  We describe two general procedures for fabricating microstructures with large
overhangs and high aspect-ratio support pillars. The first method uses a static
angled dry etch on micro- or nano-pillars to create an initial overhang,
followed by wet etching for further erosion. The second method uses a
time-dependent angled etch on a flat plane patterned with protective resin, to
reduce the number of lithography steps needed to make these objects. The
time-dependent dry etch is again followed by a wet etch. For the second method
we derive a formula that provides the rate at which the attack angle must
evolve, given a known etch rate within the target material, the depth of the
desired overhang (undercut), and the instantaneous attack angle.
