Fabrication Of Microchannels Research Articles

Highly efficient fabrication of reentrant microchannels with micro serrated pin fins using a micro staggered multi-edge ball-end milling tool in a single process

Microchannels with micro pin fins and reentrant cavities can increase the heat dissipation area and enhance heat transfer, which are promising for high-performance microchannel heat sinks for heat dissipation of high-heat-flux devices. Nevertheless, their fabrication is time-consuming and cost-inefficient for conventional methods. To this aim, we in this study developed a novel micro staggered multi-edge ball end milling tool (SMBMT) to fabricate a unique type of reentrant microchannels with micro serrated pin fins (RMSPF) in a single process. The formation feasibility of the RMSPF was demonstrated, and they were of narrow exit slots with a width of 500 μm on the top, reentrant circular cavities with a diameter of 800 μm at the bottom, and micro serrated pin fins with a width of about 52 μm and a height of 35 μm on the wall surface of reentrant cavities. More microscale serrated pin fins with much smaller sizes than the micro cutting edges of the SMBMT were obtained due to the staggered arrangement and overlapping effect of the multiple micro cutting edge. A geometrical model of the SMBMT with discrete multiple edges was developed by considering the structure of the RMSPF. The formation process mechanism of RMSPF and its chip formation process was investigated with both experiments and finite element (FE) simulations. Compared to conventional micro ball end milling tool (CBM) with continuous cutting edges, the SMBMT suppressed the burr formation inside reentrant microchannels and improved the surface quality, and reduced the cutting force by up to 53%. The enhanced cutting performance of SMBMT can be attributed to that the multiple discrete cutting edges of SMBMT effectively decreased the contact area of tool-workpiece and the friction between cutting tool and chips. This study offered a highly efficient method to fabricate microchannels with surface microstructures in a single micromilling process, which provided valuable insights for the development of high-performance microchannel heat sinks in a wide range of application areas.

Investigation of ablation threshold and microchannel fabrication on stainless steel using ultrafast laser

ABSTRACT Ultrafast laser processing is a highly versatile tool for creating microscale structures in many materials. The ablation and micromachining characteristics of AISI 304 stainless steel were examined using a femtosecond-pulsed laser. Parameters such as power, scanning speed, transverse overlap, scanning strategies, and shielding gases were systematically varied. The ablation threshold fluence for SS 304 was calculated as 0.16 J/cm2. Two ablation regimes were observed: the gentle regime, where smooth crater walls were formed under low pulse energy (below 20 µJ), and the strong regime, characterized by rough walls created under high pulse energy (above 20 µJ). The optimal parameters for fabricating microchannels on SS 304 surfaces comprised a laser power of 100 mW, a scanning speed of 30 mm/s, a line-to-line distance of 5 µm, and a parallel scan strategy along the major axis. This study provides a practical approach for enhancing the microchannel fabrication process on stainless steel.

Optimization of abrasive slurry assisted rotating ultrasonic machining for enhanced micro-channel fabrication on ceramic silicon wafer (111)

This study examined the impact of abrasive slurry assisted Rotating Ultrasonic Machining (RUM) using Boron Carbide (B4C) powder of three mesh sizes: 400 Mesh, 600 Mesh, and 800 Mesh. The effects of abrasive size, feed rate, and tool rotation on Material Removal Rate (MRR) and Surface Roughness (SR) were investigated. The highest MRR of 3.454 mm³/min was achieved with 400 mesh, 30 mm/min feed rate, and 1250 rpm due to larger abrasive size, medium feed rate, and medium tool rotation velocity, while the lowest MRR of 0.284 mm³/min was noted with 600 mesh, 30 mm/min feed rate, and 1500 rpm, attributed to intermediate abrasive size and high tool rotation. The lowest SR of 1.16 μm was observed at 800 mesh, 15 mm/min feed rate, and 1500 rpm, resulting from smaller abrasive size and higher tool rotation facilitating polishing action and vibrational dampening. The highest SR of 3.71 μm occurred at 400 mesh, 45 mm/min feed rate, and 1500 rpm, due to larger abrasive size, higher feed rate, and tool rotation, increasing surface corrosion. ANOVA and regression analyses highlighted mesh size as the most significant parameter for both MRR and SR, with strong model-experimental value correlations. The findings demonstrate the suitability of abrasive slurry assisted RUM for fabricating micro-channels in X-Ray, optoelectronic, and semiconductor applications.

