This project will attempt to display images onto cloth dyed with thermochromatic ink.
I want to display images on a canvas of fabric dyed with thermochromatic ink. In order to do this, I need to somehow transfer heat onto the cloth in the shape of the image that I want to display.
At first I was thinking about using a heated stencil of some sort. But during a discussion on twitter, someone suggested I try sending hot air into an air hockey table draped with the fabric. That got me thinking about a design that uses a grid of holes to direct air into pixels.
By directing warm air into selected pixel holes I can display a low resolution image on the fabric.
Today I tried a few different ways to make this display. For now I am focusing on ways to transfer air to the pixels in thermally conductive, but controlled ways.
I bought a couple yards of thermally conductive fabric from http://bodyfaders.com/. Pink/blue and orange/yellow on the recommendation of a physicist friend who told me that the other colors have higher activating temperatures.
For testing I made a simple rig that holds the fabric taught in an embroidery hoop.
I tried laser cutting stencils into corrugated cardboard and 1/4" plywood and blowing hot air across them as I pressed them against the cloth. I used a heat gun for the hot air. These were the results. The broken Arduino logo is the one that was made out of wood.
The cardboard is not a good solution because hot air can easily enter the cardboard and actually heat up the surface. The edges are really bleedy.
The wood is better at insulating from heat than cardboard. But still, the edges are not very sharp. I need to find another solution.
For this version I used a two layer stencil that was laser cut in wood and mylar. I decided to experiment with mylar sheet because of it's thermal reflective properties. I used the wood layer because the mylar is really flimsy. I like the way this looks. It's really fast and easy to laser cut mylar. I will experiment a bit more with this.
I laser cut a mylar stencil of Marilyn Monroe and was going to try using that as a heat shield stencil. Similar how I had done with the HI stencil. First I had a hard time taping the material flat, so the laser had bad focus.
The cut seemed to melt and then form back across the cut so that the cuts turn out to be more perforated. I was able to separate the weed the stencil, but I had to pull a bit at the mylar.
I was surprised at how strong it is. Even really small details did not get ripped off when I pulled hard.
I realized that it would be too flimsy to use as a stencil. I needed a wood backing to hold it. But I thought that I could test the overall concept with just wood.
I have to retry laser cutting mylar. As I wrote about this step, it made me realize that the focus of the laser could be making all the difference. It's such a thin material.
I love working with mylar because I got a lot of it for free when a student bought it for a project. Also it has great thermal reflective properties.
I hope I can get a good laser cut from it. According to my research, I should be able to cleanly cut this if I can dial in on the right settings. It
I laser cut Marilyn on a wood stencil and tried using that as a heat sheild. It kind of works. But I think that the air moving through the stencil is turbulent, so it sort of ripples around the edges and causes a bleeding edge. I want to find a way to make the edges more crisp.
I wanted to try a more direct way of transferring heat to the cloth. Warm air works okay, but it is turbulent and the images tend to bleed on the edges. Also, I have to use a heat gun or another way to warm and move the air.
I realized that it's easy to heat wire, so I am experimenting a bit with this technique.
I wove 30 AWG enamel wire through my "Hi" stencil. Running 6 volts (4 AA batteries) was enough to heat it up and display the writing. I also tried placing some tinfoil between the wire and the cloth. The tinfoil seemed to disperse the heat. Not the effect I'm looking for. Also the batteries got really hot. I'll have to find a safer way to run current through the wire.
I had an idea to create a seven segment display and I could heat up individual segments to display numbers on the cloth.
I decided to test the idea with a few different materials.
First I laser cut and etched a template with six parallel diamond shaped segments. I wove three different conductors (22 gauge wire, 30 gauge wire, and conductive thread) across the segments. I covered those with Kapton tape to keep them down. I covered those with diamond shaped copper tape that I cut on the vinyl cutter
Then I used a benchtop power supply to send current through each of the materials. None of them really worked that well. They took too long to heat up.
Then I remembered that I had some nichrome wire in the lab. I tested that and it worked well. The last picture IMG_5883 shows a few of the segments "lit-up".
I started to think a lot about how I could use this technique to make a clock that magically displays the time on cloth. Maybe like a throw pillow that is also a clock!
After a few days of thinking about this, I realized that I did not like the 7 segment esthetics that much. It was very different from the heated wire look. I started to think about ways that I could take advantage of the curved wire look. Maybe even display the numbers in a cursive like font...