  Additive manufacturing, such as 3D printing, offers unparalleled
opportunities for rapid prototyping of complex three-dimensional objects, but
typically requires simultaneous building of solid supports to minimize
deformation and ensure contact with the printing surface. Here, we
theoretically and experimentally investigate the concept of material extrusion
on an "air bed", a judiciously engineered acoustic field that supports the
material by contactless radiation force. We study the dynamics of polylactic
acid filament (PLA), a commonly used material in 3D printing, as it interacts
with the acoustic potential during extrusion. We develop numerical models to
determine optimal transducer arrangements and printing conditions, and we build
and demonstrate a concept prototype that integrates a commercial 3D printer and
open-source control code. Our results point towards alternative, contactless
support mechanisms with potential benefits such as fewer surface defects, less
material waste, lower cost, and reduced manufacturing time. These features
could become crucial as additive manufacturing continues to evolve into a
foundational tool in engineering and beyond.
