Summary
Active Time
2-3 hours
Total Project Time
2-3 hours
Key Concepts
Wearables, circuits
Credits
Jennifer Lee, Science Buddies
This project is based on DuoSkin by Hsin-Liu (Cindy) Kao, Christian Holz, Asta Roseway, Andres Calvo, and Chris Schmandt.
Introduction
When you think of wearable devices, Apple watches, VR headsets, and Fitbits may come to mind. What about something even more personal like a circuit directly on your skin? Using simple tools you can find at your local craft store, design your own light-up temporary tattoo.
This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Materials
Crafting
- Metal leaf
- Adhesive spray compatible with metal leaf
- Metal leaf sealer
- Temporary tattoo paper
- Con-Tact vinyl paper (should not be substituted with other brands)
- Conductive fabric tape
- Paper towels
- Masking tape
Tools
- Hobby knife
- Paintbrush
- Foam brush
- Tweezers
- Scissors
- Ballpoint pen
- Access to printer
Electronics
- LED stickers, available from Amazon or Adafruit.com
- CR2032 lithium coin cell battery
- Coin cell battery holder
Prep Work
- Set up a workstation with a flat surface you can cut on and good lighting.
- Prepare a separate well-ventilated area with a flat surface covered with scrap paper/paper towels/cardboard.
Instructions
Creating your template:
- Download and print the activity template. Cut a large rectangle around the shape (an inch of space around the shape). Tape it down onto your workspace.
- Cut a piece of Con-Tact paper slightly larger than the piece you cut out of the template. Lay Con-Tact paper over template (make sure it is completely covering the shape). The transparent side should be up and the side with writing and the grid of lines should be down.
- Tape the Con-Tact paper around the edges onto your workspace. Begin outlining the template shape with a straightedge and your ballpoint pen onto the transparent side of the Con-Tact paper.
- Remove both the template paper and the Con-Tact paper from the workspace. Cut a piece of glossy temporary tattoo backing paper that is larger than your shape. The glossy tattoo paper is in your temporary tattoo kit and is the 1-layer white, glossy sheet (not colored, not double ply). Double check to make sure the shiny tattoo paper is SMALLER than your Con-Tact vinyl shape, but BIGGER than your drawn shape.
- Carefully peel the backing off the Con-Tact sheet. This is the side with the words and grid lines and without the traced template shape. Slowly apply the vinyl (the transparent part of the Con-Tact sheet) onto the glossy tattoo paper (the temporary tattoo backing paper) as you peel off the backing of the Con-Tact sheet, smoothing out the vinyl so that there are minimal air bubbles. You can use a card/cardboard to smooth out any air bubbles. See video for clarification if you find these instructions confusing.
- Trim the edges with a pair of scissors. You can roughly cut a half-inch rectangle around the template shape.
- Take your knife and cut lightly around the edges of the traced shape so that only the vinyl is cut. Carefully cut the outline of the shape using a straightedge for assistance. Make sure not to cut outside of the outline.
- Carefully take your tweezers and peel the vinyl from the inside of the shape (the shaded part of the original printed template) off the glossy temporary tattoo backing paper.
- This is what you should have at the end of these steps.
Applying the metal leaf:
- Relocate to a well-ventilated area. Place the Con-Tact Vinyl paper and shiny tattoo backing sheet on scrap paper/paper towels/cardboard, with the vinyl side facing up.
- Spray the vinyl temporary tattoo backing sheet with a light layer of spray adhesive. Spray from about 12–15 inches away in a sweeping motion. Do not spray too much adhesive. A thin layer is important.
- Wait 10 seconds for the glue to get sticky. Place metal leaf onto the paper so that it adheres to the glue, press down.
- Dab with a dry foam brush to reinforce the adhesion between the metal leaf and the paper. Do not brush the foam brush across. Make sure to use light pressure and firmly dab. Apply extra pressure around the edges and corners with a paint brush using the same dabbing motion.
- Repeat steps 1-3 two more times on the same sheet of metal leaf. There should be a total of three layers of metal leaf.
If you do not have enough metal leaf, you can use the extra scraps from previous layers on the adhesive.
- At the end of this step, you should have your temporary tattoo backing, vinyl on top, and three layers of metal leaf.
Creating the metal leaf circuit:
- Perforate the edges of the shape with small light cuts, shown along dotted lines in the image below. Cut the remaining vinyl and metal leaf layers into smaller manageable pieces using straight cuts along the solid lines shown in the image. This will help with removing the vinyl without tearing the metal leaf.
- Using tweezers, carefully peel the remaining vinyl and the metal leaf off of the glossy temporary tattoo backing. This leaves only the parts of the tattoo you want on the paper. The metal leaf can tear easily, so be extra careful around sharp turns and corners.
