(483j) High-Throughput Microfluidic Particle Filtration Via Biomimicry of the Manta Ray’s Feeding Mechanism

Microparticle filtration plays an important role in many medical and biological systems. However, most current technologies of microparticle filtration are limited by low-throughput or clogging [1]. Interestingly, the Manta Ray uses a non-clogging filtering mechanism to feed on 50 µm and greater zooplankton [2]. The Manta Ray’s mouth is lined with filter lobes creating small channels exiting the buccal cavity. Due to abrupt changes in geometry, water and smaller particles are expelled through the channels, while larger particles follow their inertial path rather than the fluid path. Therefore, larger particles, which are smaller than the outlet channels, ricochet off the lobes, without passing through the filter lobe channels, effectively separating particles based on size [2]. However, most current applications of microparticle filtration, including blood cell separation and water treatment, require separation sizes under 50 µm. We have developed a microfluidic filtration system bioinspired by this filtration mechanism to filter particles under 50 µm with precise control and high-throughput. Here we developed a microfluidic platform through standard photo and soft-lithography techniques to utilize the Manta Ray’s feeding mechanism to successfully filter 25 µm and larger fluorescent particles. ANSYS Fluent CFD simulations were used to help determine various device design choices prior to fabrication. To test device performance, combinations of 25 µm, 15 µm, 6 µm, and 2 µm fluorescent particles were pushed through the microfluidic device at various flow rates. Fluorescent images were taken of the device during operation, as well as representative samples of the inlet and both outlets. A custom MATLAB image processing algorithm was developed to analyze fluorescent images to determine the efficiency of the microparticle filter. We have identified two significantly different flow regimes that can result in high filtration efficiencies. Particle filtration efficiency is high at slower flows around 0.5 mL/min and drops drastically before increasing logarithmically with increasing flow rates. We have explored several parameters to explain filtration efficiency, including the Reynold’s Particle Number and changes in simulation-derived velocity boundary layer thicknesses. The device operates up to a maximum flow rate of 20 mL/min, permitting high-throughput filtration of 25 µm particles from smaller particles. Filtration efficiency increases with fluid flow rate, signaling that particle inertial effects play a key role in ricochet filter separation. Additionally, simulation-derived boundary layer thickness along the filter lobes indicate an explanation for filtration efficiency – particle filtration succeeds when the boundary layer thickness is smaller than the particle size. This high-throughput, Manta Ray-inspired filtration mechanism can passively and efficiently filter particles in the tens of microns range, making it a prime candidate for various industrial applications, such as microplastic removal from much of the globe’s water supply.

References:

1. Cheng, Y., Ye, X., Ma, Z., Xie, S. & Wang, W. High-throughput and microfluidic filtration platform for on-chip cell separation from undiluted whole blood. Biomicrofluidics 10, 014118 (2016).
2. Divi, R. V., Strother, J. A. & Misty Paig-Tran, E. W. Manta rays feed using ricochet separation, a novel nonclogging filtration mechanism. Sci. Adv. 4, (2018).