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.

Microfluidic Actuation via 3D-Printed Molds toward Multiplex Biosensing of Cell Apoptosis.

Multiplexed analysis of biochemical analytes such as proteins, enzymes, and immune products using a microfluidic device has the potential to cut assay time, reduce sample volume, realize high-throughput, and decrease experimental error without compromising sensitivity. Despite these huge benefits, the need for expensive specialized equipment and the complex photolithography fabrication process for the multiplexed devices have, to date, prevented widespread adoption of microfluidic systems. Here, we present a simple method to fabricate a new microfluidic-based multiplexed biosensing device by taking advantage of 3D-printing. The device is an integration of normally closed (NC) microfluidic valving units which offer superior operational flexibility by using PDMS membrane (E ∼ 1-2 MPa) and require minimized energy input (1-5 kPa). To systematically engineer the device, we first report on the geometrical and operational analysis of a single 3D-printed valving unit. Based on the characterization, we introduce a full prototype multiplexed chip comprising several microfluidic valves. The prototype offers-for the first time in a 3D-printed microfluidic device-the capability of on-demand performce of both a sequential and a parallel biochemical assay. As a proof of concept, our device has been used to simultaneously measure the apoptotic activity of 5 different members of the caspase protease enzyme family. In summary, the 3D-printed valving system showcased in this study overcomes traditional bottlenecks of microfabrication, enabling a new class of sophisticated liquid manipulation required in performing multiplexed sensing for biochemical assays.