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Particle movement and fluid behavior visualization using an optically transparent 3D-printed micro-hydrocyclone.

A hydrocyclone is a macroscale separation device employed in various industries, with many advantages, including high-throughput and low operational costs. Translating these advantages to microscale has been a challenge due to the microscale fabrication limitations that can be surmounted using 3D printing technology. Additionally, it is difficult to simulate the performance of real 3D-printed micro-hydrocyclones because of turbulent eddies and the deviations from the design due to printing resolution. To address these issues, we propose a new experimental method for the direct observation of particle motion in 3D printed micro-hydrocyclones. To do so, wax 3D printing and soft lithography were used in combination to construct a transparent micro-hydrocyclone in a single block of polydimethylsiloxane. A high-speed camera and fluorescent particles were employed to obtain clear in situ images and to confirm the presence of the vortex core. To showcase the use of this method, we demonstrate that a well-designed device can achieve a 95% separation efficiency for a sample containing a mixture of (desired) stem cells and (undesired) microcarriers. Overall, we hope that the proposed method for the direct visualization of particle trajectories in micro-hydrocyclones will serve as a tool, which can be leveraged to accelerate the development of micro-hydrocyclones for biomedical applications.