This is NOT a stretch sensor, but rather the opposite, a way of making a stretchy connection/lead/trace. A tube knit from conductive thread with round elastic inserted. Before finishing the ends, the knit tube is stretched to it’s max and elastic’s max stretch (or other max can be taken) and then fixed. You can work with different qualities of elastic/stretch.
The black band in the photos is a rubber stretch sensor. The knit conductor was made to match the stretchiness of the rubber.
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