I find with IR touch based e-readers the film and screen are often smaller and more lightweight because it uses infrared beams built into the bezel. (goodereader.com)
The sensing works with a separate infrared beam, which travels alongside the ultraviolet beam in the fiber and through the polymer thread. (sciencemag.org)
This team created a solution to energy waste; a system of infrared beams which work together to identify when no - one is nearby, and switch off the unnecessary streetlights in the area. (education-today.co.uk)