This work is mainly to combine fractal principle with multi-objective genetic algorithm, and the multi-objective optimization of the Cantor fractal baffle micromixer is carried out. At different ...Reynolds numbers (Res), the three-dimensional Navier-Stokes equation is employed to numerically analyze the fluid flow and mixing in the microchannel. We choose the ratio of the three parameters associated with the geometry of the micromixer as design variables, and take the mixing index and pressure drop at the outlet of the micromixer as two objective functions for optimization. For the parameter study of the design space, the Latin hypercube sampling (LHS) method is used as an experimental design technique, and it is used to select design points in the design space. We use the proxy modeling of the response surface analysis (RSA) to approximate the objective function. The genetic algorithm is used to get the Pareto optimal frontier of the micromixer. K-means clustering is used to classify the optimal solution set, and we select representative design variables from it. Through multi-objective optimization, when Re = 1 and 10, the optimized mixing efficiency of the micromixer increased by 20.59% and 14.07% compared with the reference design, respectively. And we also prove that this multi-objective optimization method is applicable to any Res.
This paper studies the Non-Newtonian fluid and Newtonian fluid in the electroosmotic micromixer. We study the effect of voltage amplitude, frequency and fluid inlet velocity on its mixing performance ...based on the Koch fractal micromixer. The Carreau–Yasuda model is used to simulate blood in a non-Newtonian shear thinning fluid. Newtonian fluid chooses water. The study finds that on both fluids, the mixing index of the micromixer is proportional to the voltage and frequency values, and inversely proportional to the inlet velocity. The maximum mixing index of the electroosmotic micromixer for blood simulation (EMFB) is 0.7616, and the maximum mixing index of the electroosmotic micromixer for water simulation (EMFW) is 0.9744. The results show that in the electroosmotic micromixer, the vortices generated by the fluid under the effect of the electric field promote adequate mixing of the fluid. The concentration surface contour circulation is more intense. Finally, we discuss the effect of the power-law index on the mixing index. The analysis reveals that the mixing performance of shear-thinning fluids (
n
< 1) is better than that of shear-thickening fluids (
n
> 1).
•Aiming at the problem that the electroosmotic effect is small when the conductivity is high, we have studied the influence of alternating current heating on fluid mixing.•We apply the film heater to ...influence the fluid mixing through an external heat source.•The temperature in the microchannel can be flexibly adjusted by changing the amplitude of the AC voltage and the heat of the film heater.
In order to solve the problem of difficult mixing of high-conductivity solutions, this paper designs a new mixing method of micromixer based on the alternating current (AC) heating effect. We set up the AC electrode and the film heater at the bottom of the microchannel. Under their joint action, the fluid in the microchannel will be affected by the Joule heat generated internally and the external heat source, so that the fluid disturbance and temperature distribution can be flexibly adjusted. It is characterized by joint numerical simulation. The key structural parameters of the micromixer, such as the electrode width ratio, the size of the film heater and the channel structure, are obtained to influence the performance of the micromixer. At the same time, the influence of the applied voltage amplitude and solution conductivity on the performance of the micromixer is analyzed. The results show that when only AC electrodes are applied, that is, the fluid in the microchannel is only affected by the Joule heat generated inside, the mixing efficiency of the micromixer can reach up to 83%. After we apply the film heater, that is, when in the combined action of an AC electrode and an external heat source, it is observed that the relatively high conductivity is as high as 0.2 S/m, and the mixing efficiency exceeds 90%. The two different fluids are almost completely mixed in the microchannel.
The synthesis of nanoparticles is affected by many reaction conditions, and their properties are usually determined by factors such as their size, shape and surface chemistry. In order for the ...synthesized nanoparticles to have functions suitable for different fields (for example, optics, electronics, sensor applications and so on), precise control of their properties is essential. However, with the current technology of preparing nanoparticles on a microreactor, it is time-consuming and laborious to achieve precise synthesis. In order to improve the efficiency of synthesizing nanoparticles with the expected functionality, the application of machine learning-assisted synthesis is an intelligent choice. In this article, we mainly introduce the typical methods of preparing nanoparticles on microreactors, and explain the principles and procedures of machine learning, as well as the main ways of obtaining data sets. We have studied three types of representative nanoparticle preparation methods assisted by machine learning. Finally, the current problems in machine learning-assisted nanoparticle synthesis and future development prospects are discussed.
