Fabrication of meso sized structures through controlled viscous fingering in Lifting Plate Hele-Shaw Cell with holes and slots

Lifting plate Hele-Shaw cell involves a high viscous fluid sandwiched between two parallel plates. The low viscosity fluid (air) enters from the periphery when one of the plates is lifted away from another plate. The air penetrates a high viscous fluid at various points from the periphery. This penetration causes the formation of a tree-branch-like structure called viscous fingering. Due to this insertion, sandwiched fluid changes its structure. This structural change is known as instability. The viscous fingers generated through this flow are highly random and unstable. This study presents methods to control the instabilities. The study reports control techniques by providing anisotropies (holes and slots) on any one of the plates. The study further presents the effect of size, position, and the orientation of these holes and slots on the viscous fingering exhaustively. Deployment of these control techniques leads to the emergence of new fabrication techniques with the potential to develop meso-sized finger patterns spontaneously without expensive setup as otherwise required in the lithography process. To demonstrate the capability of this proposed fabrication technique, various net-shaped patterns available in nature are mimicked. These developed miniature patterns can be used in various applications such as micro-mixers, micro-heat exchangers, etc.