Piezoelectric fibre-based woven acoustic fabrics for highly-sensitive (nanometre-scale) vibration sensing

All fabrics vibrate in response to audible sounds, though these vibrations are on the scale of nanometers — far too small to ordinarily be sensed. To capture these imperceptible signals, we have created a flexible fiber designed from a “piezoelectric” material that produces an electrical signal when bent or mechanically deformed, providing a means for the fabric to convert sound vibrations into electrical signals.

Inspired by the auditory system, we introduce a fabric that operates as a sensitive audible microphone while retaining the traditional qualities of fabrics, such as machine washability and draping. Woven into the fabric is a thermally drawn composite piezoelectric fibre that conforms to the fabric and converts the mechanical vibrations into electrical signals. Key to the fibre sensitivity is an elastomeric cladding that concentrates the mechanical stress in a piezocomposite layer with a high piezoelectric charge coefficient of approximately 46 picocoulombs per newton, a result of the thermal drawing process.

Concurrent measurements of electric output and spatial vibration patterns in response to audible acoustic excitation reveal that fabric vibrational modes with nanometre amplitude displacement are the source of the electrical output of the fibre. With the fibre subsuming less than 0.1% of the fabric by volume, a single fibre draw enables tens of square metres of fabric microphone. We have also demonstrated three different applications: a woven shirt with dual acoustic fibres that measure the precise direction of an acoustic impulse, a bidirectional communication established between two fabrics working as sound emitters and receivers, and a shirt that auscultates cardiac sound signals.

This project is a collaboration led by Dr. Wei Yan (NTU) from Fibers@MIT group. Image Credits: Greg Hen.

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Publication Yan, W., Noel, G., Loke, G., Meiklejohn, E., Khiduyev, T., Marion, J., Rui, G., Lin, J., Cherston, J., Saharasbudhe, A., Wilbert, J., Wicaksono, I., Hoyt, R.W., Missakian, A., Zhu, L., Ma, C., Joannopoulos, J., and Fink, Y., 2022. Single fibre enables acoustic fabrics via nanometre-scale vibrations. Nature,