Tactile Sensor Research Articles

ZnO Nanowall Network-Based Tactile/Gesture Sensors and Prediction with Machine Learning.

In low-dimensional material systems, augmented physical and chemical properties may be witnessed through a unique morphological evolution. Here, we report the development of an optimized nanowall network of ZnO for the fabrication of a flexible single-electrode triboelectric nanogenerator (STENG)-based tactile and gesture sensors. The chemically grown nanowall network with an adequate pore area endows superior triboelectric output (current ∼0.6 μA and power ∼20 μW/cm2) by offering an optimum surface area and dielectric constant for pressure sensing applications. The rational comparison of the triboelectric properties of nanowall and nanorod structures of ZnO reveals that the higher surface area offered by the hollow walls leads to superior output characteristics. The demonstration of pressure sensitivity of the STENG ∼1 V/N is promising for self-powered tactile sensing applications. The array of STENG sensors, when attached to a user hand, generates distinguishable signals while holding objects of varying curvature and mass. Again, the observation of sensitivity of ∼0.1 V per degree during finger movement activity indicates the gesture sensing ability of the nanowall-based TENG system, facilitating sign language expression through the movement of fingers. Further, the generated electrical signals during tactile and gesture sensing can be classified and recognized through the deployment of machine learning (ML) techniques. In fact, the implementation of Random Forest and K-Nearest Neighbor models has offered an accuracy of 96% while recognizing the output signals generated by the sensor arrays. The demonstration of superior sensing characteristics with the optimized nanowall network may be advantageous in innovating prototype sensors for the differently abled people to distinguish or classify objects on the basis of material, morphology, and mass during their regular activities.

Artificial Tactile Sensory Finger for Contact Pattern Identification Based on High Spatiotemporal Piezoresistive Sensor Array.

Human fingertip tactile perception relies on the activation of densely distributed tactile receptors to identify contact patterns in the brain. Despite significant efforts to integrate tactile sensors with machine learning algorithms for recognizing physical patterns on object surfaces, developing a tactile sensing system that emulates human fingertip capabilities for identifying contact patterns with a high spatiotemporal resolution remains a formidable challenge. In this study, we present the development of an artificial tactile finger for accurate contact pattern identification, achieved through the integration of a high spatiotemporal piezoresistive sensor array (PRSA) and a convolutional neural network (CNN) model. Spatiotemporal characterization tests reveal that the artificial finger exhibits a fast temporal resolution of approximately 7 ms and achieves a two-point threshold of 1.5 mm, surpassing that of the human fingertip. To compare the performance of the artificial finger with the human finger in recognizing different patterns, we acquired pressure images by pressing the artificial finger, coated with a flexible PRSA film, onto both simple embossed and complex curved patterns while also recording human recognition results of perceiving these patterns. Experimental findings demonstrate that the artificial finger achieves higher classification accuracy in recognizing both simple and complex patterns (99.0 and 96.1%, respectively) compared to the human fingertip (69.1 and 22.7%). This artificial finger serves as a promising platform with great potential for various robotic tactile sensing applications including prosthetics, skin electronics, and robotic surgery.

Artificial Skin Based on Visuo‐Tactile Sensing for 3D Shape Reconstruction: Material, Method, and Evaluation

AbstractArtificial skin has shown great potential in robot perception and human healthcare. It provides multifunctional tactile sensing, including 3D shape reconstruction, contact feedback, and temperature perception, where the 3D reconstruction function is indispensable for dexterous hands in tactile cognition and interaction. Vision‐based tactile sensor (VTS) is an innovative bionic tactile sensor and supports high‐resolution, high‐precision, and high‐density tactile reconstruction compared with electronic tactile sensors. Considering the unique contribution of visuo‐tactile sensing to artificial skin, this review focuses on the 3D reconstruction techniques of the VTS. 3D reconstruction methods are classified into five categories based on sensing modalities, hardware categories, and modeling approaches: 1) photometric stereo, 2) binocular depth calibration, 3) optical flow, 4) deep learning, and 5) ToF (time of flight). In addition, the association and difference of reconstruction methods are analyzed from the hardware perspective, and the development and technological details of 3D reconstruction are summarized. On this basis, the challenges and development direction are discussed. This review can be viewed as a technology guide to provide references for interested researchers. Furthermore, it is expected to promote the extensive application of the VTS in artificial skins.

