Metamaterials are manmade materials which are designed to address a problem by engineering the micro-features. The characteristics of metamaterials are dominated by their newly designed microstructures as compared to the base material. Metamaterials are usually made of repeating unit cells with dimensions smaller than the wavelength of the phenomenon they are designed to interact with. Several topological parameters determine how a permeable metamaterial behaves in different environments. Those topological parameters include the unit cell shape, the pore size, the ligament cross-section shape, and the base material. Among the four main noted characteristics, the pore size is the most important parameter in determining the noise reduction. Pore size is also the main parameter that determines the mechanical, heat transfer, optical, or fluid flow characteristics of permeable metamaterials.
In this research, smart permeable materials, which can sense and interact with their environment has been developed. The predecessors of these permeable metamaterials are open-cell foams, which have been used for decades to interact with fluid flow (i.e. in filters, heat exchangers, radiation shielding, and thermo-acoustics). The problem is that the medium the foams deals with is not always constant and in many cases it varies spatially and temporally. Some recent studies have tried to use additive manufacturing (AM) to optimize topology distribution throughout the structure. Even though the topology optimized permeable metamaterials have several advantages over uniform foams, they still lack the ability of dynamic change in their temporal and local properties which can further increase their functionality for different applications. In this research, innovative active meta-materials have been designed and fabricated which can be used under a multitude of applications. These hybrid metamaterials are composed of an additively manufactured passive skeleton over which an active coating is applied. The active coating changes shape with the help of a pneumatic control mechanism.
Smart permeable porous metamaterials have many potential applications that will contribute to more sustainable and healthier society. The applications include: aero-acoustics (AE), wind-energy, filters (ChemE), crashworthiness and impact damping, vibration damping, and biomedical implants.