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Haptic Augmented Reality (HAR) is a method that actively modulates the perceived haptics of physical objects by presenting additional haptic feedback using a haptic display. However, most of the proposed HAR research focuses on modifying the hardness, softness, roughness, smoothness, friction, and surface shape of physical objects. In this paper, we propose an approach to augment the perceived stickiness of a physical object by presenting additional tactile feedback at a particular time after the finger lifts off from the physical object using a thin and soft tactile display suitable for HAR. To demonstrate this concept, we constructed a thin and soft tactile display using a Dielectric Elastomer Actuator suitable for HAR. We then conducted two experiments to validate the effectiveness of the proposed approach. In Experiment 1, we showed that the developed tactile display can augment the perceived stickiness of physical objects by presenting additional tactile feedback at appropriate times. In Experiment 2, we investigated the stickiness experience obtained by our proposed approach and showed that the realism of the stickiness experience and the harmony between the physical object and the additional tactile feedback are affected by the frequency and presentation timing of the tactile feedback. Our proposed approach is expected to contribute to the development of new applications not only in HAR, but also in Virtual Reality, Mixed Reality, and other domains using haptic displays. [ABSTRACT FROM AUTHOR]

Abstract In this study, we introduce a novel maze task designed to investigate naturalistic motor learning in bimanual coordination. We developed and validated an extended set of movement primitives tailored to capture the full spectrum of scenarios encountered in a maze game. Over a 3-day training period, we evaluated participants’ performance using these primitives and a custom-developed software, enabling precise quantification of performance. Our methodology integrated the primitives with in-depth kinematic analyses and thorough thumb pressure assessments, charting the trajectory of participants’ progression from novice to proficient stages. Results demonstrated consistent improvement in maze performance and significant adaptive changes in joint behaviors and strategic recalibrations in thumb pressure distribution. These findings highlight the central nervous system’s adaptability in orchestrating sophisticated motor strategies and the crucial role of tactile feedback in precision tasks. The maze platform and setup emerge as a valuable foundation for future experiments, providing a tool for the exploration of motor learning and coordination dynamics. This research underscores the complexity of bimanual motor learning in naturalistic environments, enhancing our understanding of skill acquisition and task efficiency while emphasizing the necessity for further exploration and deeper investigation into these adaptive mechanisms.

This study investigates how feedback from different modalities affect window navigation tasks performed on a touchscreen by younger and older users. Thirty-two younger and 32 older users moved a window toward one of four or eight target areas with no feedback or visual, tactile or visual–tactile feedback. Visual feedback produced significantly higher accuracy and shorter task completion times than tactile feedback. Generally, visual–tactile feedback did not produce statistically higher accuracy or shorter task completion time than visual feedback. However, visual–tactile feedback prevented both younger and older users from overshooting the windows. Additionally, when users attempted to move the window to one of the eight target areas, the visual–tactile feedback helped younger users perform better. According to theories about human processing, the reason for the subtle advantage of visual–tactile feedback is that the unintuitive tactile force induces a higher cognitive load than straightforward visual information during window navigation. Nevertheless, visual–tactile feedback elicited the best user experience, as measured by questionnaires on emotion and fatigue, gesture usability and preference. Furthermore, more older users prefer visual–tactile feedback than younger users. Therefore, visual–tactile feedback should be considered, and the tactile feedback should be modified to be more intuitive in window navigation tasks. Research Highlights Visual feedback improved task performance more than tactile feedback in window navigation task. Visual–tactile feedback did not improve task performance compared to visual feedback. Visual–tactile feedback prevented users from overshooting the window. More older users than younger users prefer visual–tactile feedback. [ABSTRACT FROM AUTHOR]

In this study, we introduce a novel maze task designed to investigate naturalistic motor learning in bimanual coordination. We developed and validated an extended set of movement primitives tailored to capture the full spectrum of scenarios encountered in a maze game. Over a 3-day training period, we evaluated participants' performance using these primitives and a custom-developed software, enabling precise quantification of performance. Our methodology integrated the primitives with in-depth kinematic analyses and thorough thumb pressure assessments, charting the trajectory of participants' progression from novice to proficient stages. Results demonstrated consistent improvement in maze performance and significant adaptive changes in joint behaviors and strategic recalibrations in thumb pressure distribution. These findings highlight the central nervous system's adaptability in orchestrating sophisticated motor strategies and the crucial role of tactile feedback in precision tasks. The maze platform and setup emerge as a valuable foundation for future experiments, providing a tool for the exploration of motor learning and coordination dynamics. This research underscores the complexity of bimanual motor learning in naturalistic environments, enhancing our understanding of skill acquisition and task efficiency while emphasizing the necessity for further exploration and deeper investigation into these adaptive mechanisms. [ABSTRACT FROM AUTHOR]

