Haptic Surface Research Articles

Dual-Wavelength Volumetric Microlithography for Rapid Production of 4D Microstructures.

4D microstructured actuators are micro-objects made of stimuli-responsive materials capable of induced shape deformations, with applications ranging from microrobotics to smart micropatterned haptic surfaces. The novel technology dual-wavelength volumetric microlithography (DWVML) realizes rapid printing of high-resolution 3D microstructures and so has the potential to pave the way to feasible manufacturing of 4D microdevices. In this work, DWVML is applied for the first time to printing stimuli-responsive materials, namely, liquid crystal networks (LCNs). An LCN photoresist is developed and characterized, and large arrays of up to 5625 LCN micropillars with programmable shape changes are produced by means of DWVML in the time span of seconds, over areas as large as ∼5.4 mm2. The production rate of 0.24 mm3 h-1 is achieved, exceeding speeds previously reported for additive manufacturing of LCNs by 2 orders of magnitude. Finally, a membrane with tunable, micrometer-sized pores is fabricated to illustrate the potential DWVML holds for real-world applications.

To Touch Time: U.S. Black Feminist Modernist Sculpture in the 1970s and 1980s

Modernist propositions long have been understood as atemporal—somehow outside of time—or insistently hailing the future. This temporal framework suppresses the contributions of those excluded from modernist canons, particularly Black women. In this article, visual and material analysis of sculptural works produced in the 1970s and 1980s by U.S. Black women artists Beverly Buchanan, Senga Nengudi, and Betye Saar reveal how Black feminists have engaged with modernist protocols in order to redress cultural erasures of Black women. These practices exemplify Black feminist modernisms, or creative practices that unsettle the racist and sexist logics of dominant cultural institutions. Each of these artists utilizes haptic surfaces as a method for defying institutional modernism’s obfuscation of the past. The analysis focuses on Buchanan’s defiance of memorial erasures, Nengudi’s reenactment of labor, including in its historical forms, and Saar’s adaptation of generational memory-making processes. Ultimately, these artists’ rejection of a “timeless” modernism demands that viewers understand the present moment in relationship to a still-evolving past. In this way, Buchanan, Nengudi, and Saar position the present as an accumulation, rather than transcendence, of historical occurrences.

Late postoperative opacification of a new type hydrophilic acrylic intraocular lens

BackgroundTo report the clinical consequences and laboratory characteristics of late postoperative opacification of a hydrophilic acrylic intraocular lens (US-860UV IOL) as well as the prognosis of IOL replacement. MethodsForty medical records (42 eyes) of patients with US-860UV IOL opacification reporting decreased or lost vision who underwent IOL explantation between 2017 and 2019 were reviewed. Explanted IOLs were analyzed by slit-lamp examination, confocal microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) at the Shandong Key Laboratory of Ophthalmology, Shandong Eye Institute, Shandong First Medical University, and Qingdao University of Science and Technology, Qingdao, China. ResultsThe mean age of the 40 patients was 74.83 ​± ​7.57 (63–92) years. The mean interval between cataract surgery and diagnosis of opacification was 32.38 ​± ​8.76 (17–48) months. Systemic diseases were found without statistical correlations, the most frequent being arterial hypertension, coronary heart disease, and diabetes mellitus. Visual acuity improved from 1.42 ​± ​1.03 to 0.31 ​± ​0.16 (logMAR) after IOL replacement. SEM, EDS and alizarin red staining showed uniformly distributed, diffuse, milk-white opacification, with calcium and phosphorus deposits on the optic and haptic surfaces that could be dissolved in 1% HCl. ConclusionsCalcium and phosphorus deposition was the main cause of hydrophilic acrylic US-860UV IOL opacification. IOL replacement can safely and effectively improve the visual acuity of patients.

Study on the Cognitive Characteristics Induced by Changes in the Intensity, Frequency and Duration of Vibratory Stimuli

The purpose of this study is to analyze the cognitive characteristics that can be induced by vibration stimuli at two intensities, three frequencies, and five presentation periods. The experiment was conducted on 20 right-handed adult males, and a subjective evaluation was performed using a questionnaire. Regression analysis was performed to observe the parameters affecting cognitive characteristics according to changes in intensity, frequency, and stimulation duration. The regression analysis results showed that the cognitive characteristics affected by changes in intensity, frequency, and stimulation duration were "heavy", "bold", "thick", and "light". The cognitive characteristics affected by two-variable combinations were "deep", "clear", "vibrating", "dense", "numb", "blunt", "shallow", "fuzzy", and "soft". Cognitive characteristics affected by either intensity, frequency, or stimulation duration were "fast", "pungent", "skinny", "thin", "slow", "ticklish", "tingling", "prickling", "tap", and "rugged". By observing the cognitive characteristics that can be induced by the combination of intensity, frequency, and stimulation duration, we confirmed that in addition to intensity and frequency, the stimulation duration is an important factor that influences the induction of various cognitive characteristics. The results presented in the study can be used to enhance the utility of haptic surfaces for extended reality applications.

