Haptic Applications Research Articles

Comparing the Psychophysical Capabilities on Fingertip and Wrist using Method of Adjustment

Haptic technology, which refers to creating the sense of touch artificially, offers a crucial source of communication between humans and computers or machines. While conventional haptic devices are designed to render vibrotactile information on the fingertip, recent trends in the field expand the tactile communication to other body locations, like the wrist. Even though the literature has many successful applications showing the validity of such haptic applications, there is no study comparing the user perception for meaningful virtual or teleoperated task scenarios due to the lack of calibration methods between alternative body locations. In this paper, we attempt to compare the perceived intensities at the fingertip and the wrist through psychophysical experiments and to answer: (i) Is there a perpetual difference between the haptic stimuli on the wrist compared to the fingertip? (ii) Is possible to form a reasonable, linear relationship (or a pattern) between the stimuli rendered at the fingertip and the wrist? (iii) If so, do different users require different relationships that would need to be obtained through calibration? We designed a user study with 13 healthy participants, receiving three levels of haptic stimuli at their fingertips while adjusting the intensities of the stimuli rendered at their wrist using the method of adjustments. Our results indicate that there is a linear pattern between the vibrotactile stimuli rendered at the fingertip and the wrist, and each participant exhibits a different pattern. Our results can be used to equalize the perceived intensities of different forms of tactile stimuli for future research investigating the perceived performance under different haptic scenarios.

Alterable Robotic Skin Using Material Gene Expression Modulation

AbstractRobotic skins that integrate artificial tactile sensing elements can substantially complement the perception dimension of social robots, presenting an indispensable part in human‐robot interaction (HRI). However, existing design frameworks compromise between versatility and sustainability due to the restricted range of characteristics available for a single constituent. Here an alterable robotic skin constructed from homogeneous sensing units are proposed, capable of cyclically realtering their inherent characteristics across a wide spectrum. Necessary characteristics to achieve positioning and pressure sensing subunits can be encoded in the feature motifs and extracted through condition‐induced differentiation, showcasing a remarkable resemblance to the gene expression in the living system. By virtue of this, up to 100‐fold differences in feature parameters are achieved, including modulus, surface state, and conductivity, to drive the target attribute coupling. The trans‐temporal reconstruction of materials enables the superb customization of functional building blocks, advancing the flexible separation and combination of different touch modes, including location, pressure, duration, and motion pattern. As a proof of concept, the alterable robotic skin is demonstrated that integrates a position‐sensing layer and a pressure‐sensing layer. It can accurately distinguish and recognize multi‐dimensional touch motions based on less‐channel data, which showcases an efficient haptic interaction application.

A Review of Olfactory Display Designs for Virtual Reality Environments

The field of Virtual Reality continues to evolve to provide an ever-greater sense of immersion to the user. However, VR experiences are still primarily constrained through the human senses of vision and audition, with some interest in haptic (mainly vibrotactile) applications. Only recently have olfactory displays—technologies that generate and deliver scent stimuli—been examined to provide the sense of smell to the human olfactory organ in virtual environments. This article presents a classification and review of olfactory-enhanced virtual reality systems, particularly those that deployed a Head-mounted Display or Cave Automatic Virtual Environment system. In addition, the article provides a discussion of the various technological and design challenges for developing an olfactory display suitable for enhancing virtual reality experiences. Finally, the article proposes future perspectives on the field and includes a table summarizing the characteristics and features of the reviewed systems.

A biocompatible triboelectric nanogenerator-based edible electronic skin for morse code transmitters and smart healthcare applications

Skin-inspired electronic devices have gained immense interest due to their application in prosthetics, healthcare, robotics, and humanmachine interactions. Mimicking human skin and incorporating multifunctional properties such as stretchability, flexibility, biocompatibility, biodegradability, and paving the way for self-powered electronic skin (e-skin) is highly desirable. The present work reports the fabrication of biocompatible triboelectric nanogenerator (TENG)-based edible electronic skins made of a biocompatible chitosan film. The fabricated chitosan film was engineered using plasticizers to enhance its flexibility and mechanical strength. To make the entire device biocompatible, edible gold leaf, which is used as a decorative layer in the sweets of the Indian subcontinent, has been used as an electrode. Both the chitosan film and the edible gold electrode were studied for their biocompatibility by immersion in acetic acid and H2O2, where the films were completely dissolved in 1 h and 50 h, respectively. The e-skins were used as the active layer in the triboelectric nanogenerator by working under both vertical contact separation and single electrode modes of triboelectrification. Furthermore, the fabricated device has been used for real-time applications in self-powered sleep monitoring systems as well as for wearable Morse code transmitters. The electrical response and performance in real-time applications prove that the developed e-skin-based device is a promising candidate for future wearable applications in health care, humanmachine interactions and haptics.

