From this pdf[1] it seems fingers have 3-5 cold sensing points per square cm, with cold sensing points being about 10x as prevalent as warm sensing points.
So I was thinking about using a combination of a thermoelectric cooler[2] coupled to some thin metal rods, which have individually wound coils around them near the top. The rods would be mounted flush to allow touching all of them at once. The cooler would ensure the rods are normally cold, and the coils would provide induction heating.
Thus by changing which coils are activated, the different rods would be either cold or not, and due to the active cooling and relatively low thermal mass should change state quite quickly. At least that's the idea.
Though perhaps we just don't have enough sensitivity in our fingers to pick this up. And it wouldn't work well for a portable device due to power draw.
edit: Found this[4] paper where they try a temporal method instead of spatial method to use temperature to convey information.
I have thought of a similar design, but little solenoids inject themselves into the cold path bridging the gap, the TEC would chill a huge thermal mass and then the individual rods could be chilled and heated rather rapidly.
I love unique interface ideas, and this one definitely counts.
What are your thoughts on how to account for the user's fingers heating up the interface rods? I'm imagining someone going back to read a previous character, and their fingers having essentially "reset" the character from body temp.
This was just off the top of my head, but I imagined the thin rods having low enough thermal mass that the active TEC cooling would not cause fingers to significantly heat up the rods.
That is, the TEC cooler should be able to relatively quickly lower the temperature after the finger is removed.
Again, off the top of my head idea so no idea if it would work or not, but doing a quick viability check should be relatively easy and cheap.
From this pdf[1] it seems fingers have 3-5 cold sensing points per square cm, with cold sensing points being about 10x as prevalent as warm sensing points.
So I was thinking about using a combination of a thermoelectric cooler[2] coupled to some thin metal rods, which have individually wound coils around them near the top. The rods would be mounted flush to allow touching all of them at once. The cooler would ensure the rods are normally cold, and the coils would provide induction heating.
Thus by changing which coils are activated, the different rods would be either cold or not, and due to the active cooling and relatively low thermal mass should change state quite quickly. At least that's the idea.
Though perhaps we just don't have enough sensitivity in our fingers to pick this up. And it wouldn't work well for a portable device due to power draw.
edit: Found this[4] paper where they try a temporal method instead of spatial method to use temperature to convey information.
[1]: https://web.as.uky.edu/Biology/faculty/cooper/bio350/Bio350%...
[2]: https://en.wikipedia.org/wiki/Thermoelectric_cooling
[3]: https://en.wikipedia.org/wiki/Induction_heating
[4]: https://www.mdpi.com/2306-5354/10/10/1156