Detecting a Thumb Touching a Finger on Same Hand?

[one_raven]

Would it be feasible to wear something on a wrist that could detect when the wearer's thumb is touching another finger on that same hand? Through changes in capacitance and/or resistance maybe – or something?
If so, would it be able to tell which finger the thumb is touching?
Where on the finger?

If not something worn on the wrist, perhaps a ring worn on the thumb (or both – as long as they're not hard-wired together?
Perhaps transmitting an RF signal and measuring the interference – kind of like the way a metal detector works?
Something else (other than visual)?

 

[berkeman]

Would it be feasible to wear something on a wrist that could detect when the wearer's thumb is touching another finger on that same hand? Through changes in capacitance and/or resistance maybe – or something?
If so, would it be able to tell which finger the thumb is touching?
Where on the finger?

If not something worn on the wrist, perhaps a ring worn on the thumb (or both – as long as they're not hard-wired together?
Perhaps transmitting an RF signal and measuring the interference – kind of like the way a metal detector works?
Something else (other than visual)?

If the user were wearing a special glove, it would make things a lot easier. Is that a possibility? Is this for a game input device?

 

[one_raven]

Not a game input device, necessarily, but an input device.
No gloves or finger sensors. It has to be as unobtrusive as possible. Either a self-contained wrist device that could pass as a bracelet or watch, a self-contained ring that just looks like a ring, or both, connected wirelessly.

Wouldn't touching a finger affect the electrical properties of your thumb in some measurable way?

 

[berkeman]

Wouldn't touching a finger affect the electrical properties of your thumb in some measurable way?

Not that I can see with a quick glance. Perhaps others can see something I'm missing.

Not a game input device, necessarily, but an input device.
No gloves or finger sensors. It has to be as unobtrusive as possible. Either a self-contained wrist device that could pass as a bracelet or watch, a self-contained ring that just looks like a ring, or both, connected wirelessly.

You probably could detect the thumb touching a finger by mechanically sensing the movement of the proximal (near) end of the 4 finger metacarpal bones. If you feel just distal (out past the end) of your wrist bones where the metacarpal bones join the wrist, you can feel each finger's metatarsal bone lift slightly when you touch your thumb to that finger. It might take some experimenting to see how good the signal-to-noise ratio is, though. You could make a sort of bracelet that extends just distal past the wrist socket to sense the movement of the ends of the 4 finger metacarpals...

http://www.physio-pedia.com/images/a/a2/Hand_and_wirst_bones.png

 

[one_raven]

What if the ring transmitted a signal, using the thumb as an antenna, and the bracelet were a receiver?
Would touching a finger change the structure of the "antenna" and allow the bracelet pick up on the difference?

 

[1rel]

...for some reason I can't find the right keyword anymore, but a while ago I did some searching on some similar concept, and there's it seems to be some active research going on in this area right now.

Some things that showed up right before:

Body area networks: https://en.wikipedia.org/wiki/Body_area_network:

A body area network (BAN), also referred to as a wireless body area network (WBAN) or a body sensor network (BSN), is a wireless network of wearable computing devices

Intra-Body Communication for Biomedical Sensor Networks,
Comparison of Approaches to Intra-Body Communication

The basic idea seems to be to use the body as a medium to transmit/receive a signal.

What if the ring transmitted a signal, using the thumb as an antenna, and the bracelet were a receiver?
Would touching a finger change the structure of the "antenna" and allow the bracelet pick up on the difference?

Or with some kind of thimble? On the thumb that makes good contact to the skin underneath, and then measure the resistance/capacitance (or some other property, like frequency attenuation of an electrical signal or even acoustic/vibrational signal), when sent out through the hat, and receive again on the surface of the thimble... to discern between every of the 4 fingers. Or even those of the other hand?

 

[jim hardy]

electronics these days is so fantastic

maybe one could look ?
https://www.amazon.com/dp/B00GJUVQOY/?tag=pfamazon01-20

 

[one_raven]

A passive NFC tag embedded into the ring... Could touching the thumb to one of the fingers cause a slight shift in the effective length of the tag's loop antenna?

 

[velvet thunder]

Have you seen Google's Project Soli?

https://atap.google.com/soli/

 

[berkeman]

Have you seen Google's Project Soli?

https://atap.google.com/soli/

That's really outstanding, Thunder! Thanks

 

[RonL]

Have you seen Google's Project Soli?

https://atap.google.com/soli/

Looks similar too and a very modern condensed version of this ?

 

[one_raven]

https://atap.google.com/soli/

That's pretty sweet!

 

[Baluncore]

If you sense the electrical motor neuron activity to the muscles that pull on the various tendons, then you will see a difference when pressure is applied between different sections of different fingers.

Maybe you are building a card counter's computer interface ?
https://en.wikipedia.org/wiki/Finger-counting
https://en.wikipedia.org/wiki/Chisanbop