A mechanically robust and facile shape morphing using tensile-induced buckling.

Inspired by the adaptive mechanisms observed in biological organisms, shape-morphing soft structures have emerged as promising platforms for many applications. In this study, we present a shape-morphing strategy to overcome existing limitations of the intricate fabrication process and the lack of mechanical robustness against mechanical perturbations. Our method uses tensile-induced buckling, achieved by attaching restraining strips to a stretchable substrate. When the substrate is stretched, the stiffness mismatch between the restraining strips and the substrate, and the Poisson's effect on the substrate cause the restraining strips to buckle, thereby transforming initially flat shapes into intricate three-dimensional (3D) configurations. Guided by an inverse design method, we demonstrate the capability to achieve complicated and diverse 3D shapes. Leveraging shape morphing, we further develop soft grippers exhibiting outstanding universality, high grasping efficiencies, and exceptional durability. Our proposed shape-morphing strategy is scalable and material-independent, holding notable potential for applications in soft robotics, haptics, and biomedical devices.

The influence of thermo-electromechanical coupling on the performance of lead-free BNT-PDMS piezoelectric composites

In recent times, there have been notable advancements in haptic technology, particularly in screens found on mobile phones, laptops, light-emitting diode (LED) screens, and control panels. However, it is essential to note that the progress in high-temperature haptic applications is still in the developmental phase. Due to their complex phase and domain structures, lead-free piezoelectric materials such as Bi0.5Na0.5TiO3 (BNT)-based haptic technology behave differently at high temperatures than in ambient conditions. Therefore, it is essential to investigate the aspects of thermal management and thermal stability, as temperature plays a vital role in the phase and domain transition of BNT material. A two-dimensional thermo-electromechanical model has been proposed in this study to analyze the thermal stability of the BNT-PDMS composite by analyzing the impact of temperature on effective electromechanical properties and mechanical and electric field parameters. However, the thermo-electromechanical modelling of the BNT-PDMS composite examines the macroscopic effects of the applied thermal field on mechanical and electric field parameters, as phase change and microdomain dynamics are not considered in this model. This study analyzes the impact of thermo-electromechanical coupling on the performance of the BNT-PDMS composite compared to conventional electromechanical coupling. The results predicted a significant improvement in piezoelectric response compared to electromechanical coupling due to the increased thermoelectric effect in the absence of phase change and microdomain switching for temperature boundary conditions below depolarization temperature ( Td∼200∘ C for pure BNT material).

In silico optimization of aligned fiber electrodes for dielectric elastomer actuators

Dielectric elastomer actuators (DEAs) exhibit fast actuation and high efficiencies, enabling applications in optics, wearable haptics, and insect-scale robotics. However, the non-uniformity and high sheet resistance of traditional soft electrodes based on nanomaterials limit the performance and operating frequency of the devices. In this work, we computationally investigate electrodes composed of arrays of stiff fiber electrodes. Aligning the fibers along one direction creates an electrode layer that exhibits zero stiffness in one direction and is predicted to possess high and uniform sheet resistance. A comprehensive parameter study of the fiber density and dielectric thickness reveals that the fiber density primary determines the electric field localization while the dielectric thickness primarily determines the unit cell stiffness. These trends identify an optimal condition for the actuation performance of the aligned electrode DEAs. This work demonstrates that deterministically designed electrodes composed of stiff materials could provide a new paradigm with the potential to surpass the performance of traditional soft planar electrodes.

Designing necks and wrinkles in inflated auxetic membranes

This article presents the potentiality of inflatable, functionally-graded auxetic membranes to produce wrinkles and necks. We obtain elastic instabilities at desired locations in axisymmetric membranes and with prescribed patterns in square membranes. First, we use an analytical approach to obtain a series of universal results providing insights into the formation of wrinkles and necks in inflated, axisymmetric membranes. For example, we prove analytically that necks and wrinkles may never overlap in pressurized, axially symmetric membranes. Second, we implement the relaxed strain energy of tension field theory into a Finite Element solver (COMSOL). By tuning spatial inhomogeneities of the material moduli, we corroborate our universal results, describe the onset of wrinkling in an averaged way, and also generate non-trivial instabilities at desired locations. This study on membranes with morphing or corrugation on demand has potential applications in Braille reading and haptics.

