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1. Toward human-resolution haptics: A high-bandwidth, high-density, wearable tactile display

   https://doi.org/10.1126/sciadv.adz5937  

   Tan, Sylvia; Peskhin, Michael A; Klatzky, Roberta L; Colgate, J Edward (November 2025, Science Advances)

   Despite advances in digitizing vision and hearing, touch still lacks an equivalent digital interface matching the fidelity of human perception. This gap limits the quality of digital tactile information and the realism of virtual experiences. Here, we introduce a step toward human-resolution haptics: a class of wearable tactile displays designed to match the spatial and temporal acuity of the human fingertip. Our device, VoxeLite, is a 0.1-millimeter-thick, 0.19-gram, skin-conformal array of individually addressable soft electroadhesive actuators (“nodes”). As users touch and move across surfaces, VoxeLite delivers high-resolution distributed forces via the nodes. Enabled by scalable microfabrication techniques, the display achieves actuator densities up to 110 nodes per square centimeter, produces stimuli up to 800 hertz, and remains transparent to real-world tactile input. We demonstrate its ability to render small-scale hapticons and virtual textures and transmit physical surfaces, validated through human psychophysics and biomimetic sensing. These findings position VoxeLite as a platform for human-resolution haptics in immersive interfaces, robotics, and digital touch communication. 

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2. Soft Growing Pin for High-Extension Shape-Changing Displays

   https://doi.org/10.1109/RoboSoft60065.2024.10522001  

   Valdivia, Antonio Alvarez; Rezqalla, Mohammad A; Swann, Sarah E; Blumenschein, Laura H (April 2024, IEEE)

   Regular user interface screens can display dense and detailed information to human users but miss out on providing somatosensory stimuli that take full advantage of human spatial cognition. Therefore, the development of new haptic displays can strengthen human-machine communication by augmenting visual communication with tactile stimulation needed to transform information from digital to spatial/physical environments. Shape-changing interfaces, such as pin arrays and robotic surfaces, are one method for providing this spatial dimension of feedback; however, these displays are often either limited in maximum extension or require bulky mechanical components. In this paper, we present a compact pneumatically actuated soft growing pin for inflatable haptic interfaces. Each pin consists of a rigid, air-tight chamber, an inflatable fabric pin, and a passive spring-actuated reel mechanism. The device behavior was experimentally characterized, showing extension to 18.5 cm with relatively low pressure input (1.75 psi, 12.01 kPa), and the behavior was compared to the mathematical model of soft growing robots. The results showed that the extension of the soft pin can be accurately modeled and controlled using pressure as input. Finally, we demonstrate the feasibility of implementing individually actuated soft growing pins to create an inflatable haptic surface. 

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3. FingerPrint: A 3-D Printed Soft Monolithic 4-Degree-of-Freedom Fingertip Haptic Device with Embedded Actuation

   https://doi.org/10.1109/RoboSoft54090.2022.9762107  

   Zhakypov, Zhenishbek; Okamura, Allison M. (April 2022, IEEE International Conference on Soft Robotics (RoboSoft))

   Wearable fingertip haptic interfaces provide tac- tile stimuli on the fingerpads by applying skin pressure, linear and rotational shear, and vibration. Designing and fabricating a compact, multi-degree-of-freedom, and forceful fingertip haptic interface is challenging due to trade-offs among miniatur- ization, multifunctionality, and manufacturability. Downsizing electromagnetic actuators that produce high torques is infea- sible, and integrating multiple actuators, links, joints, and transmission elements increases device size and weight. 3-D printing enables rapid manufacturing of complex devices with minimal assembly in large batches. However, it requires a careful arrangement of material properties, geometry, scale, and printer capabilities. Here we present a fully 3-D printed, soft, monolithic fingertip haptic device based on an origami pattern known as the “waterbomb” base that embeds foldable vacuum actuation and produces 4-DoF of motion on the fingerpad with tunable haptic forces (up to 1.3 N shear and 7 N normal) and torque (up to 25 N-mm). Including the thimble mounting, the compact device is 40 mm long and 20 mm wide. This demonstrates the efficacy of origami design and soft material 3D printing for designing and rapidly fabricating miniature yet complex wearable mechanisms with force output appropriate for haptic interaction. 

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4. Psychophysical Validation of Interleaving Narrowband Tactile Stimuli to Achieve Broadband Effects

   https://doi.org/10.1109/WHC49131.2021.9517268  

   Martinez, Juan S.; Tan, Hong Z.; Cholewiak, Roger W. (January 2021, World Haptics Conference 2021)

   Current wearable haptic display technology is limited by the lack of broadband tactors capable of delivering rich haptic effects across the entire perceptible frequency range. Audio speakers are often used in laboratory studies as broadband tactors, but it is difficult to attach them to skin and maintain contact during movement. Commercially-available narrowband tactors are small, low in cost and power efficient. We investigate the idea of interleaving narrowband tactile stimuli to achieve broadband effects. Twelve participants performed pairwise discrimination of two stimulus alternatives using two broadband tactors. One alternative was a broadband vibration composed of the sum of a mid- and a high-frequency vibration, delivered by a single tactor. The other alternative consisted of the mid-frequency component delivered by one tactor and the high-frequency by the other. The upper arm was chosen for stimulation because the tactors can be placed within the two-point limen of the skin. The sensitivity index results were significantly below 1.0, the criterion for discrimination threshold, thereby confirming that broadband haptic effects can be achieved by placing narrowband tactors with mid and high resonant frequencies within the skin’s spatial resolution. We provide guidelines and examples of applying our findings to the design of wearable haptic displays. 

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5. Development of an Innovative Magnetorheological Fluids-based Haptic Device Excited by Permanent Magnets ^*

   https://doi.org/10.1109/WHC49131.2021.9517215  

   Simonelli, Claudia; Musolino, Antonino; Rizzo, Rocco; Jones, Lynette A. (July 2021, IEEE World Haptics Conference)

   null (Ed.)

   A number of haptic displays based on smart fluidic materials such as electrorheological (ERFs) and magnetorheological fluids (MRFs) have been fabricated. These displays are relevant to medical virtual environments where it is important to create realistic simulations of soft tissues with varying stiffness. In this paper a new haptic device is described that was designed in consideration of the limitations of an earlier MRF display. The new prototype consists of 400 permanent magnets (PMs) arranged in a 20x20 array that is underneath a chamber filled with MRF. The magnetic field within the fluid is controlled by 400 PM stepping motors that move the magnets vertically. The magnetic behavior of the device was simulated using FEM which indicated that its spatial resolution was substantially improved when compared to the earlier prototype and that objects as small as 10 mm can be rendered. The device was fabricated and assembled and measurements demonstrated the accuracy of the FE model. Its novelty is demonstrated by the increased intensity of the magnetic field produced and the enhanced spatial resolution. These features will enable the dynamic presentation of haptic information such as object shape and compliance which will be characterized in future psychophysical experiments. 

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