I needed to show my students a simple way to embed LEDs on a piece of fabric, so I made a tutu that lights up. Future versions will react to sound, light or acceleration. But for right now, it's just turning on or off depending on whether the battery is in or not.

Materials:

Lining Fabric (cotton taffeta) X 1 meter
Tulle X 2 meters
Conductive Thread on a bobbin
Regular thread
LEDs
3V Coin Cell Battery
Sewable Coin Cell Battery Holder

Tools:

Sewing Machine
Sewing Needle
Pins
Multimeter
Measuring Tape
Tailor's Chalk

The amount of fabric you use will change depending on how long you want your tutu to be. I kept mine super short.

The amount of LEDs you can light up will be dependent on the LED voltage, generally 1.7 - 2.3 volts depending on the color. To make it easier on myself, I used chibitronics LED stickers. Although they were designed for paper electronics, they work very well on fabrics too!

Step 1: Making the Tutu

First I had to make a tutu. Fortunately, there are two really excellent tutorials on how to make a simple tulle skirt by Cotton and Curls and A Pair and A Spare which are really easy to follow and very well written.

You'll need to cut out two circles from your lining and from your tulle. The first circle has the radius of your waist. Find it by taking a measuring tape around your hip and dividing that number by 6.28 (or two pi if you're really into doing math). I added an extra inch on the radius to be able to slip the skirt on and off.

The second circle cut has the radius of your waist plus the desired length of your skirt.

I folded the fabric length-wise to make two layers. You can also fold once more to create four layers and save time on cutting. On the folded side, I used my measuring tape to measure the distance from the center of my circle to the edge. I then pivoted from one end of the fabric to the other, creating a half-moon shape. I did the same for the exterior circle. (see videos)

Remember, to always measure twice, cut once! I measured again just to be safe, and then cut out the half moons from the fabric. I ended up with a fabric donut!

I cut the tulle a little longer than the lining, for added tutu effect. I pinned two layers of donut-tulles and the lining together at the center waist circle, and sewed them together. You can also gather the fabric together with a baste stitch, but I skipped that step. I was more excited about the next step: Embedding the LEDs!

Step 2: Embedding the LEDs on the Tutu

This step depends on what kind of LEDs you have and the battery you're going to use to power them. I have had some bad experiences with 9 Volts and wearables (picture it: New Jersey, 2012. A techie uses a spinning wheel with steel wool to make his own conductive yarn. It hits a 9 volt battery that he dorkily had in his button-down shirt pocket. He douses the flames before the alarms go off.) Long story short, I went with a 3 V coin cell battery.

Recently, I was introduced to Chibitronics and their electronic stickers kit. They're fabulous, and they stick to fabrics well. Furthermore, the chibitronics pads are thin enough that they can be sewn through. Bunnie and Jie did a great job with their surface mount LEDs, so I was able to light up 5 of their LEDs in parallel with a single 3 Volt battery. I kept it at 3, however, because at this number of LEDs it was much brighter.

To embed them to the tutu, sew two circles near the hem of the lining with conductive thread in the bobbin. Make sure that they are not touching, or else it will short circuit! Mark one of the conductive stitches as positive, and the other as negative. Sew the LEDs on with more conductive thread.

I unfortunately forgot to take pics of the original design with just the battery holder attached to the LEDs, because I moved on and started making a sound reactive one... Just sew the coin cell holder, negative to negative and positive to positive, onto the conductive circles as well. Make sure they are not touching and short circuiting!

Because you only need to put conductive thread on the bobbin, I used a white thread as the top thread and made sure that I sewed with the tulle-side facing up. This helps keep the stitches slightly less visible. Because I used conductive thread to sew through the Chibitronics LED pads, I was able to keep the LEDs facing up on the tulle-side of the fabric. It diffused nicely beneath the tulle!

Step 3: Testing and Finishing Your Tutu

I always use a multimeter after sewing every LED to make sure that I didn't accidentally short circuit the sewn traces. Even after a quick multimeter test, I usually get anxious so I like to keep the battery handy and test if the LEDs light up after every embedding.

Finishing your project is key to keeping it wearable - you want this tutu to last, right?!

Make sure to cut any excess threads to prevent short circuiting. To prevent the conductive thread from fraying, dab a little bit of clear nail polish on the knots. Don't do too much or else it might get on your fabric. Also, keep in mind some clear nail polish is conductive when it hasn't dried. So be mindful of not short circuiting during this step.

After the nail polish is dried, you should be able to pop in your battery and wear your tutu with pride! I added a ribbon trim to keep it looking neat and also so I can tie it around my waist.

Stay tuned for more tutu related projects. I'm going to attach some sensors to it later!