TWiki > Rise Web>TWikiUsers > MelodyWu>ArmTwister (01 May 2007, MelodyWu? )

Arm Twister Skin Stretch Project

Skin stretch can be applied to a person's arm by twisting in opposite directions, in a manner similar to indian burns that kids do to each other. We want to make a portable device that is easily attachable to a person's arm so that we can study the responsiveness to skin stretch while the body is in motion (running, jogging, walking, etc). Part of the challenge is to make the device easily adjustable to differences in arm shapes and sizes.

Current Prototypes:

1. Big rings - The idea was to transpose the current rotational skin stretch device into a wearable device that encirles the entire arm. The end effectors are adjusted to fit different arm shapes and sizes. We found that this takes a long time to set up and the rings are too bulky and heavy that when the arm is moved pressure is felt on certain end effectors, which overshadows any sensation due to skin stretch/twisting.

2. Sorbothane belt - Since the big rings were too heavy and hard to set up, we experimented with materials that stick and conform easily to different shapes. I was going to try to make holes in the sorbothane so that it could be worn like a watch, but it sticks really well to itself and my skin so I didn't have to. It seemed like the skin was twisting the most only at the point of force application (pulling) and less the farther you go from that point. I thought about using push-pull cables glued to the sorbothane to actuate the pulling motion.

3. TENS electrodes - The pressure sensitive adhesive on the electrodes seemed to stick really well to skin and peel off easily without removing much arm hair.

4. Velcro-sorbothane belt - This goes along the same idea as the sorbothane belt (see above) but the sorbothane is actually not really stretched to wrap it around your arm; the velcro is bendable to fit the shape of different arms, and ensures that the sorbothane treads stay in contact with the skin. The stronger sensation is created with more, smaller sorbothane tread pieces, causing the tissue/fat in the arm to bunch up together when a twist is applied. We might need to investigate the sensation of bunching some more in trying to figure out what works and what doesn't.

5. Double-sided sticky tape in addition to Velcro-sorbothane belt - The addition of double-sided sticky tape didn't seem to affect the overall sensations much; probably just really made sure the sorbothane treads were in contact with the skin at all times.

-- MelodyWu? - 28 Apr 2007

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