I just purchased some conductive fabric and noticed that stretching the fabric reduced its resistance. This seems counter-intuitive since stretching a wire leads to an increase in its resistance. I have also found this video where you can see this happen. Why is this happening? How does stretching the fabric lead to drop in the resistance? and is there any relation between the two?
It probably causes closer contact between conductive bits, however note that your observation is not universally true. For example, this fabric from Holland Shielding has the following note:
When the material is stretched lengthwise, its conductivity increases; when you stretch it crosswise, conductivity decreases
a simple web search reveals your answer.
Eeontex fabrics are fabrics coated/doped with an inherently conductive polymer, making them conductive with quite a high resistance. But the resistance changes of distance, pressure through the material, and stretch over the material – making them ideal for sensor construction. velostat is a plastic sheet with similar properties to Eeontex, but because it is plastic it has none of the advantages of a textile.
- thus it is an insulator with conductive coating and becomes more conductive with stretching like virtual skin, gloves etc for similar applications.
- It is not a piezo electric effect but a rather wide tolerance dynamic potentiometer with not great accuracy for absolute value but great dynamic range.
there are a wide range of products and datasheets avail.
A conductor that increases with distance would be elastic and get thinner and thus increase, but this is an insulator with conductive coatings weakly connected until stretched.