Background: Tissue handling is a crucial skill for surgeons and is challenging to learn. The aim of this study was to develop laparoscopic instruments with different integrated tactile vibration feedback by varying different tactile modalities and assess its effect on tissue handling skills. Methods: Standard laparoscopic instruments were equipped with a vibration effector, which was controlled by a microcomputer attached to a force sensor platform. One of three different vibration feedbacks (F1: double vibration > 2 N; F2: increasing vibration relative to force; F3: one vibration > 1.5 N and double vibration > 2 N) was applied to the instruments. In this multicenter crossover trial, surgical novices and expert surgeons performed two laparoscopic tasks (Peg transfer, laparoscopic suture, and knot) each with all the three vibration feedback modalities and once without any feedback, in a randomized order. The primary endpoint was force exertion. Results: A total of 57 subjects (15 surgeons, 42 surgical novices) were included in the trial. In the Peg transfer task, there were no differences between the tactile feedback modalities in terms of force application. However, in subgroup analysis, the use of F2 resulted in a significantly lower mean-force application (p-value = 0.02) among the student group. In the laparoscopic suture and knot task, all participants exerted significantly lower mean and peak forces using F2 (p-value < 0.01). These findings remained significant after subgroup analysis for both, the student and surgeon groups individually. The condition without tactile feedback led to the highest mean and peak force exertion compared to the three other feedback modalities. Conclusion: Continuous tactile vibration feedback decreases the mean and peak force applied during laparoscopic training tasks. This effect is more pronounced in demanding tasks such as laparoscopic suturing and knot tying and might be more beneficial for students. Laparoscopic tasks without feedback lead to increased force application. [ABSTRACT FROM AUTHOR]

Tactile memory is the cognitive process of storing and recalling information that has been perceived through the sense of touch. Directional tactile memory involves the encoding and retrieval of sensory data associated with a tactile experience, allowing individuals to remember and recognize directional information encoded through the sense of touch. A new method for providing directional tactile feedback, at the back of the user, has been developed to investigate the efficacy of directional tactile memory, its decay over time, and its impact during a concurrent cognitive task. Two experiments were presented. In the first experiment, tactile memory deterioration, with a visual or a tactile cue, was tested with different action-cue latencies (10 s and 20 s). In the second experiment, we considered tactile memory deterioration when there was an increased cognitive load as the participants played Tetris. Forty volunteers participated in the two experiments using purpose-built tactile seats with nine motors controlled by an Arduino. The performance data (error and reaction times) were analyzed statistically, and a NASA task load index (NASA-TLX) questionnaire was administered to measure the subjective workload after each of the two experiments. The findings highlighted that the directional tactile memory of the back can guide individuals to the correct point on the screen and that it can be maintained for at least 20 s. There was no statistically significant difference in the number of errors or reaction time with a visual or tactile action cue. However, being involved in a concurrent cognitive task (playing Tetris) adversely affected the reaction time, the number of errors, and the directional tactile memory, which degraded as the time between the directional cue and the action cue increased. Participants perceived the performance while playing Tetris as significantly more mentally and perceptually demanding, requiring more mental and physical effort and being more frustrating. These trials revealed a new potential for a human–machine interface system, leveraging directional tactile memory, which might be utilized to increase the safety of autonomous vehicles. [ABSTRACT FROM AUTHOR]

Auditory and somatosensory white noise can stabilize standing balance. However, the differential effects of auditory and tactile noise stimulation on balance are unknown. Prior work on unimodal noise stimulation showed gains in balance with white noise through the auditory and tactile modalities separately. The current study aims to examine whether multimodal noise elicits similar responses to unimodal noise. We recorded the postural sway of healthy young adults who were presented with continuous white noise through the auditory or tactile modalities and through a combination of both (multimodal condition) using a wearable device. Our results replicate previous work that showed that auditory or tactile noise reduces sway variability with and without vision. Additionally, we show that multimodal noise also reduces the variability of sway. Analysis of different frequency bands of sway is typically used to separate open-loop exploratory ( 0.3 Hz) sway. We performed this analysis and showed that unimodal and multimodal white noise affected postural sway variability similarly in both timescales. These results support that the sensory noise effects on balance are robust across unimodal and multimodal conditions and can affect both mechanisms of sway represented in the frequency spectrum. In future work, the parameters of acoustic/tactile manipulation should be optimized for the most effective balance stabilization, and multimodal therapies should be explored for older adults with typical age-related balance instabilities.

