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Metallic microstructures often are the key components in many applications, e.g. in wireless communication. While these components usually are planar, a number of benefits result from being able to fabricate 3D structures – broadband antennas being an example. Here, we show that direct laser writing enables the fabrication of 3D silver microstructures via photoreduction. A number of sample structures are presented to proof the versatility of this method. Since material properties, e.g. conductivity, of 3D printed structures often differ from their counterparts fabricated by subtractive methods, we furthermore throughout characterize these properties for our 3D printed samples.
Fabrication of metallic structures by direct laser writing is based on the following mechanism: a photoreducing agent is two-photon excited by a focused laser beam and in its excited state has a higher reduction potential. Alternatively, the reducing agent may undergo a chemical reaction after excitation and its products have a higher reduction potential. In either case, this leads to the reduction of a metal precursor to neutral metal. If sufficient metal atoms are in close proximity, they nucleate and grow by adding further atoms to finally form the fundamental building block of the final structure. The complex nature of these chemical and physical processes usually limits this method to rather robust structures with large feature sizes. Here, we present how filigree silver micro-structures with feature sizes below 1 micron may be achieved using the described technique but we also show the current limits. Furthermore, the mechanical and electronic properties of these structures are characterized.
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