Novel processing of micro-channels in micro-grinding with automated laser-assistance

AbstractMicro-structures are widely utilized in various fields such as optical, medical, defense, and aerospace. The accuracy and performance of micro-structures depend on fabrication methods, including conventional and non-conventional machining. High-quality micro-channel fabrication is challenging by conventional micro-grinding (CMG) which uses a micro-pencil grinding tool during micro-machining. However, in CMG, high-cutting forces act in the machining zone leading to tool deflection, tool failure, high temperature, and poor surface finish. The challenges of CMG can be overcome by using automated laser-assisted micro-grinding (LAMG), one of the modern micro-machining processes for fabricating high-quality, precise micro-channels. The novel processing of micro-channels in this work is through the in tandem use of LAMG and CMG. In this, the laser structuring is performed using LAMG followed by a micro-pencil grinding tool processing in a sequential manner on a same machine tool to achive high-quality parts and accuracy. This helps in fabrication of a micro-channel directly in one go without the need to remove the part to perform the two operations on two different machining setups, thereby reducing systematic fixturing errors which are significant when we are working at the micro-scale. This paper thus investigates the effect of various parameters viz. laser input energy densities and laser power on cutting forces and surface roughness on the tool as well as the work surface with two distinct scan patterns. In LAMG, at lower laser input energy density (pattern 1), the tangential and normal forces decreased by 10.3% and 20.5%, and surface roughness Sa and Sq reduced by 24% and 22% compared to CMG. Similarly, a normal force decreased by 20.5% in pattern 1 and 38% less in pattern 2. Still, the higher laser energy density (pattern 2) is unsuitable for structure due to an increase in Sa and Sq by 11% and 14.6%, respectively. Results have shown a maximum reduction in the normal and tangential force magnitude by 31 and 44% at 25 W compared to CMG. The work concludes that LAMG with novel laser assistance scan patterns has lower dynamic deflections resulting in better dimensional accuracy and surface finish compared to CMG with a lower tool.

Fabrication of Microchannels on Aluminium-Coated Polymethyl Methacrylate (PMMA) Using a Low Power CO2 Laser

Fabrication of Microchannels on Aluminium-Coated Polymethyl Methacrylate (PMMA) Using a Low Power CO2 Laser

Fabrication of microchannels and through-holes in Borofloat glass using Cr thin film with positive photoresist as the masking layer through wet etching

The present work investigates the efficiency of the masking layer, composed of Cr thin film and positive photoresist (AZ1512HS), to fabricate microchannels and through-holes in Borofloat glass wafers via wet etching, utilizing 20 % HF. The initial phase of the work emphasizes microchannel fabrication. ∼50 µm deep and well-defined microchannels are accomplished with no discernible surface defects on the wafer. In the later phase, predominantly sharp-edged through-holes are successfully fabricated in the wafer, without any observable pinholes, during etching for 300 min. The masking layer constantly exhibited robust adhesion to the wafer throughout the etching process, affirming its effectiveness. This work demonstrates the first instance of fabricating 500 µm deep through-holes in glass with Cr thin film and photoresist as a masking layer.

