High-Throughput Manipulation of Micro- and Nanoparticles Using Elasto-Inertial Microfluidics for Environmental and Biomedical Applications

QC 2025-02-06

Abstract

Particles in the micrometer and nanometer size range are present in the environment (e.g., microplastics, nanoplastics) as well as in living organisms(e.g., cells, bacteria, tumors, and exosomes) in different forms and structures. Regardless of their compositions, there is a need to understand how these particles can be manipulated for both environmental and biomedical applications.

Nature and our daily lives are surrounded by micro- and nanoplastics. Their presence carries potential risks for the environment and the health of living beings. Although plastics were initially invented because of their advantages in industrial fields, such as low cost and versatility, their degradation results in small particles that are not easy to monitor or detect, and can penetrate into the body while staying in nature potentially for hundreds of years. Their detection, identification, and analysis are crucial to determine their danger level for all. The rise of global plastic production has led to the increasing prevalence of micro and nanoplastics in the environment. The absence of standardized handling methods complicates efforts to manage their environmental impact. The current state of this issue, along with projections for the upcoming years, appears bleak, prompting scientists and legislators to intensify efforts to develop and implement better solutions.

Biological particles, such as bacteria, platelets, circulating tumor cells, or extracellular vesicles, either through their presence or their concentration levels in bodily fluids or tissues, contain critical information about the state of a living organism. Isolation of these particles from blood or plasma is crucial to enable downstream analysis needed to assess the current status of a patient. Thus, high-throughput and high-resolution particle manipulation are needed for diagnostics and therapeutical applications.

In this thesis, we presented novel microfluidic devices with high aspect ratio geometries utilizing elasto-inertial microfluidics. These devices show a capacity to manipulate both micro- and nanoplastics, and biological particles.

In Paper I, we reported a microfluidic device comprising a single-inlet and high aspect ratio straight microchannels with two sections: focusing and migration section. Here, we aimed at focusing microparticles in the focusing section and then separating pre-focused particles based on their sizes in the migration section. Moreover, we presented an extensive study on particle focusing, investigating parameters affecting particle focusing, such as particle size, viscoelastic concentration, flow rate, and channel geometry. Finally, we showed how to increase throughput of the system by increasing the channel depth. The presented results demonstrate the potential of high aspect ratio microchannels in an elasto-inertial microfluidics setup for applications that require high throughput and high-resolution particle separation.

In Paper II, we presented a high aspect ratio microchannel with a smaller channel width than the one presented in the first paper. Here, we demonstrated, for the first time, the focusing of submicron particles down to 25 nm using elasto-inertial microfluidics. Furthermore, we confirmed these results using biological nanoparticles, namely liposomes and exosomes. Focusing of such small biological particles in a low-cost microfluidic device has great potential for developing further particle manipulation strategies in biomedical applications.

In Paper III, we presented a method that combines elasto-inertial microfluidics and optical coherence spectroscopy. A typical elasto-inertial microfluidic setup employs fluorescently labelled particles and a fluorescence microscope to track the position of the labelled particles. However, such a setup can only provide two-dimensional information. Using optical coherence microscopy, information about the third dimension in a microfluidic channel can be provided, which is critical to understand particle motion in a viscoelastic fluid.

In Paper IV, we reported a novel acoustofluidic device called the EchoGrid. This device was used for the enrichment of microplastics at high flow rate, which can be used for sample preparation in environmental applications. In addition, we developed a method using silica particles as an enrichment strategy in samples with a low concentration of microplastics.

In Paper V, we improved our findings from Paper IV and worked to capture of nanoplastics by modifying the acoustic field and the sample flow lines. The method relied on the EchoGrid device and the angle of transducer that was integrated in the device. We employed computational methods to determine the optimal angle and demonstrated the capture of nanoplastics down to size of 25nm at high throughput.

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