We live in an increasingly touchy-feely tech world, with various ways for smart phones and tablet computers to sense our finger taps and gestures. Now a new type of touch technology, developed by researchers at the University of Munich and the Hasso Plattner Institute, could lead to touch sensitivity being added to everyday items such as clothing, headphone wires, coffee tables, and even pieces of paper. The new touch technology relies on something called Time Domain Reflectometry (TDR), which has been used for decades to find damage in underwater cables. TDR is simple in theory: send a short electrical pulse down a cable and wait until a reflection of the pulse comes back. Based on the known speed of the pulse and the time it takes to come back, software can determine the position of the problem—damage in the line or some sort of change in electrical conductance.
The TDR implementation is straightforward, For one demonstration, researchers taped two parallel strips of copper to a piece of paper. Metal clips connect the copper strips to a pulse generator and detector. Pico-second-long electrical pulses are sent out, and if there's any change in capacitance between the two strips of copper—produced by a finger close to or touching the wires, for instance—part of the pulse is reflected back. An oscilloscope shows the changing waveform produced by the reflected pulse, and software on a connected computer analyzes the waveform to determine the position of the touch. To make a surface touch-sensitive requires only two wires (or metal traces of conductive ink), which can be configured in various patterns to get the necessary coverage. In contrast, a capacitive touch screen like the one in the iPhone uses a matrix of wires coming out of two sides of the screen.
More information:
http://www.technologyreview.com/computing/39036/
More information:
http://www.technologyreview.com/computing/39036/