were either congruent or incongruent with the digitalized audio-visual contexts of the respective scenarios. Relative to previous findings observed in young adults, although highly plausible vibrotactile stimulations confirming with contextual expectations also elicited higher brain hemodynamic responses in middle-aged and old adults, this effect was limited to virtual scenarios with extreme expectancy violations. Moreover, individual differences in plausibility-related frontal activity did not correlate with plausibility violation costs in the sensorimotor cortex, indicating less systematic frontal context-based sensory filtering in older ages. These findings have practical implications for advancing digital technologies to support aging societies. [ABSTRACT FROM AUTHOR]

Objective: This preliminary study suggests a way to artificially extend vibrissae of blind dogs to assist ambulation and avoiding facial contact with obstacles. Procedures: Fourteen irreversibly blind dogs had 5–6 mystacial vibrissae on each side of the face supplementally extended by attaching carefully chosen adult pig hairs to them and were subjected to a maze test before and after the procedure. In three of these dogs the test was repeated one more time after all the extensions had fallen off. Collision counts and course times with and without extensions were analyzed and compared. A p-value > 0.05 was considered significant. Results: Median number of collisions was significantly higher post-extensions (5 IQR 2.25) and after extensions had fallen off (4 IQR 7.50) compared to pre-extensions (1 IQR 1), p = 0.021. Median times were significantly higher pre-extension (25.6 IQR 8.98) and after the extensions had fallen off, compared to the post-extension performance (22.8 IQR 8.55), p = 0.04. Conclusion: Vibrissae play an important role in the tactile perception of blind dogs, and our preliminary results suggest that extending this sensory organ possibly improves obstacle location and their quality of life. [ABSTRACT FROM AUTHOR]

It is a challenging task to localize and track an in-hand object in robotic domain. Researchers were mainly using the vision as major modality for extracting object's pose. The vision approaches are fragile when the object is occluded by the robotic arm and hand. To this end, we propose a tactile-based DTI-Tracker (tracking object's pose via Dynamic Tactile Interaction) approach and formalize the object's tracking as a filter problem. An Extended Kalman Filter (EKF) is used to estimate the in-hand object pose exploiting the high spatial resolution tactile feedback. Given the initial estimation error, the proposed approach rapidly converges the estimation result to the real pose and the statistic evaluation shows the robustness of the proposed approach. We evaluate this method in physics simulation and real multi-fingered grasping setup while the object is static and movable. The proposed method is a potential tool to foster future research on dexterous manipulation using multifingered robotic hand. [ABSTRACT FROM AUTHOR]

Introduction: The foot sole endures high magnitudes of pressure for sustained periods which results in transient but habitual cutaneous ischemia. Upon unloading, microvascular reactivity in cutaneous capillaries generates an influx of blood flow (PORH: post-occlusive reactive hyperemia). Whether pressure induced cutaneous ischemia from loading the foot sole impacts mechanoreceptor sensitivity remains unknown. Methods: Pressure induced ischemia was attained using a custom-built-loading device that applied load to the whole right foot sole at 2 magnitudes (15 or 50% body weight), for 2 durations (2 or 10 minutes) in thirteen seated participants. Mechanoreceptor sensitivity was assessed using Semmes-Weinstein monofilaments over the third metatarsal (3MT), medial arch (MA), and heel. Perceptual thresholds (PT) were determined for each site prior to loading and then applied repeatedly to a metronome to establish the time course to return to PT upon unload, defined as PT recovery time. Microvascular flux was recorded from an in-line laser speckle contrast imager (FLPI-2, Moor Instruments Inc.) to establish PORH peak and recovery rates at each site. Results: PT recovery and PORH recovery rate were most influenced at the heel and by load duration rather than load magnitude. PT recovery time at the heel was significantly longer with 10 minutes of loading, regardless of magnitude. Heel PORH recovery rate was significantly slower with 10minutes of loading. The 3MT PT recovery time was only longer after 10 minutes of loading at 50% body weight. Microvascular reactivity or sensitivity was not influenced with loading at the MA. A simple linear regression found that PORH recovery rate could predict PT recovery time at the heel (R2=0.184, p<0.001). Conclusion: In populations with degraded sensory feedback, such as diabetic neuropathy, the risk for ulcer development is heightened. Our work demonstrated that prolonged loading in healthy individuals can impair skin sensitivity, which highlights the risks of prolonged loading and is likely exacerbated in diabetes. Understanding the direct association between sensory function and microvascular reactivity in age and diabetes related nerve damage, could help detect early progressions of neuropathy and mitigate ulcer development. [ABSTRACT FROM AUTHOR]