- This is what you should be left with.
Adding the LED:
- Hold the circuit so the metal leaf is oriented like the letter "C." At the middle of the left most edge, press your LED face down where you want it to be, then remove the LED. The LED should make an imprint in the metal leaf, as shown in this picture.
- Cut a small rectangular strip around the LED imprint through the metal leaf and temporary tattoo backing. You are making a hole for the LED peek through.
- Lightly place LED face down (LED wax paper side up). Take note which sides of the LED are positive and negative. On the LED, there should be a "+" to indicate the positive side and a "-" to indicate the negative side. This is what it should look like from the back. You can make note of the positive and negative side of the LED onto the paper backing with your pen.
- Secure each lead of the LED to the metal leaf with a small strip of conductive fabric tape.
- This is what it should look like at the end of these steps:
(back side)
(front side)
Adding the battery:
- Place the coin cell battery into the battery holder. Note which side of the battery is positive and which is negative on the battery holder.
- Cut two small 1 inch strips of conductive fabric tape. Attach them to the metal leaf at the open end of the circuit. You will use these to connect to the battery holder.
- Test the battery by placing the battery holder (with the battery in it) on extended conductive fabric tape leads. Make sure the metal tabs on the sides of the battery holder are in contact with the conductive fabric tape. Make sure the "+" sign on the battery holder is on the same side as the "+" sign on the LED. Also, note that the battery holder should be bottom side up as it will be attached directly to the skin.
- If it works, the LED will light up. If it does not light up, double-check the "+" and "-" signs on your LED and the "+" and "-" signs on your battery. If you have the connection backward, flip your battery.
- Seal the circuit! Apply a thin layer of sealer with the paintbrush all over the metal leaf traces and the conductive fabric tape.
- Wait for it to dry for 30 minutes. It should no longer be sticky to the touch when the sealant is fully dried.
- This is what it should look like:
Skin application:
- Cut the temporary tattoo adhesive film into a similar size as your circuit. Double-check to make sure the size is correct and that it covers the entire tattoo.
- Peel off the colored backing to the adhesive film. You should have a transparent film with one side glossy and the other sticky. Avoid touching sticky side.
- Place the adhesive film onto the metal leaf sticky side down. Make sure the adhesive film covers the entire metal leaf circuit.
- Use your fingernails or a credit card to press it down into the tattoo paper. Trim edges of the temporary tattoo metal leaf circuit. Do not cut into the metal leaf or the conductive fabric tape.
- Prep location on skin to place the temporary tattoo by lightly brushing off dust. The skin should be dry and free of makeup or lotion. Peel the clear plastic film off the electronic tattoo.
- Firmly place the sticky-side down onto the skin. The LED should be facing up.
- Lightly pat a damp paper towel over the tattoo. Remove the paper backing to the circuit. It should easily peel off.
- Remove the conductive fabric tape backing. Tape the coin cell battery in the correct orientation onto the conductive fabric tape. Your electronic tattoo is complete!
Cleanup
- Make sure to take out the battery or remove the battery holder when not in use.
- Close the bottle of sealer tightly so it does not dry out.
- Vacuum remaining metal leaf or wipe away with wet paper towel.
- Throw away any paper or cardboard the adhesive got on. Make sure to not get tattoo paper wet and store it dryly.
- To remove the tattoo, gently rub a wet towel with soapy water onto the tattoo. The tattoo should peel off in strips.
What Happened?
Did your LED light up? When you connected the LED to the battery using the metal leaf, you made a closed circuit. The battery provided electricity to the LED, making it light up.
If your LED did not light up, you might have had an open circuit, meaning one or more of the connections in your circuit was broken. You also might have had your LED backwards. LEDs only let electricity flow through them in one direction. For your LED to light up, you must connect the LED's positive side to the battery's positive side.
Digging Deeper
When you made an electronic tattoo, you created a wearable device. Wearable devices are any sort of electronic device that can be worn on your body. This includes any electronic jewelry, accessories, medical devices, clothing, etc. For example, a virtual reality (VR) headset is a wearable device. Wearable technology can be used in healthcare, sports, entertainment, fashion, and security.
Ask an Expert
Curious about the science? Post your question for our scientists.
For Further Exploration
- Can you add more LEDs to your circuit? Look up the difference between series and parallel circuits. What would happen if you add more LEDs in series? What would happen if you add more LEDs in parallel?
- Instead of an LED, can you add other output? For example, can you add a speaker? What about a motor?
- You might want to be able to turn off your circuit without removing the battery. Can you add a switch to your circuit?
- Can you make your circuit a different shape? As long as you form a closed circuit between the battery and the LED with the metal leaf, you can make your tattoo into almost any shape you want.
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