Matrix – Interdigitation

Optimizing Pressure Matrices: Interdigitation and Interpolation Methods for Continuous Position Input.
Paul Strohmeier, Victor Hakansson, Cedric Honnet, Daniel Ashbrook, Kasper Hornbaek
Publication DOI / Open access

This paper provides resources and design recommendations for optimizing position input for pressure sensor matrices, a sensor design often used in eTextiles. Currently applications using pressure matrices for precise continuous position control are rare. One reason designers opt against using these sensors for continuous position control is that when the finger transitions from one sensing electrode to the next, jerky motion, jumps or other non-linear artifacts appear. We demonstrate that interdigitation can improve transition behavior and discuss interpolation algorithms to best leverage such designs. We provide software for reproducing our sensors and experiment, as well as a dataset consisting of 1122 swipe gestures performed on 17 sensors.


Designing a Multi-Touch eTextile for Music Performances.

Maurin Donneaud, Cedric Honnet, Paul Strohmeier Open access publication

We present a textile pressure sensor matrix, designed to be used as a musical multi-touch input device. An evaluation of our design demonstrated that the sensors pressure response profile fits a logarithmic curve (R² = 0.98). The input delay of the sensor is 2.1ms. The average absolute error in one direction of the sensor was measured to be less than 10% of one of the matrix’s strips (M = 1.8mm, SD = 1.37mm). We intend this technology to be easy to use and implement by experts and novices alike: We ensure the ease of use by providing a host application that tracks touch points and passes these on as OSC or MIDI messages. We make our design easy to implement by providing open source software and hardware and by choosing evaluation methods that use accessible tools, making quantitative comparisons between different branches of the design easy. We chose to work with textile to take advantage of its tactile properties and its malleability of form and to pay tribute to textile’s rich cultural heritage.