Dynamic Vortex Generation, Pulsed Injection, and Rapid Mixing of Blood Samples in Microfluidics Using the Tube Oscillation Mechanism

Vortex-Enhanced Microfluidic Chip for Efficient Mixing and Particle Capturing Combining Acoustics with Inertia

Vortex-based microfluidics has received significant attention for its unique characteristics of high efficiency, flexible control, and label-free properties for the past decades. Herein, we present a vortex-based acousto-inertial chip that allows both fluid and particle manipulation within a significantly wider flow range and lower excitation voltage. Composed of contraction-expansion array structures and vibrating microstructures combined with bubbles and sharp edges, such a configuration results in more vigorous vortical fluid motions. The overall improvement in device performance comes from the synergistic effect of acoustics and inertia, as well as the positive feedback loop formed by vibrating bubbles and sharp edges. We characterize flow patterns in the microchannels by fluorescence particle tracer experiments and uncover single- and double-vortex modes over a range of sample flow rates and excitation voltages. On this basis, the ability of rapid and efficient sample homogenization up to a flow rate of 200 μL/min under an excitation voltage of 15 Vpp is verified by a two-fluid fluorescence mixing experiment. Moreover, the recirculation motion of particles in microvortices is investigated by using a high-speed imaging system. We also quantitatively measure the particle velocity variation on the trajectory and illustrate the capturing mechanism, which results from the interaction of the microvortices, particle dynamics, and composite microstructure perturbations. Further utilizing the shear forces derived by microvortices, our acousto-inertial chip is demonstrated to lysis red blood cells (RBCs) in a continuous, reagent-free manner. The high controllability and multifunction of this technology allow for the development of multistep miniaturized "lab-on-chip" analytical systems, which could significantly broaden the application of microvortex technology in biological, chemical, and clinical applications.

Tube Oscillation Drives Transitory Vortices Across Microfluidic Barriers

Here, the generation of dynamic vortices across microscale barriers using the tube oscillation mechanism is demonstrated. Using a combination of high-speed imaging and computational flow dynamics, the cyclic formation, expansion, and collapse of vortices are studied. The dynamics of vortices across circular , triangular, and blade-shape barriers are investigated at different tube oscillation frequencies. The formation of an array of synchronous vortices across parallel blade-shaped barriers is demonstrated. The transient flows caused by these dynamic vortex arrays are harnessed for the rapid and efficient mixing of blood samples . A circular barrier scribed with a narrow orifice on its shoulder is used to facilitate the injection of liquid into the microfluidic channel, and its rapid mixing with the main flow through the dynamic vortices generated across the barrier. This approach facilitates the generation of vortices with desirable configurations, sizes, and dynamics in a highly controllable, programmable, and predictable manner while operating at low static flow rates.

Enrichment and detection of VEGF165 in blood samples on a microfluidic chip integrated with multifunctional units

In this paper, a multifunctional microfluidic chip integrated with a centrifugal separation zone, aqueous two-phase system (ATPS) mixing zone and enrichment detection zone was proposed and fabricated. An automatic and efficient separation and quantitative analysis method for vascular endothelial growth factor 165 (VEGF₁₆₅) in whole blood samples was established with the designed microfluidic chip. A blood sample was divided into blood cells and plasma in the centrifugation zone. In the ATPS mixing zone, plasma was mixed with PEG/KH₂PO₄ aqueous two-phase solution containing Apt-Au NP nanoprobes. In the enrichment detection zone, the mixture was separated on CN140 modified with a ZnO NP-anti VEGF₁₆₅ nanostructure. The VEGF₁₆₅ captured by Apt-Au NPs was distributed in the PEG phase, concentrated at the front of CN140 and combined with anti-VEGF₁₆₅ to form a sandwich structure. The sensitive detection of VEGF₁₆₅ was achieved through fluorescence resonance energy transfer between rhodamine B and Au NPs on the nanoprobe. Under the optimized rotation program, capillary and centrifugal forces propelled the fluid in the whole process of pretreatment and detection. The detection linear range was between 1 pg mL^-1 and 50 ng mL^-1, the detection limit of VEGF₁₆₅ in blood was 0.22 pg mL^-1 and the enrichment efficiency was 983. It was illustrated that a convenient and reliable way for detection of tumor markers based on the multifunctional microfluidic chip was provided and it has a potential value for early screening and prognosis of clinical cancer.

Modular microfluidics for life sciences

The advancement of microfluidics has enabled numerous discoveries and technologies in life sciences. However, due to the lack of industry standards and configurability, the design and fabrication of microfluidic devices require highly skilled technicians. The diversity of microfluidic devices discourages biologists and chemists from applying this technique in their laboratories. Modular microfluidics, which integrates the standardized microfluidic modules into a whole, complex platform, brings the capability of configurability to conventional microfluidics. The exciting features, including portability, on-site deployability, and high customization motivate us to review the state-of-the-art modular microfluidics and discuss future perspectives. In this review, we first introduce the working mechanisms of the basic microfluidic modules and evaluate their feasibility as modular microfluidic components. Next, we explain the connection approaches among these microfluidic modules, and summarize the advantages of modular microfluidics over integrated microfluidics in biological applications. Finally, we discuss the challenge and future perspectives of modular microfluidics.