Simon Voelker, Christian Cherek, Jan Thar, Thorsten Karrer, Christian Thoresen, Kjell Ivar Øvergård, Jan Borchers
In Proceedings of UIST' 15, ACM, 351 - 356
Publication year: 2015



Tangible objects on capacitive multi-touch surfaces are usually only detected while the user is touching them. When the user lets go of such a tangible, the system cannot distinguish whether the user just released the tangible, or picked it up and removed it from the surface. We introduce PERCs, persistent capacitive tangibles that “know” whether they are currently on a capacitive touch surface or not. This is achieved by adding a small field sensor to the tangible to detect the touch screen’s own, weak electromagnetic touch detection probing signal. Thus, unlike previous designs, PERCs do not get filtered out over time by the adaptive signal filters of the touch screen. We provide a technical overview of the theory be- hind PERCs and our prototype construction, and we evaluate detection rates, timing performance, and positional and angular accuracy for PERCs on a variety of unmodified, commercially available multi-touch devices.Through their affordable circuitry and high accuracy, PERCs open up the potential for a variety of new applications that use tangibles on today’s ubiquitous multi-touch devices.

The Talk

The Team

PERCs is a research project by Simon Voelker, Christian Cherek, Jan Thar, Torsten Karrer, and Jan Borchers from the Media Computing Group and Christian Thoresen and Kjell Ivar Øvergård from the University College of Southeast Norway. It is funded in part through the German B-IT Foundation and through the MACS project.


 author = {Voelker, Simon and Cherek, Christian and Thar, Jan and Karrer, Thorsten and Thoresen, Christian and \Overg{\aa}rd, Kjell Ivar and Borchers, Jan},
 title = {PERCs: Persistently Trackable Tangibles on Capacitive Multi-Touch Displays},
 booktitle = {Proceedings of the 28th Annual ACM Symposium on User Interface Software \&\#38; Technology},
 series = {UIST '15},
 year = {2015},
 isbn = {978-1-4503-3779-3},
 location = {Charlotte, NC, USA},
 pages = {351--356},
 numpages = {6},
 url = {},
 doi = {10.1145/2807442.2807466},
 acmid = {2807466},
 publisher = {ACM},
 address = {New York, NY, USA},
 keywords = {capacitivemulti-touch, tabletop interaction, tangible user interfaces},