Haptic artificial muscle skin for extended reality.

Existing haptic actuators are often rigid and limited in their ability to replicate real-world tactile sensations. We present a wearable haptic artificial muscle skin (HAMS) based on fully soft, millimeter-scale, multilayer dielectric elastomer actuators (DEAs) capable of significant out-of-plane deformation, a capability that typically requires rigid or liquid biasing. The DEAs use a thickness-varying multilayer structure to achieve large out-of-plane displacement and force, maintaining comfort and wearability. Experimental results demonstrate that HAMS can produce complex tactile feedback with high perception accuracy. Moreover, we show that HAMS can be integrated into extended reality (XR) systems, enhancing immersion and offering potential applications in entertainment, education, and assistive technologies.

Biodegradable, Self‐Adhesive, Stretchable, Transparent, and Versatile Electronic Skins Based on Intrinsically Hydrophilic Poly(Caproactone‐Urethane) Elastomer

In biomedical sciences, there is a demand for electronic skins with highly sensitive tactile sensors that have applications in patient monitoring, human–machine interfaces, and on‐body sensors. Sensor fabrication requires high‐performance conductive surfaces that are transparent, breathable, flexible, and easy to fabricate. It is also preferable if the electrodes are easily processable as wastes, for example, are degradable. In this work, the design and fabrication of hydrophilic silanol/amine‐terminated poly(caprolactone‐urethane) (SA‐PCLU) elastomer‐based breathable, stretchable, and biodegradable electrodes are reported. Ag nanowires dispersed in water are sprayed onto the intrinsically hydrophilic electrospun SA‐PCLU that became embedded into the scaffold and formed conformal hydrophilic polyurethane‐based conductive networks (HPCN). The electrodes are used to fabricate capacitive, curvature, and strain sensors, all having monomaterial composition. In addition to displaying particularly good transparencies at low sheet resistances, stretchability, hydrophilicity, and tight and conformal bonding with the target surface, the electrodes also allow the evaporation of perspiration, making them suitable for epidermal sensors for long‐time use. The application of the HPCN electrodes in flexible electronics and bionic skin applications is demonstrated through gesture monitoring experiments and swelling sensors.

Microstructured Self-Healing Flexible Tactile Sensors Inspired by Bamboo Leaves.

Wearable electronic devices with multifunctions such as flexible, integrated, and self-powered play a crucial role in the fields of health monitoring, motion monitoring, and human-computer interaction. However, their core basic components, flexible pressure sensors, face challenges including poor long-term stability and insufficient real-time sensing accuracy. In order to solve the challenges of long-term, stable, and accurate sensing of the sensor, this paper prepares polydimethylsiloxane (SHPDMS) with intrinsic self-healing property and designs a high-sensitivity self-healing capacitive flexible pressure sensor with dual microstructures (grating microstructured electrodes and microporous dielectric layer) as the substrate based on SHPDMS. Specifically speaking, the self-healing of the sensor under mild conditions was realized by introducing reversible imine bonds with low bonding energy into the polydimethylsiloxane (PDMS) flexible substrate, which solved the problem of the material's long-term service durability. A grating-like microstructure was introduced into the flexible electrode by using a spotted bamboo taro leaf as a template, and a dual microstructure sensor was constructed by combining it with a microporous dielectric layer doped with single-walled carbon nanotubes. This way reduces the elastic modulus of the dielectric layer, improves the dielectric constant of the sensor under loading, and thus significantly improves the sensor's sensitivity and extends the measurement accuracy in a low-stress range. The prepared self-healing flexible sensor achieves a sensitivity of 3.6 kPa-1, a minimum detection limit of 5 Pa, a response recovery time of less than 80 ms, and stability over 5000 cycles, which exceeds most previously reported silicone rubber-based capacitive flexible sensors.

An evaluation by dental clinicians of cutting characteristics and haptic perceptions in 3D-printed typodont teeth: A pilot study.