Abstract Background Sensory reafferents are crucial to correct our posture and movements, both reflexively and in a cognitively driven manner. They are also integral to developing and maintaining a sense of agency for our actions. In cases of compromised reafferents, such as for persons with amputated or congenitally missing limbs, or diseases of the peripheral and central nervous systems, augmented sensory feedback therefore has the potential for a strong, neurorehabilitative impact. We here developed an untethered vibrotactile garment that provides walking-related sensory feedback remapped non-invasively to the wearer’s back. Using the so-called FeetBack system, we investigated if healthy individuals perceive synchronous remapped feedback as corresponding to their own movement (motor awareness) and how temporal delays in tactile locomotor feedback affect both motor awareness and walking characteristics (adaptation). Methods We designed the system to remap somatosensory information from the foot-soles of healthy participants (N = 29), using vibrotactile apparent movement, to two linear arrays of vibrators mounted ipsilaterally on the back. This mimics the translation of the centre-of-mass over each foot during stance-phase. The intervention included trials with real-time or delayed feedback, resulting in a total of 120 trials and approximately 750 step-cycles, i.e. 1500 steps, per participant. Based on previous work, experimental delays ranged from 0ms to 1500ms to include up to a full step-cycle (baseline stride-time: µ = 1144 ± 9ms, range 986-1379ms). After each trial participants were asked to report their motor awareness. Results Participants reported high correspondence between their movement and the remapped feedback for real-time trials (85 ± 3%, µ ± σ), and lowest correspondence for trials with left-right reversed feedback (22 ± 6% at 600ms delay). Participants further reported high correspondence of trials delayed by a full gait-cycle (78 ± 4% at 1200ms delay), such that the modulation of motor awareness is best expressed as a sinusoidal relationship reflecting the phase-shifts between actual and remapped tactile feedback (cos model: 38% reduction of residual sum of squares (RSS) compared to linear fit, p

This research article describes the HAPOVER (a haptic pronunciation improver device), which was produced to help second language learners' pronunciation skills as part of their foreign language learning process. The device comprises eight independent vibration motors connected to the fingers other than the thumb. The developed tactile feedback device was utilized to enhance pronunciation via speech processing and using vibration motor. The acoustic difference between the reference and the participant's recorded pronunciation signal was calculated with the help of Mel Frequency Cepstral Coefficients (MFCC) and Dynamic Time Warping (DTW) and converted into haptic codes that guide the speaker. The article describes the haptic codes' features and the creation method thereof. The device was tested by psychophysical evaluation. The results indicate an 80.74% improvement in word pronunciation with haptic guidance post training. Therefore, the results corroborate that word pronunciation data can be transmitted via tactile codes. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Electrotactile stimulation through matrix electrodes is a promising technology to restore high-resolution tactile feedback in extended reality applications. One of the fundamental tactile effects that should be simulated is the change in the size of the contact between the finger and a virtual object. The present study investigated how participants perceive the increase of stimulation area when stimulating the index finger using static or dynamic (moving) stimuli produced by activating 1 to 6 electrode pads. To assess the ability to interpret the stimulation from the natural cues (natural decoding), without any prior training, the participants were instructed to draw the size of the stimulated area and identify the size difference when comparing two consecutive stimulations. To investigate if other "non-natural" cues can improve the size estimation, the participants were asked to enumerate the number of active pads following a training protocol. The results demonstrated that participants could perceive the change in size without prior training (e.g., the estimated area correlated with the stimulated area, p < 0.001; ≥ two-pad difference recognized with > 80% success rate). However, natural decoding was also challenging, as the response area changed gradually and sometimes in complex patterns when increasing the number of active pads (e.g., four extra pads needed for the statistically significant difference). Nevertheless, by training the participants to utilize additional cues the limitations of natural perception could be compensated. After the training, the mismatch in the activated and estimated number of pads was less than one pad regardless of the stimulus size. Finally, introducing the movement of the stimulus substantially improved discrimination (e.g., 100% median success rate to recognize ≥ one-pad difference). The present study, therefore, provides insights into stimulation size perception, and practical guidelines on how to modulate pad activation to change the perceived size in static and dynamic scenarios. [ABSTRACT FROM AUTHOR]

Low-intensity focused ultrasound stimulation (LIFUS) has been proved effective in eliciting vibrotactile in addition to warm, cold and nociceptive pain when applied to human peripheral endings. However, if it can evoke fine tactile sensations has been rarely investigated by far despite the importance of fine tactile feedback in motor control. To explore this issue, 14 healthy volunteers were recruited in this study. A psychophysical experiment was firstly conducted to determine the appropriate range of pulse repetition frequency (PRF) and acoustic intensity (AI). Then, participants were asked to perceive and discriminate different tactile stimulations under LIFUS, so as to evaluate if multiple fine tactile sensations could be reliably elicited by modulating the PRF and AI. For objective assessment, the local blood perfusion volume (BPV) response beneath stimulated fingertip was recorded and characterized. Our results showed that four types of tactile sensations, including tapping, vibrating, electrical, and pressure could be reliably elicited by modulating the PRF and AI within a specific range, and there was a significant impact of PRF and AI on both participants’ tactile discrimination and amplitude features of BPV response. This study would facilitate the application of LIFUS to some human-machine interaction scenarios, and shed valuable insights on the physiological mechanisms of peripherally applied ultrasound stimulation.

