Design and characterization of a coating device to enable multilayer structures in microscale selective laser sintering

The microscale selective laser sintering process (µ-SLS) is an additive manufacturing technique that enables the creation of metal features with sub-5 µm in-plane resolution. In this process, a layer of metal nanoparticle ink is deposited onto a substrate and positioned beneath an optical subsystem with a nanopositioning stage. Using a digital micromirror device, a laser is spatially modulated to selectively heat particles in desired regions to cause sintering. The substrate is then moved to a coating station where the sintered features are recoated by a meniscus-guided coating process. The slot-die coating process was originally proposed and adopted as the recoating method for this critical step. Due to challenges with depositing consistent ink thickness across the recoated part and limitations with the volumetric resolution, a new meniscus-guided approach inspired by blade coating has been implemented and is able to recoat parts with layer thicknesses of less than 1 µm. Additionally, the multilayer performance of µ-SLS has improved significantly, now able to produce fully sintered layers up to a depth of 50 microns of material.