A Systematic Approach for Developing 3D High-Quality PDMS Microfluidic Chips Based on Micromilling Technology

In recent years, there has been an increased interest in exploring the potential of micro-and mesoscale milling technologies for developing cost-effective microfluidic systems with high design flexibility and a rapid microfabrication process that does not require a cleanroom. Nevertheless, the number of current studies aiming to fully understand and establish the benefits of this technique in developing high-quality microsystems with simple integrability is still limited. In the first part of this study, we define a systematic and adaptable strategy for developing high-quality poly(methyl methacrylate) (PMMA)-based micromilled structures. A case study of the average surface roughness (Ra) minimization of a cuboid column is presented to better illustrate some of the developed strategies. In this example, the Ra of a cuboid column was reduced from 1.68 μm to 0.223 μm by implementing milling optimization and postprocessing steps. In the second part of this paper, new strategies for developing a 3D microsystem were introduced by using a specifically designed negative PMMA master mold for polydimethylsiloxane (PDMS) double-casting prototyping. The reported results in this study demonstrate the robustness of the proposed approach for developing microfluidic structures with high surface quality and structural integrability in a reasonable amount of time.

Study on the Polishing Characteristics of the Rotating Cylinder-Based Magnetic Gel Abrasive Finishing

Magnetic gel abrasive finishing is a high-precision polishing method that uses magnetic forces to attract and restrain a gel abrasive, composed of aqueous slime gel, steel grits, and silicon carbon (SiC), for polishing workpieces. However, the magnetic adsorption performance of the gel abrasive will drop quickly when polishing non-ferromagnetic material such as stainless-steel or brass. Moreover, centrifugal force will push out the gel abrasive from the machining surface reducing the stability of polishing. Therefore, this paper developed a rotating cylinder-based magnetic finishing setup to allow the gel abrasive and workpieces to tumble and rotate together during the polishing process. To make the gel abrasive produce irregular and complicated movement paths for improving the polishing performance, this study first analyzed and compared the average surface roughness and removed material weight of workpieces using three kinds of motor operating modes; a unidirectional trapezoidal wave mode, a bidirectional sine wave mode, and a bidirectional trapezoidal wave mode. After identifying the best motor operating mode, the study further compared the polishing characteristics using several SiC particle and steel grit sizes. The experimental results showed that the rotating cylinder driven using a bidirectional trapezoidal wave could obtain better results for average surface roughness and removed material weight than the other two operating modes, while use of the larger steel grit size also obtained improved results. However, different silicon carbide particle sizes did not have a significant impact on the polishing characteristics.

EFFECT OF ABRASIVE TYPE ON THE SURFACE ROUGHNESS AND MRR IN MAF OF AISI 304 STEEL

In this study, the effects of experimental parameters on average surface roughness and material removal rate (MRR) were experimentally investigated by machining of AISI 304 stainless steel plates by magnetic abrasive finishing (MAF) method. In the study in which three different abrasive types were used (Al2O3, B4C, SiC), the abrasive grain size was changed in two different levels (50 and 80[Formula: see text][Formula: see text]m), while the machining time was changed in three different levels (30, 45, 60[Formula: see text]min). Surface roughness values of finished surfaces were measured by using three-dimensional (3D) optical surface profilometer and surface topographies were created. MRRs were measured with the help of precision scales. The abrasive particles’ condition before and after the MAF process was examined and compared using a scanning electron microscope. As a result of the study, the surface roughness values of plates were reduced from 0.106[Formula: see text][Formula: see text]m to 0.028[Formula: see text][Formula: see text]m. It was determined that the best parameters in terms of average surface roughness were 60[Formula: see text]min machining time with 50[Formula: see text][Formula: see text]m B4C abrasives, while the best result in terms of MRR was taken in 30[Formula: see text]min with 50[Formula: see text][Formula: see text]m SiC abrasives.

Using Atomic Force Microscopy to Evaluate Microstructure for Direct Metal Laser Melted Titanium

Additive Manufacturing (AM) is a relatively new technology that could potentially revolutionize industrial manufacturing. Currently, papers have studied the mechanical properties and microstructure of AM materials without the use of Atomic Force Microscopy (AFM). This paper utilizes AFM to analyze the Widmanstätten microstructure and porosity of Direct Metal Laser Melted (DMLM) titanium samples. The mechanical properties of the titanium samples were collected, and the samples exhibited favorable yield and tensile strengths, but suboptimal ductile properties. The DMLM titanium seemed to have an increase in yield and tensile strength while the ductility seemed to decrease as a result of the fast cooling rate utilized in the DMLM process. AFM was used when analyzing the Widmanstätten microstructure which had an average surface roughness of 142 nm and the pore depth of one sample was 3.3 μm. The substantial depth of the pores could potentially be related to the decrease in ductility and it could increase the potential of future premature fractures. AFM provided a lot of useful information for this study and could provide even more information within the metallurgical field when studying the microstructure and porosity of metals, especially for AM materials.