Introduction: Carpal tunnel syndrome (CTS) is the most common nerve entrapment neuropathy, which causes numbness and pain in the thumb, the index and middle fingers and the radial side of the ring finger. Regular hand exercises may improve the symptoms and prevent carpal tunnel surgery. This study applied a novel ultrasonic stimulation method to test tactile sensitivity in CTS and also a mixed-reality-assisted (MR-assisted) exercise program which measured hand movements and provided haptic feedback for rehabilitation. Methods: Twenty patients with mild unilateral CTS took part in the experiments. A mid-air haptics device (Ultrahaptics STRATOS Explore) was used to apply amplitude-modulated ultrasound waves (carrier frequency: 40 kHz) onto the skin to create tactile stimulation mechanically. Participants performed a twoalternative forced-choice task for measuring tactile thresholds at 250-Hz modulation frequency. They were tested at the index fingers and the thenar eminences of both hands. Additionally, 15 CTS patients used an MR-assisted program to do hand exercises with haptic feedback. Exercise performance was assessed by calculating errors between target and actual hand configurations. System Usability Scale (SUS) was adopted to verify the practical usability of the program. Results: Thresholds at the thenar eminences of the affected and healthy hands were not significantly different. While the thresholds at the healthy index fingers could be measured, those of the affected fingers were all higher than the stimulation level produced by the maximum output from the ultrasound device. In the exercise program, a significant positive correlation (p = 0.89, p < 0.001) was found between the performance scores and the SUS scores, which were above the criterion value established in the literature. Discussion: The results show that thenar tactile sensitivity is not affected in mild CTS as expected from the palmar cutaneous branch of the median nerve (PCBm), but index finger threshold is likely to be higher. Overall, this study suggests that mid-air haptics, with certain improvements, may be used as a preliminary test in the clinical setting. Moreover, the device is promising to develop gamified rehabilitation programs and for the treatment follow-up of CTS. [ABSTRACT FROM AUTHOR]

Tactile feedback can effectively improve the controllability of an interactive intelligent robot, and enable users to distinguish the sizes/shapes/compliance of grasped objects. However, it is difficult to recognize object roughness/textures through tactile feedback due to the surface features cannot be acquired with equipped sensors. The purpose of this study is to investigate whether different object roughness/textures can be classified using machine vision and utilized for human-machine haptic interaction. Based on practical application, two classes of specialized datasets, the roughness dataset consisted of different spacing/shapes/height distributions of the surface bulges and the texture dataset included eight types of representative surface textures, were separately established to train the respective classification models. Four kinds of typical deep learning models (YOLOv5l, SSD300, ResNet18, ResNet34) were employed to verify the identification accuracies of surface features corresponding to different roughness/textures. The human fingers' ability to objects roughness recognition also was quantified through a psychophysical experiment with 3D-printed test objects, as a reference benchmark. The computation results showed that the average roughness recognition accuracies based on SSD300, ResNet18, ResNet34 were higher than 95%, which were superior to those of the human fingers (94% and 91% for 2 and 3 levels of object roughness, respectively). The texture recognition accuracies with all models were higher than 84%. Outcomes indicate that object roughness/textures can be effectively classified using machine vision and exploited for human-machine haptic interaction, providing the feasibility of functional sensory restoration of intelligent robots equipped with visual capture and tactile stimulation devices.

Orientation processing in the human brain plays a crucial role in guiding grasping actions toward an object. Remarkably, despite the absence of visual input, the human visual cortex can still process orientation information. Instead of visual input, non-visual information, including tactile and proprioceptive sensory input from the hand and arm, as well as feedback from action-related processes, may contribute to orientation processing. However, the precise mechanisms by which the visual cortices process orientation information in the context of non-visual sensory input and action-related processes remain to be elucidated. Thus, our study examined the orientation representation within the visual cortices by analyzing the blood-oxygenation-level-dependent (BOLD) signals under four action conditions: direct grasp (DG), air grasp (AG), non-grasp (NG), and uninformed grasp (UG). The images of the cylindrical object were shown at +45° or -45° orientations, corresponding to those of the real object to be grasped with the whole-hand gesture. Participants judged their orientation under all conditions. Grasping was performed without online visual feedback of the hand and object. The purpose of this design was to investigate the visual areas under conditions involving tactile feedback, proprioception, and actionrelated processes. To address this, a multivariate pattern analysis was used to examine the differences among the cortical patterns of the four action conditions in orientation representation by classification. Overall, significant decoding accuracy over chance level was discovered for the DG; however, during AG, only the early visual areas showed significant accuracy, suggesting that the object's tactile feedback influences the orientation process in higher visual areas. The NG showed no statistical significance in any area, indicating that without the grasping action, visual input does not contribute to cortical pattern representation. Interestingly, only the dorsal and ventral divisions of the third visual area (V3d and V3v) showed significant decoding accuracy during the UG despite the absence of visual instructions, suggesting that the orientation representation was derived from action-related processes in V3d and visual recognition of object visualization in V3v. The processing of orientation information during non-visually guided grasping of objects relies on other non-visual sources and is specifically divided by the purpose of action or recognition. [ABSTRACT FROM AUTHOR]

