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Microfluidic technology is an emerging interdisciplinary field that uses micropipes to handle or manipulate tiny fluids in chemistry, fluid physics, and biomedical engineering. As one of the rapid prototyping methods, the three-dimensional (3D) printing technique, which is rapid and cost-effective and has integrated molding characteristics, has become an important manufacturing technology for microfluidic chips. Polymethyl-methacrylate (PMMA), as an exceptional thermoplastic material, has found widespread application in the field of microfluidics. This paper presents a comprehensive process study on the fabrication of fused deposition modeling (FDM) 3D-printed PMMA microfluidic chips (chips), encompassing finite element numerical analysis studies, orthogonal process parameter optimization experiments, and the application of 3D-printed integrated microfluidic reactors in the reaction between copper ions and ammonium hydroxide. In this work, a thermal stress finite element model shows that the printing platform temperature was a significant printing parameter to prevent warping and delamination in the 3D printing process. A single printing molding technique is employed to fabricate microfluidic chips with square cross-sectional dimensions reduced to 200 μm, and the microchannels exhibited no clogging or leakage. The orthogonal experimental method of 3D-printed PMMA microchannels was carried out, and the optimized printing parameter resulted in a reduction in the microchannel profile to Ra 1.077 μm. Finally, a set of chemical reaction experiments of copper ions and ammonium hydroxide are performed in a 3D-printed microreactor. Furthermore, a color data graph of copper hydroxide is obtained. This study provides a cheap and high-quality research method for future research in water quality detection and chemical engineering.

This paper proposes an effective processing method for fabricating microchannels on the polycarbonate (PC) substrate with CO 2 laser. The width of microchannel has close relationship with CO 2 laser parameters including laser power, laser moving velocity, and length of microchannel. In order to optimize the width of the microchannel, the orthogonal experiment method is successfully applied in this experiment with L 9 (3 3 ) orthogonal test table. Then, the optimal machining parameters are obtained and a verified experiment is confirmed. Finally, the optimal microcahnnels on the PC can be obtained with the presented process parameters.

Applications of membranes in microfluidics solved many thorny problems for analytical chemistry and bioscience, so that the use of membranes in microfluidics has been a topic of growing interest. Many different examples have been reported, demonstrating the versatile use of membranes. This work reviews a lot of applications of membranes in microfluidics. Membranes in microfluidics for applications including chemical reagents detection, gas detection, drug screening, cell, protein, microreactor, electrokinetical fluid, pump and valve and fluid transport control and so on, have been analyzed and discussed. In addition, the definition and basic concepts of membranes are summed up. And the methods of manufacturing membranes in microfluidics are discussed. This paper will provide a helpful reference to researchers who want to study applications of membranes in microfluidics.

CO 2 laser cutting is an advanced processing technology, which can, according to the computer-aided design graphics, cut a variety of shapes in the surfaces of many polymer sheets. This work aims to analyze the effect of laser power, scanning speed, and processing times on the surface roughness of polymethyl-methacrylate microchannels with CO 2 laser LCJG-1290 cutting process. There are several experiments designed by us, and the results were analyzed by orthogonal experimental method. Finally, optimal power, scanning speed, and processing times were obtained, and in the optimal case, the arithmetical mean roughness (Ra) can reach as small as 110 nm.

This paper aims at study and analysis on samples mixing performance of micromixers with serpentine microchannels by numerical simulations in depth. The research on shapes of microchannels is a meaningful issue for improving the samples mixing index in passive micromixers. Lots of productive numerical analysis show that the direction of streamlines changes constantly due to the shape change of microchannels, which enhance molecular diffusion and increases samples mixing index. The simulation and analysis of six microchannel shapes and further numerically analyzed the advantages of the square-wave micromixer have been completed, whose correctness are proved by several mixing experiments. Lots meaningful simulations shows that square-wave microchannels are the best for improving samples mixing among six kinds of micromixers. Adjusting the ratio of microchannels and the number of square-wave units is a effective and simple method to achieve a better mixing performance. It can be demonstrated that the presented design method of microchanel shape is a simple, flexible and efficient technology to improve samples mixing in microfluidic devices.

Two-dimension Y-type micromixers and T-type micromixers have been systematically researched based on fractal theory and generalized Murray’s law. Effect of geometry parameters on mixing efficiency and pressure drop was analyzed. For Y-type micromixers, bifurcation angle is a very important parameter that influences mixing performance. The bifurcation angles θ = 30°, θ = 45°, θ = 60°, θ = 75°, θ = 90°, θ = 105°, and θ = 120° were studied, and the best bifurcation angle was obtained. For T-type micromixers, T Symmetry, Semicircle-T Symmetry, T Asymmetry and Semicircle-T Asymmetry were compared. A comprehensive series of simulations were performed and the optimum structure was obtained.

Purpose The purpose of this study is to provide a micromixer for achieving effective mixing of two liquids. The mixing of two liquids is difficult to achieve in microfluidic chips because they cannot form turbulence at small dimensions and velocities. Design/methodology/approach In this paper, four kinds of passive micromixers based on splitting–recombination and chaotic convection are compared. First, a better E-shape mixing unit based on the previous F-shape mixing unit has been designed. Then, the E-shape mixing units are further combined to form three micromixers (i.e. E-mixer, SESM and FESM). Findings Finally, the mixing experimental results show that the mixing indexes of E-mixer, SESM and FESM are more than those of F-mixer when the Reynolds number range is from 0.5 to 100. And at Re = 15, the lowest mixing index of E-mixer is 71%, which is the highest of the four micromixers. Originality/value At Re = 80, the highest mixing index of F-mixer and E-mixer is 92 and 94 per cent, respectively, and then it begins to decrease. But the mixing index of SESM and FESM remains close to 100 per cent.

