Nylon Finally Takes its Place as a Piezoelectric Textile
upstart writes in with an IRC submission for RandomFactor:
Nylon finally takes its place as a piezoelectric textile:
Nylon might seem the obvious go-to material for electronic textiles-not only is there an established textiles industry based on nylon, but it conveniently has a crystalline phase that is piezoelectric-tap it and you get a build-up of charge perfect for pressure sensing and harvesting energy from ambient motion.
Unfortunately, forming nylon into fibers while getting it to take on the crystal structure that has a piezoelectric response is not straightforward. "This has been a challenge for almost half a century," explains Kamal Asadi, a researcher at the Max-Planck Institute for Polymer Research, Germany, and professor at the University of Bath, U.K. In a recent Advanced Functional Materials report, he and his collaborators describe how they have now finally overcome this.
The piezoelectric phase of nylon holds appeal not just for electronic textiles but all kinds of electronic devices, particularly where there is demand for something less brittle than the conventional piezoelectric ceramics. However, for decades, the only way to produce nylon with the crystalline phase that has a strong piezoelectric response has been to melt it, rapidly cool it and then stretch it so that it sets into a smectic ' phase. This produces slabs typically tens of micrometers thick-far too thick for applications in electronic devices or electronic textiles.
The presence of piezoelectric behavior stems from the amide moieties on the repeating units in a nylon polymer chain, and their interaction with those on the neighboring chain. When these amides are free to align their dipoles with an electric field, it is possible to exploit the piezoelectric effect in the material, as first observed as far back as the 1980s. However, what happens in most of the nylon's crystalline phases is that these amides form strong hydrogen bonds with amides on other polymer chains that lock them in position, preventing them from reorienting and aligning. The challenge was thus to find a way to produce the phase that left the amides free to reorient but was not so limited in the morphologies it can produce as the melt, cool and stretch approach.
Journal Reference:
Saleem Anwar, Morteza Hassanpour Amiri, Shuai Jiang, et al. Piezoelectric Nylon11 Fibers for Electronic Textiles, Energy Harvesting and Sensing [open], Advanced Functional Materials (DOI: 10.1002/adfm.202004326)
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