week 12 - Skin Electronics
Integrating wearables technology into make-up and skin.
Skin Masquerade party
I wanted to leave the circuits showing on the skin to make a futuristic look. My first idea inspired by the last assigment was to use silicon to apply the circuit on the skin, because of its transparency and maleability. Following the idea of the mask, I decided I could show the circuits on the face, as a cyborg, partially human and partially robot.
fig 12.1 - Inspirational image for skin electronics with silicon.
fig 12.2 - The comics character Cyborg was used as reference for the design of the mask.
We as a group experimented building a circuit directly on the skin using conductive ink. For that we printed a vinyl with the negative shape in the plotter to use as stencil for the ink. After applying it on the skin, we waited for the ink to dry before removing the vinyl mask.
Unfortunately when we tried to remove it we realized the conductive ink formed a thick layer on top of the mask and was being removed with it. With a wet cotton, we moiturized the ink again in order for it to detach from the mask.
After managing to remove the mask we measured the conductivity with the multimeter and unfortunately the dry ink was cracked in some paths, because of the flexiblity of the skin. Where it was not cracked the resitance was very high.
fig 12.3 - Experimenting with condutive ink on skin using vinyl as stencil.
fig 12.4 - Unfortunately in the experiment the circuit could not be transfered perfectly to the skin.
I decided to draw a circular eye with neopixels on top of a textile that would cover the user's eye to simulate the cyborg face. I measured on my face what would be the ideal diameter of this circle and place on a paper the amount of neopixels that could give the results I wanted, which would be a blinking circular eye.
My plan is to cut the circuit in the copper tape using the plotter, solder the components and embbed it in a silicon layer sandwitch.
After that I inserted the components in Eagle software to draw the circuits. Since my skills with this software are not so good I was taking a long time to draw it.
I decided that it would be much easier for me to draw the circuit in Illustrator once I had the components in the right size so I exported the file as .dxl to Illustrator.
fig 12.5 - Attempt to draw the circuit of the mask in Eagle.
fig 12.6 - First circuit drawn for the mask in Illustrator.
Cutting the circuit in the copper tape using the vinyl cutter is not as simple as I had initially thought and I was advised to has as fewer corner as possible and try to simply the drawing. For this reason I switched the 8 neopixels that composed the circle to a circular neopixel that has only one input, one output, the ground and VCC and added ony one more neopixel in the center.
Building the mask
After redesigning the circuit I exported the expanded lines in .dxf file from Illustrator and opened it in the Silhouette software of the Silhouette cutting machine. In this software I had to adjust the size of the paper and resize the drawing to the right dimensions. Then I taped 2 pieces of copper tape in the cutting sheet to build the area that my circuit was going to be cut following the grid on the sheet. I also adjusted the depth of the blade to 4 and performed a quick test on the material. The material was coming out of the sheet to easily. For this reason I changed the depth of the blade to 3 and sent it to print. While cutting, some parts of the circuit were detaching from the sheet and not every line was cut correctly. I still continued with that sample and managed to correct it aftwards using a cutting blade. I managed to transfer it to an acetate sheet by sticking many small pieces of tape while removing the parts that were not part of the circuit (fig. 11.10).
The initial idea was to place the circuit on a silicon but talking to Adriana Cabrera I realized the circuit would be unstable in silicon. For this reason I changed the material to acetate which was quite fortunate. The acetate not only give stability to the circuit but also is clear and transparent, improving the aesthetic.
After transfering the circuit to the acetate I went on to soldering the components. Because the circular neopixel has connections as holes, I decided to solder wires to the circuit that would connect to the holes. I also decided to solder wires to the connections of the single neopixel for they are placed in the bottom of it and it would be difficul to solder it directly in the copper circuit.
fig 12.12 - Top view of the neopixel soldered in the circuit.
fig 12.7 - Checking the recommended the depth of the blade.
fig 12.8 - Adjusting the depth of the blade in the machine.
fig 12.9 - Fixing the circuit with the cutting blade.
fig 12.10 - Removing the material.
fig 12.11 - Transfer mask completed.
fig 12.13 - Soldered wires which will connect to the circular neopixel.
To make the eyepad I cutted a circle of 45 mm diameter of the synthetic leather using the laser cutter and glued it in the back part of the acetate with a strong glue. After that I checked the conductivity of all paths with the multimeter and there were no failing connections.
Concerning the batteries, first I joined 2 coin batteries of 3V with tape, connecting the negative (-) of one battery to positive (+) of the other. Then I measured the joint batteries and designed a battery holder to be cutted in acetate. I cutted it in the laser cutter, making the tests previously to find the correct settings for speed, power and frequency (S=100, P=90 and F=50). This settings though it cutted the acetate it left on it a yellowish shade. Due to time constraints poceeded with it. Having the holder ready I glued it in the mask design and created a copper path to connect the circuit to the positive side of the battery. I also had to solder this new path because it had initially no conductivity.
Programming the Attiny
For the Attiny and neopixel programming, we had a quick tutorial with Adriana Cabrera. Here are the steps that have to be followed:
1. Install the Adafruit neopixel library and add Attiny in Arduino's board manager.
2. Open the example of ArduinoISP, which will tell the Arduino to act as a programmer of the Attiny. In the menu Tool, the AVRISP mkll should be selected in Programmer.
3. Connected the Attiny to the Arduino using a breadboard as follows:
ATtiny Pin 2 to Arduino Pin 13 (or SCK of another programmer)
ATtiny Pin 1 to Arduino Pin 12 (or MISO of another programmer)
ATtiny Pin 0 to Arduino Pin 11 (or MOSI of another programmer)
ATtiny Reset Pin to Arduino Pin 10 (or RESET of another programmer)
VCC to VCC and GND to GND.
4. In the tools menu, change the board and processor to Attiny85, clock to 8MHz and programmer to Arduino ISP
5. Click on "Burn bootloader" if it is the first time that the Attiny is programmed.
6. On the Adafruit Neopixel samples, open the desired type and change the pins used and the number of neopixel.
7. To transfer the code to the Attiny, click on "Upload using programmer" in the menu Sketch.
After programming the Attiny, Adriana also helped me testing it in my mask with the breadboard and crocodile clips. After assuring that everything was working, I soldered the Attiny and neopixel circle in the mask. I also finalized the design by cutting the shape of the mask and sewing an elastic band that would fix the mask on the face.
Unfortunately the connections of the neopixel circle to the wires and coppertape was not very strong and it broke before I could put the mask on. Still I managed to have a video of the results with the help of Adriana.