ETextiles: Stretch Circuit

Making circuits on the body often means limiting where they can be placed. I have been experimenting with stretchy etextile techniques which can fit tightly to the body and bend and stretch allowing the wearer more freedom of movement.

This technique shows you how to make a stretch etextile circuit with an LED and a button. The panel is from the work-in-progress outfit shown above: it is a side panel at the waist. The materials used are powernet and stretch conductive fabric. The technique involves bonding the conductive fabric between two layers of powernet using a special fusing which is designed to stretch and recover.

This is part of a larger project called Second Skin, which is a design for a prototyping suit which uses etextiles, tubing and cabling to make a foundation garment which can be used for rapid prototyping on the body, allowing you to reconfigure circuits and wiring to test concepts. As different parts of the project are prototyped I will upload them as instructables, including etextiles, cable housing and connectors. Once there is a full working prototype the entire pattern will be digitised and open sourced for others to download and use for similar projects.

To see more images of the Second Skin protoyping suit and details of the other circuit layouts, take a look at the Flickr album:

https://www.flickr.com/photos/rachelfreirestudio/albums/72157672844768976

Materials:
- powernet fabric
- stretch fusible film --> http://www.extremtextil.de/catalog/Sewfree-elastic-iron-on-adhesive-film-small-piece::1783.html
- conductive lycra --> http://lessemf.com/fabric1.html#321
- conductive thread

Electronics:
- sewable lillypad micro LED --> https://www.sparkfun.com/products/retired/10753
- sewable lillypad button --> https://www.sparkfun.com/products/8776
- coin cell battery and holder

Tools:
- sharp scissors
- iron
- crocodile clips
- pins
- sewing needle

Preparing the fabrics

Make sure the lines for the circuit are clearly marked onto the pattern piece. The cut-outs indicate areas with fabric, but no glue. This will be where the LED, button and connector pads will be.

Trace and cut two pieces of powernet (without any cut-outs).

Trace the pattern piece on to the fusing and cut it out, including all the holes.

Iron a long strip of fusing to the conductive lycra and cut 5mm strips for the circuit, and circles for the connector pads.

Fusing the circuit

Place the powernet fabric over the pattern piece and use it as a guide to glue the circuit.

Peel the backing from the 5mm strips and press them lightly with the iron to tack them in place. Because the lycra is stretchy it will bend around the corners.

Place the circles for the connectors and tack with the iron, making sure they overlap the strips to make a connection. The glue will sink into the fabric and allow conductivity between the two layers.

Once all the circuit is in place, cover with a pressing cloth and press for 10 seconds to set the bond.

Take the pattern piece cut from fusing and lay it over the circuit, being careful that you can see all of the pads and the holes for the LED and button through the gaps. These gaps will create pockets for the components to sit inside.

Iron the fusing to the powernet, making sure the glue has stuck to the fabric. When it has cooled, peel the paper backing off.

Lay the second piece of powernet over the top of the circuit and cover with a pressing cloth. Press for ten seconds while applying pressure to make a permanent bond.

Use small scissors to snip away the circles for the connector pads. As there is no glue here, they can be snipped out to expose the connector pads.

Notes: I am using two weights of powernet, one light and one heavy. The heavier one will be the base, and the lighter one will sit on top allowing the circuit inside to be more visible.

On the back of the panel, snip two small holes for the LED and button. Cut the holes much smaller than the components as the fabric will stretch.

Insert the components and use conductive thread to add a few stitches to either side to secure them. Make sure not to catch the front of the fabric so the stitches aren't visible from the front.

Make sure the stitches are knotted tightly so they won't come undone when stretched.

The circuit can be tested by attaching crocodile clips directly to the connector pads.

An easier way to attach the clips is to use pins and connect the crocodile clips to the pins. Straight pins are fine for testing, but I plan to start by making safety pin connectors before this goes on a human.

the LED can be lit alone, or connected to the button, to test the stretch circuit.

test!