Increasing evidence based on the safety and benefits of robot-assisted surgery indicates the disadvantage of the lack of tactile feedback. A lack of tactile feedback increases the risk of intraoperative complications, prolongs operative times, and delays the learning curve. A 40-year-old female patient presented to our hospital with a positive fecal occult blood test. A colonoscopy revealed type 2 advanced cancer of the sigmoid colon, and histological examination showed a well-differentiated adenocarcinoma. Furthermore, abdominal contrast-enhanced computed tomography revealed a tumor in the sigmoid colon and several swollen lymph nodes in the colonic mesentery without distant metastases. The patient was diagnosed with cStage IIIb (cT3N1bM0) sigmoid cancer and underwent sigmoidectomy using the Saroa Surgical System, which was developed by RIVERFIELD, a venture company at the Tokyo Medical and Dental University, and the Tokyo Institute of Technology. Based on adequate simulation, surgery was safely performed with appropriate port placement and arm base-angle adjustment. The operating time was 176 min, with a console time of 116 min and 0 ml blood loss. The patient was discharged 6 days postoperatively without complications. The pathological diagnosis was adenocarcinoma, tub1, tub2, pT2N1bM0, and pStage IIIa. Herein, we report the world's first surgery for sigmoid cancer using the Saroa Surgical System with tactile feedback in which a safe and appropriate oncological surgery was performed. [ABSTRACT FROM AUTHOR]

Prosthetic limb embodiment remains a significant challenge for many amputees due to traditional designs’ lack of sensory feedback. To address this challenge, the effectiveness of non-invasive neuromuscular electrical stimulation (NMES) controlled by a hybrid proportional-differential (PD)-Fuzzy logic system was evaluated for providing real-time proprioception and tactile feedback. The study used a human-in-the-closed-loop approach with ten participants: five upper limb amputees and five non-disabled individuals as the control group. An applied force, the joint angle of a prosthetic hand’s finger, and surface electromyography signals generated by the biceps muscle all regulate the intensity of sensory feedback. Additionally, the C6 and C7 myotomes were selected as elicitation sites. The average threshold for detecting action motion and force was around 21° and 1.524N, respectively. The participants successfully reproduced desired joint angles within the range of 0°-110° at five separate intervals. In the weight recognition experiment, the amputee participant’s minimum number of false predictions was four. The highest accuracy achieved was 80.66% in detecting object size and stiffness. Additionally, unpaired t-tests were performed for the means of the results of the experiments to determine statistically significant differences between groups. The results suggest that stimulation of myotomes by NMES is an effective non-invasive method for delivering rich multimodal sensation information to individuals with disabilities, including upper limb amputees, without needing visual or auditory cues. These findings contribute to the development of non-invasive sensory substitution in prostheses.

Rigid leukotape applied to the skin of the trunk dorsum, superficial to the lumbar paraspinals, has been shown to reduce lumbar flexion in repetitive lifting, with the potential to reduce the risk of injury in jobs requiring the handling of material. It is unclear which mechanism underpins this reduction, and whether a tape with more elastic properties (i.e., kinesio tape) can yield similar results. In this study, twelve participants were randomly allocated into two groups, and practiced a repetitive lifting task with either leukotape or kinesio tape applied to the skin of their trunk dorsum. The participants also performed a sagittal plane repositioning task to assess changes in lumbar proprioception. The results showed a small reduction in lumbar flexion in the kinesio tape group and a moderate reduction in the leukotape group, and suggested a reduction in repositioning errors in the kinesio tape group only. We suggest that leukotape may correct the movement and improve performance during a flexion-based task, while kinesio tape may improve lumbar proprioception and promote learning. These results have implications for the choice and use of wearable textiles aiming to reduce injury risks in the manual handling industry. [ABSTRACT FROM AUTHOR]

