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A locally resonant meta-surface for preferential excitation of a guided mode in a hollow pipe can improve ultrasonic guided wave inspection of pipelines. The proposed meta-surface comprises a periodic arrangement of bonded prismatic rod-like resonators in the circumferential and axial directions of the pipe. We demonstrate the presence of bandgaps for the low-frequency axisymmetric longitudinal modes L(0,1) and L(0,2) and the torsional mode T(0,1). The generated bandgaps can be used to filter the higher harmonics associated with the system nonlinearity to improve nonlinear ultrasonic measurements on pipes. These bandgaps exist even for the non-axisymmetric flexural modes but with their hybridized dispersion curves exhibiting mode-coupling for higher circumferential orders. Moreover, a “partial” bandgap is obtained where preferential transmission of the L(0,2) mode over L(0,1) is possible. We discuss the potential advantages of this partial bandgap to improve pipeline inspections using the L(0,2) mode. Time-domain finite element analyses are used to validate the presence of these bandgaps under radial, circumferential, and axial excitation that mimics the excitation using a ring of piezoelectric transducers. Finally, we discuss the influence of resonator spacing, filling fraction, and the number of resonator rings on the bandgaps for an informed meta-surface design.
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This content will become publicly available on August 1, 2026
Multi‐Mode Mechanochromic Responses from Cholesteric Liquid Crystal Elastomer Tubes of Uniform Sheath
Abstract Materials that exhibit varied optical responses to different modes of mechanical stimuli are attractive for complex sensing and adaptive functionalities. However, most mechanochromic materials are fabricated from films or fibers with limited actuation modes. Here, hollow tubes of a symmetric sheath are created using cholesteric liquid crystal elastomers (CLCEs) at the sub‐millimeter scale. The oligomeric precursor is sheared in an elastomeric microchannel to form uniform thickness, overcoming gravity effect and Plateau‐Rayleigh instability. In addition, the coloration is achieved to be faster and have higher reflectivity compared to that of solid fibers. The tube can undergo axial, circumferential, and radial strains upon extension and inflation. The combination of molecular anisotropy and geometry of the tube enables highly sensitive mechanochromic responses in both azimuthal and axial directions: inflation causes red‐to‐violet shift (≈220 nm) at a circumferential strain of 0.57. The inflation of a bent tube generates another mechanochromic mode with a higher sensitivity to strain. Finally, display of 26 alphabets is achieved using 5 tubes, of which the positions can be reconfigured, and curvature‐dependent 3D photonic skins are demonstrated from tubes wrapped around 3D objects. The multi‐mode mechanochromic tubes will find applications for soft robotics, adaptive displays, wearable sensors, and spectrometers.
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- Award ID(s):
- 2037097
- PAR ID:
- 10650909
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 37
- Issue:
- 34
- ISSN:
- 0935-9648
- Page Range / eLocation ID:
- 2504461
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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