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As I am disabled I have to use a headstick (see picture below) to do stuff on the computer. I also have a phone with a resistive touchscreen, which works well with my headstick.

headstick

But here is the problem: I cannot operate any devices with capacitive touchscreens, since the tip of the headstick is made of plastic. I heard, though, of conducting polymers, and wondered if my problem could be solved using those. So basically I thought of just making a new tip of such a conductive plastic.

What do you think about this approach? How expensive are these materials? What can yu say about their electrical properties vs. human skin? Would this be a good idea?

Would something different work? Like putting a little coil inside the tip of the headstick?

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  • \$\begingroup\$ You've come to the right place to ask about the design of capacitive touchscreens and how to design a stylus for these screens, but (1) this is not a forum, and (2) this is not a place to ask about where to buy consumer electronics (like a capacitive stylus <- Link to Amazon where you can buy the thing you need already built :)). I'll leave the technical question here, though, as the principles behind these styluses (styli?) are interesting. \$\endgroup\$ – Kevin Vermeer Oct 20 '11 at 20:15
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    \$\begingroup\$ FYI, you may find that a stylus is not enough - you may have to put a conductive plate as a sort of ground plane behind the phone - often times they will not register finger touches reliably if they are on a non-conductive surface but work fine when over a conductive one or held in a hand. \$\endgroup\$ – Chris Stratton Oct 21 '11 at 5:55
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As a quick experiment, a rolled up piece of metalized anti-static bag sometimes can work as a capacitive-screen stylus.

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  • \$\begingroup\$ Yes, indeed. It did respond, but not very reliably though. Dont know if its because I didnt have good contact with the bag (wrapped it around the stick) or something else \$\endgroup\$ – Evgeni Oct 22 '11 at 14:37
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Instructables has a guide to making your own "iPhone gloves". Here, they use some conductive thread between finger and outer surface. I assume you could do the same between your head and the end of the stick.

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The tip is presumably made of plastic to prevent damage to the touched surface.

Butyl rubbers are available which are loaded with carbon-black to make them conductive. A tip of such rubber with a conductive path may work.

You can mix carbon-black into various adhesives to make them conductive. This may includes silicone rubbers and epoxy resins. Conductive silicone rubber is liable to be non damaging.

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  • \$\begingroup\$ Simply conductive is not enough, as lightly touching a capacitive phone screen with a blunt metal object will demonstrate. \$\endgroup\$ – Chris Stratton Oct 21 '11 at 5:53
  • \$\begingroup\$ @Chris Actually, a capacitive touchscreen reacts to metal. You can type with a spoon. \$\endgroup\$ – Evgeni Oct 21 '11 at 11:34
  • \$\begingroup\$ @Evgeni B. Yours might react to metal objects, mine does not. So it's not a reliable solution. \$\endgroup\$ – Chris Stratton Oct 22 '11 at 3:23
  • \$\begingroup\$ @Chris What kind of phone do you have? I tried a Samsung Galaxy S and a Sony Experia Arc and both responded well to touches with metal \$\endgroup\$ – Evgeni Oct 22 '11 at 14:23
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Capacitive touch screen systems react to a local change of capacitance on the touch panel. Human finger as well as conductive material like a coin are working because electronic charges attracted by them. Putting a conductive surface on top of an insulator (the touch screen cover is like an insulator) is making a capacitor, right?

What is important is not only the conductive property of the touching material, but also the size of contact area. The larger the better!

Remind this formula enter image description here

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