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1. Micromixers
1. Micromixers
This paper systematically investigated the bionic fractal baffle micromixers based on Murray's Law. It focused on the influence of Murray's Law fractal parameters on the mixing performance of bionic fractal baffle micromixers. We varied Murray's Law fractal parameters such as Murray's Law fractal order, distribution position of fractal baffles, Murray's Law initial length, and the number of fractal baffles. The results indicated that increasing the fractal order, adopting an interleaved arrangement structure, increasing the initial length, and employing a larger number of fractal baffles can significantly improve the mixing performance, with mixing efficiency reaching 98.92% at Re = 100. Furthermore, the reason for the significant enhancement of mixing performance lies in the influence of Murray's Law fractal parameters on the number and area of vortices. This study establishes a theoretical foundation for understanding the interaction between fractal parameters and mixing performance in bionic fractal baffle micromixers based on Murray's Law.
This paper systematically investigated the bionic fractal baffle micromixers based on Murray's Law. It focused on the influence of Murray's Law fractal parameters on the mixing performance of bionic fractal baffle micromixers. We varied Murray's Law fractal parameters such as Murray's Law fractal order, distribution position of fractal baffles, Murray's Law initial length, and the number of fractal baffles. The results indicated that increasing the fractal order, adopting an interleaved arrangement structure, increasing the initial length, and employing a larger number of fractal baffles can significantly improve the mixing performance, with mixing efficiency reaching 98.92% at Re = 100. Furthermore, the reason for the significant enhancement of mixing performance lies in the influence of Murray's Law fractal parameters on the number and area of vortices. This study establishes a theoretical foundation for understanding the interaction between fractal parameters and mixing performance in bionic fractal baffle micromixers based on Murray's Law.
Figure cited from Han, W., Li, W., & Zhang, H. (2024). Insight into mixing performance of bionic fractal baffle micromixers based on Murray's Law. International Communications in Heat and Mass Transfer, 157, 107843.
2. Droplets/Bubbles Generation
2. Droplets/Bubbles Generation
Microfluidic gas-liquid two-phase flow in microchannels plays a crucial role in diverse applications, from electronics cooling to biomedical engineering. Precisely controlling microbubble formation and breakup is essential for industrial microfluidic processes. This study investigates microbubble breakup in microchannels with V-shaped obstacles. Four breakup patterns are identified: no breakup, breakup with permanent gaps, breakup with partly obstruction, and breakup with permanent obstruction. The bubble breakup with permanent obstruction could maintain a wider flow pattern range. The bubble breakup process is categorized into three stages: squeezing, transition, and pinch-off. We observe power-law relationships between bubble characteristics and dimensionless time in each stage, and the impact of the capillary number Ca and liquid phase viscosity μL on bubble properties. This research deepens our understanding of gas-liquid two-phase flow in microchannels with obstacle structures and is relevant to analytical chemistry and fine chemical engineering applications.
Microfluidic gas-liquid two-phase flow in microchannels plays a crucial role in diverse applications, from electronics cooling to biomedical engineering. Precisely controlling microbubble formation and breakup is essential for industrial microfluidic processes. This study investigates microbubble breakup in microchannels with V-shaped obstacles. Four breakup patterns are identified: no breakup, breakup with permanent gaps, breakup with partly obstruction, and breakup with permanent obstruction. The bubble breakup with permanent obstruction could maintain a wider flow pattern range. The bubble breakup process is categorized into three stages: squeezing, transition, and pinch-off. We observe power-law relationships between bubble characteristics and dimensionless time in each stage, and the impact of the capillary number Ca and liquid phase viscosity μL on bubble properties. This research deepens our understanding of gas-liquid two-phase flow in microchannels with obstacle structures and is relevant to analytical chemistry and fine chemical engineering applications.
Figure cited from Han, W., Wang, X., Li, W., Zheng, Y., Liu, B., & Zhang, H. (2024). Numerical simulation study of bubble breakup mechanism in microchannels with V-shaped obstacle. Chemical Engineering and Processing-Process Intensification, 200, 109791.