Elucidating Diurnal Patterns in Touch Desire Using Social Media Data Toward Design of Haptic Applications and Displays.

Advances in haptic technology have led researchers and engineers to seek out killer applications in which users can enjoy an experience of touch in AR/VR spaces. Such applications will respond appropriately to human desire for haptic experiences (i.e., touch desire) and thus it is essential for researchers and engineers to understand the nature of people's touch desires as they arise in the course of daily life. In this study, we employed Twitter data analysis to investigate a diurnal pattern in touch desire. Our results showed that touch desire identified in and extracted from Twitter texts did reveal a diurnal pattern. Touch desire tended to be at its lowest in the morning and increased as the day progressed. The time at which it peaked varied with the specific target of touch desire. Touch desire in relation to other people and objects reached its peak at night, but touch desire in relation to animals reached its peak at noon. These results were confirmed not only by our Twitter text analysis but also by data from other social media and an online survey. In addition, we found that the diurnal pattern of touch desire for each target shows a strong correlation with that of visual desire for the same target. This suggests that the diurnal pattern of touch desire is not limited to the sense of touch but is common to other sensory desires for each target. Our findings suggest that researchers need to take the time of day into account when investigating touch desire. Our findings also offer valuable insights for developers into the design of haptic applications and displays that takes into account the timing of daily peaks in touch desire.

HM-Array: A Novel Haptic Magnetism-based Leader-follower Platform for Minimally Invasive Robotic Surgery.

Ensuring the safety and authenticity of haptic feed2 back is crucial in the domain of surgical operations, particularly in procedures like Natural Orifice Transluminal Endoscopic Surgery (NOTES) and Minimally Invasive Robotic Surgery (MIRS). To enhance the control efficiency of the robotic operating console, we propose a haptic magnetism-based array (HM7 Array). This system employs a solenoid array and a detection stylus to achieve controller localization without the need for additional sensors, while simultaneously generating haptic effects. The device effectively controls the surgical robot's pose through a localization-haptic combined loopback. The entire system is scheduled on a finite state machine (FSM), seamlessly fusing localization and haptic generation. Psychometric evaluations con14 ducted through user studies have demonstrated the device's pre15 cision and accuracy. Teleoperation experimental results further confirm its potential value in surgical treatments and broader medical haptic applications.

Magnetic haptic device using miniature SmFeN powder magnets in PCB-on-MEMS system

This paper reports a magnetic microactuator for haptic applications. The actuator consists of a Si chip and two printed circuit boards (PCBs), and the total size of the device is 7.8 mm × 7.8 mm × 2.4 mm. A tiny magnet is embedded into the Si chip and actuated by a current flowing in the PCBs. The mechanical and electrical parts are separated on the Si chip and the PCBs, respectively, and there is no electrical connection between them, allowing simple fabrication and assembly. The magnet, made from a mixture of SmFeN magnetic powder and wax, exhibits a large magnetic field of 0.4 T. The magnet is supported by soft springs of parylene, enabling a large displacement amplitude, a low resonance frequency, and high mechanical robustness. The measured resonance frequency and amplitude are 139 Hz and 62 µm, respectively. The rise and fall times of the vibration of the device at 100 mA drive are 19 ms and 52 ms, respectively. Sensory analysis revealed that the haptic device created the haptic sensation on a scale of three, weak, medium, and strong intensity, with input currents from 50 mA to 200 mA.

Development of Compact 3-Degree-of-Freedom Oscillatory Actuator

Haptics applications are receiving increasing attention in entertainment, medical support systems, and various industries. Three-dimensional (3D) haptics is important to provide users real experiences. Conventional haptic devices consist of many motors and mechanical elements grounded in an environment. Therefore, they are large in size and heavy. Haptic devices using asymmetric vibrations can display illusion forces with mobile structures. However, they need additional structures (comprising actuators) to generate a 3D illusion force; however, the operational mechanism becomes complex. To solve this problem, we propose the use of a 3-degree-of-freedom (3DOF) oscillatory actuator that can generate a 3DOF vibration using only one actuator. This study describes the basic characteristics and operating verification of the 3DOF oscillatory actuator. The static thrust characteristics are quantified and analyzed using a finite element method. The dynamics are calculated based on numerical simulations using a dynamic model. The prototype’s experimental results show that the 3DOF actuator can generate 3DOF vibration.

