■ Elastic Metamaterials

Elastic metamaterials are manufactured materials exhibiting extraordinarily mechanical properties not found in natural materials, such as infinite/near-zero/negative density/stiffness or extreme anisotropy. Our research goal is to understand wave physics and realize extraordinary wave phenomena such as elastic wave mode conversion, sensing and actuation enhancement, and wavefront manipulation using elastic metamaterial concept. This concept not only provides new insights into understanding wave phenomena in elastic solids but also opens a new paradigm for manipulating elastic waves.

Elastic Wave Mode (or Polarization) Conversion 

The multi-modal characteristic of elastic waves enriches their wave phenomena, the most unique of which is mode (or polarization) conversion. Anisotropic metamaterials provide a novel and promising strategy for the realization of not only longitudinal-to-transverse mode conversion but also linear-to-circular polarization conversion of an “elastic” wave, previously thought to be impossible. The application range is wide, from flow measurement to thickness measurement to sludge inspection. 

Sensing and Actuation Enhancement

Elaborate and high-efficiency actuation and sensing of guided waves are essential for non-destructive testing or structural health monitoring using guided waves. We develop novel resonant-type elastic metamaterials that can substantially enhance the actuation and sensing efficiency of transducers for guided waves. Actual experiments confirmed a 300% far-field output enhancement when the proposed resonators surrounded the transducer. 

Wavefront manipulation

Wavefront manipulation is a key application in fields utilizing elastic waves, such as non-destructive testing and medical ultrasonic devices. Conventional ultrasonic devices that manipulate elastic waves are often bulky and expensive. We develop thin and passive structures using the metamaterial concept to manipulate the wavefronts of elastic waves.