On cavitation inception and cavitating flow patterns in a multi-orifice microfluidic device with a functional surface

During the last decade, hydrodynamic cavitation has been implemented in various applications such as energy harvesting and biomedical applications. Facile hydrodynamic cavitation methods are required for fulfilling the requirements in these applications. In this study, a new generation microfluidic device containing eight parallel micro-orifices with a new design was fabricated and tested with the purpose of intensifying the cavitating flows and early cavitation inception. The roughness elements in the micro-orifices facilitated cavitation inception. This study presents a general perspective of occurrence of different cavitating flow patterns in microscale and addresses the ambiguities about the conditions for the formation of a specific flow pattern. Cavitation inception occurred with the appearance of small bubbles emerging from roughness elements at a rather low upstream pressure in the open loop experimental setup. A reduction in the cavitation number resulted in the formation of different flow patterns such as cavitation clouds, twin cavities, sheet cavities, and bubbly flows. Having several flow patterns with different intensities all together within a single microfluidic device is the main advantage of the proposed device over the state of the art microfluidic devices. Generation of flow patterns with various released energy levels makes this proposed device a unique multi-functional platform, which can be implemented to a lab on a chip platform for applications such as nanoparticle synthesis and wound healing.

Engineered Lateral Roughness Element Implementation and Working Fluid Alteration to Intensify Hydrodynamic Cavitating Flows on a Chip for Energy Harvesting

Morteza Ghorbani, Luis Guillermo Villanueva Torrijo

Hydrodynamic cavitation is considered an effective tool to be used in different applications, such as surface cleaning, ones in the food industry, energy harvesting, water treatment, biomedical applications, and heat transfer enhancement. Thus, both characterization and intensification of cavitation phenomenon are of great importance. This study involves design and optimization of cavitation on chip devices by utilizing wall roughness elements and working fluid alteration. Seven different microfluidic devices were fabricated and tested. In order to harvest more energy from cavitating flows, different roughness elements were used to decrease the inlet pressure (input to the system), at which cavitation inception occurs. The implemented wall roughness elements were engineered structures in the shape of equilateral triangles embedded in the design of the microfluidic devices. The cavitation phenomena were also studied using ethanol as the working fluid, so that the fluid behavior differences in the tested cavitation on chip devices were explained and compared. The employment of the wall roughness elements was an effective approach to optimize the performances of the devices. The experimental results exhibited entirely different flow patterns for ethanol compared to water, which suggests the dominant effect of the surface tension on hydrodynamic cavitation in microfluidic channels.

2019

On "Cavitation on Chip" in Microfluidic Devices With Surface and Sidewall Roughness Elements

Morteza Ghorbani, Ahmad Reza Motezakker, Luis Guillermo Villanueva Torrijo

In this paper, cavitating flows are characterized in 29 microfluidic devices in order to achieve a comprehensive perspective regarding flow patterns in microscale, which is crucial in the applications, such as energy harvesting and biomedical treatment. While the assessment of size effects is vital for the design and development of microfluidic devices involving phase change, surface/sidewall roughness and pressure pulses as a result of nanomechanical oscillations increase the performance with respect to cavitation by providing more cavitation bubbles. A typical device generates cavitating flows under different conditions (from inception to choked flow). In this device, a restrictive element and a big channel downstream of the restrictive element-where the cavitation is formed and developed-are included. The cavitating flows are obtained inside 24 sidewall roughened and 5 surface roughened/plain microfluidic devices at different pressure drops. The length and height of the sidewall roughness elements are varied to achieve the most optimum performance in terms of cavitation generation. Moreover, different surface roughened and plain devices are considered to provide a comprehensive overview of cavitation generation in microscale. The results show that sidewall roughness elements have a remarkable effect on the cavitation inception and flow patterns.

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2019

Design and fabrication of a vigorous "cavitation-on-a-chip" device with a multiple microchannel configuration

Morteza Ghorbani, Mohammad Jafarpour, Luis Guillermo Villanueva Torrijo, Merve Zuvin

Hydrodynamic cavitation is one of the major phase change phenomena and occurs with a sudden decrease in the local static pressure within a fluid. With the emergence of microelectromechanical systems (MEMS), high-speed microfluidic devices have attracted considerable attention and been implemented in many fields, including cavitation applications. In this study, a new generation of 'cavitation-on-a-chip' devices with eight parallel structured microchannels is proposed. This new device is designed with the motivation of decreasing the upstream pressure (input energy) required for facile hydrodynamic cavitation inception. Water and a poly(vinyl alcohol) (PVA) microbubble (MB) suspension are used as the working fluids. The results show that the cavitation inception upstream pressure can be reduced with the proposed device in comparison with previous studies with a single flow restrictive element. Furthermore, using PVA MBs further results in a reduction in the upstream pressure required for cavitation inception. In this new device, different cavitating flow patterns with various intensities can be observed at a constant cavitation number and fixed upstream pressure within the same device. Moreover, cavitating flows intensify faster in the proposed device for both water and the water-PVA MB suspension in comparison to previous studies. Due to these features, this next-generation 'cavitation-on-a-chip' device has a high potential for implementation in applications involving microfluidic/organ-on-a-chip devices, such as integrated drug release and tissue engineering.

SPRINGERNATURE2021