3. Ion Transport in the Nanochannel
3. Ion Transport in the Nanochannel
The detection of ultra-low concentration of biomacromolecules remains the focus of research in micro-nanofluidic systems. Sample enrichment is primarily targeted at very low concentration of sample detection tasks. The use of ion concentration polarization principle is the most efficient means to solve the problem of electrokinetic ion enrichment. In this paper, numerical simulation of nano-electrokinetic ion enrichment in a micro-nanofluidic preconcentrator with nanochannel’s Cantor fractal wall structure was performed based on Poisson–Nernst–Planck equation combined with the Navier–Stokes equation. The results show that reducing the initial length L0, increasing the initial height h0, increasing the fractal step n and using the unstaggered structure in the Cantor fractal principle can increase the ion enrichment concentration and peak voltage. The initial ion concentration is 0.1 mol/m3. When the applied voltage is 30 V and the initial height h0 increases from 35 to 45 nm, the ion enrichment concentration drastically increases from 1.007 to 1.410 mol/m3 by 40%. This study provides a theoretical basis and a novel design method for improving the sensitivity of micro-nanofluidic chips and the design of ultra-low concentration sample testing equipment.
The detection of ultra-low concentration of biomacromolecules remains the focus of research in micro-nanofluidic systems. Sample enrichment is primarily targeted at very low concentration of sample detection tasks. The use of ion concentration polarization principle is the most efficient means to solve the problem of electrokinetic ion enrichment. In this paper, numerical simulation of nano-electrokinetic ion enrichment in a micro-nanofluidic preconcentrator with nanochannel’s Cantor fractal wall structure was performed based on Poisson–Nernst–Planck equation combined with the Navier–Stokes equation. The results show that reducing the initial length L0, increasing the initial height h0, increasing the fractal step n and using the unstaggered structure in the Cantor fractal principle can increase the ion enrichment concentration and peak voltage. The initial ion concentration is 0.1 mol/m3. When the applied voltage is 30 V and the initial height h0 increases from 35 to 45 nm, the ion enrichment concentration drastically increases from 1.007 to 1.410 mol/m3 by 40%. This study provides a theoretical basis and a novel design method for improving the sensitivity of micro-nanofluidic chips and the design of ultra-low concentration sample testing equipment.
Figure cited from Han, W., & Chen, X. (2020). Nano-electrokinetic ion enrichment in a micro-nanofluidic preconcentrator with nanochannel’s Cantor fractal wall structure. Applied Nanoscience, 10(1), 95-105.
4. Wear Debris Detection Sensors
4. Wear Debris Detection Sensors
In the field of marine engineering, the friction and wear experienced by rotating mechanisms are recognized as significant contributors to the failure of marine machinery. In order to enhance the safety and dependability of marine ship operations, the implementation of on-line oil wear debris particle detection sensors enables the on-line monitoring of oil and facilitates the rapid identification of abnormal wear locations. This paper provides a critical review of the recent research progress and development trends in the field of sensors for on-line detection of oil wear debris particles. According to the method of sensor detection, wear debris particle detection sensors can be classified into two distinct categories: electrical and non-electrical sensors. Electrical sensors encompass a range of types, including inductive, capacitive, and resistive sensors. Non-electrical sensors encompass a range of technologies, such as image processing sensors, optical sensors, and ultrasonic sensors. Finally, this review addresses the future research directions for wear debris particle detection sensors in light of the challenging problems currently faced by these sensors.
In the field of marine engineering, the friction and wear experienced by rotating mechanisms are recognized as significant contributors to the failure of marine machinery. In order to enhance the safety and dependability of marine ship operations, the implementation of on-line oil wear debris particle detection sensors enables the on-line monitoring of oil and facilitates the rapid identification of abnormal wear locations. This paper provides a critical review of the recent research progress and development trends in the field of sensors for on-line detection of oil wear debris particles. According to the method of sensor detection, wear debris particle detection sensors can be classified into two distinct categories: electrical and non-electrical sensors. Electrical sensors encompass a range of types, including inductive, capacitive, and resistive sensors. Non-electrical sensors encompass a range of technologies, such as image processing sensors, optical sensors, and ultrasonic sensors. Finally, this review addresses the future research directions for wear debris particle detection sensors in light of the challenging problems currently faced by these sensors.
