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Most interfaces built with touch screens require the user to constantly look at them in order to see which part of the screen they are touching. Tactile feedback on touch screens would enhance their utility in many situations.
This idea is to use electrical stimulation to provide tacticle feedback.
The electrical stimulation would be accomplished by applying high voltage electricity in a software controllable manner to portions of the screen. This would allow the user to "feel" lines, buttons, and dot patterns to allow them to feel their way to the appropriate parts of the interface. Pressing harder would activate these controls.
One method which could accomplish this application would be to lay out a 2 layer grid of horizontal and vertical transparent conductors across the screen. A finger would touch the exposed part of vertical conductor as well as an exposed part of a horizontal conductor, completing the circuit and providing an electrical path through the nerves in the finger. Current would be regulated in order to provide consistent sensation among varying skin resistances. The very thin nature of the conductors would act as a passive safety device in order to further limit current. The grid of conductors would be scanned in a method similar to a passive matrix LCD in order to provide any pattern desired to either complement what is being displayed on the screen or provide feedback for actions such as a button press.
The grid of conductors used for output could also be used in place of a traditional capacitive or resistive touch screen input sensor in order to cut costs.
US patent 5,977,867
similar invention - touch screen is mounted with at least one vibrator to produce a tactile feedback [xaviergisz, Apr 30 2006]
||Up the voltage when the user accesses naughty websites or as a negative reinforcer for pushing the wrong buttons. "Hmmm lets try this, hehe--ZZZORCH! Yow!"