Cavitation-driven Deformable Microchambers Inspired by Fast Microscale Movements of Ferns

Annulus cells of fern sporangia spontaneously deform driven by water transpiration and cavitation, resulting in the peculiar macroscale catapult-like movement of the sporangium. Annulus cells' behavior, if artificially replicated, can inspire a novel class of fast actuators composed of annulus-mimicking units. However, the transpiration and cavitation-driven dynamics observed in annulus cells is never reproduced. Here, prismatic microcavities are assembled with a polydimethylsiloxane (PDMS) microfilm to realize artificial microchambers that mimic the annulus cells, replicating for the first time their evaporation-driven collapse and their fast return triggered by the nucleation of bubbles. The microchambers, in turn, can be fabricated in adjacency, resulting in bending arrays driven by transpiration. Working with an artificial system allows this study to investigate the fluidic phenomena arising from the interplay of a soft, semi-permeable membrane with a micro-confined liquid bounded by rigid walls. First, the microchambers aspect ratio influences the membrane dynamics and the bubble shape (either spherical or non-spherical). Second, the growth rate of the bubble interplay with the membrane in the expansion dynamics. This study's results demonstrate the artificial replication of annulus cells' behavior, offering a plant-like solution to realize fast, microscale movements, and a novel tool to investigate complex fluidic mechanisms involving micro-confined cavitation.

Automated summary

Annulus cells of fern sporangia exhibit unique catapult-like movement driven by water transpiration and cavitation. This study successfully replicated the evaporation-induced collapse and fast recovery of annulus cells, providing inspiration for artificial fast actuators composed of annulus-mimicking units.