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Materials search for college project

atm's Avatar

I'm looking for a sensitive material that can pick up inputs from the force of a tendon contracting.

My and my classmates are trying to create a system for which a disabled person can communicate with the small movements of their index finger and thumb. The area of movement in these two fingers is very small so instead of measuring the force in the fingertips, we decided to try to make a kind of brace that would go around the wrist to measure the tendons when the patient moves the finger tips of the index or thumb.

I'm having trouble finding a push-button like material that would even be able to pick up any kind of pressure these tendons could produce.

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williamj's Avatargold

Perhaps a small coil and center pin. With current running through the coil a slight movement in the pin would cause a small change in voltage.

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williamj's Avatargold

Note to above...

it's the same principle as a microphone.

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rpontius's Avatarg8_badge

I vaguely recall a material (I think it was at www.inventables.com) that measured force directly (i.e., it measured force as it stretched). I didn't immediately find it at that site today but will keep my eyes open.

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williamj's Avatargold

Robert, thanks for shaking some cobwebs loose. I don't know what the name of the material is either but the device or circuit that does the work is an accelerometer. I didn't think of it because those that I am familiar with are for large industrial uses. But after you posted I remembered that some smartphones have them.

Good thinking.

Robert Pontius
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bertventures's Avatargold

AGM, if you are looking for just on-off type of signal, one idea come to mind is to place  small magnet in a glove index finger tip which can activate different switches on a pre wired tablet by placing it right on top of the desired switch. Number of switches will depend on the range of the person ability to move their index finger.  

Robert Pontius
williamj
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kevin_johnson's Avatar

AGM, look into piezoelectric films and sensors.  Good luck.

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