Compression of surface texture acceleration signal based on spectrum characteristics

BackgroundAdequate data collection can enhance the realism of online rendering or offline playback of haptic surface textures. A parallel challenge is to reduce communication delays and improve storage space utilization. MethodsBased on the similarity of the short-term amplitude spectrum trend, this study proposes a frequency-domain compression method. A compression framework is designed, which first maps the amplitude spectrum into grayscale images, compresses them with a still image compression method, and then adaptively encodes the maximum amplitude and part of the initial phase for each time window to achieve the final compression. ResultsThe comparison between the original signal and the recovered signal shows that when the time-frequency similarity is 90%, the average compression ratio of our method is 9.85% in the case of a single interaction point. The subjective score for similarity was found to be high, with an average of 87.85. ConclusionsOur method can be used for offline compression of vibrotactile data. For multi-interaction points in space, the trend similarity grayscale image can be reused, and the compression ratio is further reduced.

Transforming musculoskeletal anatomy learning with haptic surface painting.

Anatomical body painting has traditionally been utilized to support learner engagement and understanding of surface anatomy. Learners apply two-dimensional representations of surface markings directly on to the skin, based on the identification of key landmarks. Esthetically satisfying representations of musculature and viscera can also be created. However, established body painting approaches do not typically address three-dimensional spatial anatomical concepts. Haptic Surface Painting (HSP) is a novel activity, distinct from traditional body painting, and aims to develop learner spatial awareness. The HSP process is underpinned by previous work describing how a Haptico-visual observation and drawing method can support spatial, holistic, and collaborative anatomy learning. In HSP, superficial and underlying musculoskeletal and vascular structures are located haptically by palpation. Transparent colors are then immediately applied to the skin using purposive and cross-contour drawing techniques to produce corresponding visual representations of learner observation and cognition. Undergraduate students at a United Kingdom medical school (n=7) participated in remote HSP workshops and focus groups. A phenomenological study of learner perspectives identified four themes from semantic qualitative analysis of transcripts: Three-dimensional haptico-visual exploration relating to learner spatial awareness of their own anatomy; cognitive freedom and accessibility provided by a flexible and empowering learning process; altered perspectives of anatomical detail, relationships, and clinical relevance; and delivery and context, relating to curricular integration, session format, and educator guidance. This work expands the pedagogic repertoire of anatomical body painting and has implications for anatomy educators seeking to integrate innovative, engaging, and effective learning approaches for transforming student learning.

Rapid change of friction causes the illusion of touching a receding surface.

Shortly after touching an object, humans can tactually gauge the frictional resistance of a surface. The knowledge of surface friction is paramount to tactile perception and the motor control of grasp. While potent correlations between friction and participants' perceptual response have been found, the causal link between the friction of the surface, its evolution and its perceptual experience has yet to be demonstrated. Here, we leverage new experimental apparatus able to modify friction in real time, to show that participants can perceive sudden changes in friction when they are pressing on a surface. Surprisingly, only a reduction of the friction coefficient leads to a robust perception. High-speed imaging data indicate that the sensation is caused by a release of a latent elastic strain over a 20 ms timeframe after the activation of the friction-reduction device. This rapid change of frictional properties during initial contact is interpreted as a normal displacement of the surface, which paves the way for haptic surfaces that can produce illusions of interacting with mechanical buttons.

Individuals with and without Visual Impairments Use a Force Feedback Device to Identify the Friction and Hardness of Haptic Surfaces

The general purpose of this study is to promote access to haptic virtual environments. Using a haptic device, people with and without visual impairments (VI) are able to feel different textures and compare these textures based on different surface properties, i.e., friction and hardness. The objectives of this study were to examine the following: (a) whether the variables of friction and hardness were identifiable through the Touch device (Phantom Omni) and could therefore function as 3D haptic variables; (b) if there were differences between people with VI and sighted individuals in terms of their performance; (c) the differences that should exist between the values of each variable so that the virtual surfaces could be identified as different to each other; and (d) if the individual characteristics of participants have an impact on their performance. The results showed that it is necessary to use surfaces which are differentiated based on the degree of friction and hardness because the haptic properties of a virtual object are then better perceived. Individuals with VI need more time and more effort to understand friction and hardness, respectively. With the motivation of increasing access to object perception for people with VI in a virtual environment, accessibility advisors and experts can extract useful information for the development of functional and efficient 3D objects for haptic perception.

