Stick&Slip - Altering Fingerpad Friction via Liquid Coatings

September 2022 - June 2023

Published: CHI '24; Also showcased at the 2024 IEEE Haptics Symposium
Authors: Alex Mazursky, Jacob Serfaty, Pedro Lopes
Affiliation: UChicago Human-Computer Integration Lab

Video Showcase

Abstract

We present Stick&Slip, a novel approach that alters friction between the fingerpad & surfaces by depositing liquid droplets that coat the fingerpad. The liquid coating modifies the finger’s coefficient of friction, allowing users to feel surfaces up to ±60% more slippery or sticky. We selected our fluids to rapidly evaporate so that the surface returns to its original friction. Unlike traditional friction-feedback, such as electroadhesion or vibration, our approach: (1) alters friction on a wide range of surfaces and geometries, making it possible to modulate nearly any non-absorbent surface; (2) scales to many objects without requiring instrumenting the target surfaces (e.g., with conductive electrode coatings or vibromotors); and (3) both in/decreases friction via a single device. We identified nine liquids and characterized their practicality by measuring evaporation rates, etc. To illustrate the applicability of our approach, we demonstrate how it enables friction in virtual/mixed-reality or, even, while using everyday objects/tools. 

What did I contribute?

• Designed and programmed an Augmented Reality demo for the Microsoft Hololens 2 using the Unity game engine

  • Created an alignment system that allows administrators to align the game with a real-world surface before starting the game

  • Implemented a smart tracking system that allows a virtual car to smoothly drive alongside the user's finger on a 2D surface

    • Modified this tracking system to support driving along certain predefined 3D surfaces such as flat and curved ramps

  • Programmed a Mario-kart-inspired racing management system that defines races through predefined checkpoints and spawns in new regions  whenever a checkpoint is reached

  • Programmed haptic detection zones and integrated them into the racing system to spawn haptic zones when the car crosses key environmental features

• Organized and ran a 12-person user study to evaluate the effectiveness of the haptic effects when playing the racing game

• Worked with Alex to design an improved communication API for the fluid-dispensing device

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