Viscous fingering in volatile fluid towards spontaneous evolution of well-ordered 3D patterns

Mimicking nature using artificial technologies has always been a quest/fascination of scientists and researchers of all era. This paper characterizes viscous fingering instability-based, lithography-less, spontaneous, and scalable process for fabricating 3D patterns like a nature-inspired honeycomb structure with ultra-high aspect ratio walls. Rich experimental data on volatile fluids shaping in uniport and multiport lifted Hele-Shaw cells (ULHSC and MLHSC) obtained through extensive experiments is represented on a non-dimensional phase plot. The phase 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’ evolution. A new non-dimensional ratio of the velocity of evaporating static interface vs. lifting velocity is proposed for the same. This work establishes a solid foundation with valuable insights for scalable manufacturing of devices useful for application in biomedical and other domains.