**1. Introduction**

Micrometer features with hollow parts are increasingly common in many applications [1]. Microneedles, drug delivery systems, and vacuum micro-electronics operating at millimeter-wave frequencies all have hollow micro-structures with dimensions that extend from half millime‐ ter to 1 μm scale. However, mass producing hollow objects at micron resolution is a known challenge in the field of micro-fabrication [2]. Preliminary information about the enabling technologies for realization of suspended or hollow micro-structures is discussed in the sections which follow.

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