Bifurcation-based acoustic switching and rectification

• Published in: Nature materials Vol. 10; no. 9; pp. 665 - 668
• Main Authors: Boechler, N., Theocharis, G., Daraio, C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24-07-2011; Nature Publishing Group
• Subjects: 639/301/1023/303; Acoustics; Bifurcations; Biomaterials; Chaos theory; Chemistry and Materials Science; Condensed Matter Physics; Crystal defects; Devices; Energy conservation; Filtering; Insulation; letter; Materials Science; Nanotechnology; Optical and Electronic Materials; Rectification; Rectifiers; Switching
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat3072

Acoustic rectifiers are of relevance for applications such as biomedical ultrasound imaging. In these systems, amplification increases gradually with signal amplitude. A new approach based on bifurcation in chaotic systems now enables a sharp switching between rectification states that could be used in nonlinear acoustic devices.
Switches and rectification devices are fundamental componentsused for controlling the flow of energy in numerous applications. Thermal
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and acoustic
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rectifiers have been proposed for use in biomedical ultrasound applications
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, thermal computers
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, energy- saving and -harvesting materials
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, and direction-dependent insulating materials
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,
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,
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. In all these systems the transition between transmission states is smooth with increasing signal amplitudes. This limits their effectiveness as switching and logic devices, and reduces their sensitivity to external conditions as sensors. Here we overcome these limitations by demonstrating a new mechanism for tunable rectification that uses bifurcations and chaos. This mechanism has a sharp transition between states, which can lead to phononic switching and sensing. We present an experimental demonstration of this mechanism, applied in a mechanical energy rectifier operating at variable sonic frequencies. The rectifier is a granular crystal, composed of a statically compressed one-dimensional array of particles in contact, containing a light mass defect near a boundary. As a result of the defect, vibrations at selected frequencies cause bifurcations and a subsequent jump to quasiperiodic and chaotic states with broadband frequency content. We use this combination of frequency filtering and asymmetrically excited bifurcations to obtain rectification ratios greater than 10
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. We envisage this mechanism to enable the design of advanced photonic, thermal and acoustic materials and devices.