Lateral Skin Stretch Research Articles

Providing Skin Stretch On The Lower Back - Design And Psychophysical Evaluation With A Stepping Task.

Haptic devices are becoming popular in many applications, including medical, gaming, and consumer devices. Yet, the majority of studies focus on the use of haptics for the upper limbs, with much less attention to the stimulation of other regions of the body such as the lower back. In this study, we designed three types of skin stretch stimulation devices that can be placed on a belt and apply tactile stimulation on the lower back. We present these devices that apply lateral, longitudinal, and rotational skin stretch stimulation on the lower back, and evaluate their effectiveness in providing haptic commands for the lower limbs of healthy participants. We designed psychophysical experiments that quantify the discrimination accuracy of participants with a stepping task. The results demonstrate the ability of participants to discriminate two out of three features of stimulation provided on the lower back. These results demonstrate that skin stretch on the lower back can effectively transmit haptic signals and elicit responses in the lower limb for various applications. Future studies are needed to optimize providing skin stretch on the lower back to benefit various applications such as training, rehabilitation, gaming, and assistive devices.

Head rotation and illusory force sensation by lateral skin stretch on the face

Various methods for inducing an illusory force sensation to present a sense of force to users in energy-saving and space-saving systems have been proposed. One of them is the illusion of force sensation induced by cutaneous sensory stimulation. In this study, we hypothesized and empirically verified that lateral skin stretch alone on the face can induce an illusory force sensation in the direction of the stretch. We focused on the anterior temporal and cheekbone regions, in which the cushion part of the head-mounted display contacts the skin, and applied skin stretches of different intensities to these regions, envisioning a force presentation device built into the head-mounted display. Head rotations of approximately 40 and 50 degrees were generated by skin stretches in the anterior temporal and cheekbone regions, respectively, confirming the illusory force sensation in the direction of rotation. We confirmed a positive correlation between the head-turning angle and the amount of skin deformation. The intensity of the illusory force sensation can be controlled by changing the amount of lateral skin deformation; this may be applied to the development of a new force presentation head-mounted device.

SuP-Ring: A pneumatic tactile display with substitutional representation of contact force components using normal indentation.

Shear force is important for tumour detection and can contribute to minimally invasive surgery (MIS). A popular method uses lateral skin stretch to produce shear force but has some limitations. We have developed a ring-type pneumatic tactile display that employs normal indentation substituted for lateral skin stretch to represent normal and shear feedback, called SuP-Ring. Psychophysical experiments were conducted to evaluate how users perceive the provided feedback and the effectiveness of SuP-Ring in tumour localisation. The experimental results show that the participants could perceive the provided normal and shear feedback well. Shear feedback enables users to enhance their performance in localising the tumour and normal feedback could contribute to ensuring the safety requirements in MIS. The proposed tactile display could be useful for intraoperative tumour localisation and has the potential to be used in a wide variety of applications.

Usability Testing for a Mobile Application of Plantar Tactile Sensitivity Measurement

The purpose of this study is to develop a new tactile measurement system that can be used for the early detection of a decrease in tactile sensitivity. The tactile stimuli presentation device consisted of a small precision automatic stage. This system could present lateral skin stretch in the direction horizontal to the tactile sensitivity of the plantar skin. In our previous study, the utility of the measurement method was established in healthy participants, and the measurement data of tactile sensitivity was not influenced by posture and plantar region during measurement. In this study, a new mobile application (App) was developed to operate for a tactile stimuli presentation device. The user can control the tactile device by App using a tablet computer (e.g., laptop, phablet, tablet, or smart device) and understand the measurement methodology of tactile sensitivity. This study was conducted to evaluate a new tactile sensitivity measurement application using a tablet computer. We found that this App could be easily used for participants. In conclusion, an App was developed to operate the tactile stimuli presentation device, and this App was simple to use.

A Multisensory Approach to Present Phonemes as Language Through a Wearable Haptic Device

Communication is an important part of our daily interactions; however, communication can be hindered, either through visual or auditory impairment, or because usual communication channels are overloaded. When standard communication channels are not available, our sense of touch offers an alternative sensory modality for transmitting messages. Multi-sensory haptic cues that combine multiple types of haptic sensations have shown promise for applications, such as haptic communication, that require large discrete cue sets while maintaining a small, wearable form factor. This article presents language transmission using a multi-sensory haptic device that occupies a small footprint on the upper arm. In our approach, phonemes are encoded as multisensory haptic cues consisting of vibration, radial squeeze, and lateral skin stretch components. Participants learned to identify haptically transmitted phonemes and words after training across a four day training period. A subset of our participants continued their training to extend word recognition free response. Participants were able to identify words after four days using multiple choice with an accuracy of 89% and after eight days using free response with an accuracy of 70%. These results show promise for the use of multisensory haptics for haptic communication, demonstrating high word recognition performance with a small, wearable device.

