Shape-morphing polymers for tunable frequency selective surfaces and reflectarray elements

This work presents a route to rapidly configuring electromagnetic metamaterials and elements such as reflectarrays from a generic 'blank'. The concept is based upon the thermal-shrinkage properties of prestrained polystyrene (PPS), which is utilized in two distinct designs: In the first, an array of resonant split rings is printed upon a sheet of PPS. It is shown that heating to near the glass transition temperature of the sheet can controllably shrink the entire structure, thereby tuning its spectral transmission or reflection. A second application is to make coupled resonant elements, one of which is placed on a hinge of PPS that can be deformed via optical illumination, providing an optical route to tuning the resonance. This kind of element can show a large range of phase shifts in the reflected radiation, and opens the door to the creation of optically configurable reflectarrays.