A New Method for Intense Cavitation Bubble Generation on Layer-by-Layer Assembled SLIPS

Abstract

The importance of surface topology for the generation of cavitating flows in micro scale has been emphasized during the last decade. In this regard, the utilization of surface roughness elements is not only beneficial in promoting mass transportation mechanisms, but also in improving the surface characteristics by offering new interacting surface areas. Therefore, it is possible to increase the performance of microfluidic systems involving multiphase flows via modifying the surface. In this study, we aim to enhance generation and intensification of cavitating flows inside microfluidic devices by developing artificial roughness elements and trapping hydrophobic fluorinated lubricants. For this, we employed different microfluidic devices with various hydraulic diameters, while roughness structures with different lengths were formed on the side walls of microchannel configurations. The surface roughness of these devices was developed by assembling various sizes of silica nanoparticles using the layer-by-layer technique (D2). In addition, to compare the cavitating flow intensity with regular devices having plain surfaces (D1), highly fluorinated oil was trapped within the pores of the existing thin films in the configuration D2 via providing the Slippery Liquid-Infused Porous Surface (D3). The microfluidic devices housing the short microchannel and the extended channel were exposed to upstream pressures varying from 1 to 7.23 MPa. Cavitation inception and supercavitation condition occured at much lower upstream pressures for the configurations of D2 and D3. Interestingly, hydraulic flip, which rarely appears in the conventional conical nozzles at high pressures, was observed at moderate upstream pressures for the configuration D2 proving the air passage existence along one side of the channel wall.

Fundamentals, biomedical applications and future potential of micro-scale cavitation-a review

“…It is worth mentioning that the homogenous nucleation mechanism does not have a dominant role in micro-scale cavitation. 31,32,49,50 Surface modification effects on the bubble generation. In a previous study, Mishra and Peles 32 discussed heterogeneous nucleation, which was attributed to the utilized microfabrication method.…”

“…It is worth mentioning that the homogenous nucleation mechanism does not have a dominant role in micro-scale cavitation. 31,32,49,50…”

“…These two studies indicate that the nucleation site population could be optimized by surface engineering in micro-scale. In a late study, Aghdam et al 50 investigated the possibility of increasing the performance of cavitation on-a chip devices by modifying the microfluidic device surface by assembling various sizes of silica nanoparticles using the layer-by-layer (LbL) technique. They suggested that utilizing the LbL technique as an advanced surface engineering technique raises the number of nucleation sites and enhanced the interacting surface area for heterogeneous nucleation.…”

“…Hydrodynamic cavitation in microfluidic devices occurs when the fluid flow experiences a considerable static pressure drop when it passes through a flow restrictive element inside a microchannel. In this regard, different geometries (micro-orifices, 15 micro-Venturis, 28,64 micro-diaphragms, 28,64 micro-pillar, 65 micro-steps 46 ), functional surfaces (hydrophilic or hydrophobic, 50 roughen or patterned 66 ), working fluids (isotropic or anisotropic, 67 pure or impure, 28,68 mixtures 29 ) were utilized to characterize various micro-scale cavitation flow patterns. In a pioneering study, Mishra et al 15 developed the first microfluidic device to study micro-scale cavitation using water as the working fluid.…”

Tailoring the Icephobic Performance of Slippery Liquid-Infused Porous Surfaces through the LbL Method

“…The nanoscale thickness of the thin film and the simplicity of its application on the surface, regardless of the geometry of the substrate, are the outstanding advantages of using the LbL method for creating a stable SLIPS surfaces. Using the fluidic LbL deposition technique, we applied LbL-based SLIPS thin films inside microfluidic channels to obtain cavitating flows for biomedical and energy applications, − which is not easy to achieve by other techniques and methods.…”