This study investigates the crossmodal associations between naturally occurring sound textures and tactile textures. Previous research has demonstrated the association between low-level sensory features of sound and touch, as well as higher-level, cognitively mediated associations involving language, emotions, and metaphors. However, stimuli like textures, which are found in both modalities have received less attention. In this study, we conducted two experiments: a free association task and a two alternate forced choice task using everyday tactile textures and sound textures selected from natural sound categories. The results revealed consistent crossmodal associations reported by participants between the textures of the two modalities. They tended to associate more sound textures (e.g., wood shavings and sandpaper) with tactile surfaces that were rated as harder, rougher, and intermediate on the sticky-slippery scale. While some participants based the auditory-tactile association on sensory features, others made the associations based on semantic relationships, co-occurrence in nature, and emotional mediation. Interestingly, the statistical features of the sound textures (mean, variance, kurtosis, power, autocorrelation, and correlation) did not show significant correlations with the crossmodal associations, indicating a higher-level association. This study provides insights into auditory-tactile associations by highlighting the role of sensory and emotional (or cognitive) factors in prompting these associations. [ABSTRACT FROM AUTHOR]

Tactile perception of fabrics is a complex process challenging to parse and understand. Most studies examined fabric tactile perception through subjective means. Alternatively, neural and electrodermal signals can be used to examine fabric properties that elicit responses via tactile stimulation. Among the fabric properties, some may generate strong responses while others produce weaker responses. Here, we have shown that by studying the electroencephalography signal from the scalp areas corresponding to the sensory cortex, and the galvanic skin responses that occurred during active tactile sensation of varied fabrics, the influence of individual fabric properties can be determined. Eight subjective properties, from twenty female subjects, and seventeen objective properties, measured using Kawabata Evaluation System, were independently correlated to the biosignals. We have shown that properties related to thickness and volume were the most influential, followed by surface frictional properties. Fuzziness and linearity of compression were the least influencing properties affecting the biosignals. [ABSTRACT FROM AUTHOR]

Shear force sensors play an indispensable role in tactile perception for robot manipulation tasks. However, recent advancements in shear force sensors have been hindered by issues such as direction sensitivity and integration limitations. This paper proposes a microcolumn array dielectric layer produced using photolithography technology that enables tunability of sensor sensitivity and detection range by adjusting the aspect ratio and interval of the microstructures. Meanwhile, the impact of five constant normal force couplings on the sensitivity of shear force perception is investigated. The structure array with a 1:2 aspect ratio and 600 µm interval demonstrates an ultrahigh sensitivity of 6.189 N−1 and outstanding linearity (R2 = 0.9873) within the range up to 0.1 N. The sensor exhibits low hysteresis and robust stability over 3000 cycles. Additionally, it exhibits remarkable anisotropic direction sensitivity, enabling accurate positioning within a quarter‐circle angle. An intentionally designed orthogonal array is employed to extend the shear angle range up to 360°. Owing to the high performance of the sensor, it is further integrated onto a gripper to facilitate the grasping operation and effectively capture delicate movements. The experimental outcomes highlight that the designed sensor holds promise for applications in robotic applications and electronic skin domains. [ABSTRACT FROM AUTHOR]