Machine learning-assisted synthesis of nanoparticles.
Peach (
L. Batsch) trees grow vigorously and are subject to intense pruning during orchard cultivation. Reducing the levels of endogenous gibberellins (GAs) represents an effective method for ...controlling branch growth. Gibberellin 2-oxidases (GA2oxs) deactivate bioactive GAs, but little is known about the GA2ox gene family in peach. In this study, we identified seven
genes in the peach genome, which were clustered into three subgroups: C
-GA2ox-I, C
-GA2ox-II, and C
-GA2ox-I. Overexpressing representative genes from the three subgroups,
,
, and
, in tobacco resulted in dwarf plants with shorter stems and smaller leaves than the wild type. An analysis of the GA metabolic profiles of the transgenic plants showed that PpGA2ox-5 (a member of subgroup C
-GA2ox-II) is simultaneously active against both C
-GAs and C
-GAs,which implied that C
-GA2ox-II enzymes represent intermediates of C
-GA2oxs and C
-GA2oxs. Exogenous GA
treatment of shoot tips activated the expression of all seven
genes, with different response times: the
-
genes were transcriptionally activated more rapidly than the
genes. GA metabolic profile analysis suggested that C
-GA2ox depletes GA levels more broadly than C
-GA2ox. These results suggest that the
gene family is responsible for fine-tuning endogenous GA levels in peach. Our findings provide a theoretical basis for appropriately controlling the vigorous growth of peach trees.
Abstract
Nanoparticles play irreplaceable roles in optoelectronic sensing, medical therapy, material science, and chemistry due to their unique properties. There are many synthetic pathways used for ...the preparation of nanoparticles, and different synthetic pathways can produce nanoparticles with different properties. Therefore, it is crucial to control the properties of nanoparticles precisely to impart the desired functions. In general, the properties of nanoparticles are influenced by their sizes and morphologies. Current technology for the preparation of nanoparticles on microfluidic chips requires repeated experimental debugging and significant resources to synthesize nanoparticles with precisely the desired properties. Machine learning-assisted synthesis of nanoparticles is a sensible choice for addressing this challenge. In this paper, we review many recent studies on syntheses of nanoparticles assisted by machine learning. Moreover, we describe the working steps of machine learning, the main algorithms, and the main ways to obtain datasets. Finally, we discuss the current problems of this research and provide an outlook.
The method of using a surface acoustic wave (SAW) to drive fluid mixing on a microfluidic chip has been widely investigated by researchers because of its advantages of not directly contacting the ...fluid and not changing the chemical properties of the fluid. In this paper, we investigate the potential mechanism of SAW-driven fluid mixing. A SAW device is designed by us and modal and harmonic response analyses are performed on it. Because the mechanisms of the traveling SAW (TSAW) and the standing SAW (SSAW) on a fluid are different, we have performed transient simulations for each of them in order to clearly understand their differences. The effect of voltage values on the intensity of acoustic pressure is also studied by us. Finally, we perform a comprehensive analysis of acoustic-fluid force-driven fluid mixing. For TSAW- and SSAW-driven fluid mixing, we discuss and analyze the mixing effect at different voltages separately. The velocity fields of the two types of SAW-driven micromixers are also investigated. It is found that the mixing effect of both micromixers is enhanced with increasing voltage. However, the TSAW-driven micromixer produces a single vortex flow through the channel in the acoustic action region, while the SSAW-driven micromixer produces a symmetric double vortex flow. The difference between the TSAW- and SSAW-driven fluids can be clearly analyzed by the velocity field results. The TSAW drives the fluid mainly on one side of the microchannel, while the SSAW drives the fluid by superposition of the acoustic flow force on both sides of the microchannel. The results of this study contribute to a better understanding of the SAW-driven effect on the flow properties of fluids. Moreover, this work lays a theoretical foundation for practical applications in areas such as biochemical reactions and polymer synthesis.