Figure cited from Han, W., Mu, X., Liu, Y., Wang, X., Li, W., Bai, C., & Zhang, H. (2023). A critical review of on-line oil wear debris particle detection sensors. Journal of Marine Science and Engineering, 11(12), 2363.
5. Particle Separation
5. Particle Separation
Surface acoustic wave (SAW)-based microfluidic particle separation offers exceptional biocompatibility and precision for biological applications. This study establishes a multiphysics coupling model integrating piezoelectric dynamics, acoustic-structural interactions, and fluid-particle mechanics to optimize SAW separator design. Systematic analysis of interdigital transducer geometry and flow-acoustic coupling reveals that electrode width governs acoustic wavelength distribution, with 50 μm electrodes achieving optimal pressure gradients. Increasing electrode pairs (N = 5) enhances acoustic pressure inversion, while applied voltage (20 V) proportionally amplifies radiation forces. Notably, channel height exhibits negligible impact on the acoustic field. The optimized device achieves efficient separation of 5–15 μm particles through synergistic flow focusing and acoustic node alignment. This work provides a systematic framework for high-purity biological particle separation, advancing SAW-based microfluidics in diagnostics and cellular analysis.
Surface acoustic wave (SAW)-based microfluidic particle separation offers exceptional biocompatibility and precision for biological applications. This study establishes a multiphysics coupling model integrating piezoelectric dynamics, acoustic-structural interactions, and fluid-particle mechanics to optimize SAW separator design. Systematic analysis of interdigital transducer geometry and flow-acoustic coupling reveals that electrode width governs acoustic wavelength distribution, with 50 μm electrodes achieving optimal pressure gradients. Increasing electrode pairs (N = 5) enhances acoustic pressure inversion, while applied voltage (20 V) proportionally amplifies radiation forces. Notably, channel height exhibits negligible impact on the acoustic field. The optimized device achieves efficient separation of 5–15 μm particles through synergistic flow focusing and acoustic node alignment. This work provides a systematic framework for high-purity biological particle separation, advancing SAW-based microfluidics in diagnostics and cellular analysis.
Figure cited from Han, W., Zou, H., Yue, H., Zhong, Y., Li, W., Zhang, C., & Zhang, H. (2025). Particle separation using surface acoustic waves based on microfluidic chip. Chaos, Solitons & Fractals, 198, 116557.
6. Rotating Detonation Engine
6. Rotating Detonation Engine
The solid-fuel rotating detonation engine with gas generator is experimentally studied in this paper. This study solved the problems of ignition and stable detonation of pre-combustion gasification injection. The feasibility of solid pre-combustion rotating detonation is verified. A set of gas generators was designed and ignition tests were carried out. The detonation wave velocity is about 2625 m/s in the stable stage, which is about 20% higher than that generated by hydrogen/oxygen detonation. A maximum thrust of 69 N is obtained. Stable detonation pressure signal was obtained in our experiments. It is found that the detonation wave has experienced four stages in the formation process: deflagration, deflagration to detonation transition (DDT) process, galloping detonation, and stable detonation. In the stable detonation stage, coexistence of detonation waves with different strength is identified by high-speed photography images.
The solid-fuel rotating detonation engine with gas generator is experimentally studied in this paper. This study solved the problems of ignition and stable detonation of pre-combustion gasification injection. The feasibility of solid pre-combustion rotating detonation is verified. A set of gas generators was designed and ignition tests were carried out. The detonation wave velocity is about 2625 m/s in the stable stage, which is about 20% higher than that generated by hydrogen/oxygen detonation. A maximum thrust of 69 N is obtained. Stable detonation pressure signal was obtained in our experiments. It is found that the detonation wave has experienced four stages in the formation process: deflagration, deflagration to detonation transition (DDT) process, galloping detonation, and stable detonation. In the stable detonation stage, coexistence of detonation waves with different strength is identified by high-speed photography images.
