Nature Materials | Letter
Multimaterial piezoelectric fibres
- Journal name:
- Nature Materials
- Year published:
- (2010)
- DOI:
- doi:10.1038/nmat2792
- Received
- Accepted
- Published online
Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation1, 2, 3, 4, nonlinear optical mechanisms in silica glass fibres5, 6, 7, 8 and electroactively modulated polymer fibres9. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30 μm thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry–Perot optical resonator and a piezoelectric transducer is fabricated and measured.
Figures at a glance
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Figure 1: Structure of piezoelectric fibres. a, Schematic of the fabrication process of a cylindrical piezoelectric fibre. A preform is constructed by consolidating a shell of P(VDF-TrFE), shells containing CPC/indium electrodes and poly(carbonate) (PC) cladding. b, SEM micrograph of the cross-section of a cylindrical piezoelectric fibre. c, XRD patterns of P(VDF-TrFE) samples extracted from drawn fibres and taken from melt-pressed films used in the preforms. The diffraction peaks indicate β-phase P(VDF-TrFE).
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Figure 2: Acoustic emission from piezoelectric fibres. a, Schematics of the laser Doppler vibrometer used to characterize the speed and frequency of the surface vibration of a fibre modulated at frequency ωD. b,c, Measured frequency-modulation side bands as a function of ωD for piezoelectric fibres with cylindrical and rectangular cross-sections, respectively. The frequency range is illustrated in b as a red rectangle. d, Near-field pressure patterns of the acoustic emission at 1.3 MHz from a circular fibre, a triangular fibre and a rectangular fibre with cross-sectional dimensions about 2 mm.
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Figure 3: Acoustic transmission characterization. a, Experimental set-up for acoustic characterization of piezoelectric fibres. An acoustic wave travels across a water tank from a water-immersion acoustic transducer to a fibre sample, and vice versa. b, Temporal traces of electrically amplified acoustic signals detected by a piezoelectric fibre, shown together with the excitation signals. c, Acoustic signal detected (blue curve) and emitted (red curve) by a piezoelectric rectangular fibre around 1 MHz. The dotted line is the power spectrum of the (1 MHz-centred) transducer used.
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Figure 4: Integrated piezoelectric-modulated optical fibre. a, Schematic of the fabrication process of an integrated piezoelectric Fabry–Perot (FP) rectangular fibre. A Fabry–Perot optical cavity is embedded with the piezoelectric structure in a preform. The preform is thermally drawn into a microstructured fibre. b, SEM micrograph of the cross-section of an integrated piezoelectric Fabry–Perot fibre. c, Piezoelectricity of the fibre characterized with the fibre-optic heterodyne interferometer. Inset: Reflection spectrum of the piezoelectric Fabry–Perot fibre measured with Fourier transform infrared spectroscopy. d, Two-dimensional device fabric constructed by knitting the piezoelectric/Fabry–Perot fibres as threads. Inset: Photograph of an individual fibre.