This study aimed to compare the haptic perception of clinicians to the cutting response of 3D-printed typodont teeth and commercial typodont teeth and human extracted teeth. Twenty clinicians were asked to perform a Class I cavity preparation on commercial typodont teeth, 3D-printed typodont teeth, and human extracted teeth, while the forces were recorded via a three-axis load cell. The haptic perception of clinicians was also evaluated through a response questionnaire comparing commercial and 3D-printed typodont teeth. The study found that clinicians used similar forces (p=0.53) to cut both the 3D-printed typodont teeth (1.37 N) and the human extracted teeth (1.44 N), but more force was needed to cut the commercial typodont teeth (3.71 N). The response questionnaire indicated that clinicians rated the 3D-printed typodont teeth highly compared to the commercial teeth. The 3D-printed dentine received favorable feedback from clinicians, and the 3D-printed enamel was rated higher compared to the commercial equivalents. The results of the study suggest that 3D-printed typodont teeth offer a comparable haptic perception to human extracted teeth and can be used as an effective tool for preclinical dental learning. Moreover, the study highlights the advantages of 3D-printed typodont teeth over commercial typodont teeth in terms of haptic perception.

Ankle tendon electrical stimulation to enhance sensation of walking on a slope in walking-in-place

This study aimed to develop an effective VR locomotion technique for walking through virtual environments with sloped ground. Thus, this paper presents a novel method for inducing the sensation of walking on a slope in walking-in-place (WIP) using ankle tendon electrical stimulation (TES), which induces the body tilt sensation. We conducted two experiments to evaluate the effectiveness of the proposed method. In Experiment 1, we evaluated the sensation of ascending and descending slopes induced by the proposed method in a setup where electricity flows when the feet are grounded by comparing it to the sensation on a real slope. Experiment 1 demonstrated a marginally significant effect of electrical stimulation on the sensation of ascending or descending slopes. We attributed this to the short duration of ankle TES and the influence of the user’s interpretation of the ankle TES. Based on the findings, Experiment 2 was conducted in a setup where ankle TES was constantly applied. The results indicated that participants who focused on the subjective body tilt sensation elicited by TES and those unaware of the TES effect experienced an ascending sensation with an anterior ankle TES and a descending sensation with a posterior ankle TES. Conversely, those who focused on the tactile or force sensation induced by ankle TES experienced the opposite effect. Based on this finding, we have constructed an implementation guide for a WIP system that incorporates ankle TES to present the desired sensation of ascending or descending slopes in virtual environments.

Randomised controlled trial comparing different intersession intervals of intermittent theta burst delivered to the dorsal medial prefrontal cortex

BackgroundIntermittent theta burst stimulation (iTBS) is a form of repetitive transcranial magnetic stimulation (rTMS) that can be administered in a fraction of the time of standard rTMS. Applying multiple daily...

Directional Characteristic Enhancement of an Omnidirectional Detection Sensor Enabled by Strain Partitioning Effects in a Periodic Composite Hole Substrate.

An omnidirectional stretchable strain sensor with high resolution is a critical component for motion detection and human-machine interaction. It is the current dominant solution to integrate several consistent units into the omnidirectional sensor based on a certain geometric structure. However, the excessive similarity in orientation characteristics among sensing units restricts orientation recognition due to their closely matched strain sensitivity. In this study, based on strain partition modulation (SPM), a sensitivity anisotropic amplification strategy is proposed for resistive strain sensors. The stress distribution of a sensitive conductive network is modulated by structural parameters of the customized periodic hole array introduced underneath the elastomer substrate. Meanwhile, the strain isolation structures are designed on both sides of the sensing unit for stress interference immune. The optimized sensors exhibit excellent sensitivity (19 for 0-80%; 109 for 80%-140%; 368 for 140%-200%), with nearly a 7-fold improvement in the 140%-200% interval compared to bare elastomer sensors. More importantly, a sensing array composed of multiple units with different hole configurations can highlight orientation characteristics with amplitude difference between channels reaching up to 29 times. For the 48-class strain-orientation decoupling task, the recognition rate of the sensitivity-differentiated layout sensor with the lightweight deep learning network is as high as 96.01%, superior to that of 85.7% for the sensitivity-consistent layout. Furthermore, the application of the sensor to the fitness field demonstrates an accurate recognition of the wrist flexion direction (98.4%) and spinal bending angle (83.4%). Looking forward, this methodology provides unique prospects for broader applications such as tactile sensors, soft robotics, and health monitoring technologies.

