Knit Circuit Board

Different textile methods have been used to create conductive paths for circuits.  This includes sewing, applique, and weaving with conductive and nonconductive materials to create these pathways.  Different projects have been made with knitting and electronics, however usually in the form of creating sensors or breadboard surfaces.  In this project, I wanted to combine traditional methods of color knitting (intarsia) with using conductive and nonconductive materials to create traces for an ATtiny85 microcontroller.  By investigating and creating this process,  this can lead to explorations in more complicated knitted circuit boards or large scale productions of this process. 

Why knit? 

Knitted fabrics can be constructed from different materials with minimal waste. Rather than cutting a larger fabric down to specific shapes, knitted fabrics can be directly constructed into those shapes. By knitting with conductive and nonconductive yarns, a circuit can be knit into the fabric using intarsia, a traditional method used for creating patterns. This process would create a soft, flexible circuit that is constructed and embedded with the conductive materials to create connection points.

Precedent work: 

Jesse Seay has developed a method of knitting with wire and soldering components to create a wearable circuit. Although this allows for open forms of creation like with a perfboard, it is not entirely suitable for wearables considering its potential to scratch the wearer or create short circuits while wearing. 

Andrew Quitmeyer has created a lasercut, appliqued textile breakout board for an ATtiny85.  This inexpensive board can be easily reproduced to work with technology while out in the wild.  This work inspired the use of the ATtiny85 since it's an inexpensive and versatile component, and not have to rely on ever shifting and changing designs of existing wearable microcontroller designs. 

In making this project I needed to use an insulated yarn.  Most conductive yarns are uninsulated, which could cause shorts, especially when knitting on a small, close scale.  Current commercial insulated yarns usually have a polymer sheath.  Although strong, this material does not offer other potentials of natural fibers such as wool to felt or provide heat resistance. 

To create this conductive material for this project, a yarn was made by spinning wool thread around a conductive thread core. A modified rope machine was made to create the insulated yarn. Six strands of thread are wound separately and then twisted together around a conductive core thread to create a single piece of yarn. 

The knit circuit was then made via hand knitting.  The ATtiny85, programmed to blink a light, was then placed onto the circuit. Possible future iterations could include embedding all the traces for all the components on one knitted surface to eliminate the alligator clips in the final circuit.  The next step would also be figuring out different applications this circuit could be used in.