We are developing a product where:

  • a child holds an electronic stylus
  • she uses it in conjunction with a book that has multiple choice questions
  • when she touches the right answer, the stylus will give positive feedback
  • when she touches the wrong answer, the stylus will give appropriate feedback

The way that we currently have implemented this is using conductive ink (black) and a conductivity sensor on the tip of the stylus. We already have a line of products based on this system.

The CORRECT answer has a 1/4" black dot next to it (printed with conductive ink). The WRONG answer has a 1/4" black dot next to it (printed with normal ink).

THE CHALLENGE: - we're making a new system for younger kids - questions have PICTURE multiple choice answers (b/c younger kids want to touch the stylus to the PICTURE and not the black dot) - we want the printing technology to not obstruct the picture

Any ideas on a system here? We're aware of the Leapfrog stylus that reads a small pattern of dots on a page. This technology is too expensive for us.

I'm looking for a list of technologies to investigate for on/off, true/false detection.

  • \$\begingroup\$ The reverse side of the page could selectively have whole pictures backed by conductive ink and capacitance could be used. If the conductive ink is optically dark then you need to do something to avoid the big visual hint like laminate an opaque sheet behind it. \$\endgroup\$ – George White Jan 17 '14 at 0:10
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    \$\begingroup\$ Screw the book and make this into a Android app instead. Then you don't even need a klunky stylus anymore. \$\endgroup\$ – Olin Lathrop Jan 17 '14 at 0:24
  • \$\begingroup\$ Less $ at stake if the book falls in the bathtub, can be larger, lighter for uncoordinated hands, can be used unsupervised and I would recommend iOS before Android. \$\endgroup\$ – George White Jan 17 '14 at 0:34
  • \$\begingroup\$ Good point about the stylus. If capacitive system is used the stylus could be replaced by finger. \$\endgroup\$ – George White Jan 17 '14 at 0:35
  • \$\begingroup\$ Should I just ask about the conductive ink technology here to make it more specific? I'm actually hoping that this community will help with some technology suggestions that I may not be aware of. Can I ask for technologies to look into or will that still be too open ended? \$\endgroup\$ – milesmeow Jan 20 '14 at 19:51

Oh. Simple. Ultraviolet reactive ink. Stylus has a large hollow tip that has a small uv diode with visual sensor of some sort that won't work on just uv light reflecting. Since UV reactive ink glows in the visible range when uv is shined on it, a digital color sensor would work.

Hell, skip the electronics, and just use a uv flashlight or stylus with just a smd uv diode at the tip, turns on when pressed down, the kid sees the picture glow.

  • \$\begingroup\$ I'll expect my 2% royalties in the mail. \$\endgroup\$ – Passerby Jan 22 '14 at 6:22
  • \$\begingroup\$ Didn't Questron do this in the '80s with an IR sensor? \$\endgroup\$ – John U Jan 22 '14 at 10:51
  • \$\begingroup\$ @JohnU Actually that's a great solution (with caveats): UV-reactive clear inks with emission in the infrared + red part of the spectrum are available, so a tiny UV LED in the tip would cause the invisible ink to glow both visibly and in IR. A daylight-filtered IR sensor (Vishay, etc) will sense the IR, and the user can see the red glow. Now the catch: Most UV-reactive inks I can think of are not child safe, and we all know kids love chewing on things. \$\endgroup\$ – Anindo Ghosh Jan 22 '14 at 11:25
  • \$\begingroup\$ A very interesting suggestion...I'll have to look into this. Cost is a big issue, hopefully the ink and sensor is not expensive. \$\endgroup\$ – milesmeow Jan 22 '14 at 21:57

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