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Traditional artificial skin gels often only focuses on a single perspective and overlooks the necessity of multidimensional synergistic design for sensitivity enhancement. To address these problems, the innovative introduction of dual solvents on the surface of polyacrylamide/sodium alginate gel induces to the transformation of supramolecular interactions including ion coordination, crystalline alcohol, and phase separation, synergistically achieving adjustable wrinkle wavelengths (304.2 ± 19.9 to 2393.5 ± 95.9 µm) and modulated chemical compositions with tunable moduli (87.5 ± 3.3 to 157.6 ± 3.7 kPa). This flexible strategy allows the construction of long‐range ordered wrinkled microstructures of three‐dimensional surfaces and complex morphologies. Meanwhile, the bridge effect induced by crystalline alcohols directs the insertion of ethanol molecules into the polymer chains, effectively reducing intramolecular friction. Benefiting from the small wavelength and low modulus dominated by crystalline alcohol, the wrinkled gel exhibits extremely high sensitivity of 164 kPa−1 (<0.5 kPa) and wide detection range (44.3 kPa). The wrinkled gel remains stable high sensitive to detect micro‐ and large stress, tactile perception, and human motion behaviors. This work proposes a new strategy for constructing highly sensitive bioinspired skin from multiple dimensions, showing broad application prospects in the fields of bioengineering and behavioral cognition. [ABSTRACT FROM AUTHOR]

Our mental representation of our body depends on integrating various sensory modalities, such as tactile information. In tactile distance estimation (TDE) tasks, participants must estimate the distance between two tactile tips applied to their skin. This measure of tactile perception has been linked to body representation assessments. Studies in individuals with fibromyalgia (FM), a chronic widespread pain syndrome, suggest the presence of body representation distortions and tactile alterations, but TDE has never been examined in this population. Twenty participants with FM and 24 pain-free controls performed a TDE task on three Body regions (upper limb, trunk, lower limb), in which they manually estimated the interstimuli distance on a tablet. TDE error, the absolute difference between the estimation and the interstimuli distance, was not different between the Groups, on any Body region. Drawings of their body as they felt it revealed clear and frequent distortions of body representation in the group with FM, compared to negligible perturbations in controls. This contrast between distorted body drawings and unaltered TDE suggests a preserved integration of tactile information but an altered integration of this information with other sensory modalities to generate a precise and accurate body representation. Future research should investigate the relative contribution of each sensory information and prior knowledge about the body in body representation in individuals with FM to shed light on the observed distortions.

Abstract In the case of a visually impaired person, literal communication often relies on braille, a system predominantly dependent on vision and touch. This study entailed the development of a visual and tactile perception technique for braille character recognition. In the visual perception approach, a braille character recognition was performed using a deep learning model (Faster R-CNN–FPN–ResNet-50), based on custom-made braille dataset collected through data augmentation and preprocessing. The attained performance was indicated by an mAP50 of 94.8 and mAP75 of 70.4 on the generated dataset. In the tactile perception approach, a braille character recognition was performed using a flexible capacitive pressure sensor array. The sensor size and density were designed according to braille standards, and a single sensor with a size of 1.5 mm × 1.5 mm was manufactured into a 5 × 5 sensor array by using a printing technique. Additionally, the sensitivity was improved by incorporating a pressure-sensitive micro dome-structured array layer. Finally, braille character recognition was visualized in the form of a video-based heatmap. These results will potentially be a cornerstone in developing assistive technology for the visually impaired through the fusion of visual-tactile sensing technology.

Highlights The tactile performance of ultralight multifunctional sensors can reach the level of human tactile perception. An individual sensor can provide multiple tactile sensations: pressure, temperature, materials recognition, and 3D location. Therefore, it is no longer necessary to integrate multiple sensing modules with different functions, which greatly simplifies system complexity and reduces energy loss. The tactile system with multimodal learning algorithms has universality and can accommodate object recognition tasks in various application scenarios (e.g., Mars and Kitchen).