Can we Effectively Combine Tangibles and Ultrasound Mid-Air Haptics? A Study of Acoustically Transparent Tangible Surfaces.

We propose to study the combination of acoustically transparent tangible objects (ATTs) and ultrasound mid-air haptic (UMH) feedback to support haptic interactions with digital content. Both these haptic feedback methods have the advantage of leaving users unencumbered, and present uniquely complementary strengths and weaknesses. In this article, we provide an overview of the design space for haptic interactions covered by this combination, as well as requirements for their technical implementation. Indeed, when imagining the concurrent manipulation of physical objects and delivery of mid-air haptic stimuli, reflection and absorption of sound by the tangibles may impede delivery of the UMH stimuli. To demonstrate the viability of our approach, we study the combination of single ATT surfaces, i.e. the basic building blocks for any tangible object, and UMH stimuli. We investigate attenuation of a focal point focused through various plates of acoustically transparent materials, and run three human subject experiments investigating the impact of acoustically transparent materials on detection thresholds, discrimination of motion, and localization of ultrasound haptic stimuli. Results show that tangible surfaces which do not significantly attenuate ultrasound can be fabricated with relative ease. The perception studies confirm that ATT surfaces do not impede perception of UMH stimulus properties, and thus that both may viably be combined in haptics applications.

Design and Optimization of a Spherical Magnetorheological Actuator

Recently, an increasing number of electromagnetic devices have been using smart fluids. These include ferrofluids, electrorheological fluids, and magnetorheological (MR) fluids. In the paper, magnetorheological fluids are considered for use in a spherical actuator for haptic applications. An approach is presented to the design and optimization of such a device, using finite element method modelling linked with differential evolution (DE). Much consideration was given to the construction of the objective function to be minimized. A novel approach to objective function assembly was used, using reference values based on the model design and created with parameters set to the midpoint values of the selected range. It was found to be a useful strategy when the reference values are unknown. There were four parameters to be optimized. Three of them gravitated towards the boundary value, and the fourth (actuator radius) was somewhere in between. The value of the objective function reached a minimum in the range of actuator radius between 42.9880 mm and 45.0831 mm, which is about a 5% difference in regard to the actuator radius. Three passes of optimization were performed with similar results, proving the robustness of the algorithm.

Exploring the applicability of haptic actuators in aquatic environments

The use of high-tech wearable devices and real-time biomechanical feedback (RTBF) is widespread in modern sports and physical rehabilitation. While the use of kinematic sensors for RTBF is well established, the question of the most efficient and appropriate way to present feedback information to the user remains largely unanswered. The haptic modality has only been used in a limited number of relatively simple studies and applications, and it has never been studied in an aquatic environment. In this study, the main motivation was to design, develop, implement, and test an RTBF system for sports and physical rehabilitation with haptic actuators suitable for use in aquatic environments. The developed miniature remote-controlled device with vibration motors as actuators was tested to determine how people perceive the haptic modality in and out of water. The results of the exploratory study with 34 participants suggest that the feedback device can be further developed for future studies. The results show that both simple and complex haptic stimuli can be understood by athletes both outdoors and in water, as well as while standing and performing simple physical activities. This study tested the use of both head and waist mounted haptic actuators, with both showing similar and promising results. The results of this study provide evidence that haptic feedback can be perceived in water, highlighting the potential for real-time haptic interventions in aquatic environments. In summary, this study represents a significant contribution to the evolving field of RTBF in modern sport training and physical rehabilitation. The development of a haptic feedback device that can be worn during aquatic and other activities is a significant advance in the field of feedback actuators. This study provides a foundation for future usability studies and the development of haptic RTBF applications in both aquatic and outdoor environments.

