Micromachines

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20 pages, 5026 KiB

Open AccessArticle

Numerical Modeling Using Immersed Boundary-Lattice Boltzmann Method and Experiments for Particle Manipulation under Standing Surface Acoustic Waves

by Fatima Alshehhi, Waqas Waheed, Abdulla Al-Ali, Eiyad Abu-Nada and Anas Alazzam

Micromachines 2023, 14(2), 366; https://doi.org/10.3390/mi14020366 - 31 Jan 2023

Cited by 4 | Viewed by 1852

Abstract

In this work, we employed the Immersed Boundary-Lattice Boltzmann Method (IB-LBM) to simulate the motion of a microparticle in a microchannel under the influence of a standing surface acoustic wave (SSAW). To capture the response of the target microparticle in a straight channel [...] Read more.

In this work, we employed the Immersed Boundary-Lattice Boltzmann Method (IB-LBM) to simulate the motion of a microparticle in a microchannel under the influence of a standing surface acoustic wave (SSAW). To capture the response of the target microparticle in a straight channel under the effect of the SSAW, in-house code was built in C language. The SSAW creates pressure nodes and anti-nodes inside the microchannel. Here, the target particle was forced to traverse toward the pressure node. A mapping mechanism was developed to accurately apply the physical acoustic force field in the numerical simulation. First, benchmarking studies were conducted to compare the numerical results in the IB-LBM with the available analytical, numerical, and experimental results. Next, several parametric studies were carried out in which the particle types, sizes, compressibility coefficients, and densities were varied. When the SSAW is applied, the microparticles (with a positive acoustic contrast factor) move toward the pressure node locations during their motion in the microchannel. Hence, their steady-state locations are controlled by adjusting the pressure nodes to the desired locations, such as the centerline or near the microchannel sidewalls. Moreover, the geometric parameters, such as radius, density, and compressibility of the particles affect their transient response, and the particles ultimately settle at the pressure nodes. To validate the numerical work, a microfluidic device was fabricated in-house in the cleanroom using lithographic techniques. Experiments were performed, and the target particle was moved either to the centerline or sidewalls of the channel, depending on the location of the pressure node. The steady-state placements obtained in the computational model and experiments exhibit excellent agreement and are reported. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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18 pages, 18619 KiB

Open AccessArticle

Less Is More: Oligomer Extraction and Hydrothermal Annealing Increase PDMS Adhesion Forces for Materials Studies and for Biology-Focused Microfluidic Applications

by Larry J. Millet, Anika Jain and Martha U. Gillette

Micromachines 2023, 14(1), 214; https://doi.org/10.3390/mi14010214 - 14 Jan 2023

Cited by 1 | Viewed by 1640

Abstract

Cues in the micro-environment are key determinants in the emergence of complex cellular morphologies and functions. Primary among these is the presence of neighboring cells that form networks. For high-resolution analysis, it is crucial to develop micro-environments that permit exquisite control of network [...] Read more.

Cues in the micro-environment are key determinants in the emergence of complex cellular morphologies and functions. Primary among these is the presence of neighboring cells that form networks. For high-resolution analysis, it is crucial to develop micro-environments that permit exquisite control of network formation. This is especially true in cell science, tissue engineering, and clinical biology. We introduce a new approach for assembling polydimethylsiloxane (PDMS)-based microfluidic environments that enhances cell network formation and analyses. We report that the combined processes of PDMS solvent-extraction and hydrothermal annealing create unique conditions that produce high-strength bonds between solvent-extracted PDMS (E-PDMS) and glass—properties not associated with conventional PDMS. Extraction followed by hydrothermal annealing removes unbound oligomers, promotes polymer cross-linking, facilitates covalent bond formation with glass, and retains the highest biocompatibility. Herein, our extraction protocol accelerates oligomer removal from 5 to 2 days. Resulting microfluidic platforms are uniquely suited for cell-network studies owing to high adhesion forces, effectively corralling cellular extensions and eliminating harmful oligomers. We demonstrate the simple, simultaneous actuation of multiple microfluidic domains for invoking ATP- and glutamate-induced Ca²⁺ signaling in glial-cell networks. These E-PDMS modifications and flow manipulations further enable microfluidic technologies for cell-signaling and network studies as well as novel applications. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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11 pages, 7243 KiB

Open AccessArticle

Microfluidic Chip Fabrication of Fused Silica Using Microgrinding

by Pyeong An Lee, Ui Seok Lee, Dae Bo Sim and Bo Hyun Kim

Micromachines 2023, 14(1), 96; https://doi.org/10.3390/mi14010096 - 30 Dec 2022

Cited by 5 | Viewed by 2081

Abstract

Although glass is in high demand as a material for microfluidic chips, it is still difficult to fabricate microstructures on glass. In this paper, polycrystalline diamond tools were fabricated through electrical discharge machining, and the microgrinding process for fused silica using the tools [...] Read more.