Individual differences in tactile acuity have been correlated with age, gender and finger size, whereas the role of the skin's stiffness has been underexplored. Using an approach to image the 3‐D deformation of the skin surface during contact with transparent elastic objects, we evaluate a cohort of 40 young participants, who present a diverse range of finger size, skin stiffness and fingerprint ridge breadth. The results indicate that skin stiffness generally correlates with finger size, although individuals with relatively softer skin can better discriminate compliant objects. Analysis of contact at the skin surface reveals that softer skin generates more prominent patterns of deformation, in particular greater rates of change in contact area, which correlate with higher rates of perceptual discrimination of compliance, regardless of finger size. Moreover, upon applying hyaluronic acid to soften individuals' skin, we observe immediate, marked and systematic changes in skin deformation and consequent improvements in perceptual acuity in differentiating compliance. Together, the combination of 3‐D imaging of the skin surface, biomechanics measurements, multivariate regression and clustering, and psychophysical experiments show that subtle distinctions in skin stiffness modulate the mechanical signalling of touch and shape individual differences in perceptual acuity. Key points: Although declines in tactile acuity with ageing are a function of multiple factors, for younger people, the current working hypothesis has been that smaller fingers are better at informing perceptual discrimination because of a higher density of neural afferents.To decouple relative impacts on tactile acuity of skin properties of finger size, skin stiffness, and fingerprint ridge breadth, we combined 3‐D imaging of skin surface deformation, biomechanical measurements, multivariate regression and clustering, and psychophysics.The results indicate that skin stiffness generally correlates with finger size, although it more robustly correlates with and predicts an individual's perceptual acuity.In particular, more elastic skin generates higher rates of deformation, which correlate with perceptual discrimination, shown most dramatically by softening each participant's skin with hyaluronic acid.In refining the current working hypothesis, we show the skin's stiffness strongly shapes the signalling of touch and modulates individual differences in perceptual acuity. [ABSTRACT FROM AUTHOR]

In the case of a visually impaired person, literal communication often relies on braille, a system predominantly dependent on vision and touch. This study entailed the development of a visual and tactile perception technique for braille character recognition. In the visual perception approach, a braille character recognition was performed using a deep learning model (Faster R-CNN–FPN–ResNet-50), based on custom-made braille dataset collected through data augmentation and preprocessing. The attained performance was indicated by an mAP50 of 94.8 and mAP75 of 70.4 on the generated dataset. In the tactile perception approach, a braille character recognition was performed using a flexible capacitive pressure sensor array. The sensor size and density were designed according to braille standards, and a single sensor with a size of 1.5 mm × 1.5 mm was manufactured into a 5 × 5 sensor array by using a printing technique. Additionally, the sensitivity was improved by incorporating a pressure-sensitive micro dome-structured array layer. Finally, braille character recognition was visualized in the form of a video-based heatmap. These results will potentially be a cornerstone in developing assistive technology for the visually impaired through the fusion of visual-tactile sensing technology. [ABSTRACT FROM AUTHOR]

Underfoot haptics, a largely unexplored area, offers rich tactile information close to that of hand-based interactions. Haptic feedback gives a sense of physicality to virtual environments, making for a more realistic and immersive experience. Augmented Virtuality offers the ability to render virtual materials on a physical object, or haptic proxy, without the user being aware of the object's physical appearance while seeing their own body. In this research, we investigate how the visual appearance of physical objects can be altered virtually to impact the tactile perception of the object. An Augmented Virtuality system was developed to explore this, and two tactile perception experiments, consisting of 18 participants, were conducted. Specifically, we explore whether changing the visual appearance of materials affects a person's underfoot tactile perception and which tactile perception is most affected by the change through a within-subjects experiment. Additionally, the study examines whether people are aware of changes in visual appearance when focused on other tasks through a between-subjects experiment. The study showed that a change in visual appearance significantly impacts the tactile perception of roughness. Matching visual appearance to physical materials was found to increase awareness of tactile perception. [ABSTRACT FROM AUTHOR]

This article proposes a reframing of the contemporary media Narcissus through the lens of the interactive installation Liquid Views: Narcissus Virtual Mirror (henceforth Liquid Views), created by Monika Fleischmann and Wolfgang Strauss in 1992. The installation explores the transformative encounter between the self and the other, employing the first high-resolution multi-touch interface, realized as a generative, performative, audiovisual experience. Conventional notions of the self are challenged to reflect on identity, connectivity and the interplay between the tangible and the virtual. In the early 1990s, Liquid Views demonstrated a new way of seeing as observer and observed by looking at ourselves while simultaneously becoming publicly visible to others. A more recent example of seeing the self in the other is Mirror (2022), a street art commentary on the Israeli–Palestinian conflict by Norwegian artist AFK. Like Liquid Views, it captures the essence of self-discovery in the other, recalling Carl Gustav Jung's observation in Modern Man in Search of a Soul (1933). It raises the question of whether the narcissistic self-image of the past can be transformed into an aesthetic of the empathetic gaze. This could be an extended act of mirroring, corresponding to a world that is tele-present. [ABSTRACT FROM AUTHOR]

