E-ElasticityAn Electrotactile Method to Simulate Elasticity


Overview
Accurately perceiving the elasticity of virtual objects is crucial in virtual reality; however, existing approaches are often cumbersome and impractical.


We introduce E-Elasticity, an electrotactile method for simulating elasticity in VR. The system determines whether the contact surface is in a static or slipping state based on the magnitude of stretching and the pinch force. It conveys this information through synchronized electrotactile and visual feedback, helping users understand and perceive the elasticity of the target object.


User studies have demonstrated that E-Elasticity enables participants to accurately distinguish predefined stiffness levels, offering a lightweight, efficient haptic solution for rendering elasticity in virtual environments.


Previous Work
This research builds on my earlier research, Slip-Grip (CHI ’25).
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ContributionCo-First Author 

DurationNov. 2024 – May. 2025 (7 months)

InstructorTeng Han (Director of HCI lab, Institute of Software, Chinese Academy of Sciences)

Key WordsElectrotactile Technology, VR, Elasticity Perception

StatusSubmitted to CHI 2026





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Research Gap of Creating a Perception of Elasticity
Haptic feedback is essential for enhancing realism and performance in virtual and augmented reality, teleoperation, and VR-based training. Elasticity, a fundamental property in object interaction, remains particularly challenging to render without mechanical actuation. Previous research has used grounded devices, exoskeletons, or pseudo-haptics to simulate elasticity. But these approaches either lack realism or rely too heavily on vision. Slip and contact cues, which are critical to elasticity perception, remain underexplored. 






Electrotactile TechnologyElectrotactile is an emerging technology. It fabricates electrode arrays on thin, flexible printed circuits (FPCs), offering advantages such as flexibility, thinness, light weight, and high precision. Electrotactile devices directly generate local skin current that triggers neural potentials, which the brain interprets as tactile stimuli. By varying waveform, frequency, duration, or location, it can evoke sensations such as vibration, sliding, pressure, or button-clicking. We designed two high-density 7×7 fingertip arrays for the index finger and thumb to support subsequent electrotactile research.




E-Elasticity: An Electrotactile Method to Simulate ElasticityHuman perception of elasticity depends on the relationship between the applied force and the resulting deformation. When stretching one end of an elastic cylinder, the normal force maintains the grip, the lateral force produces deformation, and the reaction force pushes back. To prevent slipping during stretching, the maximum friction generated by the grip force must exceed the lateral reaction force. For a given deformation, higher elasticity produces stronger reaction forces and therefore requires a greater normal grip force. The brain integrates tactile, proprioceptive, and visual cues to infer elasticity.

We introduce E-Elasticity, a method that simulates elasticity via electrotactile stimulation. The system continuously monitors lateral motion and normal force, determines contact states (static friction/slip/release), and generates corresponding visual and electrotactile feedback to modulate the perceived elasticity.







E-Elasticity System OverviewThe pinch force and fingertip position are transmitted to the computer in real time, where the system determines the contact state with the virtual elastic object—gripping with static contact, gripping with slipping contact, or released. Corresponding visual rendering and electrotactile stimulation signals are then generated and delivered to both the VR headset and the fingertip electrotactile interface (updated every 5 ms). 

  • Hand motion is tracked using a Qualisys motion-capture system with three Arqus A5 cameras and QTM 2021.2. 
  • The state-determination and VR-rendering program was developed in Unity 3D with C#. 
  • Visual scenes are streamed to a Meta Quest 2 headset via Oculus Link over a wired connection.





Key Hardware
The electrotactile system includes a driver unit, power module, fingertip interface, and pressure-sensor driver. The fingertip interface, worn on the dominant index finger, integrates two 7×7 FPC electrode arrays (index and thumb sides) and a thin-film SingleTact pressure sensor beneath the thumb-side array. All components are mounted on a rigid PLA frame with retroreflective motion-capture markers, while the pressure-sensor driver sits on the back of the hand. Each electrode array is driven by a high-voltage module built with a Raspberry Pi Pico RP2040, Microchip HV513 chips, and a CH9120 Ethernet controller. The HV513 provides high-voltage outputs for independent electrode control (three states), and the 64-channel array updates within 1 μs. Communication runs via UDP over 10Base-T Ethernet. The system is powered by a 12 V DC supply, with converters generating low-voltage logic rails and a high-voltage HV264 amplifier (0–200 V). Safety features include current monitoring through a voltage divider and self-resetting fuses/relays that cut off high voltage during overload.





Key Algorithm
The system continuously monitors the user’s lateral motion and normal force and determines the contact state (static, slip, or release) on every frame of the Unity program, providing corresponding visual and electrotactile feedback. The distinction between static contact and slip depends on whether the actual grip force 𝐹user exceeds the expected force 𝐹exp; the calculation of the expected grip force required to prevent slipping (𝐹exp) is shown in Fig.E. The release state occurs when there is no contact between the fingertip and the object, during which the cylinder returns to its initial position at a constant velocity.






User Experiments
We conducted a series of experiments to systematically evaluate the perceptual effectiveness of the E-Elasticity system.







Applications





1.    Robotic TeleoperationHaptic feedback in teleoperation control loops can enhance perception, coordination, and complex task performance. During stretching, twisting, or bending with the gripper, electrotactile stimulation on fingers provides haptic feedback of variable resistance and stiffness. We demonstrated this in tasks like:
A.    Twisting a wet cloth
B.    Stretching tissue
C.    Bending a USB cable




2.    Education
Force and kinesthetic feedback enhance learners’ reasoning and conceptual understanding. With its rich force and tactile cues, the E-Elasticity system can support tasks such as:
A.    Perceiving pulleys
B.    Perceiving elastic materials
C. D.    Perceiving gears





3.    VR Gaming and Life
E-Elasticity enables realistic haptic perception in VR gaming and everyday VR interactions, enhancing the accuracy of material perception:
A.    Helps users control slingshots precisely
B.    Simulates fabric elasticity in virtual fashion





4.    Surgical TrainingHaptic feedback conveys key tissue properties, Such as hardness and position. Most surgical training systems lack these cues, hindering surgeons’ quick and accurate perception and response. E-Elasticity addresses this by rendering force and stiffness through electrotactile feedback:
A.    Thyrocricocentesis surgery
B.    Cardiovascular interventions









Hongyu Yue  岳洪宇
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