HAPSEA: Hydraulically Amplified Soft Electromagnetic Actuator for Haptics

Novel actuators that can provide squeeze, vibration, and localized forces while remaining soft and comfortable are essential for next-generation augmented reality applications. Despite this need, there are currently few soft actuator topologies that can provide high forces and high bandwidths at low voltages and temperatures. In this work, we present a new type of soft electromagnetic actuator architecture for haptics. These low-cost, easy-to-manufacture, and conformal actuators are composed of a coil, magnet, thin-film material, and water. Adding a thin ferromagnetic sheet further enables the creation of a latching actuator variant, which can improve force output while reducing power consumption. Each actuator combines low voltage (up to 2 V), high-bandwidth electromagnetics with hydraulics to amplify force output. In addition to force amplification, the hydraulics provide cooling and thermal mass, which enable the actuator to be used safely in wearables for longer durations. In this work, we characterize the output forces, frequency response, efficiency, and thermal profiles of the prototype actuators. Results from tabletop experiments show that with hydraulic amplification, a nonlatching actuator is able to exert 1.3 N of force at 4 A, and a latching actuator is able to exert up to 5.2 N when preloaded with 3.7 N of compression. Furthermore, the prototype actuator has a bandwidth of 30 Hz when operating in air. After 120 s of continuous operation (1.3 W) in ambient air (26 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C), the maximum actuator temperature reaches 36 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C, making it safe for haptic applications. Using these designs, we develop a prototype wearable wristband device that can render body-grounded squeeze and vibration. By expanding on the operating principles described in this work, novel augmented reality applications can potentially become possible.

Macro-fiber composite-based tactors for haptic applications.

Haptic technology is a critical component of human-computer interfaces. Traditional haptic actuators are often unable to provide the broad frequency range and latency that is required in many advanced applications. To address this problem, we propose a new type of tactor based on macro-fiber composites (MFCs), composites of piezoelectric fibers. We propose a physics-based model for the actuation of the tactors, calibrated and validated through experiments. As our tactors are intended for haptic applications, we consider the role of skin on their response, an aspect seldom analyzed in the literature. In our experiments, we simulate the presence of the skin with a rubber membrane in contact with the tactor, with varying pre-stretch, mimicking different indentations of the tactor on the skin. The MFC-based tactor can always generate vibration amplitudes higher than skin discrimination thresholds, over the range of frequencies of interest for haptics, with a latency much smaller than traditional actuators. We theoretically investigate the effect of the skin on tactor vibrations, highlighting the individual roles of skin stiffness and damping and their combined effect across a series of pre-stretches. Our tactor shows promise in haptic applications, including assistive technologies and real-time feedback systems for training, safety, and monitoring.

Haptic technology in society: A sentiment analysis of public engagement

With the rapid rise of metaverse spaces, the integration of haptic technology has become an integral part of users' immersion and engagement in different domains. This study shades the light on public engagement with haptic technology applications in various contexts. The YouTube Application Programming Interface was used to extract data about haptic technology within a specific time period. Public engagement was estimated based on users' cognitive and behavioral engagement with haptic-video materials. A topic modeling approach was used to extract the main topics associated with haptic technology. The main types of users’ emotions and their word association were extracted using the association rules mining technique. The results showed that public engagement with haptic technology was mostly observed in few categories (e.g., gaming). Joy and positive sentiments were strongly associated with the extracted topics. The findings offer new insights into the tendency of utilizing haptic technology across communities. The outcomes can help industries and decision makers understand ways to improve the integration of haptic technology in according to the needs of specific domains.

Engagement detection and enhancement for STEM education through computer vision, augmented reality, and haptics

STEM (Science, technology, engineering, and mathematics) based education is being revolutionized with the rapid development of the applications of intelligent Haptics. Theoretical knowledge may now be put into practice, and complex ideas can now be presented using three-dimensional models that are enhanced in the actual environment via Augmented Reality (AR) and computer Haptics to enhance the student's interest in concepts and studies. This article presents a novel design and development of an AR and Haptics-based STEM product comprising of World Map with Haptic feedback using Vuforia, Unity 3D, and Open-Haptics to enhance student engagement. To detect students' engagement in online learning, a computer vision-based system is also designed and deployed in the real-time website that uses the features, such as facial emotions, pose estimation, and head rotation. Marker-based augmentation is employed, and a sense of touch is included for an immersive experience for the students with the use of the haptic Touch Omni device. Hence, the proposed approach can improve classroom learning activities by using Augmented reality and Haptics-based STEM product and by its evaluation using a computer vision system. To validate the improvement in engagement, a comprehensive user study is performed and analyzed on the proposed setup.

A survey on wearable hand robotics design for assistive, rehabilitative, and haptic applications

A survey on wearable hand robotics design for assistive, rehabilitative, and haptic applications