On the Machinability and Formation of Gas Film Thickness in ECDM of Silica based Pyrex Glass

Electrochemical discharge machining (ECDM) stands out as a preferred method for microfluidic channel fabrication due to its ability to produce required shapes with the least thermal damage along with close tolerances and dimensional accuracy. Recently, there has been significant progress made in the domain of ECDM for parametric analysis, focusing on discharge regime characteristics, but precise control of the hydrodynamic regime remains a challenge. With this view, the present study has been targeted on analyzing the effect of various auxiliary electrodes on the formation of gas film thickness and discharge energy during the fabrication of microchannels using ECDM on silica-based Pyrex glass under varying conditions. Experiments were conducted on an ECDM setup to achieve near damage-free edges of microchannels on the surface silica-based Pyrex glass. Results show the effect of various auxiliary electrodes, applied voltage, and electrolyte concentration on gas film thickness, spark energy, rate of material removal (MRR), and width of overcut (WOC). The optimum parametric level of applied voltage, electrolyte concentration, and auxiliary electrode were 68 V, 35 wt%, and A2 auxiliary electrode, respectively and the best response values were 0.4134 mg min−1, and 40 μm, respectively, for MRR and WOC. In addition, tool wear rate, heat affected zone, and surface morphology of fabricated microchannels was examined using scanning electron microscopy, optical microscope, and energy-dispersive X-ray spectroscopy.

Fabrication of microchannels on silica glass by femtosecond laser multi-scan: From surface generation mechanism to morphology control

Femtosecond laser processing has become a critical technique for the microfabrication of hard and brittle materials, particularly in microfluidic device applications. This study focuses on the fabrication of microchannels with controllable cross-sectional profiles in silica glass, a material known for its excellent physical and chemical properties. Through a combination of experimental research and theoretical analysis, the surface generation mechanisms governing microchannel morphology are investigated, alongside the influence of various processing parameters on the surface roughness at the microchannel bottom. A comprehensive optimization method is developed to control sidewall taper and surface roughness by adjusting laser scanning paths and modes. Utilizing a composite scanning approach, the study achieves near-rectangular microchannels with average sidewall taper angles below 5° and surface roughness (Sa) of 2.53 μm. These results provide a new strategy for precise control of microchannel morphology in silica glass, offering significant potential to enhance the efficiency and precision of microfluidic device fabrication, with broad applications in both industrial and research settings.

Optimization of Hot Embossing Condition Using Taguchi Method and Evaluation of Microchannels for Flexible On-Chip Proton-Exchange Membrane Fuel Cell.

Hot embossing is a manufacturing technique used to create microchannels on polymer substrates. In recent years, microchannel fabrication technology based on hot embossing has attracted considerable attention due to its convenience and low cost. A new evaluation method of microchannels, as well as an approach to obtaining optimal hot embossing conditions based on the Taguchi method, is proposed in this paper to fabricate precise microchannels for a flexible proton-exchange membrane fuel cell (PEMFC). Our self-made hot embossing system can be used to fabricate assorted types of micro-channel structures on polymer substrates according to various applications, whose bottom width, top width, height and cross-sectional area vary in the aims of different situations. In order to obtain a high effective filling ratio, a new evaluation method is presented based on the four parameters of channel structures, and the Taguchi method is utilized to arrange three main factors (temperature, force and time) affecting the hot embossing in orthogonal arrays, quickly finding the optimal condition for the embossing process. The evaluation method for microchannels proposed in this paper, compared to traditional evaluation methods, incorporates the area factor, providing a more comprehensive assessment of the fabrication completeness of the microchannels. Additionally, it allows for the quick and simple identification of optimal conditions. The experimental results indicate that after determining the optimal embossing temperature, pressure and time using the Taguchi method, the effective filling rate remains above 95%, thereby enhancing the power density. Through variance analysis, it was found that temperature is the most significant factor affecting the hot embossing of microchannels. The high filling rate makes the process suitable for PEMFCs. The results demonstrate that under optimized process conditions, a self-made hot embossing system can effectively fabricate columnar structure microchannels for PEMFCs.