•This article introduces the optimization of a micromixer based on the Cantor structure.•The response surface function model is used as the proxy model of the objective function.•The Latin hypercube ...sampling method is used as an experimental design technique.•The intelligent simulated annealing algorithm is used to optimize the objective function.•The micromixer with the Cantor structure greatly improves the mixing performance.
To maximize the mixing performance of the micromixer with the Cantor fractal baffle structure, single-objective optimization of the micromixer with different Reynolds (Res) is carried out. The three-dimensional Navier-Stokes equation is used to numerically analyze the fluid flow and mixing in the micromixer. We choose three parameters related to the geometry of the Cantor fractal baffle inside the microchannel as the best design variables. The mixing index at the outlet of the micromixer is used as the objective function. And conduct parameter studies to explore the influence of the design variables on the objective function. For the parameter study of the design space, the Latin hypercube sampling (LHS) method is used as an experimental design technique. It is used to select design points in the design space. We use surrogate modeling of response surface functions to approximate the objective function. When Re is different, the simulated annealing algorithm is used to optimize the objective of the established surrogate modeling, and finally the optimal structure configuration of the micromixer is obtained. In this article, we combine the fractal principle with the simulated annealing algorithm to improve the mixing performance of the micromixer. This is not involved in previous studies. The results show that the mixing performance of the optimized micromixer has indeed been significantly improved. When Re = 0.1, 1, 10, and 100, the mixing efficiency of the optimized micromixer is increased by 7.64%, 17.75%, 14.08%, and 0.91%, respectively, compared with the reference design.
•The Poiseuille number is proposed to evaluate the safety and reliability of the micromixer.•Orthogonal experiment is used to ensure that the number of experiments is small and evenly ...distributed.•Grey relational analysis is used to find the micromixer with the best overall performance.•A new type of micromixer with Cantor fractal baffle is proposed.
This paper proposes a multi-objective optimization method for a micromixer with Cantor fractal baffles through grey relational analysis, and evaluates the comprehensive performance of the micromixer through two aspects. The height of the baffle (h), the distance of the baffle (p), the width of the microchannel (L) and the height of the microchannel (H) are selected as design variables, and the orthogonal experiment table L16(44) is obtained. The optimized performance characteristics take into account the mixing index and Poiseuille number. Numerical simulations are used to obtain the results of each experimental design group. We use the grey relational degree as an index to evaluate the comprehensive performance of the multi-objective of the micromixer, and optimize to find a set of optimal design variables. Finally, we judge the influence of the four design variables on the two performance characteristics respectively, so as to obtain the importance of different design variables. The results show that the optimized micromixer, namely CFM-11, has a maximum increase of 23.75% in mixing index and a maximum decrease in Poiseuille number of 34.40%. Among all the parameters, the h and the L have a greater impact on the performance characteristics. This work can provide a good analysis method for multi-objective research and structural optimization related to micromixers.
With the development of surface acoustic wave devices, the separation of micron-sized particles based on standing surface acoustic waves (SSAW) has been studied, and the method has the advantages of ...high efficiency and ease of operation. In this paper, we design a two steps SSAW-based model for separating three different sizes of particles. The particle with the largest diameter is separated in the first sorting step region, and the remaining two particles are separated in the second sorting step region. During the study, we investigate the SSAW device firstly. We chose three different materials for the comparative analysis of the piezoelectric substrates. Next, we investigate the effects of fork-finger pairs and input voltage of the interdigital transducer (IDT) on the stability of the output waveform and sound pressure intensity. Finally, we select the appropriate number of fork-finger pairs and determine the acoustic pressure intensity in the low and high voltage regions respectively, so that three different particles could be successfully sorted in two steps. This research result can provide a certain theoretical basis for practical research fields such as cell sorting and drug detection.
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