Harnessing asymmetry to reprogram nonlinear metamaterials on-the-fly with no moving parts

Abstract

Various two-dimensional fabrication methods, such as deposition, etching, milling, laser cutting, and water jetting, suffer from asymmetry between the top and the bottom surface of fabricated parts. Such asymmetry is usually undesirable and can compromise functionality, or at least add uncertainty to fabricated components. The common practice is to assume symmetry between the top and the bottom surfaces by using average dimensions. In this study, we harness such asymmetry to realize metamaterials with dynamically tunable (i.e., re-programmable) properties. Our metamaterial is composed of identical unit cells with two concentric Archimedean spiral cuts and a permanent magnet embedded in the unit cell's center. By utilizing external electromagnets, we further amplify the fabrication asymmetry, through the inherent asymmetry between a repulsive vs attractive state between the permanent magnets and the electromagnets. We demonstrate the utility of our metamaterials by programming its spatiotemporal response in both time and frequency even in the presence of high amplitude harmonic excitation. Our findings can be utilized for broad range of applications, from seismic sensing at low frequency to ultrasonic imaging at higher frequencies.

Keywords

• Phononic metamaterials
• Programmable metamaterials
• Nonlinear metamaterials
• Asymmetric unit cell