Rapid and versatile, micro-patterning and functionalization of complex structures on ultra-thin and flexible polymeric substrates

Microscale patterning on flexible substrates is important in many applications such as in wearable sensors and microfluidics-based diagnostics, therefore low-cost fabrication methods which are scalable and amenable to mass production have attracted the interest of many companies and research groups. Dry film resists (DFRs) are commercially available materials with properties compatible with their implementation on flexible substrates to cover a wide range of applications, which also offer environmental and sustainability benefits due to the low waste generation compared to the liquid resists. However, there are limited detailed reports in the literature regarding the use of DFRs for the fabrication of microfluidic channels or other micropatterns (i.e., posts) on thin and flexible substrates. Herein we present in detail the fabrication of: a) microfluidic channels of width ranging from 50 μm up to 800 μm, and depth ranging from 30 μm up to 270 μm and b) square posts 80 μm × 80 μm in size and 30 μm in height. Particularly, our method enables the fabrication of ultra-deep microchannels (depth > 250 μm), highly ordered post arrays over large area (appr. 60 cm2), as well as complex designs with hierarchical scale features (80 μm posts inside 800 μm microchannels or micro-nanotexturing inside microchannels) on ultra-thin flexible substrates. To demonstrate the versatility of the method, three different DFRs were used on ultra-thin (30 μm), flexible, single-sided copper-clad polyimide substrates. It is also demonstrated that DFRs can be effectively modified using plasma etching to tune the surface wetting properties towards applications such as pumpless capillary action, where such functionality is required.

Modelling Studies of Rotary Magnetic Field in ECDM for Microchannel Fabrication of Silica Glass

Modelling Studies of Rotary Magnetic Field in ECDM for Microchannel Fabrication of Silica Glass

Fabrication of Ceramic Microchannels with Periodic Corrugated Microstructures as Catalyst Support for Hydrogen Production via Diamond Wire Sawing.

Hydrogen energy is the clean energy with the most potential in the 21st century. The microchannel reactor for methanol steam reforming (MSR) is one of the effective ways to obtain hydrogen. Ceramic materials have the advantages of high temperature resistance, corrosion resistance, and high mechanical strength, and are ideal materials for preparing the catalyst support in microchannel reactors. However, the structure of ceramic materials is hard and brittle, and the feature size of microchannel is generally not more than 1 mm, which is difficult to process using traditional processing methods. Diamond wire saw processing technology is mainly used in the slicing of hard and brittle materials such as sapphire and silicon. In this paper, a microchannel with a periodic corrugated microstructure was fabricated on a ceramic plate using diamond wire sawing, and then as a catalyst support when used in a microreactor for MSR hydrogen production. The effects of wire speed and feed speed on the amplitude and period size of the periodic corrugated microstructure were studied using a single-factor experiment. The microchannel surface morphology was observed via SEM and a 3D confocal laser microscope under different processing parameters. The microchannel samples obtained under different processing parameters were supported by a multiple impregnation method. The loading strength of the catalyst was tested via a strong wind purge experiment. The experimental results show that the periodic corrugated microstructure can significantly enhance the load strength of the catalyst. The microchannel catalyst support with the periodic corrugated microstructure was put into the microreactor for a hydrogen production experiment, and a good hydrogen production effect was obtained. The experimental results have a positive guiding effect on promoting ceramic materials as the microchannel catalyst support for the development of hydrogen energy.

Optimize projected mask images for improving three-dimensional printing accuracy for digital light processing based vat photopolymerization

Additive manufacturing technology, specifically digital light processing (DLP) based vat photopolymerization (VPP), is extensively employed for fabricating complex constructs. Nevertheless, the accuracy of DLP-VPP is hindered by challenges such as light diffraction during propagation and light penetration along the exposure axis within the photopolymeric resin. To mitigate these issues, regulating the grayscale of projected mask images offers a reliable approach to reduce undesired curing. In this study, we introduce a voxel-based multi-layer solidification model to predict the exposure dose distribution of printed parts. Based on this model, we propose a pixel-level grayscale optimization method using the gradient descent technique. This method allows us to control the accumulated exposure dose of each voxel by modifying the grayscale of individual pixels in the projected mask images, thereby improving the accuracy of the printed parts. To validate our optimization method, we conducted a series of experiments involving the printing of four representative structures using both the traditional method and our proposed optimization method. The results demonstrate that the structures produced using our optimization method exhibit superior consistency with the target geometry. This indicates a significant improvement in accuracy achieved through our optimization technique. Furthermore, our optimization method has successfully enabled the fabrication of microchannels that are previously unattainable using traditional method. This achievement highlights the immense potential of our optimization method in the realm of printing microchannels.