Optical and Morphological Properties of Silver Nanoparticles Synthesis by Q-Switched Nd-YAG Laser

Laser ablation of a silver target immersed in distilled water utilizing Nd: YAG laser with wavelengths of 532nm,1064nm, and 1320nm was carried out to fabricate silver nanoparticles. The synthesis of Ag NPs was carried out using various laser energy (200-1000 mJ) and different pulses (200-1000 pulse). Optical properties for the Ag nanoparticles solution were tested using UV-Visible spectrum, while the morphological properties for the Ag-nanoparticles solution after deposited on glass were tested using the atomic force microscope (AFM). The results showed that the synthesis of the Ag-nanoparticles using pulsed laser ablation in liquid (PLAL) (water) gives nanoparticles with homogeneous grain distribution and uniform surface roughness. It was found that the absorption peaks of Ag NPs increase by increasing the number of pulses shoot for the same laser wavelength and laser energy, and the reported maximum value of absorption peak is 0.363 when using 1000 pulses shoot. AFM results showed that the average diameter of the Ag NPs prepared by PLAL increases with increasing the laser wavelength. However, when using laser wavelengths of 1320nm,1064nm, and 532nm, the resulted average diameter of silver nanoparticles will be 55.38nm, 34.18nm, and 30.3nm, respectively. Finally, the average surface roughness of the Ag NPs prepared by PLAL increased with increasing the laser wavelength. The obtained average surface roughness of silver nanoparticles when using wavelengths of 1320nm,1064nm, and 532nm were 2.75nm, 1.19nm, and1.06nm, respectively.

Influence of Abrasive Water Jet (AWJ) on Surface Roughness

Abrasive water jet (AWJ) is one of the most advanced and valuable non-traditional machining processes because of its massive advantages of removing metals ranging from hard to soft. This paper focused on studying the influence of jet pressure, feed rate and standoff distance on surface roughness during cutting carbon steel using abrasive water jet cutting. A surface roughness device assessed the surface roughness by performing sixteen experiments to identify the distinct texture of the surface. Based on the experiences, the best surface roughness value was 3.14 μm at jet pressure 300 MPa, standoff distance 4mm and feed rate 30 mm/min. The Taguchi method was introduced to implement the experiments and indicate the most influential process parameters on average surface roughness. The experimental results reveal that feed rate has a significant effect on average surface roughness.

Effect of Working Conditions on the Lubricated Wear Behavior of Zn-40Al-2Cu-2Si Alloy in the As-Cast and T6 Heat-Treated States

In order to determine the effect of working conditions on the lubricated wear behavior of Zn-40Al-2Cu-2Si alloy in the as cast and T6 heat-treated states, its tribological properties were studied at different oil flow rates, contact pressures, and sliding speeds in comparison with SAE 660 bronze. It was observed that the friction coefficient, temperature, and wear volume of both materials decrease, but their average surface roughness increase with increasing oil flow rate. As the pressure increased, the friction coefficient and average surface roughness of the experimental materials decreased, but their temperature and wear volume increased. It was also found that the working temperature of these materials increased, but their wear volume showed a decrement and a subsequent increment with increasing sliding speed. In addition, their wear volume and average surface roughness showed opposite changes with the sliding speed. The results of the lubricated friction and wear tests were discussed in terms of the microstructure and mechanical properties of the experimental materials and test conditions. Zn-40Al-2Cu-2Si alloy in both as cast and heat-treated conditions showed lower wear volume and friction coefficient than SAE 660 bronze. This indicates that Zn-40Al-2Cu-2Si alloy can be used to manufacture diesel engine crankshaft journal bearings.

Experimental evaluation of electrophoretic deposition-assisted polishing

The quest for precision in manufacturing sector is continuously evolving with the introduction of modern technologies and new techniques. In this research, the characteristics and influential parameters of a recently developed polishing process, known as electrophoretic deposition-assisted polishing (EPDAP), were investigated in external surface polishing of AISI 316 L stainless steel. The results revealed the improvement of surface roughness with increasing axial load up to the certain value of 11 N. The polishing time between 6 min and 12 min was recommended for polishing surfaces having a moderate initial roughness, close to 0.1 µm. Moreover, the increase of tool rotational speed led to the improvement of surface quality, while the variation of applied voltage had insignificant effects on the surface texture. In the second series of experiments, predictive equations of average surface roughness and material removal rate (MRR) were obtained based on analysis of variance. It was concluded that axial load and tool rotational speed are the most influential parameters on surface roughness and MRR, respectively. By performing a multi-response optimization, the optimum levels of control parameters at the same voltage of 15 V were calculated as axial load of 12 N, polishing time of 10 min, and tool rotational speed of 2000 rpm. This combination reduced the average surface roughness by 54.17% relative to the worst condition, which is characterized by the lowest axial loads, rotational speed, and polishing time at the design space. The maximum MRR of 3.975 mg/min was achieved at this optimum point. Assessment of the surface features indicated that the EPDAP process created uniform roughness profiles and resulted in an enhanced surface reflectance.