Practical tips for teaching medicine in the metaverse

The metaverse is based on immersive technologies such as virtual and augmented reality, body tracking, tactile sensation, etc. A growing number of studies are demonstrating the potential of the metaverse as an attractive resource for learning medicine. However, in practice, medical teachers and students often encounter significant challenges when utilizing the underlying technologies, potentially leading to frustrating learning experiences. A significant part of the teaching time is often devoted to troubleshooting technical issues with the metaverse, and the medical content itself taking a backseat until students become proficient in navigating the metaverse environment. Therefore, it is essential to fit the metaverse's underlying technologies specifically for medical education, minimizing technical hurdles for both teachers and students. In this paper, we deal with this challenge and we present a collection of practical tips that serves as a guide for medical educators making decisions in this emerging field, where they may lack prior experience. Drawing on our observation with a cohort of 776 medical students, we conclude how to effectively identify, design, or implement educational applications tailored for efficient medical learning through the metaverse. Our work may support teachers considering metaverse learning platforms for their classrooms and it is a beneficial reference for the medical education community during the initial stages of implementing the metaverse for teaching.

Manufacturing strategies for highly sensitive and self-powered piezoelectric and triboelectric tactile sensors

Abstract Piezoelectric and triboelectric effects are of growing interest for facilitating high-sensitivity and self-powered tactile sensor applications. The working principles of piezoelectric and triboelectric nanogenerators provide strategies for enhancing output voltage signals to achieve high sensitivity. Increasing the piezoelectric constant and surface triboelectric charge density are key factors in this enhancement. Methods such as annealing processes, doping techniques, grain orientation controls, crystallinity controls, and composite structures can effectively enhance the piezoelectric constant. For increasing triboelectric output, surface plasma treatment, charge injection, microstructuring, control of dielectric constant, and structural modification are effective methods. The fabrication methods present significant opportunities in tactile sensor applications. This review article summarizes the overall piezoelectric and triboelectric fabrication processes from materials to device aspects. It highlights applications in pressure, touch, bending, texture, distance, and material recognition sensors. The conclusion section addresses challenges and research opportunities, such as limited flexibility, stretchability, decoupling from multi-stimuli, multifunctional sensors, and data processing.

Manipulator with Integrated Flexible Tactile Sensing Arrays for Kiwifruit Ripeness and Size Classification.

Fruit grading for ripeness and size is an essential process in the supply chain. Incorrect grading can easily lead to spoiled and degraded fruits entering the market, reducing consumers' confidence in purchasing. At the same time, it is easy to cause the fruit supply chain to reduce profits, unreasonable resource allocation, and related practitioners' income. The current mainstream machine vision grading and manual grading in the production line have dilemmas such as susceptibility to environmental interference, inconsistent grading standards, high cost, and labor shortage. To overcome these problems, this study proposes an integrated flexible tactile sensing array (3 × 4) manipulator for efficient, stable, low-cost, and accurate ripeness and size grading of kiwifruit. The flexible sensing manipulator grasps the kiwifruit, detects the hardness of the kiwifruit by relying on tactile sensing, and determines the ripeness level based on the hardness. The size of the kiwifruit is also differentiated according to whether there is a significant change in the resistance of the topmost sensing unit of the flexible pressure sensor array. The 0, 1, 2, 3, 4, and 5 anomalies that may occur in actual production were tested and combined with machine learning KNN, SVM, and RF algorithms for data modeling and grading. The results show that the lowest accuracy of 0, 1, 2, 3, 4, and 5 possible outliers is 86.67% (KNN), 95.83% (SVM), and 92.5% (RF), respectively. KNN has the lowest classification effect, and SVM has the best. This study overcomes the drawbacks of inefficient destructive detection and unstable manual detection and makes up for the vulnerability of single machine vision to interference from environmental factors. This study can alleviate the challenges caused by fruit wastage and promote the sustainable production and consumption of the fruit industry chain.