Finite element analysis of wire EDM process parameters on performance characteristics of Al–SiC hybrid composite with micro and nano reinforcements

Aluminum Hybrid Composites (AHC) microchannels find extensive applications in aerospace, refrigeration and air conditioning (RAC), microelectronics, automotive, biomedical, and marine industries due to their improved mechanical properties. The combination of lower density, high hardness, elevated thermal and electrical conductivity, superior elasticity, and heightened oxidizing ability at low temperatures makes machining aluminum hybrid composites challenging through orthogonal methods in an open environment. Therefore, it is imperative to investigate the impact of various machining conditions to determine optimal parameter values for microchannel fabrication in aluminum hybrid composite materials. This study aims to identify the ideal machining parameters for Al–SiC micro-SiC nano hybrid composites using wire electrical discharge machining. Four distinct process parameters (pulse on time, gap voltage, wire tension, and wire feed rate) and two response parameters (material removal rate (MRR) and surface roughness (SR)) were considered for process optimization. Additionally, finite element modeling was conducted for the aforementioned process, and the results were compared with experimental outcomes. Single-variable optimization yielded maximum MRR at 125 tons (μs), 25 SV (volt), 12 WT (kgf), and 2 WFR (m/min), and minimum SR at 125 tons (μs), 10 SV (volt), 12 WT (kgf), and 4 WFR (m/min). Single-variable optimization for simulations resulted in maximum MRR at 125 tons (μs), 40 SV (volt), 4 WT (kgf), and 6 WFR (m/min), and minimum SR at 110 tons (μs), 10 SV (volt), 12 WT (kgf), and 2 WFR (m/min). Precise modeling aids in minimizing unnecessary machining, enabling exploration of a broader range of experimental results, thereby promoting environmentally friendly and sustainable machining practices.

Experimental and numerical investigations into the fabrication of alumina ceramic surface microchannel by electrochemical discharge machining

The electrochemical discharge machining (ECDM) is an advanced and promising technology for fabricating micro structures. This method is effectively applicable for non-conductive hard and brittle materials micromachining, such as glass and ceramics. However, the ceramics high melting point and intense heat exchange effects during microchannel fabrication lead to the easy dissipation of thermal energy and the difficulty in processing. To address this issue and expanded the ECDM processing range. This paper dedicated to the investigation of the material removal mechanism and process characteristics for the alumina ceramic surfaces microchannels preparation. Firstly, this study explained the difference of the ECDM critical applied voltage and gas film generation mechanism by analyzing the volt-ampere characteristic curve of 20 wt% NaOH electrolyte with a tool immersed depth of 2 mm and 10 mm respectively. Then, a thermal removal finite element model (FEM) for ECDM was developed. The heat cumulative and intermittent cooling effects applied on the alumina ceramic surface dominated the materiel removal. Additionally, it can be found that the microchannel machining accuracy and bottom surface quality depended on the Gaussian heat source characteristics, gas film formation mechanism, heat accumulation effect, and temperatures spatial and temporal distribution. And a series of single factor experiments for evaluating the parametric studies such as the effect of discharge frequency, applied voltage, duty ratio and tool feed rate on the fabricated microchannel performance are executed. Finally, the complex three-dimensional structures of cross microchannel grid and zigzag microchannel array with variable depth were successfully fabricated on aluminum oxide ceramic surface. Notably, the results highlighted and enriched the ECDM stability, consistency and applicability for alumina ceramic surface microchannel fabrication.

