Paper-Based, Capacitive Touch Pads

1. Aaron D. Mazzeo¹, 
2. William B. Kalb¹,
3. Lawrence Chan¹, 
4. Matthew G. Killian¹,
5. Jean-Francis Bloch², 
6. Brian A. Mazzeo³,
7. George M. Whitesides^1,4,*

Article first published online: 27 APR 2012

DOI: 10.1002/adma.201200137

This paper describes low-cost, thin, and pliable touch pads constructed from a commercially available, metallized paper commonly used as packaging material for beverages and book covers. The associated electronics with the individual keys in the touch pads detect changes in capacitance or contact with fingers by using the effective capacitance of the human body and the electrical impedance across the tip of a finger. To create the individual keys, a laser cutter ablates lines through the film of evaporated aluminum on the metallized paper to pattern distinct, conductive regions. This work includes the experimental characterization of two types of capacitive buttons and illustrates their use with applications in a keypad with 10 individually addressable keys, a keypad that conforms to a cube, and a keypad on an alarmed cardboard box. With their easily arrayed keys, environmentally benign material, and low cost, the touch pads have the potential to contribute to future developments in disposable, flexible electronics, active, “smart” packaging, user interfaces for biomedical instrumentation, biomedical devices for the developing world, applications for monitoring animal and plant health, food and water quality, and disposable games (e.g., providers of content for consumer products).