Touchscreen smartphones and tablets are so intuitive that even babies can easily learn how to use them. So why can't any object work like a touchscreen? Everything from guitars to jelly might soon be able to, thanks to scientists at Carnegie Mellon University who came up with a way to use conductive spray paint to make almost any object touch-friendly.
The touchscreen display on your smartphone carries a small electrical charge that's disrupted every time your finger — which conducts electricity away — touches it. By detecting where on the screen the loss of charge has occurred, the smartphone can figure out where you've touched it. The scientists at Carnegie Mellon University's Human-Computer Interaction Institute have taken a similar approach with their new, experimental technology called Electrick, which is detailed in this paper.
Because random objects like guitars aren't designed to carry an electrical charge, they first have to be upgraded with a coat of conductive spray paint, special films or other materials that will allow them to conduct electricity. But not enough of a charge to shock someone when touched — just enough to allow a series of electrodes placed around the edge of the object to detect a change when a human finger has made contact, re-routing some of that current to the ground. In this case, the researchers used a carbon conductive aerosol paint that's designed for reducing static buildup, or for blocking radio frequency signals in sensitive electronics.
The technique used to turn that spray paint into a touchscreen is called electric field tomography, and works by sending an electrical charge through just two of the electrodes at a time, and then measuring the charge received by all of the others. Any changes in that measured charge can be used to calculate where a human is making contact with the object. The approach isn't as pinpoint accurate as a smartphone's touchscreen, but the researchers have found they can calculate the location of a finger with an accuracy of about one centimetre.
What's most important here, however, is that touchscreen surfaces no longer have to be just small and flat. The Carnegie Mellon Researchers were able to turn a 1.2m by 2.4m sheet of plasterboard into a giant touch-friendly surface, and even a human brain recreated from jelly responded to finger touches using the cheaper Electrick approach. Will it replace the technology used in smartphones and tablets? Probably not, but it could pave the way for everything else in your home to respond in the same way that your mobile devices do.