Strain Sensing with Metamaterial Composites

Abstract

Mapping strain fields in visually opaque structural composites -for which failure is often sudden, irreparable, and even catastrophic -requires techniques to locate and record regions of stress, fatigue, and incipient failure. Many composite materials are transparent in the terahertz spectral region, but their strain history is often too subtle to recover. Here, terahertz metamaterials with strain-severable junctions are introduced that can identify structurally compromised regions of composite materials. Specifically, multi-layer arrays of aluminum meta-atoms were designed and fabricated as strip dipole antennas with a terahertz frequency resonance and a strong response to cross polarized radiation that disappears when local stress irreversibly breaks their bowtie-shaped junction. By spatially mapping the local polarimetric response of this metamaterial as a function of global strain, the regions of local stress extrema experienced by a visually opaque material may be visualized. This proof-of-concept demonstration heralds the opportunity for embedding metamaterial laminates within composites to record and recover their strain-dependent history of fatigue.The widespread proliferation of composite materials in civilian, industrial, and military sectors has created a need for tools to monitor their structural health and warn of incipient failure. Many techniques have been tried, including embedded sensors, laser surface mapping, acoustic transducers, x-ray imaging, and terahertz imaging concepts. [1][2][3][4][5][6] The opacity of most composites prevents the use of common optical polarimetric techniques for measuring photoelasticity, while stress-induced birefringence produces weak refractive index anisotropies at terahertz frequencies that are difficult to measure. [7,8] Many of these techniques can identify damaged regions, but none Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

Dual-Axis Metasurface Strain Sensor Based on Polarization–Phase-Deformation Relationship

“…As a summary of the capability of sensitivity on basis of our method by comparing with research on characteristics of magnitude or frequency, the performance improved significantly. In previous studies, for the 1% strain state (which can be regarded as a slight strain applied), on characteristics of magnitude, the magnitude shift Magnitude in 1% strain state Magnitude at no strain case − 1 of concerned feature is about 25% in [28] and 10% in [27], while of frequency, the frequency shift Frequency in 1% strain state Frequency at no strain case − 1 is about 0.15% in [21] and 4% in [22]. By employing our method, the magnitude shift of co-polarized linear-polarized, left-hand, and right-hand circular-polarized component is around 20%, 40%, and 100%, respectively.…”

“…From the perspective of the operational mechanism, sensing based on the change in the resonance frequency shift [20][21][22][23][24] and the magnitude of transmissivity/reflectivity/absorptivity [25][26][27][28][29][30] with Sensors 2020, 20, 1307 2 of 12 deformation are the two principal methods for strain sensing. Also, some works of chipless radio frequency identification devices (RFID) sensors show a good sensitivity performance, which can be well-referred to sensors design [31][32][33][34].…”

“…In [20], numerical equivalent circuit calculations were used to analyze the frequency shift of an MM electric-LC resonator by obtaining its strain-dependent permittivity and permeability. A multilayer array with meta-atoms of strip dipole antenna were designed and fabricated in [28], where a strong response to cross-polarized radiation is modified by breaking the bowtie-shaped junction under the application of strain, resulting in a transmissivity change. Additionally, studies of wrinkled deformation have been performed recently.…”

Metamaterials – from fundamentals and MEMS tuning mechanisms to applications

“…In the MEMS actuated metamaterials, actuators enable the structure reconfiguration and the active control of the unit cell, Figure 1: A block-diagram illustration for the integration of microelectromechanical system (MEMS) and metamaterials: MEMS actuated metamaterials and plasmonically enhanced physical sensors. Milestones for the former include tunable emitter/absorber [40], hologram [41], tunable waveplate [41], and metalens [42] while milestones for the latter include IR detector [43], spectrometer [44], strain sensor [45] and photoswitch [46]. demonstrating advanced tunability in infrared emitters/ absorbers [39], holograms [40], waveplates [41], and metalens [42].…”

“…The plasmonically enhanced physical sensor makes use of the engineered spectral response from metamaterials, such as extraordinary optical transmission, wavelength selectivity, and enhanced absorption. Milestones include metamaterial integrated IR detector [43], spectrometer [44], strain sensor [45] and photoswitch [46]. Furthermore, we note that there could be certain ambiguities when the terms "metamaterials" and "plasmon" are used.…”