Bone conduction is a promising haptic feedback modality for upper-limb prosthesis users, however, its potential and characteristics as a non-invasive feedback modality have not been thoroughly investigated. This study aimed to establish the temporal and spatial characteristics of non-invasive bone conduction as a sensory feedback interface for upper-limb prostheses. Psychometric human-subject experiments were conducted on three bony landmarks of the elbow, with a vibrotactile transducer affixed to each to provide the stimulus. The study characterized the temporal domain by testing perception threshold and resolution in amplitude and frequency. The spatial domain was evaluated by assessing the ability of subjects to detect the number of simultaneous active stimulation sites. The experiment was conducted with ten able-bodied subjects and compared to two subjects with trans-radial amputation. The psychometric evaluation of the proposed non-invasive bone conduction feedback showed results comparable to invasive methods. The experimental results demonstrated similar amplitude and frequency resolution of the interface for all three stimulation sites for both able-bodied subjects and subjects with trans-radial amputation, highlighting its potential as a non-invasive feedback modality for upper-limb prostheses. [ABSTRACT FROM AUTHOR]

Haptics plays a significant role not only in the rehabilitation of neurological disorders, such as stroke, by substituting necessary cognitive information but also in human–computer interfaces (HCIs), which are now an integral part of the recently launched metaverse. This study proposes a unique, soft, monolithic haptic feedback device (SoHapS) that was directly manufactured using a low-cost and open-source fused deposition modeling (FDM) 3D printer by employing a combination of soft conductive and nonconductive thermoplastic polyurethane (TPU) materials (NinjaTek, USA). SoHapS consists of a soft bellow actuator and a soft resistive force sensor, which are optimized using finite element modeling (FEM). SoHapS was characterized both mechanically and electrically to assess its performance, and a dynamic model was developed to predict its force output with given pressure inputs. We demonstrated the efficacy of SoHapS in substituting biofeedback with tactile feedback, such as gripping force, and proprioceptive feedback, such as finger flexion–extension positions, in the context of teleoperation. With its intrinsic properties, SoHapS can be integrated into rehabilitation robots and robotic prostheses, as well as augmented, virtual, and mixed reality (AR/VR/MR) systems, to induce various types of bio-mimicked feedback. [ABSTRACT FROM AUTHOR]

A frame providing tactile feedback for the reproducibility of deep inspiratory breath-hold (DIBH) is described. The frame, fitted across the patient, comprises a horizontal bar, parallel to the patient's long axis, and holds a graduated pointer perpendicular to it. The pointer provides individualized tactile feedback for reproducibility of DIBH. Within the pointer is a movable pencil, bearing a 5 mm coloured strip which becomes visible only during DIBH, and acts as a visual cue to the therapist. The average variation in separation in the planning and pretreatment cone-beam computed tomography of 10 patients was 2 mm (confidence interval 1.95-2.05). Frame-based tactile feedback is a novel, reproducible technique for DIBH. [ABSTRACT FROM AUTHOR]

Human–machine interaction (HMI) refers to systems enabling communication between machines and humans. Systems for human–machine interfaces have advanced significantly in terms of materials, device design, and production methods. Energy supply units, logic circuits, sensors, and data storage units must be flexible, stretchable, undetectable, biocompatible, and self-healing to act as human–machine interfaces. This paper discusses the technologies for providing different haptic feedback of different natures. Notably, the physiological mechanisms behind touch perception are reported, along with a classification of the main haptic interfaces. Afterward, a comprehensive overview of wearable haptic interfaces is presented, comparing them in terms of cost, the number of integrated actuators and sensors, their main haptic feedback typology, and their future application. Additionally, a review of sensing systems that use haptic feedback technologies—specifically, smart gloves—is given by going through their fundamental technological specifications and key design requirements. Furthermore, useful insights related to the design of the next-generation HMI devices are reported. Lastly, a novel smart glove based on thin and conformable AlN (aluminum nitride) piezoelectric sensors is demonstrated. Specifically, the device acquires and processes the signal from the piezo sensors to classify performed gestures through an onboard machine learning (ML) algorithm. Then, the design and testing of the electronic conditioning section of AlN-based sensors integrated into the smart glove are shown. Finally, the architecture of a wearable visual-tactile recognition system is presented, combining visual data acquired by a micro-camera mounted on the user's glass with the haptic ones provided by the piezoelectric sensors. [ABSTRACT FROM AUTHOR]