Highlights: The tactile performance of ultralight multifunctional sensors can reach the level of human tactile perception. An individual sensor can provide multiple tactile sensations: pressure, temperature, materials recognition, and 3D location. Therefore, it is no longer necessary to integrate multiple sensing modules with different functions, which greatly simplifies system complexity and reduces energy loss. The tactile system with multimodal learning algorithms has universality and can accommodate object recognition tasks in various application scenarios (e.g., Mars and Kitchen). Humans can perceive our complex world through multi-sensory fusion. Under limited visual conditions, people can sense a variety of tactile signals to identify objects accurately and rapidly. However, replicating this unique capability in robots remains a significant challenge. Here, we present a new form of ultralight multifunctional tactile nano-layered carbon aerogel sensor that provides pressure, temperature, material recognition and 3D location capabilities, which is combined with multimodal supervised learning algorithms for object recognition. The sensor exhibits human-like pressure (0.04–100 kPa) and temperature (21.5–66.2 °C) detection, millisecond response times (11 ms), a pressure sensitivity of 92.22 kPa−1 and triboelectric durability of over 6000 cycles. The devised algorithm has universality and can accommodate a range of application scenarios. The tactile system can identify common foods in a kitchen scene with 94.63% accuracy and explore the topographic and geomorphic features of a Mars scene with 100% accuracy. This sensing approach empowers robots with versatile tactile perception to advance future society toward heightened sensing, recognition and intelligence. [ABSTRACT FROM AUTHOR]

Perception plays a pivotal role in both biological and technological interactions with the environment. Recent advancements in whisker sensors, drawing inspiration from nature's tactile systems, have ushered in a new era of versatile and highly sensitive sensing technology. Whisker sensors, which mimic the tactile hairs of mammals, offer both high sensitivity and multifunctionality. They excel in capturing fine-grained environmental data, detecting various stimuli with precision, and finding applications in diverse domains. This review explores the integration of whisker sensors in potential marine applications. Categorized into six types, these sensors are invaluable for tasks such as marine structure monitoring, measurement instruments, tactile perception in marine robots, and non-contact sensing in the marine environment. Challenges and potential solutions are examined, along with the prospects of whisker sensors in the field of marine science and engineering. In an era that demands adaptable sensing solutions, whisker sensors emerge as pivotal components, enabling machines and devices to perceive and respond to external stimuli with heightened sensitivity and versatility. Their application in the marine domain holds substantial promise, propelling advancements in the realms of marine science and engineering. [ABSTRACT FROM AUTHOR]

In recent years, research on new technologies for expressing and exchanging information through tactile vibration has been the focus of researches. In this paper, by choosing a suitable coding scheme and a vibrating motor arrangement, we designed a device to express semantic information through vibrotactile. Three types of experiments were designed to test the usability of the encoding scheme and the device. Firstly, the vibration intensity was experimented when designing the encoding scheme, and the results showed that the encoding scheme was better with Braille units of 0.2 and 0.3 vibration intensities. In addition, the learning experiment and sentence recognition accuracy experiment were carried out to verify the usability of the device. The learning experiment results show that subjects were able to memorize Braille characters with an accuracy more than 90%, and to recognize a Chinese character (consisting of two Braille cells) with an average of 90.8% accuracy. The sentence recognition accuracy test experiment results show that the average recognition rate of the three poems used for the test was 93.33%. The device can be used for semantic information expression and touch-reading of Braille, and it can realize the reading experience of paper Braille. [ABSTRACT FROM AUTHOR]

In this paper, the results of new investigations on the relationship between physical surface parameters of polymer-based coatings, skin hydration levels and tactile friction are presented. For this purpose, the chemical composition of the investigated coatings was varied on the basis of the curing and binding agent and also with respect to the addition of selected fillers. This allowed the adjustment of various surface parameters such as hardness, surface wettability and roughness over a wide range. Tribological tests were carried out in which the coefficient of friction between the finger pad and the respective coating was measured for different skin hydration levels. A specially developed setup was used that minimized changing skin hydration levels during the experiments that would impede reproducible friction measurements. While for dry skin the perceived friction correlates well to the coefficient of friction and surface hardness, this is not the case for moist finger skin. The results are explained under the assumption of adhesion dominated friction and the application of the Hertz contact theory. This finding was further investigated through contact mechanic simulations using the finite element method (FEM). To this end, the contact area formation dependence on the reaction force was studied for surfaces of different hardness and skin with different mechanical properties reflecting various hydration levels. The results qualitatively confirmed the experimental findings and the analysis based on the Hertz contact theory. [ABSTRACT FROM AUTHOR]

