Proceedings Article | 18 April 2023
KEYWORDS: Microfluidics, Particles, Optical fibers, Fluid dynamics, Capillaries, Computational fluid dynamics, Photonic crystal fibers, Modeling, Biomedical applications, Biological research
Optical fibers are reliable sensors and can provide accurate measurements in microfluidic systems. Photonic crystal fibers are a variation of the conventional optical fiber, where the difference is the distribution of an array of hollow cores along the length of the fiber. These types of fibers are used as sensors in microfluidic cell cultures and offer the unique accessibility of using the hollow cores as a transport mechanism for biological samples. This type of system can benefit the biomedical and healthcare industry by reducing unnecessary manufacturing costs, while modeling complicated systems such as the interaction between the blood and cancer cells in the circulatory system. This manuscript briefly reviews recent literature on optical fiber sensors exploiting the hollow core technology of these optical fibers in real-time monitoring applications while transporting biological compounds. The significance of using biological samples such as human or animal cells integrated with optical fiber sensors can enhance research and clinical testing in modern industry. The remaining portion of the manuscript is an analysis on an experimental system designed to transport a cell culture through a photonic crystal fiber that is connecting two microfluidic devices. The internal diameter of the hollow core of the fiber is 22 µm, and the diameter of the cell is approximately 15 µm, indicating no extreme limitations in transport. Spectroscopic data confirms the presence of a cellular aggregate impeding the flow rate either within the hollow cores of the fiber, or the region transitioning between the microfluidic device and the fiber. The analysis consists of determining the mechanisms that contribute to cellular aggregation in microfluidic theory, to accurately model this phenomenon. The introduction of the analysis examines the experimental configuration with a class of dimensionless quantities that are often used in microfluidic theory. The Reynold’s, Peclet, capillary, Knudsen number, and Transcapillary conductance are dimensionless quantities used in recent literature in describing microfluidic transport. An analysis on these quantities led to the Lattice Boltzmann method for modeling the behavior in the experimental configuration. The Lattice Boltzmann method is a method in computational fluid dynamics that operates by imposing a discrete lattice to stimulate the fluid environment. The system evolves through collision and streaming processes, and along with Brownian dynamics, dictates the behavior of deformable particle mechanics. The combination of these two models is applied to the problem cellular aggregation in the experimental configuration. A simulation depicting the scenario of cellular aggregation in the hollow core fiber under conditions of Poiseuille flow with pressure differential of ∆p = 102 Pa, fluid velocity U = 103 µm/sec, with a particle diameter to constriction diameter of 10/15 measured at the microscale (10−6 m). This is in comparison with conditions the experimental system operated at under a pressure differential ∆p = 1 bar, volumetric flow rate Q = 1.2 µL/min, at room temperature, with a particle to constriction diameter of 15/22. The analysis as approximated by the dimensionless quantities provides support that modeling aggregation in microfluidics is acceptable under the Lattice Boltzmann and Brownian dynamics method. Future directions of those research include repetition of these transports under varying conditions, to determine an environment for transport to occur. An examination into molecular interactions and properties, such as pressure differential, surface characteristics, and excluded volume, affecting aggregation and fluid flow is also to be considered.
