Custom Capacitive Sensing Yarn:
According to the original announcement, there were three main challenges in this. First, you needed a yarn that could withstand industrial manufacturing machines. Second, they wanted it to not be grey, and Third, they wanted it to be responsive to capacitive touch. Because they are Google, they were able to work with industrial suppliers to engineer their own yarn which consists of three magnet wires or filaments in the core (middle) which were then braided (on a very fun to watch maypole machine!) with a dyeable and durable fiber: silk. They used copper because its very conductive; silk because its really strong and dyes into really brilliant colors; and a braided structure because it could withstand large amounts of force. While we can note that this was certainly not the first conductive yarn to be core spun or to allow for capacitive touch sensing, what is interesting is what is possible with you have access to equipment that is otherwise unaccessible. They could really precisely tune the material to the function they hand in mind and the infrastructure that they would need it to work within.
Touch using Arduino ADC pin
Swept Frequency Capacitive Sensing
2D Capacitive Grid