Learning to Feel Textures: Predicting Perceptual Similarities From Unconstrained Finger-Surface Interactions.

Whenever we touch a surface with our fingers, we perceive distinct tactile properties that are based on the underlying dynamics of the interaction. However, little is known about how the brain aggregates the sensory information from these dynamics to form abstract representations of textures. Earlier studies in surface perception all used general surface descriptors measured in controlled conditions instead of considering the unique dynamics of specific interactions, reducing the comprehensiveness and interpretability of the results. Here, we present an interpretable modeling method that predicts the perceptual similarity of surfaces by comparing probability distributions of features calculated from short time windows of specific physical signals (finger motion, contact force, fingernail acceleration) elicited during unconstrained finger-surface interactions. The results show that our method can predict the similarity judgments of individual participants with a maximum Spearman's correlation of 0.7. Furthermore, we found evidence that different participants weight interaction features differently when judging surface similarity. Our findings provide new perspectives on human texture perception during active touch, and our approach could benefit haptic surface assessment, robotic tactile perception, and haptic rendering.

Felt-Concrete Composites in Architecture and Design

The paper explores the possibilities of a composite of needle-felt fibres and cement-based matrix for designing and fabricating architectural elements. It summarizes the longer standing design-research undertaking in needle-felting as a novel method for creating materially graded objects without the use of formwork. The work is conducted on a design prototype of a chair to emphasise the integrative nature of this material system. This approach allows the study of all aspects from the fabrication process, the function of details, structural behaviour, and user experience.
 Needle fleeting has a long tradition in arts and craft for manually forming intricate objects such as figurines or applying ornaments to textile objects. The main feature of felt material is that it can bring fibrous material into a stable shape. This process has been digitized by Disney Research proposing needle felting as a way of 3D-printing fibrous material[1]. Becker et al. also proposed a robotic process for robotically 3D-printing felt shapes [2] which form the base for a material composite of felt-fibers and a cement based matrix. Their paper argues for functionally graded architectural elements where the composite of felt and cement can provide for tensile reinforcement, compressive strength, insulation, and different haptic surfaces. Based these methods here a replica of IKEA® Leifarne chair is realized, showcasing a range of felt-concrete composite applications integrated in a single object.

Perception by Palpation: Development and Testing of a Haptic Ferrogranular Jamming Surface.

Tactile hands-only training is particularly important for medical palpation. Generally, equipment for palpation training is expensive, static, or provides too few study cases to practice on. We have therefore developed a novel haptic surface concept for palpation training, using ferrogranular jamming. The concept’s design consists of a tactile field spanning 260 x 160 mm, and uses ferromagnetic granules to alter shape, position, and hardness of palpable irregularities. Granules are enclosed in a compliant vacuum-sealed chamber connected to a pneumatic system. A variety of geometric shapes (output) can be obtained by manipulating and arranging granules with permanent magnets. The tactile hardness of the palpable output can be controlled by adjusting the chamber’s vacuum level. A psychophysical experiment (N = 28) investigated how people interact with the palpable surface and evaluated the proposed concept. Untrained participants characterized irregularities with different position, form, and hardness through palpation, and their performance was evaluated. A baseline (no irregularity) was compared to three irregularity conditions: two circular shapes with different hardness (Hard Lump and Soft Lump), and an Annulus shape. 100% of participants correctly identified an irregularity in the three irregularity conditions, whereas 78.6% correctly identified baseline. Overall agreement between participants was high (κ= 0.723). The Intersection over Union (IoU) for participants sketched outline over the actual shape was IoU Mdn = 79.3% for Soft Lump, IoU Mdn = 68.8% for Annulus, and IoU Mdn = 76.7% for Hard Lump. The distance from actual to drawn center was Mdn = 6.4 mm (Soft Lump), Mdn = 5.3 mm (Annulus), and Mdn = 7.4 mm (Hard Lump), which are small distances compared to the size of the field. The participants subjectively evaluated Soft Lump to be significantly softer than Hard Lump and Annulus. Moreover, 71% of participants thought they improved their palpation skills throughout the experiment. Together, these results show that the concept can render irregularities with different position, form, and hardness, and that users are able to locate and characterize these through palpation. Participants experienced an improvement in palpation skills throughout the experiment, which indicates the concepts feasibility as a palpation training device.

Liquid Crystal Elastomers with Enhanced Directional Actuation to Electric Fields.