On material removal analysis in ECSM process during micro-channelling with rough tool: Experimental investigation and numerical simulation

The prevailing ECSM investigation using rough tools exhibits its superior performance, especially during micro-channelling. However, the critical aspects related to microchannel quality, such as straightness error, depth/width ratio, MRR and surface quality, have not been thoroughly explored in the existing literature. This research endeavours to fill this gap by addressing these pertinent issues. It also introduces a finite element-based model to analyze the transient temperature distribution and material removal rate, considering the influence of multiple spark discharges generated by rough tools during micro-channelling. The research encompasses theoretical analysis, simulations accounting for partition energy, and experimental assessment of various ECSM parameters for fabricating microchannels with better MRR, depth/width ratio and straightness without compromising the machined surface quality. Theoretical and simulation analyses emphasize the superior performance of rough tools in achieving efficient micro-channel fabrication compared to smooth tools, attributed to a substantial 245 % higher electric field distribution over the entire rough tool surface. Particularly, under low-energy interactions (70 V, 20 % electrolyte concentration, 6 mm/min tool feed, and 3 ms pulse on time), the close alignment between experimental, simulation and regression model results validates the accuracy of the FEM model in capturing the performance of the rough tool in ECSM micro-channelling. This comprehensive investigation provides valuable insights into the benefits of employing rough tools and the factors influencing the quality and efficiency of ECSM for microchannel fabrication.

Thermal performance improvement in wavy microchannels using secondary channels

PurposeThis study aims to minimize the pressure drop across wavy microchannels using secondary branches without compromising its capacity to transfer the heat. The impact of secondary flows on the pressure drop and heat transfer capabilities at different Reynolds numbers are investigated numerically for different wavy microchannels. Finally, different channels are evaluated using performance evaluation criteria to determine their effectiveness.Design/methodology/approachTo investigate the flow and heat transfer capabilities in wavy microchannels having secondary branches, a 3D conjugate heat transfer model based on finite volume method is used. In conventional wavy microchannel, secondary branches are introduced at crest and trough locations. For the numerical simulation, a single symmetrical channel is used to minimize computational time and resources and the flow within the channels remains single-phase and laminar.FindingsThe findings indicate that the suggested secondary channels notably improve heat transfer and decrease pressure drop within the channels. At lower flow rates, the secondary channels demonstrate superior performance in terms of heat transfer. However, the performance declines as the flow rate increased. With the same amplitude and wavelength, the introduction of secondary channels reduces the pressure drop compared with conventional wavy channels. Due to the presence of secondary channels, the flow splits from the main channel, and part of the core flow gets diverted into the secondary channel as the flow takes the path of minimum resistance. Due to this flow split, the core velocity is reduced. An increase in flow area helps in reducing pressure drop.Practical implicationsMany complex and intricate microchannels are proposed by the researchers to augment heat dissipation. There are challenges in the fabrication of microchannels, such as surface finish and achieving the required dimensions. However, due to the recent developments in metal additive manufacturing and microfabrication techniques, the complex shapes proposed in this paper are feasible to fabricate.Originality/valueWavy channels are widely used in heat transfer and micro-fluidics applications. The proposed wavy microchannels with secondary channels are different when compared to conventional wavy channels and can be used practically to solve thermal challenges. They help achieve a lower pressure drop in wavy microchannels without compromising heat transfer performance.

