Fabrics, by virtue of their composition and structure, have traditionally been used as acoustic absorbers1,2. Here, inspired by the auditory system3, we introduce a fabric that operates as a sensitive audible microphone while retaining the traditional qualities of fabrics, such as machine washability and draping. The fabric medium is composed of high-Young’s modulus textile yarns in the weft of a cotton warp, converting tenuous 10−7-atmosphere pressure waves at audible frequencies into lower-order mechanical vibration modes. 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. Three different applications exemplify the usefulness of this study: a woven shirt with dual acoustic fibres measures the precise direction of an acoustic impulse, bidirectional communications are established between two fabrics working as sound emitters and receivers, and a shirt auscultates cardiac sound signals.
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All data supporting the findings of this study are available within the article and its Extended Data and Supplementary Information. Representative source data for figures (Figs. 2h, 3, 4, 5g, i, Extended Data Figs. 1c, 2–5, 6c, 7b, 8 and Supplementary Figs. 13, 17) are publicly available at https://doi.org/10.5281/zenodo.5753073. Additional data are available from the corresponding authors upon reasonable request. Source data are provided with this paper.
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Y.F. acknowledges the MIT MRSEC through the MRSEC Program of the National Science Foundation under award number DMR-1419807 and the US Army Research Laboratory and the US Army Research Office through the Institute for Soldier Nanotechnologies, under contract number W911NF-13-D-000, and the Government of Israel, Ministry of Defense, Mission to the USA (no. 4440884397). L.Z. acknowledges the National Science Foundation, Division of Materials Research, Polymers Program (DMR-2103196). G.N. acknowledges the National Science Foundation Graduate Research Fellowship grant no. 1745302. C.M. and J.L. acknowledge funding support from the University of Wisconsin–Madison start-up package and Wisconsin Alumni Research Foundation. The authors thank D. Bono at DMSE, MIT for his contribution to the design of the circuit board, H. Cheung at DMSE, MIT for setting up some experiments and K. Psaltos for drawing some schematics. We have complied with all relevant ethical regulations. The opinions or assertions contained herein are the private views of the author(s) and are not to be construed as official or reflecting the views of the US Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations. Project 2022-R/RC-157 funded under award NA18OAR4170105 from the National Sea Grant College Program of the NOAA.
The authors declare no competing interests.
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Extended data figures and tables
a, Schematic of the fabrication flow of the piezocomposite. The detailed description is shown in Methods. The nanoparticles must be homogeneously distributed in the P(VDF-TrFE) matrix as aggregation can deteriorate energy conversion and causes fibre breakage during the draw. This requirement is achieved by using a planetary centrifugal mixing process that applies ultrastrong shearing forces to the composite suspension. b, SEM micrograph of a piezocomposite thin film fabricated without centrifuging treatment (left) and with centrifuging treatment (right). The inset in the left image highlights a severe agglomeration of BaTiO3 nanoparticles, whereas the inset in the right image presents a homogenous distribution of nanoparticles. c, Wide-angle X-ray scattering characterization of the hot-pressed as-cast composite and drawn P(VDF-TrFE)/BaTiO3 fibre showing the β phase of P(VDF-TrFE) and tetragonal phase of the BaTiO3 nanoparticles. The sharp equatorial arcs in the diffraction pattern of the drawn sample demonstrates that the thermal drawing process aligns the polymer chains along the draw direction. DD, fibre-drawing direction; TD, fibre transverse direction. d, Bright-field TEM image of the BaTiO3 nanoparticles harvested from the fibre. The inset shows the selected-area electron diffraction pattern from transmission electron microscopy (TEM) characterization of a BaTiO3 nanoparticle. Each nanoparticle is monocrystalline in the tetragonal phase. The particle size distribution is shown in Supplementary Fig. 32. The TEM diffraction was performed using an FEI Tecni (G2 Spirit TWIN) under 120 kV.
a, Electric polarization versus electric field hysteresis loops of a pure P(VDF-TrFE) fibre and fibres with varying weight percentages of BaTiO3 nanoparticles (10, 20, 25 wt%). b, Stepwise poling method. The poling voltage is increased to 3,300 V in 100-V steps. The schematics show the dipole orientation before and after the poling process.
a, Temperature profile of the tower furnace. The draw temperature at the neck-down region is around 160 °C. The top surface of the furnace in the fibre draw tower was set to be the zero position. b, Rheological properties of the SEBS and piezocomposite. The oscillatory shear rheology of SEBS is slightly lower than that of the piezocomposite at the draw temperature. Thus, to ensure a smooth flow of the molten piezocomposite, two Cu wires instead of one wire are embedded in each of the two CPE electrodes. The tension applied on the four wires during the draw exerts compressive stress onto the molten piezocomposite in the neck-down region, thus preventing capillary breakup of the piezocomposite and creating highly uniform fibres (Extended Data Fig. 3c). c, Characterization of the fibre size for two different configurations. The 4-Cu wire configuration leads to a highly uniform fibre, whereas the fibre size in the 2-Cu wire configuration fluctuates a lot because of the fluid instability.
