From microlattices to 3d microprinting of multiphase micro-components: Resolution limits and mechanical properties under extreme conditions
October 2 – 7, 2022
Two-photon lithography (TPL) enables the fabrication of metamaterials such as polymer micro-lattices. They are designed to achieve their envisioned mechanical properties through stretching and bending of individual trusses. Several novel approaches are developed here to a) directly print metal microlattices, b) fabricate multiphase composite microlattices and c) shrink the truss diameter below the diffraction limit of light, all with the ultimate goal to enable fabrication of a full dense material with microprinted 3D architecture of different phases. Copper microlattices and micropillars with truss diameters in the few micron range were printed directly via fluid AFM based local electroplating . It was identified that microcrystalline copper micropillars deform in a singleshear like manner exhibiting a weak strain rate dependence at all strain rates. Ultrafine grained (UFG) copper micropillars, however, deform homogenously via barreling and show strong rate-dependence and small activation volumes at strain rates up to ∼ 0.1 s−1, suggesting dislocation nucleation as the deformation mechanism. At higher strain rates, yield stress saturates remarkably, resulting in a decrease of strain rate sensitivity implying a transition in deformation mechanism to collective dislocation nucleation. Finally, the copper microlattices are shown to increase in strength if conformally coated with Nickel with thicknesses in the several 100nm range.
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Johann Michler, Jakob Schwiedrzik, Manish Jain, Rajaprakash Ramachandramoorthy, Szilvia Kalacska, and Alexander Groetsch, "From microlattices to 3d microprinting of multiphase micro-components: Resolution limits and mechanical properties under extreme conditions" in "Nanomechanical Testing in Materials Research and Development VIII", Sandra Korte-Kerzel, RWTH Aachen University, Germany Eds, ECI Symposium Series, (2022). https://dc.engconfintl.org/nanomechtest_viii/87