IntroductionThe foot sole endures high magnitudes of pressure for sustained periods which results in transient but habitual cutaneous ischemia. Upon unloading, microvascular reactivity in cutaneous capillaries generates an influx of blood flow (PORH: post-occlusive reactive hyperemia). Whether pressure induced cutaneous ischemia from loading the foot sole impacts mechanoreceptor sensitivity remains unknown.MethodsPressure induced ischemia was attained using a custom-built-loading device that applied load to the whole right foot sole at 2 magnitudes (15 or 50% body weight), for 2 durations (2 or 10 minutes) in thirteen seated participants. Mechanoreceptor sensitivity was assessed using Semmes-Weinstein monofilaments over the third metatarsal (3MT), medial arch (MA), and heel. Perceptual thresholds (PT) were determined for each site prior to loading and then applied repeatedly to a metronome to establish the time course to return to PT upon unload, defined as PT recovery time. Microvascular flux was recorded from an in-line laser speckle contrast imager (FLPI-2, Moor Instruments Inc.) to establish PORH peak and recovery rates at each site.ResultsPT recovery and PORH recovery rate were most influenced at the heel and by load duration rather than load magnitude. PT recovery time at the heel was significantly longer with 10 minutes of loading, regardless of magnitude. Heel PORH recovery rate was significantly slower with 10minutes of loading. The 3MT PT recovery time was only longer after 10 minutes of loading at 50% body weight. Microvascular reactivity or sensitivity was not influenced with loading at the MA. A simple linear regression found that PORH recovery rate could predict PT recovery time at the heel (R2=0.184, p

Multimodal integration is the formation of a coherent percept from different sensory inputs such as vision, audition, and somatosensation. Most research on multimodal integration in speech perception has focused on audio-visual integration. In recent years, audio-tactile integration has also been investigated, and it has been established that puffs of air applied to the skin and timed with listening tasks shift the perception of voicing by naive listeners. The current study has replicated and extended these findings by testing the effect of air puffs on gradations of voice onset time along a continuum rather than the voiced and voiceless endpoints of the original work. Three continua were tested: bilabial ("pa/ba"), velar ("ka/ga"), and a vowel continuum ("head/hid") used as a control. The presence of air puffs was found to significantly increase the likelihood of choosing voiceless responses for the two VOT continua but had no effect on choices for the vowel continuum. Analysis of response times revealed that the presence of air puffs lengthened responses for intermediate (ambiguous) stimuli and shortened them for endpoint (non-ambiguous) stimuli. The slowest response times were observed for the intermediate steps for all three continua, but for the bilabial continuum this effect interacted with the presence of air puffs: responses were slower in the presence of air puffs, and faster in their absence. This suggests that during integration auditory and aero-tactile inputs are weighted differently by the perceptual system, with the latter exerting greater influence in those cases where the auditory cues for voicing are ambiguous.

Somatosensory tactile experience is a key aspect of our interaction with the environment. It is involved in object manipulation, in the planning and control of actions and, in its affective components, in the relationships with other individuals. It is also a foundational component of body awareness. An intriguing aspect of sensory perception in general and tactile perception in particular is the way in which stimulation comes to consciousness. Indeed, although being aware of something seems a rather self-evident and monolithic aspect of our mental states, sensory awareness may be in fact modulated by many different processes that impact on the mere stimulation of the skin, including the way in which we perceive our bodies as belonging to us. In this review, we first took into consideration the pathological conditions of absence of phenomenal experience of touch, in the presence of implicit processing, as initial models for understanding the neural bases of conscious tactile experience. Subsequently, we discussed cases of tactile illusions both in normal subjects and in brain-damaged patients which help to understand which high-order processes impact tactile awareness. Finally, we discussed the observations reported in the review in light of some influential models of touch and body representation.