Although glass is in high demand as a material for microfluidic chips, it is still difficult to fabricate microstructures on glass. In this paper, polycrystalline diamond tools were fabricated through electrical discharge machining, and the microgrinding process for fused silica using the tools was studied. In order to improve the productivity, the machining effects of the high feed rate and depth of cut on the surface roughness of the channel bottoms and edge chipping were studied. A toolpath for the microchannels of a microfluidic chip was also studied and a microfluidic chip array was fabricated using this method. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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11 pages, 4478 KiB

Open AccessArticle

Terahertz Combined with Metamaterial Microfluidic Chip for Troponin Antigen Detection

by Yen-Shuo Lin, Shih-Ting Huang, Shen-Fu Hsu, Kai-Yuan Tang, Ta-Jen Yen and Da-Jeng Yao

Micromachines 2022, 13(12), 2257; https://doi.org/10.3390/mi13122257 - 19 Dec 2022

Cited by 3 | Viewed by 1847

Abstract

In this paper, we use terahertz combined with metamaterial technology as a powerful tool to identify analytes at different concentrations. Combined with the microfluidic chip, the experimental measurement can be performed with a small amount of analyte. In detecting the troponin antigen, surface [...] Read more.

In this paper, we use terahertz combined with metamaterial technology as a powerful tool to identify analytes at different concentrations. Combined with the microfluidic chip, the experimental measurement can be performed with a small amount of analyte. In detecting the troponin antigen, surface modification is carried out by biochemical binding. Through the observation of fluorescent antibodies, the average number of fluorescent dots per unit of cruciform metamaterial is 25.60, and then, by adjusting the binding temperature and soaking time, the average number of fluorescent dots per unit of cruciform metamaterial can be increased to 181.02. Through the observation of fluorescent antibodies, it is confirmed that the antibodies can be successfully stabilized on the metamaterial and then bound to the target antigen. The minimum detectable concentration is between 0.05~0.1 μg/100 μL, and the concentration and ΔY show a positive correlation of R² = 0.9909. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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18 pages, 4964 KiB

Open AccessArticle

Rapid Customization and Manipulation Mechanism of Micro-Droplet Chip for 3D Cell Culture

by Haiqiang Liu, Chen Yang and Bangbing Wang

Micromachines 2022, 13(12), 2050; https://doi.org/10.3390/mi13122050 - 23 Nov 2022

Viewed by 2811

Abstract

A full PDMS micro-droplet chip for 3D cell culture was prepared by using SLA light-curing 3D printing technology. This technology can quickly customize various chips required for experiments, saving time and capital costs for experiments. Moreover, an injection molding method was used to [...] Read more.

A full PDMS micro-droplet chip for 3D cell culture was prepared by using SLA light-curing 3D printing technology. This technology can quickly customize various chips required for experiments, saving time and capital costs for experiments. Moreover, an injection molding method was used to prepare the full PDMS chip, and the convex mold was prepared by light-curing 3D printing technology. Compared with the traditional preparation process of micro-droplet chips, the use of 3D printing technology to prepare micro-droplet chips can save manufacturing and time costs. The different ratios of PDMS substrate and cover sheet and the material for making the convex mold can improve the bonding strength and power of the micro-droplet chip. Use the prepared micro-droplet chip to carry out micro-droplet forming and manipulation experiments. Aimed to the performance of the full PDMS micro-droplet chip in biological culture was verified by using a solution such as chondrocyte suspension, and the control of the micro-droplet was achieved by controlling the flow rate of the dispersed phase and continuous phase. Experimental verification shows that the designed chip can meet the requirements of experiments, and it can be observed that the micro-droplets of sodium alginate and the calcium chloride solution are cross-linked into microspheres with three-dimensional (3D) structures. These microspheres are fixed on a biological scaffold made of calcium silicate and polyvinyl alcohol. Subsequently, the state of the cells after different time cultures was observed, and it was observed that the chondrocytes grew well in the microsphere droplets. The proposed method has fine control over the microenvironment and accurate droplet size manipulation provided by fluid flow compared to existing studies. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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13 pages, 3861 KiB

Open AccessArticle

Numerical Study of Heat Transfer Enhancement within Confined Shell and Tube Latent Heat Thermal Storage Microsystem Using Hexagonal PCMs

by Apichit Maneengam, Sameh E. Ahmed, Abdulkafi Mohammed Saeed, Aissa Abderrahmane, Obai Younis, Kamel Guedri, Muflih Alhazmi and Wajaree Weera

Micromachines 2022, 13(7), 1062; https://doi.org/10.3390/mi13071062 - 30 Jun 2022

Cited by 12 | Viewed by 2259

Abstract

Thermophoresis represents one of the most common methods of directing micromachines. Enhancement of heat transfer rates are of economic interest for micromachine operation. This study aims to examine the heat transfer enhancement within the shell and tube latent heat thermal storage system (LHTSS) [...] Read more.