Measurement of Plantar Tactile Sensitivity to Lateral Skin Stretch on Standing or Sitting Posture

Measurement of Plantar Tactile Sensitivity to Lateral Skin Stretch on Standing or Sitting Posture

Soft Wearable Skin-Stretch Device for Haptic Feedback Using Twisted and Coiled Polymer Actuators.

Soft and integrated design can enable wearable haptic devices to augment natural human taction. This paper proposes a novel, soft, haptic finger-worn wearable device based on compliant and adhesive silicone skin and lightweight twisted and coiled polymer (TCP) actuators using ultra high molecular weight polyethylene (UHMWPE) fibers to provide lateral skin stretch sensations. Recently, silicone elastomers have been used in wearable sensors and in haptic applications for their high compliance or adhesion. TCP actuators have also demonstrated high power to weight ratios, large stroke length, simple mechanism, and inherent softness. Lateral skin stretch is sensitive to small motions and has been used for intuitive proprioceptive feedback applications. We combined these characteristics to design and manufacture a wearable, functional haptic prototype. Prototype performance was evaluated using an optical tracking system, a force gauge test bench, and compared to vibrotactile haptic feedback in a experiment with 14 healthy participants. Results showed that participant mean reaction times were comparable to those of a vibrotactile feedback system, though task completion times were longer. This paper is the first to employ TCP actuators for haptic stimulation and could serve as a foundation for future applications involving soft wearable haptics in gaming, health, and virtual reality.

Multi-Sensory Stimuli Improve Distinguishability of Cutaneous Haptic Cues.

Wearable haptic systems offer portable, private tactile communication to a human user. To date, advances in wearable haptic devices have typically focused on the optimization of haptic cue transmission using a single modality, or have combined two types of cutaneous feedbacks, each mapped to a particular parameter of the task. Alternatively, researchers have employed arrays of haptic tactile actuators to maximize information throughput to a user. However, when large cue sets are to be transmitted, such as those required to communicate language, perceptual interference between transmitted cues can decrease the efficacy of single-sensory systems, or require large footprints to ensure salient spatiotemporal cues are rendered to the user. In this paper, we present a wearable, multi-sensory haptic feedback system, MISSIVE (Multi-sensory Interface of Stretch, Squeeze, and Integrated Vibration Elements), that conveys multi-sensory haptic cues to the user's upper arm. We present experimental results that demonstrate that rendering haptic cues with multi-sensory components-specifically, lateral skin stretch, radial squeeze, and vibrotactile stimuli-improved perceptual distinguishability in comparison to similar cues with all-vibrotactile components. These results support the incorporation of diverse stimuli, both vibrotactile and nonvibrotactile, for applications requiring large haptic cue sets.

Lower Extremity Lateral Skin Stretch Perception for Haptic Feedback.

Tactile feedback in recent decades has allowed humans to receive information through technology beyond traditional visual and auditory senses. Lateral skin stretch has the potential to be a mode of tactile feedback, reliably enabling the perception of directional cues through the use of a single actuator. Experiments were conducted to explore sensitivity to skin stretch on nine locations on the human lower leg. Thirty-two stimuli were presented to subjects, exploring effects of displacement (from 0.2-2.0 mm) and speed (from 0.5-4.0 mm/s) on the perception of left and right directions. Higher accuracy came from stimuli having higher displacements and speeds. Three of the locations: soleus, calcaneal tendon (upper), and fibularis longus (lower) all had a mean accuracy of at least 85 percent and are suitable locations for a skin stretch tactile feedback device.

Evaluation of Tactile Feedback Methods for Wrist Rotation Guidance.

