  We present the design and fabrication of 3D printed holographic beamforming
antennas. The antennas utilize additively manufactured hollow rectangular
waveguides that feed radiating rectilinear slots inserted into the upper
conducting wall. The lengths of the individual slots are altered to implement a
holographic beamforming solution designed using a coupled dipole formalism. For
rapid verification, the designed antennas are fabricated using a desktop
dual-extrusion fused filament 3D printer. The body of each antenna and its
inner conducting surface are respectively printed using polylactic acid and
biodegradable conductive polyester composite material (i.e., Electrifi), which
is later deposited with a layer of copper on its surface to improve surface
conductivity and reduce surface roughness. The beamforming performance of the
fabricated antennas is confirmed via experiments. The 3D printed metasurface
antennas using the proposed fabrication technique illustrate emerging
capabilities in the rapid prototyping of complex electromagnetic structures.
