Vacuum pouch microfluidic system and its application for thin-film micromixers

A microfluidic chip with integrated plasma separation for sample-to-answer detection of multiple chronic disease biomarkers in whole blood

Point-of-care testing of multiple chronic disease biomarkers is crucial for timely intervention and management of chronic diseases. Here, a "sample-to-answer" microfluidic chip was developed for simultaneous detection of multiple chronic disease biomarkers in whole blood by integrating a plasma separation module. The whole detection process is very convenient, i.e., just add whole blood and get the results. The chip successfully achieved the simultaneous detection of total cholesterol, triglycerides, uric acid, and glucose in undiluted whole blood within 21 min, including 6 min for plasma separation and 15 min for enzymatic chromogenic reactions. Moreover, the sensitivity levels of on-chip detection of chronic disease biomarkers can also meet clinically relevant thresholds. The chip is easy to use and has significant potential to improve home self-management of chronic diseases and enhance healthcare outcomes.

Branch-convergence structure based on double-layer chip: a universal method for enhancing microfluidic mixing

Microfluidic mixing has significant applications in various fields, including materials synthesis and biochemical analysis. In this study, we propose a universal strategy to enhance mixing efficiency in microfluidic chips. This strategy initially divides the liquid into branches, which then converge in an interdigitated manner at the beginning of the mixing segment. This branch-convergence structure reduces the flow width of each liquid, thereby decreasing the diffusion distances required for mixing. Under the conditions of this study, the mixing efficiency could be improved by approximately 10 times. Importantly, this enhancement strategy only requires changing the structure of the liquid inflow channel without changing the structure of the mixing segment. Thus, this strategy has broad applicability, any mixing section with different principles and structures can be connected downstream of the branch-convergence structure. In addition, we applied this universal mixing enhancement strategy to the continuous synthesis of lactic-co-glycolic acid nanoparticles, resulting in a higher uniformity of synthesized nanoparticles compared to unenhanced devices.

Magnetic Non-Spherical Particles Inducing Vortices in Microchannel for Effective Mixing

Mixing in microfluidic channels is dominated by diffusion owing to the absence of chaotic flow. However, high-efficiency microscale mixing over short distances is desired for the development of lab-on-chip systems. Here, enhanced mixing in microchannels achieved using magnetic nonspherical particles (MNSPs), is reported. Benefiting from the nonspherical shape of the MNSPs, secondary vortices exhibiting cyclical characteristics appear in microchannels when the MNSPs rotate under an external magnetic field. Increasing the rotation rate enlarges the secondary vortices, expanding the mixing zone and enhancing the mixing, resulting in a mixing efficiency exceeding 0.9 at Re of 0.069-0.69. Complementary micro-particle image velocimetry (µPIV) for flow field analysis clarifies the mixing mechanism. In addition, a chaotic vortex area is generated in the presence of two MNSPs, which shortens the distance required for achieving an appropriate mixing efficiency. This study demonstrates the potential of employing MNSPs as efficient mixers in lab-on-chip devices.

Microelectromechanical Systems Based on Magnetic Polymer Films

Microelectromechanical systems (MEMS) have been increasingly used worldwide in a wide range of applications, including high tech, energy, medicine or environmental applications. Magnetic polymer composite films have been used extensively in the development of the micropumps and valves, which are critical components of the microelectromechanical systems. Based on the literature survey, several polymers and magnetic micro and nanopowders can be identified and, depending on their nature, ratio, processing route and the design of the device, their performances can be tuned from simple valves and pumps to biomimetic devices, such as, for instance, hearth ventricles. In many such devices, polymer magnetic films are used, the disposal of the magnetic component being either embedded into the polymer or coated on the polymer. One or more actuation zones can be used and the flow rate can be mono-directional or bi-directional depending on the design. In this paper, we review the main advances in the development of these magnetic polymer films and derived MEMS: microvalve, micropump, micromixer, microsensor, drug delivery micro-systems, magnetic labeling and separation microsystems, etc. It is important to mention that these MEMS are continuously improving from the point of view of performances, energy consumption and actuation mechanism and a clear tendency in developing personalized treatment. Due to the improved energy efficiency of special materials, wearable devices are developed and be suitable for medical applications.

Passive micropumping in microfluidics for point-of-care testing

Suitable micropumping methods for flow control represent a major technical hurdle in the development of microfluidic systems for point-of-care testing (POCT). Passive micropumping for point-of-care microfluidic systems provides a promising solution to such challenges, in particular, passive micropumping based on capillary force and air transfer based on the air solubility and air permeability of specific materials. There have been numerous developments and applications of micropumping techniques that are relevant to the use in POCT. Compared with active pumping methods such as syringe pumps or pressure pumps, where the flow rate can be well-tuned independent of the design of the microfluidic devices or the property of the liquids, most passive micropumping methods still suffer flow-control problems. For example, the flow rate may be set once the device has been made, and the properties of liquids may affect the flow rate. However, the advantages of passive micropumping, which include simplicity, ease of use, and low cost, make it the best choice for POCT. Here, we present a systematic review of different types of passive micropumping that are suitable for POCT, alongside existing applications based on passive micropumping. Future trends in passive micropumping are also discussed.

Towards practical sample preparation in point-of-care testing: user-friendly microfluidic devices

Microfluidic technologies offer a number of advantages for sample preparation in point-of-care testing (POCT), but the requirement for complicated external pumping systems limits their wide use. To facilitate sample preparation in POCT, various methods have been developed to operate microfluidic devices without complicated external pumping systems. In this review, we introduce an overview of user-friendly microfluidic devices for practical sample preparation in POCT, including self- and hand-operated microfluidic devices. Self-operated microfluidic devices exploit capillary force, vacuum-driven pressure, or gas-generating chemical reactions to apply pressure into microchannels, and hand-operated microfluidic devices utilize human power sources using simple equipment, including a syringe, pipette, or simply by using finger actuation. Furthermore, this review provides future perspectives to realize user-friendly integrated microfluidic circuits for wider applications with the integration of simple microfluidic valves.