Dynamically reconfigurable metamaterials using pneumatics, flexibility and structural nonlinearity

Metamaterials are composites consisting of sub‐wavelength resonant elements aiming to manipulate the material's electromagnetic properties. One of the advantages of artificially created materials over natural materials is the possibility to custom design and tune their properties as one desires. Metamaterials continue to draw the attention of the research community as new and significantly enhanced phenomena associated with them are discovered. Significant effort has also been devoted to integrating them with existing structures for potential applications in sensing, defence and next generation devices. Due to the resonant nature of the metamaterial elements, the desired properties are achieved only within a narrow frequency band. For various applications, it is desirable to be able to tune their frequency response. Although the connection between the modification of geometry of the resonators and resultant variations in their response individually and as an effective media has been extensively studied, the area of dynamic tuning could benefit from further investigation. The major contribution made by this work includes investigation of real time tuning possibilities and developing new approaches for altering the shapes and orientations of metamaterial resonators, post fabrication, as means of widening flexibility in the design and improving variety of responses. A novel pneumatic switching approach is demonstrated for alteration of the shape of the resonators via addition or retraction of pneumatic elements, as well as application of this method to the realisation of a switchable graded index lens. Further, suspended resonators with mechanical degrees of freedom have been realised which allow shifts in their position and orientation leading to nonlinear effects. A new microfabricated mesh substrate with significantly reduced mass was developed. Embedding resonators into elastic substrates has also been explored for stretching and conformal adhesion purposes. Most of the work is for metamaterials operating in the microwave frequency range (GHz), except elastic metamaterial intended for far infrared (THz) frequencies. In summary, metamaterial tuning approaches have been extended to dynamic manipulation of both shape and orientation of resonators providing greater flexibility and control over effective material parameters.