Tactile feedback facilitates monitoring and adjusting the contact state by the manipulator, but operational compliance with the object's physical properties remains challenging. This paper proposes a fingertip-shaped visuo-tactile sensor (FVTS) compatible with multiple manipulators. The FVTS has micron-level tactile sensitivity and a detection efficiency of 30 fps. On this basis, we propose a two-stage adaptive grasping strategy, leveraging a pre-grasping controller and a stability adjustment controller for micro-contact judgment and grasping stability adjustment. The pre-grasp promotes the manipulator to establish compliance with the object's physical properties and provides non-invasive grasping protection, then depending on stability adjustment to deepen property cognition. The adaptive grasping tests of fragile, flexible, and heavy objects are performed to evaluate the grasping performance of the manipulator under tactile and non-tactile feedback. The experimental results show that the FVTS has rigid–flexible grasping ability and enhances cognition of physical properties in manipulators, especially providing grasping protection for fragile/flexible objects. [Display omitted] • Design a universal fingertip-shaped visuo-tactile sensor (FVTS) for integration with multiple models of two-finger manipulators. • Propose a two-stage adaptive grasping strategy based on visuo-tactile sensing to balance flexible/rigid grasping and dynamic contact changes. • Integrate the pre-grasping and stability adjustment controller into the unified control framework to enhance the manipulator's cognition of the object's physical properties. [ABSTRACT FROM AUTHOR]

Conventional key-based passcode entry systems, typically implemented through physical keyboards, are widely used for protecting and inputting personal data. However, these devices are vulnerable to attacks such as shoulder surfing. Therefore, this study proposes a matrix pressure capacitive sensing pin-pad for digital passcode entry based on pressure levels. The capacitive pressure sensing component is composed of copper foil electrodes and air dielectric, forming parallel plate capacitors, and assembled with an elastic mechanical structure. When a finger presses the electrode's elastic layer, the capacitance value changes as the electrode plate approaches. A square wave voltage signal is used as the excitation signal, and the pressure's magnitude can be recognized by distinguishing the voltage values passing through the sensing device. This device can sense finger pressure in the effective range of 0–20 kPa and can differentiate between light pressure (less than 10 kPa) and heavy pressure (greater than 10 kPa) ranges. When using this device to enter a digital passcode, the complexity of the passcode can be increased based on the pressure's magnitude. The study conducted two validation experiments. In the experiment with 33 participants to evaluate whether tactile feedback could improve the input accuracy of pressure passcodes, participants demonstrated only a 46 % accuracy rate in distinguishing tactile feedback. In the tactile feedback passcode input experiment, the device provides different tactile feedback based on the participants' pressure levels. The results show that without tactile feedback, the success rate of correctly entering the passcode was 58.6 %, while with tactile feedback, the success rate was 68.2 %, representing a 9.6 % increase in accuracy. In the shoulder surfing experiment, 17 participants were recruited to capture three different angles of entering composite passcodes, ultimately forming a 7-minute video containing 35 samples. Additionally, an online questionnaire experiment was conducted, collecting experimental data from 41 participants. The shoulder surfing success rate for numerical passcodes was as high as 80.5 %, while for pressure passcodes, it was only 47.1 %, demonstrating that composite passcodes can increase the success rate of shoulder surfing attacks. Furthermore, different angles did not significantly affect the success rate of shoulder surfing attacks. Therefore, the proposed pin-pad with tactile feedback and pressure-level digital passcode entry method can effectively resist shoulder surfing attacks, thereby improving passcode security. [Display omitted] • Pressure Pin-pad resists shoulder surfing. • Input passcodes without habit changes. • Capacitive pad with real-time feedback. [ABSTRACT FROM AUTHOR]

In the last decade, several new haptic devices have been developed, contributing to the definition of more realistic virtual environments. An overview of this topic requires a description of the various technologies employed in building such devices, and of their application domains. This survey describes the current technology underlying haptic devices, based on the concept of “wearability level”. It reviews more than 90 devices newly developed and described in scientific papers published in the period 2010-2021. The reviewed devices provide either haptic illusions or novel haptic feedback for teleoperation, entertainment, training, education, guidance and notification. They are categorized into grounded, hand-held and wearable devices; the latter are further split into exoskeletons and gloves, finger-worn devices, and arm-worn devices. For the systems in each of these categories, descriptions and tables are provided that analyze their structure, including device mass and employed actuators, their applications, and other characteristics such as type of haptic feedback and tactile illusions. The survey also provides an overview of devices worn in parts of the human body other than arms and hands, and precisely haptic vests, jackets and belts, and haptic devices for head, legs and feet. Finally, the paper discusses research gaps and challenges, and potential future directions.

