  Many emerging applications in microscale engineering rely on the fabrication
of three-dimensional architectures in inorganic materials. Small-scale additive
manufacturing (AM) aspires to provide flexible and facile access to these
geometries. Yet, the synthesis of device-grade inorganic materials is still a
key challenge towards the implementation of AM in microfabrication. Here, we
present a comprehensive overview of the microstructural and mechanical
properties of metals fabricated by most state-of-the-art AM methods that offer
a spatial resolution $\leq$10$\mu$m. Standardized sets of samples were studied
by cross-sectional electron microscopy, nanoindentation and microcompression.
We show that current microscale AM techniques synthesize metals with a wide
range of microstructures and elastic and plastic properties, including
materials of dense and crystalline microstructure with excellent mechanical
properties that compare well to those of thin-film nanocrystalline materials.
The large variation in materials performance can be related to the individual
microstructure, which in turn is coupled to the various physico-chemical
principles exploited by the different printing methods. The study provides
practical guidelines for users of small-scale additive methods and establishes
a baseline for the future optimization of the properties of printed metallic
objects $-$ a significant step towards the potential establishment of AM
techniques in microfabrication.
