Introduction: Three Soft Wearable Circuit Techniques

In this instructable, I will present three techniques for creating a light-weight, sturdy circuit on stretchy material. Soft tech can get very bulky, very fast, and stretchy fabric is an easy way to lighten to the load. However stretchy materials present their own problems, needing a deliberate hand to sew accurately. These techniques will present how to lay, insulate and connect a circuit pattern accurately with minimal sewing, making the process easy even for novices.

I used these techniques in the speaker circuit pictured above.

Step 1: Mounting Hardware

To mount any non-soft parts of of your circuit (batteries, speakers, light board, micro controllers) you'll need to create a sturdy place on the fabric. The technique Im about to show uses fusible interfacing to combine two fabrics. Heat fusing is a sturdy was to attach a stiff fabric to a stretchy fabric, leaving strong stiff edges where they meet and requiring no sewing skills.

For this you'll need:
-a stiff, non-fraying fabric. ( Ive used felt )
-fusible interfacing
-a stretchy fabric
-an iron
-your hardware

1. Cut the fusible interfacing into tiny pieces, and arrange them carefully on your felt.
2. Lay the thinner fabric over the top. (Always put the thinner material on top when using interfacing. Thick materials are frustrating to iron.)
3. Apply iron until the edges of the thicker material begin to form edges. This indicates the fabrics have been glued together. Repeat for any other pieces you may need to attach.
4. You now have sturdy points that do not budge when you stretch the fabric.
5. Mount your hardware through your preferred means.

Step 2: Laying and Insulating a Circuit Path

My suggested material choice for circuit path is iron-on conductive fabric. Though you can lay paths with conductive thread, it often requires more complex forms of insulation that may lead to a bulkier circuit. Conductive thread when sewn properly can stretch with the fabric, but if you simply need to maintain some flexibility and want the circuit as thin as possible, conductive fabric is the better choice.

For this you will need:
-sports fabric
-conductive fabric
-nail polish (or another kind of liquid plastic.)

1.Cut your desired path out of the conductive fabric, lay it on the sports fabric, and apply the iron. The iron can be on as high your fabric can take it, and the fabric will fuse very fast.
2. Take your desired nail polish, and shake it if you see any separation. Apply on top of the circuit path, letting it go over the edge and onto the fabric.
-Get enough around the edge of the path or it wont be properly insulated.
-You may need to apply multiple layers depending on the viscosity of the polish.
- Older nail polishes that have thickened up with age are better for this process.
3. If you want to keep your paths extra tidy, you can tape-off the outer edge around your path to maintain a clean line. When you pull the tape away, you'll have a tidy, even path of polish.
4. Continue applying the polish up to about a centimeter from the end of you path. You leave this exposed to be connected to other parts of the circuit.

Step 3: Connecting Your Hardware to Your Circuit Path

If youre lucky enough to be making a soft circuit using a Lilypad controller, this technique may not be necessary as the pad is designed to be sewn right onto circuits. However, this last technique is applicable to all micro controllers, sensors, LEDs and more.

For this you'll need:
needle nose pliers
-needle and thread
-soldering iron and solder
-a soft circuit path

1. Take a small length of wire and solder it to the necessary connection.
2. Use the needle nose pliers to twist the wire into a small coil. Be delicate as you do this or you might snap your solder connection.
3. You can now sew the coil directly on top of the soft circuit path. Creating a solid connection between your hardware and path.