Knitting with fluids: architected elastic structures formed by capillary flow in Hele-Shaw cell.

We propose a methodology to fabricate 2D elastic networks using the rules and tools of fluid mechanics. Our approach consists in pouring a polymeric solution on top of a Hele-Shaw cell, whose top wall presents a series of holes. Owing to capillary forces, the fluid invades the cell and spreads in a pattern defined by the location of the holes. Eventually, the polymer cures and freezes the flow in a 2D elastic material. Depending on the position and the distance between the holes, connected networks of cellular structures or architectured structures of connected polygons can be easily fabricated. We study this problem theoretically to rationalize the composition and geometry of the myriad structures we observe in our experiments.