A Rare Entity of Idiopathic Clitoromegaly with HBsAg Positive Status Managed with Dorsal Nerve Sparing Clitoroplasty

Clitoromegaly, defined as an enlarged clitoris with a clitoral index of more than 35 mm2 is a frequently seen congenital malformation but an idiopathic entity is a rare one. The most acceptable method of treatment of clitoromegaly is clitoroplasty with preservation of neurovascular pedicle to glans to achieve normal genital anatomy and to preserve tactile sensation. We present a rare case of idiopathic clitoromegaly managed by dorsal nerve sparing reduction clitoroplasty in an HBsAg-positive patient.

Simulation and theory for wiring compaction of robot skin tactile sensor by frequency-selective triboelectric-piezoelectric filters

Abstract Abstract: Robots are increasingly equipped with different sensors to better identify things and interact with their environment. One such sensor is the ability to sense and receive information through touch. A significant challenge in designing tactile sensors is to create a larger and more complex network of electrical connections to cover larger partitioned surface areas, necessitating a more compaction for electrical connections. In this study, we try to reduce the number of these array connections by designing a novel triboelectric-piezoelectric pressure sensors that will function as electromechanical frequency-selective filters. The sensor cell units are created in the form of various disk-shape layers with a basic double-lamina layers, a triboelectric lamina placed over a piezoelectric lamina. The triboelectric layer, being soft, is used for static pressure measurement and more sensitivity enhancement. In addition, an electromechanical frequency-selective filter is generated by altering geometric dimensions of that lamina, such as the radius and/or thickness. An applied pressure is calculated by measuring the electric current and the cell unit admittance. The advantage of using piezo-layer geometric manipulation for generating different operating resonant frequencies is that it is a simpler design task as compared to alter the cell electrical properties, which is the focus of previous research. In this work, a theoretical model and numerical simulations are employed to obtain the electromechanical admittance of a set of three unit cell tactile sensors.

Neuroscience of the Human Thalamus Related to Acute Pain and Chronic 'Thalamic' Pain.

The association of posterior thalamic strokes with the presence of chronic 'thalamic' pain, was described in the early 1900s and revisited in a recent review of these patients. Acute pain in corporal structures is associated with the spinothalamic tract (STT) which originates in the dorsal horn of the spinal cord, while that associated with cranial structures is associated with the spinal division of the trigeminal nucleus. These pathways terminate in the ventral posterior nucleus (VP) including its posterior and inferior subnuclei, and its core which is classically associated with tactile and haptic functions. In medial nuclei (medial dorsal and intralaminar) receptive fields are large and stimulation evokes diffuse unpleasant sensations and pain while neurons in these nuclei subserve cognitive processes of attention, alerting, and conditioning. In the lateral nuclei neurons have small receptive and projected fields and high resolution of responses to somatic stimuli. Neurons in the lateral nuclei respond to stimuli producing pain, temperature, and visceral sensations while stimulation evokes similar sensations. Small strokes in VP core versus structures located inferior and posterior are associated with 'thalamic' pain and decreased tactile, painful and cold sensations, and with decreased evoked potentials for painful (laser) heat and median nerve stimulation (electrical). Lesions of VP, but not Vmpo, are associated with 'thalamic' pain, contrary to the recent 'disinhibition' model. We review the evidence that the lateral nuclei are associated with multiple processes including tactile, nociceptive, visceral and thermal content of stimuli, while the medial nuclei are related to cognitions about those stimuli.

Self-Powered Tactile Sensors Embedded with Self-Healing Electrodes for Multifunctional Applications.

Tactile-based sensing technology represents one of the most promising methods for interacting with their surrounding environment. Consequently, flexible tactile sensing has garnered significant attention from researchers worldwide. In this study, triboelectricity and piezoelectricity were combined to propose a multifunctional self-powered tactile sensor (MSPTS). Notably, new and innovative self-healing electrodes were embedded and synthesized from HPDMS (poly(dimethylsiloxane)) and boric acid in the MSPTS, MSPTS demonstrated a linear detection range of 0.25-5 kPa with a sensitivity of 246.28 mV/kPa, indicating substantial improvements in sensor sensitivity, output performance, and anti-interference capability. Our method of forming hydrogen bonds between a self-healing material (SHM) and a liquid metal (LM) effectively addressed the issue of LM leakage within the flexible matrix under pressure, thus preventing sensor failure. The borate dynamic bonding conferred self-healing properties to the electrode when it was damaged. The MSPTS was successfully applied to pressure detection, material identification, and human body movement detection, significantly broadening the application range of flexible electronic devices.