Bone conduction is a promising haptic feedback modality for upper-limb prosthesis users, however, its potential and characteristics as a non-invasive feedback modality have not been thoroughly investigated. This study aimed to establish the temporal and spatial characteristics of non-invasive bone conduction as a sensory feedback interface for upper-limb prostheses. Psychometric human-subject experiments were conducted on three bony landmarks of the elbow, with a vibrotactile transducer affixed to each to provide the stimulus. The study characterized the temporal domain by testing perception threshold and resolution in amplitude and frequency. The spatial domain was evaluated by assessing the ability of subjects to detect the number of simultaneous active stimulation sites. The experiment was conducted with ten able-bodied subjects and compared to two subjects with trans-radial amputation. The psychometric evaluation of the proposed non-invasive bone conduction feedback showed results comparable to invasive methods. The experimental results demonstrated similar amplitude and frequency resolution of the interface for all three stimulation sites for both able-bodied subjects and subjects with trans-radial amputation, highlighting its potential as a non-invasive feedback modality for upper-limb prostheses.

Assistive technology uses multi-modal feedback devices, focusing on the visual, auditory, and haptic modalities. Tactile devices provide additional information via touch sense. Perception accuracy of vibrations depends on the spectral and temporal attributes of the signal, as well as on the body parts they are attached to. The widespread use of AR/VR devices, wearables, and gaming interfaces requires information about the usability of feedback devices. This paper presents results of an experiment using an 8-channel tactile feedback system with vibrators placed on the wrists, arms, ankles, and forehead. Different vibration patterns were designed and presented using sinusoidal frequency bursts on 2, 4, and 8 channels. In total, 27 subjects reported their sensation formally and informally on questionnaires. Results indicate that 2 and 4 channels could be used simultaneously with high accuracy, and the transducers' optimal placement (best sensitivity) is on the wrists, followed by the ankles. Arm and head positions were inferior and generally inadequate for signal presentation. For optimal performance, signal length should exceed 500 ms. Furthermore, the amplitude level and temporal pattern of the presented signals have to be used for carrying information rather than the frequency of the vibration. [ABSTRACT FROM AUTHOR]

Robots need to be able to adapt to unexpected changes in the environment such that they can autonomously succeed in their tasks. However, hand-designing feedback models for adaptation is tedious, if at all possible, making data-driven methods a promising alternative. In this paper, we introduce a full framework for learning feedback models for reactive motion planning. Our pipeline starts by segmenting demonstrations of a complete task into motion primitives via a semi-automated segmentation algorithm. Then, given additional demonstrations of successful adaptation behaviors, we learn initial feedback models through learning-from-demonstrations. In the final phase, a sample-efficient reinforcement learning algorithm fine-tunes these feedback models for novel task settings through few real system interactions. We evaluate our approach on a real anthropomorphic robot in learning a tactile feedback task. [ABSTRACT FROM AUTHOR]

Background: Providing real‐time haptic feedback is an important, but still not sufficiently explored aspect of the use of supernumerary robotic limbs (SRLs). We present a multi‐pad electrode for conveying multi‐modal proprioceptive and sensory information from SRL to the user's thigh and propose a method for stimuli calibration. Methods: Within two pilot tests, we investigated return electrode configuration and active electrode discrimination in three healthy subjects to select the appropriate electrode pad topology. Based on the obtained results and anthropometric data from the literature, the electrode was designed to have three branches of 10 pads and two additional pads that can be displaced over/under the electrode branches. The electrode was designed to be connected to the stimulator that allows full multiplexing so that specific branches can serve as a common return electrode. To define the procedure for application of this system, the sensation, localization, and discomfort thresholds applicable for the novel electrode were determined and analyzed in 10 subjects. Results: The results showed no overlaps between the three thresholds for individual pads, with significantly different average values, suggesting that the selected electrode positioning and design provide a good active range of useful current amplitude. The results of the subsequent analysis suggested that the stimuli intensity level of 200% of the sensation threshold is the most probable value of the localization threshold. Furthermore, this level ensures a low chance (i.e., 0.7%) of reaching the discomfort. Conclusions: We believe that envisioned electrotactile system could serve as a high bandwidth feedback channel that can be easily set up to provide proprioceptive and sensory feedback from supernumerary limbs. [ABSTRACT FROM AUTHOR]

Background: Robot-assisted systems have predominantly relied on teleoperation, where visual feedback is the primary source of information. However, advances in tactile sensing and displays offer new opportunities to enhance surgical transparency, efficiency, and safety., Methods: A PRISMA-guided search was conducted across PubMed, IEEE Xplore, Scopus, and Web of Science databases to identify relevant studies., Results: Out of 645 screened articles, 98 met the inclusion criteria, and 33 were included in the final review. The review discusses various tactile feedback stimulus types, applications, and challenges in the context of robot-assisted minimally invasive surgery., Conclusion: While kinaesthetic feedback has been extensively explored to restore the natural interaction between the surgeon and the surgical environment, tactile feedback remains largely confined to research settings. This is due to significant challenges in integrating tactile feedback into robotic systems and current limitations of sensing technologies., (© 2024 The Author(s). The International Journal of Medical Robotics and Computer Assisted Surgery published by John Wiley & Sons Ltd.)