Generating Multimodal Textures with a Soft Hydro-Pneumatic Haptic Ring

TL;DR

The paper tackles rendering naturalistic, multimodal tactile textures in XR by introducing a soft silicone haptic ring that delivers independent pressure, thermal, and vibrotactile cues to the proximal phalanx. It combines pneumatic actuation for contact and vibration with a hydraulic path for temperature, paired with a data-driven, action-based rendering pipeline that maps exploratory actions to sensory cues using a SENS3-derived dataset and a semi-infinite heat-transfer model to compute display temperature $T_{display}$. The contributions include the first soft multimodal ring of its kind, a robust texture-rendering methodology, and a demonstration that participants can match virtual textures to real ones with up to $90\%$ accuracy, highlighting the critical role of multimodal cues, especially temperature. This work paves the way for immersive XR wearables that preserve natural hand movements while delivering rich tactile feedback, with practical implications for future MR/AR interactions and wearable haptics design, albeit with acknowledged limitations in wearability and cue fidelity that invite further hardware simplification and integration.

Abstract

The growing adoption of extended reality, XR, has driven demand for wearable technologies that can replicate natural tactile sensations and allow users to interact freely with their surroundings using bare fingers. However, most existing wearable haptic technologies that support such free interactions can deliver sensations across limited tactile modalities. Here, we introduce a soft haptic ring and a data-driven rendering methodology to generate multimodal texture sensations. The device integrates pneumatic and hydraulic actuation to simulate roughness, thermal, and softness cues on the proximal phalanx, enabling users to explore surroundings naturally with their fingertips. The rendering methodology dynamically modulates those cues based on the user's exploratory actions. We validated our approach by conducting a user study with fifteen participants, who matched six virtual textures generated by the ring to their real counterparts and rated their perceived sensations. Participants achieved up to ninety percent accuracy in texture matching. The adjective ratings confirmed that the ring delivers distinct, perceptually rich stimuli across all rendered sensations. These findings highlight the ring's potential for immersive XR applications, offering diverse tactile feedback without restricting physical interaction.

Figures (11)

• Figure 1: a) The soft haptic ring worn on the finger. b) The ring can provide multisensory cutaneous feedback via fluidic actuators. A pneumatic chamber at the finger's base provides pressure and vibration cues, while a coiled hydraulic tube around the proximal phalanx transmits thermal sensations. c) The pneumatic actuator is in inflated mode.
• Figure 2: Schematic of the pneumatic circuit. The 2/2 solenoid valve remains open to generate vibration cues and is closed for pressure cues.
• Figure 3: Schematic of the hydraulic circuit.
• Figure 4: Rendering modalities and actuation mechanisms of the soft haptic ring in the proposed action-based rendering methodology.
• Figure 5: The texture data used from SENS3 Database Balasubramanian2024. a) Pressing force as a function of time used for softness rendering. b) Skin temperature over time used for thermal rendering. c) Top view images of surfaces used for roughness rendering.