Graded Nanotexturing Architectural Wearable Triboelectric Sensor for Programmable Haptic Exploration.

Emulating biological perception mechanisms to construct intelligent sensing devices and systems represents a paradigm for promoting human-computer interaction in the Internet of Everything era. Nonetheless, developing highly sensitive, real-time sensing and rapidly integrated intelligent interaction units remains a challenging and time-consuming endeavor. This study employs a low-temperature glow discharge technique to rapidly fabricate graded nanotexturing architectural triboelectric nanopaper, upon which wearable triboelectric sensors for real-time tactile detection are designed. The structure enhances the contact area under an external force. Additionally, the Z-stacking structure design enables the sensor to achieve a remarkable sensitivity of 10.3 kPa-1 and a rapid response time of 52 ms. Furthermore, a tactile sensor array was designed to demonstrate the triboelectric sensor's ability to recognize characteristic pressures. With programmable machine learning techniques, the object recognition rate reached 97%. This study supports material structural design across disciplines, laying a solid foundation for the rapid fabrication and integration of transient wearable electronics.

SENSORY INTEGRATION AS AN INNOVATIVE METHOD OF WORKING WITH CHILDREN WITH SPECIAL EDUCATIONAL NEEDS

The method of sensory integration is very relevant in modern science and practice, especially in the context of child development and correctional pedagogy. More and more children have difficulties in processing sensory information, which affects their behaviour, learning and socialisation, and more and more studies confirm the effectiveness of this method in working with children with autism, attention deficit hyperactivity disorder (ADHD), cerebral palsy and other neurological disorders. Purpose. To analyse and systematise sensory integration as an innovative method of working with children with special educational needs. Materials and methods. To achieve the objectives of the study, the scientific literature was analysed and information was systematised using electronic databases such as PubMed, Google Scholar and others Research results. Sensory integration is the organisation of sensations that will be used in some way. Williamson and Anzalone have identified five interrelated components that help explain how sensory integration occurs: sensory registration, orientation, interpretation, organisation of the response, and execution (carrying out) of the response. Sensory registration occurs when a person first becomes aware of a sensory event. Sensory orientation helps to pay attention to new sensory information. A person can determine which sensory information requires attention and which can be ignored. The ability to interpret sensory information helps to choose what to respond to and what not to respond to. A person compares new sensory experiences with old ones. To organise a response, the human brain determines whether a response to a sensory stimulus is required and chooses a response option. Making a motor, cognitive or emotional response to a sensory message is the final stage of the sensory integration process. The following sensory systems are distinguished: tactile (sensation of temperature, humidity, texture of the environment and objects), vestibular (perception of body position in space, interpretation of the feeling of gravity, balance), proprioceptive (feeling of muscles, joints), visual (perception of visual information), auditory (perception of auditory information), olfactory (taste and smell). Disorders in sensory integration refer to difficulties in processing and organising sensory information received by the brain. These disorders can affect various aspects of a child's development, including motor, emotional, cognitive and social skills. The disorders are manifested in the form of hypersensitivity or hyposensitivity. Hypersensitivity (or sensory hypersensitivity) occurs when a person has an unusually high response to sensory stimuli. This means that even small or ordinary stimuli can cause discomfort or even pain. Hypersensitivity (or sensory insufficiency) means that a person needs stronger or more pronounced sensory stimuli to notice or react to them. These disorders can occur in any sensory system. Conclusions. Sensory integration is the ordering of sensations that will be used in some way. When sensory integration is impaired, hypersensitivity and hypersensitivity occur in a particular sensory system. Research in this area shows that sensory impairments can also be observed in children with general development, but in children with special educational needs it is more pronounced. The inclusion of sensory integration in the correctional process significantly improves the studied indicators and contributes to a more successful adaptation of the child and his or her integration into society.

Sleep State Monitoring System Based on Flexible Pressure Sensor Arrays for Evaluating Sleep Quality

Sleep State Monitoring System Based on Flexible Pressure Sensor Arrays for Evaluating Sleep Quality