  In this paper we present an inverse-designed 3D-printed all-dielectric
stretchable millimeter wave metalens with a tunable focal distance.
Computational inverse-design method is used to design a flat metalens made of
disconnected building polymer blocks with complex shapes, as opposed to
conventional monolithic lenses. Proposed metalens provides better performance
than a conventional Fresnel lens, using lesser amount of material and enabling
larger focal distance tunability. The metalens is fabricated using a commercial
3D-printer and attached to a stretchable platform. Measurements and simulations
show that focal distance can be tuned by a factor of 4 with a stretching factor
of only 75%, a nearly diffraction-limited focal spot, and with a 70% focusing
efficiency. The proposed platform can be extended for design and fabrication of
multiple electromagnetic devices working from visible to microwave radiation
depending on scaling of the devices.