The integration of soft, stimuli-responsive materials in robotic systems is a promising approach to introduce dexterous and delicate manipulation of objects. Electrical control of mechanical response offers many benefits in robotic systems including the availability of this energy input, the associated response time, magnitude of actuation, and opportunity for self-regulation. Here, a materials chemistry is detailed to prepare liquid crystal elastomers (LCEs) with a 14:1 modulus contrast and increase in dielectric constant to enhance electromechanical deformation. The inherent modulus contrast of these LCEs (when coated with compliant electrodes) directly convert an electric field to a directional expansion of 20%. The electromechanical response of LCE actuators is observed upon application of voltage ranging from 0.5 to 6kV. The deformation of these materials is rapid, reaching strain rates of 18% s-1 . Upon removal of the electric field, little hysteresis is observed. Patterning the spatial orientation of the nematic director of the LCEs results in a 2D-3D shape transformation to a cone 8mm in height. Individual and sequential addressing of an array of LCE actuators is demonstrated as a haptic surface.

Function Follows Form: Using the Aesthetic Association Principle to Enhance Haptic Interface Design.

Novel tangible user interface technologies facilitate current trends toward seamless user interfaces. They enable the design of yet unseen interfaces and thus the creation of a new kind of haptic language. In order to use the benefits of a touch-and-feel design for a positive user experience, carefully designed haptic feedback plays an important role by providing aesthetically pleasing and sustainable product features. Haptic feedback may exceed mere acquiring of buttons and input-confirmation but enable orientation and even identification of functionality governed by the haptic impression. We employed the aesthetic association principle as a deeply grounded psychological mechanism that assists effective linkage between haptic form factors and associated functional attributes. In order to illustrate this powerful principle, we analyzed the specific associations between certain main haptic surface qualities and associated functional aspects. In a series of three subsequent studies (Pre-Study 1: perception, Pre-Study 2: similarity, and Main Study: association), we explored paradigmatic associations of that kind to develop guidelines which forms are distinct to be used in interfaces. We show how forms are implicitly categorized into functional qualities (on/off, more-less, selection), using a multidimensional scaling procedure and explore explicit form-functionality associations, using a think-aloud method in the context of an automotive interface. For a series of forms, we revealed clear associative relations to specific functions. We will discuss the general value and opportunities of an association-based approach to user experience in order to create intuitive user interfaces. We will also develop ideas for specific areas of applications.

Evaluation of the Electrowetting Effect on the Interfacial Mechanics between Human Corneocytes and Nanoasperities.

A large subset of haptic surfaces employs electroadhesion to modulate both adhesion and friction at a sliding finger interface. The current theory of electroadhesion assumes that the applied electric field pulls the skin into stronger contact, increasing friction by increasing the real contact area, yet it is unknown what role environmental moisture plays in the effect. This paper uses atomic force microscopy (AFM)to determine the effect of humidity on the adhesion and friction between the single nanoscale asperity and individual human finger corneocytes. An analytical model of the total effective load of the AFM tip is developed to explain the humidity-voltage dependence of nanoscale adhesion and friction at contacting asperities. The results show that the electrowetting effect at the interface at high humidity accounts for 35% of the adhesive force but less than 8% of the total friction, implying that the electrowetting effect can be enhanced by optimizing surface topography to promote the formation and rupture of liquid menisci.

Tuning electro-mechanical properties of EAP-based haptic actuators by adjusting layer thickness and number of stacked layers—a comparison

In our fast-changing world, human-machine interfaces (HMIs) are of ever-increasing importance. Among the most ubiquitous examples are touchscreens that most people are familiar with from their smartphones. The quality of such an HMI can be improved by adding haptic feedback—an imitation of using mechanical buttons—to the touchscreen. Thin-film actuators on the basis of electro-mechanically active polymers (EAPs), with the electroactive material sandwiched between two compliant electrodes, offer a promising technology for haptic surfaces. In thin-film technology, the thickness and the number of stacked layers of the electroactive dielectric are key parameters for tuning a system. Therefore, we have experimentally investigated the influence of the thickness of a single EAP layer on the electrical and the electro-mechanical performance of the transducer. In order to achieve high electro-mechanical actuator outputs, we have employed relaxor-ferroelectric ter-fluoropolymers that can be screen-printed. By means of a model-based approach, we have also directly compared single- and multi-layer actuators, thus providing guidelines for optimized transducer configurations with respect to the system requirements of haptic applications for which the operation frequency is of particular importance.

No need to touch this: Bimanual haptic slant adaptation does not require touch.