Steel pipes are commonly used to strengthen the concrete’s load-bearing capacity. However, they are prone to corrosion in salt erosion environments. In this study, the influence of Na2MoO4 and benzotriazole on concrete-filled steel tubes’ corrosion performance is investigated. The steel pipes’ mass loss rates (MRs), ultrasonic velocity, electrical resistance, and the AC impedance spectrum and Tafel curves of concrete-filled steel tubes were used to characterize the degree of corrosion in the steel pipes. Scanning electron microscopy–energy-dispersive spectrometry and X-ray diffraction were used for studying the composition of steel pipe rust. The research results revealed that the NaCl freeze–thaw cycles (F-C) and NaCl dry–wet alternation (D-A) actions had a reducing effect on the mass and ultrasonic velocity of the concrete-filled steel tubes. After 300 NaCl F-C and 30 NaCl D-A, the MRs were 0%~0.00470% and 0%~0.00666%. The corresponding ultrasonic velocities were 0%~21.1% and 0%~23.6%. When a rust inhibitor was added, the results were the opposite. The MRs decreased by 0%~80.3% and 0%~81.6% with the added Na2MoO4 and benzotriazole. Meanwhile, the corresponding ultrasonic velocities were 0%~8.1% and 0%~8.3%. The steel tubes were corroded after 300 NaCl F-C and 30 NaCl D-A. The addition of rust inhibitors improved the corrosion resistance of the concrete-filled steel tubes by increasing the electrical resistance before NaCl erosion. The corrosion area rate decreased by using the rust inhibitors. The corrosion resistance effect of benzotriazole was higher than that of Na2MoO4. The concrete-filled steel tube with an assembly unit comprising 5 kg/m3 of Na2MoO4 and 15 kg/m3 of benzotriazole had the best corrosion resistance under the erosion induced by NaCl F-C and D-A. Rust inhibitors reduced the content of iron-containing crystals and iron elements. The specimens with 5 kg/m3 Na2MoO4 and 15 kg/m3 benzotriazole had the lowest concentration of iron-containing crystals and iron elements.

Steel pipes are commonly used to strengthen the concrete’s load-bearing capacity. However, they are prone to corrosion in salt erosion environments. In this study, the influence of Na[sub.2] MoO[sub.4] and benzotriazole on concrete-filled steel tubes’ corrosion performance is investigated. The steel pipes’ mass loss rates (MRs), ultrasonic velocity, electrical resistance, and the AC impedance spectrum and Tafel curves of concrete-filled steel tubes were used to characterize the degree of corrosion in the steel pipes. Scanning electron microscopy–energy-dispersive spectrometry and X-ray diffraction were used for studying the composition of steel pipe rust. The research results revealed that the NaCl freeze–thaw cycles (F-C) and NaCl dry–wet alternation (D-A) actions had a reducing effect on the mass and ultrasonic velocity of the concrete-filled steel tubes. After 300 NaCl F-C and 30 NaCl D-A, the MRs were 0%~0.00470% and 0%~0.00666%. The corresponding ultrasonic velocities were 0%~21.1% and 0%~23.6%. When a rust inhibitor was added, the results were the opposite. The MRs decreased by 0%~80.3% and 0%~81.6% with the added Na[sub.2] MoO[sub.4] and benzotriazole. Meanwhile, the corresponding ultrasonic velocities were 0%~8.1% and 0%~8.3%. The steel tubes were corroded after 300 NaCl F-C and 30 NaCl D-A. The addition of rust inhibitors improved the corrosion resistance of the concrete-filled steel tubes by increasing the electrical resistance before NaCl erosion. The corrosion area rate decreased by using the rust inhibitors. The corrosion resistance effect of benzotriazole was higher than that of Na[sub.2] MoO[sub.4] . The concrete-filled steel tube with an assembly unit comprising 5 kg/m[sup.3] of Na[sub.2] MoO[sub.4] and 15 kg/m[sup.3] of benzotriazole had the best corrosion resistance under the erosion induced by NaCl F-C and D-A. Rust inhibitors reduced the content of iron-containing crystals and iron elements. The specimens with 5 kg/m[sup.3] Na[sub.2] MoO[sub.4] and 15 kg/m[sup.3] benzotriazole had the lowest concentration of iron-containing crystals and iron elements.

This paper demonstrates a novel and low-cost method for fabricating microchannel on polycarbonate (PC) sheet using CO 2 laser. In the work, many microchannels are processed by CO 2 laser beam of two-pass. Three sheets with different films are researched for increasing the cleanliness of PC sheet surface after CO 2 laser processing. The experimental results show the surface of PC sheet with transparent wallpaper is most clear, but it has very large influence on width and depth of microchannel. In the next experiment, Taguchi method is used for optimizing CO 2 laser processing parameters for decreasing the deviation of width and depth of microchannel. In the study, smaller-the-better signal-to-noise ratio is calculated. The result shows laser power is maximum influence factor and microchannel length is minimum influence factor on the deviation of width and depth of microchannel. The optimal processing parameters are laser power of 8 W, laser moving velocity of 15 mm/s and microchannel length of 100 mm. A verified experiment is preformed using the optimal processing parameters.