I am working for a safety company and we need to certify how we can use some nitrile gloves with touch screen, I read that your finger needs to be at .5mm to the touch screen to make it work. So depending on the thickness of the glove this could work or not. Any expert on this?
Electronic – Nitrile and touch screens. What is the distance required from your finger to the screen to make it work
touchscreen
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I haven't actually done this, but it seems the problem is the objects you are using are too small and don't have enough ambient capacitance. A human touching something adds capacitive coupling to the environment. Think of the size and surface area difference between a carrot and a carrot+human.
You should be able to use something conductive that is covered by a thin insulating layer, then connect the conducive part to a conductive plate under the iPhone or to ground. In this case "conductive" only needs to be not a good insulator. As you found, even something like a carrot is conductive enough. Try connecting a ground clip to the other end of the carrot, or connect it to the chassis of your machine.
Digitizer or touch screen/panel digitizer.
You can find them as replacements for small LCDs. For example, but these may not be suitable for your multi-touch requirement, and getting application information may be difficult.
They're typically laminated onto the LCD display, and can be removed safely with a controlled temperature hot-air gun (and care, they're usually very thin glass).
Best Answer
Even heavy duty nitrile gloves are a handful of mils thick (e.g., here), so you're unlikely to reach 20 mil for most gloves (roughly 0.5 mm). Some do seem to peak out at 14mil, though, so you need to be a bit careful. This paper talks about designing for glove use. Techniques involve careful tuning of the capacitive field by tweaking the distance between touch screen plates, increasing the power output of the driving electrode, and minimizing cover plate thickness.
As to how to certify, that's probably tougher. Microsoft offers a standard at this site that you might find a suitable starting point. You might find it easier just to develop a suitable specification that satisfies your customers, developing a test, and meeting it. Another option to consider would be working with a touch screen vendor to see what their standards are and whether they have a product that verifiably suits your use.