For this project I decided to use muscle wire to create a shirt with vents that open and close. The vents can be opened via a button embedded in the shirt. The original plan was to have thermistors embedded in the shirt, so that the vents open when the wearer gets hot and close when the wearer has cooled down. However, due to the time needed to construct the shirt, these did not get sewn in.
There are two pieces of muscle wire, cut to about 2 inches long each. The completed vent is in the right sleeve. The vent itself is a slit cut in the sleeve with pieces of elastic sewn along the edge. This was done so that the elastic would pull back on the muscle wire when power was removed, closing the vent. One piece of muscle wire is attached to each side of the slit. The other side of the wire is connected to an elastic band sewn into the arm. This was sewn in so that the muscle wire would have something with resistance to pull against when opening the vent.
The muscle wire was shaped into springs by wrapping it around a thin copper pipe and heating with a cigarette lighter. The springs were then stretched out flat when sewn into the shirt so that they will contract when power is applied. The ends of the wires were crimped with copper tube so that connections could be soldered on. These connections were made using copper tape run along the inside of the shirt.
The muscle wire gets very hot, so insulating cotton had to be sewn into the shirt. A layer was sewn between the wire and the shirt and then another layer was put between the wire and the person’s skin. Cotton worked pretty well to insulate, although it did burn a bit when the wire got too hot. Any fabric thicker than cotton affected the contraction of the muscle wire.