Materials

To build your artificial skin interface, you need:

• Muca board
• Conductive Insulated Thread 
• Dragon Skin or EcoFlex Silicone
• Ecoflex Gel Silicone
• Silicone pigments

Tools (optional)

The fabrication process is faster with the help of digital fabrication tools. However, they are not required.

• Vacuum chamber, to remove the bubbles from the silicone
• Laser cutter

Fabrication steps

1. Create the top layer

The top layer is equivalent to the epidermis of the human skin. It is around 1mm thick and is the visible part of the interface.

1. Mix your DragonSkin ( or EcoFlex) silicone with skin-tone pigments
2. Pour this layer to form a think film. Get some help from a spatula to spread it evenly.
3. (Optional: At this stage, you can draw or paint veins on the surface that will face down on the final prototype)

Tip: If you want to create wrinkles and skin pores, you can pour this layer on top of a textured sheet. Look around you, some materials have the perfect features: leather, book covers, or dividers for files!

2. Place the electrodes

This step consists in placing the grid of electrodes, that will be connected to the Muca board. Keep in mind that the muca board supports 12x21 electrodes.

1. Once cured, position the top layer on a pane, with the texture facing down.
2. Place the conductive threads in a perpendicular grid on top of the artificial epidermis to form the electrodes.
3. (Optional: Pour an additional thin layer of silicone)

Tip: I used a laser cutter to form the stencil to help me sew the electrodes. Although not needed, it facilitates the process and ensure an even distribution of the electrodes. The template can be downloaded here. For this prototype, I set up a spacing of 8mm between each electrode wires.

3. Create the fat layer

What is important to replicate human skin is to create a fat layer, equivalent to the hypodermis layer of the skin.

1. Prepare a rectangular mold, the size of the desired artificial skin
2. Place it on top of the electrodes.
3. Pigment the Ecoflex Gel and pour it in the mold

Tip: To create the mold, I laser cut a box in acrylic. I made this box with the tool Makercase. The dimensions are [Spacing between the RX electrodes] x [Number of RX Electrodes] by [Spacing between the TX electrodes ] x [Number of TX electrodes]

4. Connect the electrodes

Finally, connect the electrodes to the Muca board. Connect all vertical lines to the TX electrodes (1 to 12), in the correct order. Connect all the horizontal electrodes to the RX ( 1 to 21).

Tip: You can solder the thread directly to the pins. If you want a robust prototype, lock them in place with some hot glue or epoxy.

Tip: The yarn is insulated: the “black” part of the yarn has to be burnt before soldering. You can either do it with a lighter and burn 5mm, or if you insist a lot while soldering, the heat will burn the black layer and the solder will stick to the copper core.

Software

All the software for detecting touch input can be found on Github