The circular liquid film interface disintegrates randomly at multiple places because of Saffman Taylor instability, producing air fingers on the boundary. Plate separation induces a parabolic pressure drop in the liquid film dragging the surrounding low viscous air into the film. In LHSC, a viscous liquid droplet is first sandwiched and squeezed between two parallel plates to form a circular film and then the plates are separated after a small delay.

A lifted Hele-Shaw cell (LHSC) 17, 18, 19, 20, 21 is a modified version of a conventional Hele-Shaw cell. Fluid flow in porous media 8, 9, and fluid flow in a linear 7, 10, 11 or radial 12 Hele-Shaw cell experience this fingering instability 12, 13, 14, 15, 16. It is an interfacial instability that occurs when a low viscous fluid is forced to flow into a high viscous fluid film, generating fascinating fractal-like patterns. The physics behind the fluid shaping 5, 6 is based on exercising control over Saffman Taylor instability 7, also known as viscous fingering. The work thus establishes a solid foundation with valuable insights for scalable manufacturing of devices useful for application in biomedical and other domains.

This phase plot along with physical insights into the phenomena observed, pave pathways for extending the method to multiport LHSC (MLHSC) to demonstrate multiwell honeycomb structures. A new non-dimensional ratio of the velocity of evaporating static interface versus lifting velocity is proposed for the same. The plot with five orders of magnitude variation of non-dimensional numbers on each axis demarcates the regions of several newly observed phenomena: ‘No retention’, ‘Bridge breaking’, and ‘Wall formation’ with ‘stable’ and ‘unstable’ interface evolution. Rich experimental characterization data on volatile polymer solution evolution in a uniport lifted Hele-Shaw cell (ULHSC) is represented on a non-dimensional phase plot. This paper characterizes viscous fingering instability-based, lithography-less, spontaneous, and scalable process towards fabrication of 3D patterns like nature-inspired honeycomb structures with ultra-high aspect ratio walls. Mimicking nature using artificial technologies has always been a quest/fascination of scientists and researchers of all eras.

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