In capillary- or vacuum-driven microfluidics, surge backflow events are common when merging or pumping two similar or dissimilar liquids together if a pressure difference exists between them. In this work, a robust, portable micromixing device that is insensitive to backflow was designed, fabricated and characterised. A capillary-driven pressure balancing bypass connected between two inlet ports diminished the initial pressure difference caused by capillarity and gravity present in each liquid at the two inlet ports. Then, using manual syringe-assisted vacuum-driven pumping that operated based on the high gas permeability of polydimethylsiloxane, the two pre-balanced liquid streams could synchronously enter a dead-end micromixing channel without any backflow. To test the performance of this device, we first used it to mix two aqueous solutions of different coloured dyes. We varied the initial volume difference between the solutions to study the effect of gravity-induced pressure difference on mixing. Next, as a proof-of-concept application, ABO/Rh blood groups were successfully determined through detection of blood antigen-antibody agglutination. The filling time of agglutinated samples, driven by the simple syringe-assisted pumping, in the dead-end mixing channel was consistently 10% longer than that of blood samples without the agglutination reaction. Thus, the proposed device shows great potential for use in a wide variety of blood typing assays, agglutination-based assays and point-of-care or lab-on-a-chip testing applications.

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.

With the continuous development of sustainable and renewable energy, the electrocatalytic water cycle and rechargeable metal-air batteries are attracting increasing attention. As two main reactions, oxygen evolution/reduction reaction (OER/ORR) are...

Microfluidic technology has been used for precise drug delivery for many years, but microfluidic wearable devices have mostly been used for skin drug delivery. The application of eye drops is currently one of the most common ways to treat eye diseases. However, due to their low corneal bioavailability and short residence time in tears, topical eye drops must be applied multiple times a day. Contact lenses, as a wearable device for the eye, are a good platform for drug delivery. In this paper, we propose a type of microfluidic contact lens that integrates a microchannel and a micropump and uses a pressure source to trigger the release of a drug. Here, a flat microfluidic chip component is first fabricated by photolithography and then cast into a curved surface by secondary thermosetting. Through experiments, the outlet check valve opening pressure and liquid flow test were studied to prove that the liquid release is controllable. In addition, the microfluidic contact lens has good flexibility, light transmittance, and biocompatibility. Finally, we demonstrate through fluorescence experiments that the microfluidic contact lens can be loaded with different types of drugs in different regions. In general, liquid exchange between the eye and the contact lens can be realized through the mechanical action of blinking without using electronic components, meaning more safety and stability. The mechanical characteristics of a blink can be artificially regulated to a large extent; thus, it is also possible to achieve specific, personalized medicine.