Tactile motion guidance systems aim to direct the user's movement toward a target pose or trajectory by delivering tactile cues through lightweight wearable actuators. This study evaluates 10 forms of tactile feedback for guidance of wrist rotation to understand the traits that influence the effectiveness of such systems. We present five wearable actuators capable of tapping, dragging across, squeezing, twisting, or vibrating against the user's wrist; each actuator can be controlled via steady or pulsing drive algorithms. Ten subjects used each form of feedback to perform three unsighted movement tasks: directional response, position targeting, and trajectory following. The results show that directional responses are fastest when direction is conveyed through the location of the tactile stimulus or steady lateral skin stretch. Feedback that clearly conveys movement direction enables subjects to reach target positions most quickly, though tactile magnitude cues (steady intensity and especially pulsing frequency) can also be used when direction is difficult to discern. Subjects closely tracked arbitrary trajectories only when both movement direction and cue magnitude were subjectively rated as very easy to discern. The best overall performance was achieved by the actuator that repeatedly taps on the subject's wrist on the side toward which they should turn.

Cortical processing of lateral skin stretch stimulation in humans

Direction discrimination of a moving tactile stimulus requires intact dorsal columns and provides a sensitive clinical test of somatosensory dysfunction. Cortical mechanisms are poorly understood. We have applied tangential skin pulls to the right lower leg during functional magnetic resonance imaging. Healthy subjects judged the direction of the skin pulls (task experiment, n = 7) or received skin pulls passively (no task experiment, n = 8). Second somatosensory cortex (S2) was activated in the task as well as no task experiment, and there was no significant difference in cortical activation between the two experiments. Within S2 nearly all subjects had prominent activations in the caudal and superficial part, i.e., in the opercular parietal (OP) area 1. S1 was activated in only one of the subjects. Thus, S2 and especially OP 1 seems to be important for processing of lateral skin stretch stimulation. The finding suggests that a lesion of this area might cause a disturbance in tactile direction discrimination which should be relevant for clinical testing.

Tactile directional sensibility: peripheral neural mechanisms in man

Tactile directional sensibility, i.e. the ability to tell the direction of an object’s motion across the skin, is an easily observed sensory function that is highly sensitive to disturbances of the somatosensory system. Based on previous psychophysical experiments on healthy subjects it was concluded that directional sensibility depends on two kinds of information from cutaneous mechanoreceptors; spatio-temporal information and information about friction-induced changes in skin stretch. In the present study responses to similar probe movements as in the psychophysical experiments were recorded from human single mechanoreceptors in the forearm skin. All slowly adapting type 2 (SA2) units were spontaneously active, and with increasing force of friction their discharge rates were modified by probe movements at increasing distances from the Ruffini end-organ, reflecting the high stretch-sensitivity of these units. Slowly adapting type 1 (SA1) and field units responded to the moving probe within well-defined skin areas directly overlying the individual receptor terminals, and compared to the SA2 units their response properties were less dependent on the force of friction. The results suggest that SA1 and field units have the capacity to signal spatio-temporal information, whereas a population of SA2 units have the capacity to signal direction-specific information about changes in lateral skin stretch.

Tactile sensibility in the human hand: receptive field characteristics of mechanoreceptive units in the glabrous skin area.

1. Impulses in tactile units innervating the glabrous skin of the hand recorded from the median nerve of adult human subjects. The recording electrodes which were made of tungsten were inserted percutaneously in the upper arm. 2. The units were classified on the basis of their sensitivity to sustained identation and to remote stimuli. Two types of rapidly adapting units and two types of slowly adapting units were found. In accordance with earlier reports they were denoted RA and PC units, and SA I and SA II units. 3. The sensitivity profiles of the receptive fields were analysed by measuring the extent of the receptive field as a function of the identation amplitude. 4. The RA and SA I units had receptive fields with several zones of maximal sensitivity distributed over an approximately circular or oval area typically covering five to ten papillary ridges. Within this area the sensitivity was high, whereas the sensitivity diminished steeply with increasing distance from this area. 5. The PC and SA II units had receptive fields with a single zone of maximal sensitivity and gentle continuous threshold increase outside this zone. 6. The relation between the identation amplitude and the receptive field size of a unit was described by a power function. The power exponent for the RA and SA I units was well below unity, whereas the PC and SA II units had exponenets greater than unity. The variation in exponent was very small among the RA and among the SA I units. Their average exponents were therefore regarded as characteristics of the unit type. 7. The SA II units were qualitatively studied with regard to their sensitivity to lateral skin stretch. Three different types of SA II units were described with regard to the directional pattern of this sensitivity. 8. The relation of the present findings to the problem of correlation between morphological structures of nerve end-organs and physiologically defined unit types is considered. 9. Moreover, the findings, indicate that the RA and SA I units are well suited for the analysis of mechanical events on the skin surface with a high degree of spatial selectivity, whereas the PC and SA II units are suited for analysis of other mechanical events, e.g. vibration and various forms of tension in the skin and related tissues.