Building with blobs: harnessing liquid thread instability to assemble regular structures

3D printing has become an increasingly popular means of manufacturing thanks to the low-cost and accessible nature of Fused Deposition Modeling (FDM) machines, now common fixtures in most labs, workshops, and even homes. Under-extrusion is commonly encountered in FDM printing where too small of a volume of filament is supplied to the nozzle during a print. Reminiscent of a leaky faucet, the melted filament drips as the machine prints in a line, forming a sequence of viscous blobs and more finely drawn threads. Here we show that this instability can be harnessed to assemble regular lattices. We rationalize the physics at play in this problem and leverage our understanding of the problem to provide design guidelines to practitioners.