Both passive and active microfluidic chips are used in many biomedical and chemical applications to support fluid mixing, particle manipulations, and signal detection. Passive microfluidic devices are geometry-dependent, and their uses are rather limited. Active microfluidic devices include sensors or detectors that transduce chemical, biological, and physical changes into electrical or optical signals. Also, they are transduction devices that detect biological and chemical changes in biomedical applications, and they are highly versatile microfluidic tools for disease diagnosis and organ modeling. This review provides a comprehensive overview of the significant advances that have been made in the development of microfluidics devices. We will discuss the function of microfluidic devices as micromixers or as sorters of cells and substances (e.g., microfiltration, flow or displacement, and trapping). Microfluidic devices are fabricated using a range of techniques, including molding, etching, three-dimensional printing, and nanofabrication. Their broad utility lies in the detection of diagnostic biomarkers and organ-on-chip approaches that permit disease modeling in cancer, as well as uses in neurological, cardiovascular, hepatic, and pulmonary diseases. Biosensor applications allow for point-of-care testing, using assays based on enzymes, nanozymes, antibodies, or nucleic acids (DNA or RNA). An anticipated development in the field includes the optimization of techniques for the fabrication of microfluidic devices using biocompatible materials. These developments will increase biomedical versatility, reduce diagnostic costs, and accelerate diagnosis time of microfluidics technology.

A fundamental literature review of micro-scale cavitation and its applications for bio-related practices.

Hydrodynamic cavitation (HC) is a phase change phenomenon, where energy release in a fluid occurs upon the collapse of bubbles, which form due to the low local pressures.

We present new unconstrained simulations and constrained experiments of a pair of pitching hydrofoils in a leader–follower in-line arrangement. Free-swimming simulations with matched pitching amplitudes show self-organisation into stable formations at a constant gap distance without any control. Over a wide range of phase synchronisation, amplitude and Lighthill number typical of biology, we discover that the stable gap distance scales with the actual wake wavelength of an isolated foil rather than the nominal wake wavelength. A scaling law for the actual wake wavelength is derived and shown to collapse data across a wide Reynolds number range of $200 \leqslant Re \leqslant 59\,000$ . Additionally, vortex analysis uncovers that the leader’s wake wavelength-to-chord ratio, $\lambda /c$ , is the key dimensionless variable to maximise the follower’s/collective efficiency. When $\lambda /c \approx 2$ it ensures that the follower’s leading edge suction force and the net force from a nearby vortex pair act in the direction with the foil’s motion thereby reducing the follower’s power. Moreover, in both simulations and experiments mismatched foil amplitudes are discovered to increase the efficiency of hydrofoil schools by 70 % while maintaining a stable formation without closed-loop control. This occurs by (i) increasing the stable gap distance between foils to push them into a high-efficiency zone and (ii) raising the level of efficiency in these zones. This study bridges the gap between constrained and unconstrained studies of in-line schooling by showing that constrained-foil measurements can map out the potential efficiency benefits of schooling. These findings can aid in the design of high-efficiency biorobot schools.

In this study, weexplored the potential of hydrodynamic cavitation(HC) for use in dissolution of liquid and powder detergents. For this,microfluidic and polyether ether ketone (PEEK) tube HC reactors withdifferent configurations were employed, and the results from the reactorswere compared with a magnetic stirrer, as well as a tergotometer.According to our results PEEK tube HC reactors present the best performancefor dissolution of liquid and powder detergents. In the case of liquiddetergent, for the same level of initial concentration and comparablefinal dissolution, the PEEK tube consumed 16.7 and 70% of the energyand time of a tergotometer and 16.7 and 14.8% of that of a magneticstirrer, respectively. In the case of powder detergent, the PEEK tubeused 12% less power than a tergotometer and 81.2% less power thana magnetic stirrer. Additionally, the time required to dissolve thedetergent was reduced significantly from 1200 s in the tergotometerand 1800 s in the magnetic stirrer to just 50 s in the PEEK tube.These results suggest that HC could significantly improve the dissolutionrate of liquid and powder detergents and energy consumption in washingmachines.