title: A new approach to nucleation of cavitation bubbles at chemically modified surfaces.
abstract: Cavitation at the solid surface normally begins with nucleation, in which defects or assembled molecules located at a liquid-solid interface act as nucleation centers and are actively involved in the evolution of cavitation bubbles. Here, we propose a simple approach to evaluate the behavior of cavitation bubbles formed under high intensity ultrasound (20 kHz, 51.3 W cm(-2)) at solid surfaces, based on sonication of patterned substrates with a small roughness (less than 3 nm) and controllable surface energy. A mixture of octadecylphosphonic acid (ODTA) and octadecanethiol (ODT) was stamped on the Si wafer coated with different thicknesses of an aluminium layer (20-500 nm). We investigated the growth mechanism of cavitation bubble nuclei and the evolution of individual pits (defects) formed under sonication on the modified surface. A new activation behavior as a function of Al thickness, sonication time, ultrasonic power and temperature is reported. In this process cooperativity is introduced, as initially formed pits further reduce the energy to form bubbles. Furthermore, cavitation on the patterns is a controllable process, where up to 40-50 min of sonication time only the hydrophobic areas are active nucleation sites. This study provides a convincing proof of our theoretical approach on nucleation.
authors: Department of Interfaces, Max-Planck Institute of Colloids and Interfaces, Potsdam, D14476, Germany. valentina.belova@mpikg.mpg.de
authors: Valentina
authors: V
authors: Belova
authors: Dmitry G
authors: DG
authors: Shchukin
authors: Dmitry A
authors: DA
authors: Gorin
authors: Alexey
authors: A
authors: Kopyshev
authors: Helmuth
authors: H
authors: Möhwald
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D063065:Organophosphonates / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry*; D013010:Sonication / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D063065:Organophosphonates; D012833:Siloxanes; D013438:Sulfhydryl Compounds; D000535:Aluminum