Figure cited from Wu, W., Wang, Y., Han, W., Wang, G., Zhang, M., & Wang, J. (2023). Experimental research on solid fuel pre-combustion rotating detonation engine. Acta Astronautica, 205, 258-266.
7. Solar-driven Interfacial Evaporation
7. Solar-driven Interfacial Evaporation
Interfacial solar-driven water evaporation technology is considered a cost-effective strategy to mitigate the shortage of freshwater resources at present. However, the coordinated regulation of thermal and water management remains a significant challenge in the design of evaporation systems. From the practical application viewpoint, it is essential to develop an economical, expandable, and simple preparation process for high photothermal conversion capacity and super hydrophilic evaporators. Here, a novel all-in-one MXene/PDA@MF-EF solar evaporator with a porous semi-cladding structure was designed by embedding EPE foam as a base layer (named MF-EF) inside a melamine foam (MF) and coating MXene/PDA as a light-absorbent layer on the surface of MF-EF (named MXene/PDA@MF-EF). The designed MXene/PDA@MF-EF vaporizer has excellent photothermal conversion capability and water transport channel. The MXene/PDA@MF-EF evaporator exhibits an evaporation rate reaching 1.5576 kg m−2 h−1 and a photothermal conversion efficiency of 92.63 % under 1 kW m−2 irradiation. Meanwhile, it exhibits good long-term stability and salt resistance when continuously treating seawater and different concentrations of NaCl solutions. For practical application, an outdoor evaporation device was designed, and the maximum freshwater production of up to 7.170 kg m−2 was achieved under 9 h of sunlight. Hence, the MXene/PDA@MF-EF evaporator enables clean water production through the coordinated action of thermal and water management, providing a viable and stable alternative to solar water evaporation in a variety of aqueous environments. Further, it provides a solution for realizing solar-driven interfacial evaporation desalination technology for freshwater access in coastal and offshore islands.
Interfacial solar-driven water evaporation technology is considered a cost-effective strategy to mitigate the shortage of freshwater resources at present. However, the coordinated regulation of thermal and water management remains a significant challenge in the design of evaporation systems. From the practical application viewpoint, it is essential to develop an economical, expandable, and simple preparation process for high photothermal conversion capacity and super hydrophilic evaporators. Here, a novel all-in-one MXene/PDA@MF-EF solar evaporator with a porous semi-cladding structure was designed by embedding EPE foam as a base layer (named MF-EF) inside a melamine foam (MF) and coating MXene/PDA as a light-absorbent layer on the surface of MF-EF (named MXene/PDA@MF-EF). The designed MXene/PDA@MF-EF vaporizer has excellent photothermal conversion capability and water transport channel. The MXene/PDA@MF-EF evaporator exhibits an evaporation rate reaching 1.5576 kg m−2 h−1 and a photothermal conversion efficiency of 92.63 % under 1 kW m−2 irradiation. Meanwhile, it exhibits good long-term stability and salt resistance when continuously treating seawater and different concentrations of NaCl solutions. For practical application, an outdoor evaporation device was designed, and the maximum freshwater production of up to 7.170 kg m−2 was achieved under 9 h of sunlight. Hence, the MXene/PDA@MF-EF evaporator enables clean water production through the coordinated action of thermal and water management, providing a viable and stable alternative to solar water evaporation in a variety of aqueous environments. Further, it provides a solution for realizing solar-driven interfacial evaporation desalination technology for freshwater access in coastal and offshore islands.
Figure cited from Mu, X., Han, W., Zhang, H., Li, R., Bai, C., Li, W., ... & Liu, Y. (2024). All-in-one MXene/PDA@ MF-EF solar steam generator with semi-clad construction for efficient interfacial evaporation, water purification and desalination. Separation and Purification Technology, 131344.
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