Together with Viktor Miruchna, David Lindlbauer and Jörg Müller we synthesized an environmentally sensitive hydrogel (Smart Gel), which tactile properties can be controlled using heating. We use it to construct a tactile feedback layer for touch screens.
The gel-based layer can selectively transition between soft and stiff to provide tactile multi-touch feedback. It is flexible, transparent when not activated, and contains no mechanical, electromagnetic, or hydraulic components, resulting in a compact form factor (a 2 mm thin touchscreen layer for our prototype). The activated areas can be morphed freely and continuously, without being limited to fixed, predefined shapes. GelTouch consists of a poly(N-isopropylacrylamide) gel layer which lters its viscoelasticity when activated by applying heat (>32°C). We present three different activation techniques: 1) Indium Tin Oxide (ITO) as a heating element that enables tactile feedback through individually addressable taxels; 2) predefined tactile areas of engraved ITO, that can be layered and combined; 3) three-dimensional arrangements of resistance wire that create thin tactile edges. We present a tablet with 6×4 tactile areas, enabling a tactile numpad, slider, and thumbstick. We show that the gel is up to 25 times stiffer when activated and that users detect tactile features reliably (94.8%).