Methods of rapidly prototyping microstructures such as HARMs are disclosed. A high precision process uses polymeric microstructure replication techniques and sacrificial layer etching techniques to mass produce high aspect ratio metallic and polymer micromold inserts. In one embodiment, after fabrication of an initial micromold insert, high aspect ratio replications are created by casting replication material, such as PDMS, directly onto the initial micromold insert. The replicated HARM is coated with a sacrificial layer and then electroplated to replicate another set of micromold inserts. After the electroplating process is completed, the sacrificial layer is etched away to release the replicated micromold inserts.