Mrs. Hilla Ayali Aviram - M.Sc. Candidate
04/10/2026
אודיטוריום ע"ש דויד וואנג, בניין מידן, קומה 3
13:30
Natural superhydrophobic, self-cleaning surfaces, exemplified by the well-known "lotus effect", with water contact angle over 150° and contact angle hysteresis below 10°, have inspired decades of research into the role of hierarchical roughness and epicuticular wax chemistry in generating a stable Cassie–Baxter wetting state. Breynia nivosa (B. nivosa) is an a shrub whose leaves are naturally coated with a crystalline epicuticular wax layer. Native to the humid tropical regions of Asia, B. nivosa rely on its epicuticular wax layer to repel moisture, keep its leaves clean, and reduce the likelihood of fungal pathogen germination on its leaf surface. This work investigates B. nivosa as a model system for understanding how nanostructured wax governs superhydrophobicity, self-cleaning, and condensation behavior.
Using high-resolution synchrotron powder X-ray diffraction, scanning and atomic force microscopy, contact-angle measurements, gas chromatography-mass spectrometry, and condensation experiments, this study reveals for the first time the wax composition of B. nivosa, dominated by 1-triacontanol, which self-assembles into a rosette architecture of nanocrystals. Removal of this wax layer reduces surface roughness and hydrophobicity, and accelerates droplet coalescence during condensation. Damaged leaf surfaces show self-healing recovery over time.
Guided by the identified wax composition, bio-inspired synthetic surfaces were fabricated via thermal evaporation, successfully replicating the natural platelet morphology. Wettability was governed by the interplay of molecular chemistry and surface roughness, with pure long-chain alkane reaching superhydrophobic contact angles. XRD analysis of the surfaces before and after thermal treatment further revealed that processing conditions govern molecular orientation and lamellar order, distinctly for each precursor. Together, these findings establish design principles for bio-inspired superhydrophobic coatings.