It's all the rage at the March for Science and I decided to make one as a gift and then someone else really liked it so I have to make another.
I made the I-Cord using a LC-150 knitting machine but it still took a long time. I crocheted the i-cord on to give it more elasticity and give. That took a long time so at the end I just sewed the i-cord on.
I used "cashmere" yarn from alibaba which doesn't feel like cashmere at all but it was cheap, I think $20 for several skeins. I knitted the head from the crown down because I didn't know how big the recipient's head was and this way I can adjust and test before sewing on all the i-cord.