The TPad Fire is a tablet device that is able to vary friction between your finger and the surface of the screen. The main components are a TPad (tee-pad) variable friction surface, a Kindle Fire™, a circuit board, a battery, and a case.
TPad- Variable Friction Surface
The variable friction surface or TPad (tactile pattern display) operates by vibrating the glass ultrasonically. This doesn’t feel like a vibration or “buzz,” rather it feels slippery, like your finger is floating on a soft cushion of air. By increasing or decreasing the amplitude of vibration, different levels are achieved. There is no electrical stimulation involved, only microscopic motion of the glass beneath your fingertip. Instructions on how to build a TPad can be found here.
Applications for the TPad Fire are written in the Android (Java) programming language and are loaded and run just like a normal Android app. No modification or unlocking of the tablet is necessary. The communication is handled by the debug bridge. An example application can be downloaded from Github here. It is recommended that you start with the example application as it handles all of the communication with the microcontroller. The software for the microcontroller can be found here
The case that we show in the pictures is a laser cut acrylic top plate with a thermoformed plastic back case. However, it is also possible to 3D print this design or make your own. The CAD model of the case can be downloaded here.
Availability and Rights
In order to maximize the availability of the device, open-source, free to use, and commonly available technologies were used wherever possible. All electronic components including the piezoelectric actuators for the TPad Fire can be purchased from major online electronics suppliers. The communication protocol between the tablet and the microcontroller is supported by the Android operating system. The circuit board design, the case design, and the software are released under Creative Commons Attribution-NonCommercial-ShareAlike license. The TPaD technology is protected by US and international patents owned by Northwestern University. Participants in the TPaD Tablet project are granted the right to use the TPaD technology for noncommercial and research purposes only.