Fabric Thermal Display: Ultrasound-Heated Wearable for VR

Fri, 01 Sep 2023 00:00:00 +0000

Overview

Standard thermal wearables rely on Peltier thermoelectric modules — rigid, thick, and power-intensive. Fabric Thermal Display takes a different approach: weave thermally-conductive materials (copper, aluminum mesh) into a fabric glove and excite them with focused ultrasonic waves. The friction heats the conductive fibers, delivering warmth through the fabric itself.

Published at IEEE ISMAR 2023 (IEEE International Symposium on Mixed and Augmented Reality), this project delivers a proof-of-concept for ultrasound-driven textile thermal displays and demonstrates their use in VR object interaction scenarios.

The Problem

Peltier-based thermal gloves work, but they have hard constraints:

Thickness: modules are 3–5 mm, stiff, and change the hand’s natural shape
Power: each Peltier draws 3–10 W continuously
Scalability: covering all fingers requires 5+ modules, complicated wiring, and custom PCBs

Could fabric itself become the thermal actuator — flexible, lightweight, and able to conform to any body shape?

Research Question: Which fabric materials respond best to 40 kHz ultrasonic excitation, and can combinations with conductive materials achieve perceptually meaningful warmth for VR?

Research Approach

We started with a material science study before touching user testing:

Characterization phase: apply ultrasonic energy to 5 fabric types (polyester, cotton, nylon, Lycra, carbon-fiber blend), measure temperature rise over 30 s at three amplitude levels
Composite phase: integrate the best fabric (polyester) with copper mesh and aluminum foil, compare thermal curves
Perceptual phase: user study on thermal detection and level identification with the best material combination
Application phase: integrate into a glove form factor, demonstrate VR use cases

System Design

Ultrasound Setup

Ultrasound driver: Ultrahaptics STRATOS board, 40 kHz carrier, amplitude-modulated 0–100%
Focus geometry: single focal point directed at 15 cm standoff, corresponding to palm contact zone of glove
Thermal measurement: FLIR A315 thermal camera captured surface temperature maps at 9 Hz

Fabric Samples

Material	Peak Temp Rise (100% amp, 30s)	Flexibility	Notes
Polyester	+18.4°C	High	Best performance
Cotton	+9.1°C	High	Poor — high thermal mass
Nylon	+12.3°C	Medium	Acceptable
Lycra	+7.8°C	Very high	Too low output
Carbon fiber	+21.1°C	Low	Best thermal, too stiff

Winner: Polyester + Aluminum — +22.6°C peak, flexible, washable

Glove Design

Polyester base with 0.1 mm aluminum foil laminate on palm zone
Total glove weight: 28 g (vs. 95 g for Peltier glove baseline)
No wiring — ultrasound is contactless

Unity VR Integration

Unity 2021 LTS + Oculus Integration SDK (Quest 2)
Custom FabricHapticManager: maps virtual object surface temperature to ultrasound amplitude via lookup table
Demonstrated VR scenarios: picking up hot metal ingot, holding warm beverage, touching cold ice sculpture
Haptic rendering loop runs at 90 Hz, matching display refresh

User Evaluation

Study 1 — Detection Thresholds

N = 12 participants
Task: signal detection (yes/no) across 5 amplitude levels, 2-AFC paradigm
Measure: warm detection threshold (WDT)
Result: mean WDT = 38% amplitude (≈ +7.2°C skin surface delta)

Study 2 — Level Identification (Thermal JNDs)

N = 16 participants
Task: categorize warmth into 4 levels (none, low, medium, high) from ultrasound-heated glove
Condition: fabric-only vs. fabric+copper vs. fabric+aluminum
Result: fabric+aluminum achieved 78% accuracy for 4-level identification, significantly outperforming fabric-only (54%, p<.01) and fabric+copper (66%, p<.05)

Results & Key Findings

Polyester is the optimal base fabric for ultrasonic thermal generation among tested materials
Aluminum lamination provides +4.2°C improvement over copper at the same power setting
Users could reliably distinguish 4 thermal levels through the glove, meeting the threshold needed for meaningful VR thermal rendering
No participant reported discomfort over 20-minute continuous wear sessions

Impact

📄 Published: IEEE ISMAR 2023 — IEEE International Symposium on Mixed and Augmented Reality
DOI:
The material findings fed directly into the Fiery Hands glove substrate design and the broader thermal-wearables research program at MI Lab

IEEE ISMAR | Haokun Wang