Thermophoresis represents one of the most common methods of directing micromachines. Enhancement of heat transfer rates are of economic interest for micromachine operation. This study aims to examine the heat transfer enhancement within the shell and tube latent heat thermal storage system (LHTSS) using PCMs (Phase Change Materials). The enthalpy–porosity approach is applied to formulate the melting situation and various shapes of inner heated fins are considered. The solution methodology is based on the Galerkin finite element analyses and wide ranges of the nanoparticle volume fraction are assumed, i.e., (0% ≤ φ ≤ 6%). The system entropy and the optimization of irreversibility are analyzed using the second law of the thermodynamics. The key outcomes revealed that the flow features, hexagonal entropy, and melting rate might be adjusted by varying the number of heated fins. Additionally, in case 4 where eight heated fins are considered, the highest results for the average liquid percentage are obtained. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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9 pages, 4448 KiB

Open AccessArticle

Amplitude-Phase Variation in a Graphene-Based Microstrip Line

by Muhammad Yasir, Sergej Fatikow and Olaf C. Haenssler

Micromachines 2022, 13(7), 1039; https://doi.org/10.3390/mi13071039 - 30 Jun 2022

Cited by 5 | Viewed by 1974

Abstract

A graphene-based transmission line with independent amplitude and phase variation capability is proposed. Variation of graphene’s tunable conductivity by an applied DC bias is exploited in designing an attenuator and a phase shifter. The attenuator and phase shifter are separated from each other [...] Read more.

A graphene-based transmission line with independent amplitude and phase variation capability is proposed. Variation of graphene’s tunable conductivity by an applied DC bias is exploited in designing an attenuator and a phase shifter. The attenuator and phase shifter are separated from each other by an interdigitated capacitor to ensure independent control of each section through an applied DC bias. The phase shifter is designed by optimizing lengths of a tapered line and an open stub for a maximum variation of input reactance with a change in graphene resistance. The attenuator is designed by two pairs of grounded vias connected to the transmission line through graphene. Variation of graphene resistance controls the signal passing through graphene pads into the ground causing attenuation. An independent variation of 5 dB of attenuation is measured along with an independent phase variation of 23 degrees in the frequency range of 4 GHz to 4.5 GHz. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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13 pages, 5388 KiB

Open AccessArticle

Darcy-Forchheimer Flow of Water Conveying Multi-Walled Carbon Nanoparticles through a Vertical Cleveland Z-Staggered Cavity Subject to Entropy Generation

by Ghulam Rasool, Abdulkafi Mohammed Saeed, Animasaun Isaac Lare, Aissa Abderrahmane, Kamel Guedri, Hanumesh Vaidya and Riadh Marzouki

Micromachines 2022, 13(5), 744; https://doi.org/10.3390/mi13050744 - 8 May 2022

Cited by 44 | Viewed by 2160

Abstract

To date, when considering the dynamics of water conveying multi-walled carbon nanoparticles (MWCNT) through a vertical Cleveland Z-staggered cavity where entropy generation plays a significant role, nothing is known about the increasing Reynold number, Hartmann number, and Darcy number when constant conduction occurs [...] Read more.

To date, when considering the dynamics of water conveying multi-walled carbon nanoparticles (MWCNT) through a vertical Cleveland Z-staggered cavity where entropy generation plays a significant role, nothing is known about the increasing Reynold number, Hartmann number, and Darcy number when constant conduction occurs at both sides, but at different temperatures. The system-governing equations were solved using suitable models and the Galerkin Finite Element Method (GFEM). Based on the outcome of the simulation, it is worth noting that increasing the Reynold number causes the inertial force to be enhanced. The velocity of incompressible Darcy-Forchheimer flow at the middle vertical Cleveland Z-staggered cavity declines with a higher Reynold number. Enhancement in the Hartman number causes the velocity at the center of the vertical Cleveland Z-staggered cavity to be reduced due to the associated Lorentz force, which is absent when H_a = 0 and highly significant when H_a = 30. As the Reynold number grows, the Bejan number declines at various levels of the Hartmann number, but increases at multiple levels of the Darcy number. Full article

(This article belongs to the Special Issue Nano- and Microfluidic Materials and Systems)

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