Abstract Introduction root canal treatment is a challenging procedure often first encountered by undergraduate dental students, leading to various difficulties and mistakes. Objective this study aimed to identify the specific difficulties encountered by undergraduate dental students during root canal treatment and the frequency of mistakes they committed in relation to these difficulties. Material and method this study employed a cross-sectional survey design. A cohort of 60 third-year students completed a self-administered questionnaire consisting of 27 questions addressing various aspects of endodontic treatment and 11 key areas of root canal procedures. The response options for each question were based on a 4-point Likert scale. Data analysis was performed using Python programming language and heatmaps were created using the seaborn library to better understand the distribution of the data. Result students encounter challenges in developing tactile sensation, accessory cone placement, and accurately reaching the apex during canal location. Dental schools should focus on improving students' tactile skills and methods to reach the apex to enhance the effectiveness of root canal treatment education. In contrast, students reported fewer mistakes in rubber dam application and safety measures during treatment. Dental educators should emphasize proper instrument use and safety precautions during root canal treatment. Interestingly, students did not perceive these areas as problematic despite committing mistakes. Conclusion this study provides valuable insights into the challenges and mistakes encountered by undergraduate dental students during root canal treatment. Dental educators should address these issues to improve students' skills and techniques and provide optimal patient care.

The clothing fabric and skin interact continuously across the many regions of users′ bodies during wear, which can lead to both physical skin damage and discomfort. Therefore, this investigation aimed to explore the regional differences in skin friction, tactile perception, and sensitivity in both females and males during the skin-textile interaction. The static and dynamic friction coefficient and textile perception (texture, stickiness, pleasantness, and discomfort) were measured across the 36 selected testing body areas by using a friction measurement device. The results revealed there was a significant difference in skin friction, tactile perceptions, and sensitivity across the various body regions. The anterior neck had the highest skin friction in both females and males, and participants generally rated higher texture perception in their anterior aspects compared to posterior and lateral regions. There was no significant difference in skin friction, tactile perception ratings, and sensitivity between females and males. Practitioner summary: This study sought to examine regional variations in skin friction, tactile perception, and sensitivity during the skin-textile interaction. There was a significant difference in skin friction, tactile perceptions, and sensitivity across the various body regions and no significant sex effect on skin friction, tactile perception ratings, and sensitivity. [ABSTRACT FROM AUTHOR]

A multitude of sensory modalities are involved in humans' experience of wetness, yet we know little of the integratory role of vision. Therefore, the aim was to quantify the effect of physical stain volume, chroma and size on wetness perception, and to compare wetness perception under different sensory conditions, including visuotactile and visual only interactions. Eighteen participants visually observed and/or used their index fingerpad to dynamically interact with stimuli varying in physical wetness (0, 2.16 × 10−4 or 3.45 × 10−4 ml mm−2), stain chroma (clear, light, dark) and stain size (1150 or 5000 mm2). After interaction participants rated wetness perception using a visual analogue scale (very dry to very wet). In visual only conditions participants were able to differentiate between dry and wet stimuli, and could also discriminate between different magnitudes of wetness with the addition of tactile cues. In both visual only and visuotactile conditions greater stain chroma resulted in increased wetness perception. Stain size did not have a significant effect in either condition. These results show that visual cues influence wetness perception (R 2 = 0.29), but indicate that visual dominance does not apply in these sensory integrations. Findings are relevant for the design of products with wetness management properties. Graphical abstract [ABSTRACT FROM AUTHOR]

Tactile perception is processed in the somatosensory cortices of the brain. To study the electrical activity of the brain evoked by the tactile perceptions of fabric textures, electroencephalograph signals during tactile perception were evaluated using event-related potentials and recurrence quantification analysis methods. A support vector machine was used to realize the identification of electroencephalograph signals. The results showed that fabric surface with large surface roughness, critical buckling force, and fiber diameter, and low warp-weft density was preferentially perceived, need large attentional resources, and evoke strong nonstationary state of the electroencephalographic system during the tactile perception. The δ rhythm was the main rhythm of event-related potential signals evoked by tactile perception of fabrics and the main energy of the electroencephalograph rhythm was concentrated in the low frequency band. The electroencephalographic system was in a strong nonstationary and fluctuating state during the production stage of P200 and P300 components of the event-related potential wave. The combination of P200, P300, mean diagonal line length L, and trapping time TT can significantly improve the classification accuracy of the electroencephalograph signal of tactile perception to about 72%. [ABSTRACT FROM AUTHOR]

