MudPad: Fluid Haptics for Touch Surfaces

MudPad is a prototype system to explore the possibilities for localized active haptic feedback on touch surfaces. Since the introduction of the iPhone, touchscreens became very common and most people probably have used one by now. While using a touchscreen is often described as enjoyable due to more direct interaction techniques, such screens also lack tactile feedback. Over the last years mobile phones with tactile feedback were released. But as of yet they only provide feedback in a global manner applied to the whole screen, usually depending on vibrotactile feedback. Recently, first prototypes with localized tactile texture displays were presented such as TeslaTouch by Olivier Bau et al. and also by companies such as Toshiba and Nokia. Still, these devices are not capable of producing different tactile feedback for each finger touching the screen. MudPad takes a different approach: it is capable of producing localized active haptic feedback using magnetorheological (MR) fluid and an array of electromagnets to actuate the fluid. This fluid is called a "smart fluid" because one of its properties - its viscosity - can be controlled by a magnetic field:

It consists of carbonyl iron powder dissolved in glycerin. The viscosity of this fluid, when in off state, depends on the percentage of iron powder but is generally rather low (comparable to oil). When it is exposed to a magnetic field it immediately turns stiff. The reaction time of the fluid is within 2ms thereby making it suitable for real-time interactions.

The prototype below contains 84 electromagnets that are arranged in a 12x7 array. Each magnet can be controlled individually to create a tactile sensation at that specific location only. For the ACM CHI 2010 student research competition I created a small travel version (right image). It only contains one electromagnet and five sensors, each of which triggers a different feedback pattern.

Publications

Yvonne Jansen, Thorsten Karrer, Jan Borchers. MudPad: tactile feedback and haptic texture overlay for touch surfaces. ITS '10 ACM International Conference on Interactive Tabletops and Surfaces, 2010 (best note award)

Demo: Yvonne Jansen, Thorsten Karrer, Jan Borchers. MudPad: tactile feedback for touch surfaces. CHI EA '11 CHI '11 extended abstracts on Human factors in computing systems, 2011

Demo: Yvonne Jansen, Thorsten Karrer, Jan Borchers. MudPad: a tactile memory game. ITS '10 ACM International Conference on Interactive Tabletops and Surfaces, 2010 (best demo award)

Demo: Yvonne Jansen, Thorsten Karrer, Jan Borchers. MudPad: localized tactile feedback on touch surfaces. UIST '10 Adjunct proceedings of the 23nd annual ACM symposium on User interface software and technology, 

Student research competition: Yvonne Jansen. Mudpad: fluid haptics for multitouch surfaces. CHI EA '10 Extended abstracts on Human factors in computing systems, 2010