Quality enhancement of micro-milled channels with automated laser assistance

AbstractMicrochannels are utilised on material surfaces of a body, allowing coolant to pass through them and enabling heat dissipation by increased contact area. Fabrication of metal surface microchannels is primarily achieved by employing a micro-milling process, which has drawbacks such as excessive cutting forces, top burrs, tool wear, and lower tool life. Alternatively, it is also realised by using Laser micro milling, which has problems associated with lower quality of surface finish, un-desired taper, heat-affected zone, and spatters. The existing literature, after due review of the current state of the art, has brought out gaps needing attention. These gaps are limited capability to reduce surface roughness, unaddressed burr width, and irregular bottom surface morphology, which affect microchannel quality. These gaps motivate this research work to improve and sustain the microchannel quality. To achieve the goals, this research work performs the fabrication of microchannels by micro-milling with automated laser assistance being achieved in two ways (a) sequentially, (b) non-sequentially, termed as LASMM and LPCMM, which are novel for the scientific community. The effects of micro milling parameters, spindle speed and feed on the quality were analysed while machining commercially pure titanium (cp-Ti). Results show that laser assistance to micro-milling provides a lower generation of undesired forces and lesser top burrs compared to micro-milling alone. In sequential laser assistance, the channels have a mean down burr width ~ 58% lower and a maximum down burr width ~ 38% lower than the channels done non-sequentially. In the case of up-burr width, a mean value ~ 60% lower and a maximum value ~ 73% lower is achieved in channels done non-sequentially as compared to those done sequentially. In the case of surface roughness, channels done sequentially have a maximum Sa value of 1.508 µm, a maximum Sq value of 1.912 µm whereas non-sequentially, they show a maximum Sa value of 3.495 µm, maximum Sq value of 4.59 µm. Steady tool wear is observed sequentially, whereas in non-sequential, rapid tool wear occurs after 500 mm of cutting length.

Enhancing fabrication of hybrid microfluidic devices through silane‐based bonding: A focus on polydimethylsiloxane‐cyclic olefin copolymer and PDMS‐lithium niobate

AbstractEffective manipulation and control of fluids in microfluidic channels requires robust bonding between the different components. Polydimethylsiloxane (PDMS) is widely employed in microchannel fabrication due to its affordability, biocompatibility, and straightforward fabrication process. However, PDMS's low surface energy poses challenges in bonding with many organic and inorganic substrates, hindering the development of hybrid microfluidic devices. In this study, a simple and versatile three step process is presented for bonding PDMS microchannels with organic (cyclic olefin copolymer (COC)) and inorganic substrates (lithium niobate (LiNbO3)) using plasma activation and a silane coupling agent. Initially, the PDMS surface undergoes oxygen/argon plasma activation, followed by functionalization with (3‐aminopropyl) triethoxysilane (APTES). Subsequently, the COC or LiNbO3 is plasma activated and brought into contact with PDMS under a load at a specific temperature. Characterization by Fourier transform infrared, scanning electron microscopy, atomic force microscopy, and contact angle measurements confirmed the successful treatment of the substrates. In addition, bonding strength of the fabricated hybrid devices was assessed through leakage and tensile tests. Under optimized conditions (100°C and 4% v/v APTES), PDMS‐COC hybrid microchannels achieved a flow rate of 600 mL/h without leakage and a tensile strength of 562 kPa. Conversely, the PDMS‐ LiNbO3 assembly demonstrated a flow rate of 216 mL/h before leakage, with a tensile strength of 334 kPa. This bonding method exhibits significant potential and versatility for various materials in microfluidic applications, ranging from biomedical research to enhanced oil recovery.

Optimizing processing parameters in electrical discharge milling of CFRP using metaheuristics

ABSTRACT The micro-channel fabrication in carbon fiber-reinforced polymer (CFRP) composite through electrical discharge machining (EDM) process followed by the comprehensive study of dimensional deviation in the conceived micro-channels are presented in this work. The factors namely, voltage (V), tool rotational speed (TRS), and feed rate (FR) were considered for assessing their impact on channel width deviation (CWD). In addition to the variance analysis,, two potential metaheuristic optimizers, the Butterfly optimization algorithm (BOA) and the Spotted Hyena optimization algorithm (SHO) were used to identify the optimal operating parameters of the aforementioned process. The BOA revealed that the optimal process variables were FR = 5.99 µm/s, V = 150 volt, and TRS = 577.08 rpm for a CWD = 74.96 µm. In contrary, SHO revealed that FR = 5.99 µm/s, V = 150 volt, TRS = 542.96 rpm, and CWD = 74.53 µm were the corresponding optimal values. Overcuts were observed in the fabricated micro-channels and a detailed illustration of the mechanism of overcut formation was provided.