Abstract The ongoing COVID-19 pandemic has forced the fashion industry to digitalize the conventional work system. Fashion designers were required to work from home, and textile trade shows were held online. However, fabric suppliers were unable to present their fabrics in a manner that enabled their properties to be easily understood. Visual information, such as photographs, videos, and the brief explanations provided by fabric suppliers were insufficient for fashion designers to comprehend the fabric’s properties. Thus, this research aims to identify the critical information for fashion designers in their digital fabric search and to discover effective ways to present this information. The current state of online tactile information was analyzed by conducting content analysis on several online fabric retailers. Then, semi-structured one-on-one in-depth interviews with 25 fashion designers were conducted to identify the strengths and weaknesses of the existing types of visual and textual information. Results revealed the most effective ways to present fabrics online. Specific guidelines were established for photographing or writing each type of information. Finally, a conceptual framework for fabric tactile communication in digital environments was developed. This study can contribute to the improvement of a designer’s experience in online fabric markets and can be used as a fundamental guide on designer’s tactile perception of fabrics, which can support technologies, such as haptic devices and 3D clothing simulation software.

Introduction: On Earth, self-produced somatosensory stimuli are typically perceived as less intense than externally generated stimuli of the same intensity, a phenomenon referred to as somatosensory attenuation (SA). Although this phenomenon arises from the integration of multisensory signals, the specific contribution of the vestibular system and the sense of gravity to somatosensory cognition underlying distinction between self-generated and externally generated sensations remains largely unknown. Here, we investigated whether temporary modulation of the gravitational input by head-down tilt bed rest (HDBR)-a well-known Earth-based analog of microgravity--might significantly affect somatosensory perception of self- and externally generated stimuli. Methods: In this study, 40 healthy participants were tested using short-term HDBR. Participants received a total of 40 non-painful self- and others generated electrical stimuli (20 self- and 20 other-generated stimuli) in an upright and HDBR position while blindfolded. After each stimulus, they were asked to rate the perceived intensity of the stimulation on a Likert scale. Results: Somatosensory stimulations were perceived as significantly less intense during HDBR compared to upright position, regardless of the agent administering the stimulus. In addition, the magnitude of SA in upright position was negatively correlated with the participants' somatosensory threshold. Based on the direction of SA in the upright position, participants were divided in two subgroups. In the subgroup experiencing SA, the intensity rating of stimulations generated by others decreased significantly during HDBR, leading to the disappearance of the phenomenon of SA. In the second subgroup, on the other hand, reversed SA was not affected by HDBR. Conclusion: Modulation of the gravitational input by HDBR produced underestimation of somatosensory stimuli. Furthermore, in participants experiencing SA, the reduction of vestibular inputs by HDBR led to the disappearance of the SA phenomenon. These findings provide new insights into the role of the gravitational input in somatosensory perception and have important implications for astronauts who are exposed to weightlessness during space missions. [ABSTRACT FROM AUTHOR]

Ionotronic artificial motion and tactile receptor (i‐AMTR) is essential to realize an interactive human‐machine interface. However, an i‐AMTR that effectively mimics the composition, structure, mechanics, and multi‐functionality of human skin, called humanoid i‐AMTR, is yet to be developed. To bridge this technological gap, this study proposes a strategy that combines molecular structure design and function integration to construct a humanoid i‐AMTR. Herein, a silk fibroin ionoelastomer (SFIE) with double cross‐linked molecular structure is designed to mimic the composition and structure of human skin, thereby resolving the conflict of stretchability, softness, and resilience, suffered by many previously reported ionotronics. Functionally, electromechanical sensing and triboelectricity‐based tactile perception are integrated into SFIE, to enable simultaneous perception of both motion and tactile inputs. By further leveraging the machine learning and Internet of Things (IoT) techniques, the proposed SFIE‐based humanoid i‐AMTR precisely senses the movement of human body and accurately sortball objects made of different materials. Notably, the success rate for 610 sorting tests reaches as high as 92.3%. These promising results essentially demonstrate a massive potential of humanoid i‐AMTR in the fields of sorting robots, rehabilitation medicine, and augmented reality. [ABSTRACT FROM AUTHOR]