a, The ratio of the capacitance (C) after and before the fibre was bent with, from right to left, bending radii of 3.2, 2.0 and 1.2 cm for 1,000 cycles. To ensure a reliable bending radius, the fibre was mounted on a polymer substrate. After the first 1,000-cycle test, the fibre was successively subject to the second and the third 1,000-cycle tests. b, The ratio of the capacitance after and before the fibre was twisted with, from right to left, angles of 45°, 180° and 540° for 1,000 cycles. All tests were done successively.
a–d, Time-dependent waveforms of a clap (a), air blowing (b), leaves rustling (c) and birds chirping (d), detected using the fibre-on-membrane system.
a, The bending/displacement of the middle x plane of the fibre at 300 Hz (the deformation is scaled by a factor of 500) b, The bending/displacement of the middle y plane of the fibre (the deformation is scaled by a factor of 50,000). c, The Cauchy stress distribution of the line in the middle of the piezocomposite along the fibre length. All simulation results were obtained from the 3D COMSOL model.
Extended Data Fig. 7 Performance and modal patterns comparison between three fabrics where the piezoelectric fibre was woven directly.
a, The set-up used for the concurrent measurements. b, The frequency response and modal patterns of fabrics for three boundary conditions and tensions: c, A draping fabric with the top edge clamped where tension is supplied only by the fabric weight uniaxially. d, A fully clamped fabric where the only tension is supplied by fabric weight uniaxially. e, A fully clamped fabric with externally imposed uniform biaxial tension. The uniform biaxial tension was achieved using the method elaborated in Supplementary Note 5. These measurements clearly show excellent electrical signals at audible frequency from all fabrics well above the noise regardless of the specifics of tension or boundary conditions. These measurements clearly establish and substantiate not only that the fabric is sensitive under draping conditions but also that the electrical response emanates from nanometre-amplitude displacements in the fabric, which are captured by the fibre and are then transduced into electrical signals.
a, Snapshot photographs of the acoustic fabric being washed in a washing machine at room temperature. b, The constant capacitance with washing cycles (left); and the voltage versus frequency of the acoustic fabric before it is washed and after it is washed for ten cycles (right). Note that the cotton yarns in this fabric are grey, whereas the cotton yarns shown in Fig. 4 are green. The warp cotton yarn is a size 20/2 cotton with a set of 60 ends per inch and was threaded through a 12-dent reed. The weft yarn is a 1,210-dtex Twaron yarn (Tejin Aramid, The Netherlands). Four strands of Twaron yarn (strands were not twisted together) were used in the weft direction. The size of the fabric is 17 cm × 17 cm × 1 mm. The compression force the warp yarns applied to the fibre was measured to be 16.9 g using a force sensor (ZC-RP-C5ST-LF5-1024, Taidacent).
The spectrograms of the audio used to drive the fabric emitter (top) and the audio detected by the fabric receiver (bottom) shown in Fig. 5g. Signals were sampled at 50 kHz, and data are shown from 20 Hz to 10 kHz in each case. A time window of 5 ms and overlap percentage of 20% were used to produce the spectrograms.
This file contains Supplementary Notes 1–10, including Supplementary Figures 1–32, Supplementary Tables 1–3, and additional references.
The fibre-on-membrane records audible sound. The fibre-on-Mylar system records audible sound generated by a person. The fibre is 6.7 cm in length and the membrane is 8 cm by 8 cm. Detailed sample preparation is elaborated in Supplementary Note 5. The recorded electrical signal is played back, showing the high fidelity of the device.
The acoustic shirt records audible sound. A Twaron-weft/cotton-warp fabric (36 cm (l) × 23 cm (w) × 0.46 mm (t)) with a fibre (6.7 cm in length) woven inside is integrated with a regular shirt, forming an acoustic shirt. Such a shirt records audible sound generated by a person. A pure silk fabric with a fibre (6.7 cm in length) woven inside also forms an acoustic fabric. The recorded electrical signal of both fabrics is played back, showing the high fidelity of the acoustic fabrics.
The acoustic shirts conduct communications. A Twaron-weft/Twaron-warp fabric (yellow) with a fibre woven inside is integrated with a regular shirt, forming a shirt speaker (on the left). Such a shirt can broadcast audible sounds when a modulated a.c. voltage is provided. The two shirts enable bidirectional acoustic communication. The speech of “the acoustic fabric records audible sound” emitted by the fabric on the left is recorded by the fabric receiver on the right. The recorded electrical signal is played back, showing the high fidelity of the fabric receiver.
The heart sound recorded by the acoustic shirt. The high-quality heart sounds recorded using the acoustic shirt shown in Fig. 5c.
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Yan, W., Noel, G., Loke, G. et al. Single fibre enables acoustic fabrics via nanometre-scale vibrations. Nature 603, 616–623 (2022). https://doi.org/10.1038/s41586-022-04476-9
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