Dielectrophoretic microbead sorting using modular electrode design and capillary-driven microfluidics

Numerical investigation of ternary particle separation in a microchannel with a wall-mounted obstacle using dielectrophoresis

In recent years, microfluidic-based particle/cell manipulation techniques have catalyzed significant advances in several fields of science. As an efficient, precise, and label-free particle/cell manipulation technique, dielectrophoresis (DEP) has recently attracted widespread attention. This paper presents the design and investigation of a straight sheathless 3D microchannel with a wall-mounted trapezoidal obstacle for continuous-flow separation of three different populations of polystyrene (PS) particles (5, 10 and 20 µm) using DEP. An OpenFOAM code is developed to simulate and investigate the movement of particles in the microchannel. Then, the code is validated by performing various experimental tests using a microdevice previously fabricated in our lab. By comparing the numerical simulation results with the experimental tests, it can be claimed that the newly developed solver is highly accurate, and its results agree well with experimental tests. Next, the effect of various operational and geometrical parameters such as obstacle height, applied voltage, electrode pairs angle, and flow rate on the efficient focusing and separation of particles are numerically investigated. The results showed that efficient particle separation could only be achieved for obstacle heights of more than 350 µm. Furthermore, the appropriate voltage range for efficient particle separation is increased by decreasing the electrode angle as well as increasing the flow rate. Moreover, the results showed that by employing the appropriate channel design and operational conditions, at a maximum applied voltage of 10V, a sample flow rate of 2.5μL/min could be processed. The proposed design can be beneficial for integrating with lab-on-a-chip and clinical diagnosis applications due to advantages, such as simple design, no need for sheath flow, the simultaneous ternary separation of particles, and providing precise particle separation.

Novel Approaches Concerning the Numerical Modeling of Particle and Cell Separation in Microchannels: A Review

The demand for precise separation of particles, cells, and other biological matter has significantly increased in recent years, leading to heightened scientific interest in this topic. More recently, due to advances in computational techniques and hardware, numerical simulations have been used to guide the design of separation devices. In this article, we establish the theoretical basis governing fluid flow and particle separation and then summarize the computational work performed in the field of particle and cell separation in the last five years with an emphasis on magnetic, dielectric, and acoustic methods. Nearly 70 articles are being reviewed and categorized depending on the type of material separated, fluid medium, software used, and experimental validation, with a brief description of some of the most notable results. Finally, further conclusions, future guidelines, and suggestions for potential improvement are highlighted.

Continuous size-based DEP separation of particles using a bi-gap electrode pair

The design, fabrication, and characterization of an advanced microfluidic device containing a bi-gap electrode pair for the continuous separation of three different populations of particles based on their size using DEP are presented.

Nip the bubble in the bud: a guide to avoid gas nucleation in microfluidics

Gas bubbles are almost a routine occurrence encountered by researchers working in the field of microfluidics. The spontaneous and unexpected nature of gas bubbles represents a major challenge for experimentalists and a stumbling block for the translation of microfluidic concepts to commercial products. This is a startling example of successful scientific results in the field overshadowing the practical hurdles of day-to-day usage. We however believe such hurdles can be overcome with a sound understanding of the underlying conditions that lead to bubble formation. In this tutorial, we focus on the two main conditions that result in bubble nucleation: surface nuclei and gas supersaturation in liquids. Key theoretical concepts such as Henry's law, Laplace pressure, the role of surface properties, nanobubbles and surfactants are presented along with a view of practical implementations that serve as preventive and curative measures. These considerations include not only microfluidic chip design and bubble traps but also often-overlooked conditions that regulate bubble formation, such as gas saturation under pressure or temperature gradients. Scenarios involving electrolysis, laser and acoustic cavitation or T-junction/co-flow geometries are also explored to provide the reader with a broader understanding on the topic. Interestingly, despite their often-disruptive nature, gas bubbles have also been cleverly utilized for certain practical applications, which we briefly review. We hope this tutorial will provide a reference guide in helping to deal with a familiar foe, the "bubble".