In our daily life, we often interact with objects using both hands raising the question the question to what extent information between the hands is shared. It has, for instance, been shown that curvature adaptation aftereffects can transfer from the adapted hand to the non-adapted hand. However, this transfer only occurred for dynamic exploration, e.g. by moving a single finger over a surface, but not for static exploration when keeping static contact with the surface and combining the information from different parts of the hand. This raises the question to what extent adaptation to object shape is shared between the hands when both hands are used in static fashion simultaneously and the object shape estimates require information from both hands. Here we addressed this question in three experiments using a slant adaptation paradigm. In Experiment 1 we investigated whether an aftereffect of static bimanual adaptation occurs at all and whether it transfers to conditions in which one hand was moving. In Experiment 2 participants adapted either to a felt slanted surface or simply be holding their hands in mid-air at similar positions, to investigate to what extent the effects of static bimanual adaptation are posture-based rather than object based. Experiment 3 further explored the idea that bimanual adaptation is largely posture based. We found that bimanual adaptation using static touch did lead to aftereffects when using the same static exploration mode for testing. However, the aftereffect did not transfer to any exploration mode that included a dynamic component. Moreover, we found similar aftereffects both with and without a haptic surface. Thus, we conclude that static bimanual adaptation is of proprioceptive nature and does not occur at the level at which the object is represented.

Haptic Surface Display based on Miniature Dielectric Fluid Transducers

We present a lightweight, low power, and compliant miniature dielectric fluid transducer intended for haptic surface display. The actuator has a large strain and fast response without an external compressor. It consists of a thin oil-filled pouch with a 1.5 mm diameter opening covered with a silicone membrane. The application of voltage causes the pouch to squeeze the oil and form a bump by stretching the silicone membrane. The actuator produces 1.45 mm bump height at 3 kV and 13 mN at 3.5 kV using ≈10 μl of oil. The power consumption is <; 3 mW. Though the largest bump height has a bandwidth near 5 Hz, the device achieves perceivable vibration at 200 Hz with a bump height of 200 μm. The actuators can be packed closely and controlled individually to create dynamic texture displays, suitable for active surface exploration with the fingertips. The simulation results show the width of the actuator can be reduced without affecting the performance. Tests with human subjects show that users differentiated simple bump patterns with a 98.8% success rate.

Adaptive force and velocity control based on intrinsic contact sensing during surface exploration of dynamic objects

Haptic exploration is a process of using haptic feedback to interact and perceive an unknown object. It is an essential approach to understand the physical and geometrical properties of the object. While numerous research has been carried out for haptic exploration on static objects, haptic exploration on objects with dynamic movements has not been reported. It is due to the significant challenges to achieve robust force and velocity control when the object is nonstationary. In this work, a novel adaptive force and velocity control algorithm based on intrinsic contact sensing (ICS) for haptic surface exploration of dynamic objects is presented. A fuzzy-logic control framework making use of the information obtained from ICS has been developed. To validate the proposed control algorithm, extensive surface exploration experiments have been carried out on objects with different surface properties, geometries, stiffness, and concave or convex patterns. The validation results demonstrate the high accuracy and robustness of the proposed algorithm using different experimental platforms.

ENTROPiA: Towards Infinite Surface Haptic Displays in Virtual Reality Using Encountered-Type Rotating Props

In this article, we propose an approach towards an infinite surface haptic display. Our approach, named ENcountered-Type ROtating Prop Approach (ENTROPiA) is based on a cylindrical spinning prop attached to a robot's end-effector serving as an encountered-type haptic display (ETHD). This type of haptic display permits the users to have an unconstrained, free-hand contact with a surface being provided by a robotic device for the users' to encounter a surface to be touched. In our approach, the sensation of touching a virtual surface is given by an interaction technique that couples with the sliding movement of the prop under the users' finger by tracking their hand location and establishing a path to be explored. This approach enables large motion for a larger surface rendering, permits to render multi-textured haptic feedback, and leverages the ETHD approach introducing large motion and sliding/friction sensations. As a part of our contribution, a proof of concept was designed for illustrating our approach. A user study was conducted to assess the perception of our approach showing a significant performance for rendering the sensation of touching a large flat surface. Our approach could be used to render large haptic surfaces in applications such as rapid prototyping for automobile design.

Hand rehabilitation and haptic surfaces: a tentative prototype

Hand motor and sensory functions may be impaired by several causes, including healthy aging or nerve damage. It is common to practice hand or finger rehabilitation/training exercises to improve hand function and re-educate sensory information. This article presents a haptic surface prototype for hand rehabilitation/training. The device is connected to a virtual environment and allows for the practice of a variety of hand/finger exercises. The difficulty of the exercise can be adjusted by adjusting the stiffness of its surface via the Particle Jamming method.