Wearable Keyboard Using Conducting Polymer Electrodes on Textiles

A stretchable keyboard based on conducting polymer electrodes patterned on a knitted textile was demonstrated. Electrodes were made of the conducting polymer poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) and coated with polydimethylsiloxane (PDMS), and develop capacitance sensors that respond to touch by a human finger. The relevant mechanical and electrical properties were evaluated and a keyboard that works when worn by a volunteer was also demonstrated. Capacitance sensing was selected as the keyboard's mechanism of operation. A PEDOT:PSS electrode was patterned on the textile using a recently developed technique. PDMS was deposited on a negative master made of polyimide and was transferred on the textile. The conducting polymer was subsequently brush-painted on the textile, and insulated with a layer of PDMS. Touch was detected by changes in the capacitance associated with the PEDOT:PSS/PDMS/counter electrode structure, where the counter electrode is the human finger. The horseshoe-shaped structure of the textile offered a high degree of stretchability (up to 30%), and the keyboard was able to read tactile input from the finger of a volunteer