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Researchers Create Touchpads With a Can of Spray Paint (phys.org) 31

Researchers at Carnegie Mellon University have figured out a way to turn any surface into a touchpad using none other than spray paint. "Walls, furniture, steering wheels, toys and even Jell-O can be turned into touch sensors with the technology, dubbed Electrick," reports Phys.Org. From the report: The "trick" is to apply electrically conductive coatings or materials to objects or surfaces, or to craft objects using conductive materials. By attaching a series of electrodes to the conductive materials, researchers showed they could use a well-known technique called electric field tomography to sense the position of a finger touch. With Electrick, conductive touch surfaces can be created by applying conductive paints, bulk plastics or carbon-loaded films, such as Desco's Velostat, among other materials. Like many touchscreens, Electrick relies on the shunting effect -- when a finger touches the touchpad, it shunts a bit of electric current to ground. By attaching multiple electrodes to the periphery of an object or conductive coating, Zhang and his colleagues showed they could localize where and when such shunting occurs. They did this by using electric field tomography -- sequentially running small amounts of current through the electrodes in pairs and noting any voltage differences. The tradeoff, in comparison to other touch input devices, is accuracy. Even so, Electrick can detect the location of a finger touch to an accuracy of one centimeter, which is sufficient for using the touch surface as a button, slider or other control, Zhang said. You can watch a video about how it works here.
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Researchers Create Touchpads With a Can of Spray Paint

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  • by xxxJonBoyxxx ( 565205 ) on Monday May 08, 2017 @07:25PM (#54381397)
    I remember there were a few electronics kits you could buy in the 1980's that did the same trick with pencil "lead". First, you scribbled onto some paper, then you attached a lead and pressed onto the graphite square you drew to make different sounds, etc.
  • You might be able to get one centimeter of accuracy, but that's only if you calibrate each individual device. You can't even create a design and calibrate that: variations in how you spray the conductive material will greatly effect how each individual device performs, regardless of how other instances perform. Each calibration will be different. Temperature and other factors may also affect this technique, so an individual calibration may not even be good over time.

    Perhaps you could make something simple,

  • Nothing new to see here. People have been doing touch interfaces with AVR and other microcontrollers long before and have used a variety of conductive materials for that (copper traces, aluminium, very thin graphite on glass etc.).

    This story boils down to: Look Ma, we bought a can of graphite spray and connected it to some touch-sensor interface likes thousands have done before us.

  • Accuracy of +/â" 1cm is good enough for buttons? Maybe if your test users have a green complexion and talk in two-word sentences...
    • I read an article long ago about how you can't truly understand an engineering design unless you understand the context. One example they used was the dashboard of the Saab automobile. Saab, in those days, had a very clunky looking dashboard with large controls spaced far apart. To Americans it looked ugly. What they pointed out in the article was that the Saab was designed in Sweden, by Swedish engineers. The engineers assumed the driver would be wearing winter gloves most of the year and so designed the c

  • It's not like you just grab some rattle cans and go to town. It sounds more like they put in an array of sensors, connect that to special software, and apply a coating of special conductive paint. I guess we can just say that researchers have learned how to create microprocessors out of rocks as well.
  • In other news, Banksy has just declared himself an "urban control pad integrator".

  • http://web.stanford.edu/class/sts175/NewFiles/Negroponte.%20Being%20Digital.pdf [stanford.edu]

    That's only a few pages, but it gives you an idea. I had to read Negroponte's book as assigned reading, and I remember he predicted painted-on computer displays. This spray-on touchpad sounds like we're one step closer!

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