Work Package 1: Hummingbird tongue
In this work package, the focus shifted to studying ribbed sheets that mimic the structure of the annulus in the fern sporangium, revealing a rich physics when impregnated with a liquid.
A protocol was developed to manufacture thin textured sheets using techniques such as 3D printing of molds and spincoating for controlling thickness.
Collaboration was initiated with Dr. Jean Cappello, an expert in small-scale capillary flows, to leverage his expertise in the research.
Through experiments, three distinct deformation modes of the sheet were identified as the liquid evaporated, and an analytical model was developed to explain these observations.
A noteworthy finding was the ability to precisely program the deformed shape by manipulating the geometry of the textures on the sheet.
The research culminated in a publication in the Proceedings of the National Academy of Sciences (PNAS) and the receipt of the International Bionic Award from the Association of the German Engineers (VDI) for outstanding contributions to biomimetics.
Work Package 2: Bumblebee tongue
The first subtask focused on investigating the impregnation of soft brushes, which uncovered a previously unreported subcritical transition to coalescence of fibers as they were withdrawn from a liquid bath.
Collaboration with Fabian Brau led to the development of an analytical model that explained this phenomenon, and the results were published in Extreme Mechanics Letters.
Dynamical aspects of the study, particularly the impact of withdrawal speed on capillary "Cheerios" force, are currently being reviewed for publication in Physical Review Letters.
The second subtask, which involves the impregnation of controlled soft hairy surfaces, is currently ongoing, with experiments and simulations being conducted to characterize different regimes based on hair network geometry, elasticity, bath viscosity, and withdrawal speed.
Work Package 3: Design of innovative structures
Ribbed sheets with intriguing mechanical properties were designed and characterized, highlighting a strong coupling between stretching and bending in these structures.
The optimal geometry of the ribs was determined to maximize this effect. The research outcomes resulted in a publication in Physical Review Letters and recognition in Physics Magazine through a synopsis.
Furthermore, iI demonstrated that these ribbed sheets could be utilized to program 3D structures through the evaporation of an infused liquid.
Overall, the work performed during this project has advanced the understanding of fluid-structure interaction between slender hierachical structures and viscous capillary flow.
The research findings have been disseminated through high-impact publications and recognized through an award, underscoring the significance and impact of the research endeavors.
