### Flying Kites

For my shape changing textile assignment I wanted to play with not only shape but also exposing layers/color and programmed movement.  I created two blocks of color overlayed on top of two additional pieces of felt so that when they would lift up, they would expose a new color. They also seemed to resemble kites so I have named my project “flying kites”

I started out prototyping on one piece by attaching the nitinol by sodering it to conductive fabric. I then tested this by using alligator clips and attaching it to my battery to make sure that I can achieve the movement that I was looking for in the square of felt. Based on the properties of the 0.006mm nitinol, since it needs ~410mA to achieve 1 second of contraction and I was using a 3.7V battery, I calculated, using Ohm’s law, that I needed approximately 9Ω of resistance in my connection from the nitinol to the power supply.  The resistance of just the nitinol and conductive fabric was only ~5Ω so I added four additional 1Ω resistors to the connection.  I tested this, and I was not achieving as much movement as I would have liked so I removed one resistor and it seemed to move better. I recalculated the total resistance at this point and it was actually closer to 9Ω while before it was closer to 9.8Ω.  I repeated the same on the other square but used all four resistors because my measurements using my multimeter indicated I needed slightly more resistance. Perhaps my nitinol was a tiny bit longer.

I connected both squares to the mosfets and then connected them to separate Arduino pins.

Finally I programmed it so that the pink and purple “kites” alternate in their movements every few seconds and speed up in their alternations. They then progress to slow down again.

Here is my work in progress:

I added some accents (bows) on the kites to make them look more visually appealing and I also cut off some felt from the sides of the pink kite to see the effect that reducing the weight had on movement (moves up slightly higher).

Here is the finished product and accompanying video:

Calculations:

Required resistance: 3.7V/0.41Amps = 9.02Ω

 Added Resistance (using 1 Ω resistors) Total Measured Resistance Pink Kite 3 Ω 9.1Ω Purple Kite 4 Ω 9.6Ω