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The Basic Concept for Microfluidics-Based Devices
Published in Raju Khan, Chetna Dhand, S. K. Sanghi, Shabi Thankaraj Salammal, A. B. P. Mishra, Advanced Microfluidics-Based Point-of-Care Diagnostics, 2022
Thus, glass and polymers are suitable candidates to overcome the shortcomings of conventional silicon-based microfluidics devices. Properties such as optical transparency, electrical insulation, chemical inertness, and the low cost of processing make them a suitable candidate for device fabrication. Glass capillaries are also a promising option used in the fabrication of capillary-based microreactors. Still, the assembly of such capillaries requires handling skills and cumbersome operations. A microchannel on glass or quartz is fabricated via photolithography and wet or dry etching. Although glass is considered biocompatible and has widespread application in biological science, it is brittle and requires extensive care during the fabrication and handling of such devices. Also, similar to those of silicon-based microfluidics devices, the channels made in glass are also open channels and need a cleanroom environment at the time of bonding. Thus, during manufacturing, this adds up to the overall cost of glass-based microfluidics devices.
Motor Cooling
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
In this technique, a cooling fluid is forced to pass through a microchannel heatsink by an external microscale pump for achieving very high heat removal rates. Because of its high heat removal capability, the researchers at the Oregon Stator University are currently working with a motor manufacturer to design microchannel cooling systems in electric motors [11.84]. However, before this technique is successfully transplanted from electronic device cooling to high-power-density motor cooling, several difficulties must be overcome. First, the high heat-removing capability of a microchannel system is always associated with high pressure drop across the microchannels. Thus, it requires high power for driving cooling fluid through the microchannels. Second, due to the complex geometries of motor components, it is a challenge to achieve uniform cooling of the motor. Third, heat transfer processes in microchannels are somewhat different from those in ordinary size channels. The capillarity of fluid in microchannels has a strong influence on flow patterns and heat transfer rates. This mechanism must be fully understood. Finally, it is noted that two-phase flows can be quite different from single-phase flows in microchannels. It is risky to extrapolate macroscale two-phase flow maps, flow boiling heat transfer methods, and pressure drop models to microchannels. More research is necessary to understand two-phase microchannel flows and heat transfer mechanisms.
Photoresponsive Polymers for Control of Cell Bioassay Systems
Published in Severian Dumitriu, Valentin Popa, Polymeric Biomaterials, 2020
Kimio Sumaru, Shinji Sugiura, Toshiyuki Takagi, Toshiyuki Kanamori
Figure 20.12 shows the experimental result of the practical demonstration using the constructed universal microfluidic system. After micropatterned irradiation, a microchannel was formed in the hydrogel sheet along the irradiated pattern, and the fluorescent latex suspension supplied from an inlet port started to flow through the newly formed microchannels within a few minutes. A straight microchannel, a bent microchannel, a serpentine microchannel, and branched microchannels were repeatedly formed by micropatterned light irradiation. Note that it took several minutes to 10 min to fill up the long microchannels. In this scheme of microfluidic control based on the conversion of light to the volume change of the photoresponsive hydrogel, microchannels with an arbitrary width and depth along arbitrary path could be formed at an arbitrary timing. This result demonstrated that the universal microfluidic system based on this scheme would provide microfluidics with a powerful method of mass transfer control.
Liquid–liquid extraction performance of circulation-extraction method using a microchannel device
Published in Solvent Extraction and Ion Exchange, 2021
Another drawback of microchannel devices is that they are optimized for a particular process and have a fixed inner volume of channels, which makes their application in different processes challenging. When a longer residence time is required because of the variation in the liquid properties and mass transfer rate, the only option to increase the residence time is to reduce the flow rate since the inner volume of channels is fixed; however, the mass transfer rate deteriorates in this case because of the low flow velocity, resulting in a requirement of further residence time and a reduction of the flow rate and consequently the productivity. A similar drawback is also observed in the case of the multi-stage extraction process, in which the number of stages required for a particular process is determined, and the equipment system must consist of the same number of devices as the number of stages. In this scenario, the number of stages of the system is fixed, and the equipment cannot be applied to other processes requiring more stages. Increasing the number of microchannel devices to overcome issues such as the low throughput and lack of flexibility of the device and multi-stage system eventually leads to a high capital expenditure.
Modeling and Multi-objective Optimization of Heat Transfer Characteristics and Pressure Drop of Nanofluids in Microtubes
Published in Heat Transfer Engineering, 2021
Marcel Meyer, Mehdi Mehrabi, Josua Petrus Meyer
The microchannel geometry has a significant effect on the overall heat transfer performance of a microchannel. The optimization criterion of this study was to find the lowest pressure drop while having the highest Nusselt number based on the best possible combination of four input parameters. Therefore, if the effect of input parameters was to be analyzed, the geometry had to remain constant. The configuration of microchannels differs from design to design. Chein and Chen [16] studied the effects of the inlet-outlet configuration of a microchannel. Their study concluded that the V-type inlet with fluid flow entering and leaving vertically resulted in the largest heat transfer. Therefore, a microchannel with a V-type inlet used by Chein and Chen [16] and Abdollahi et al. [17] was selected for this study. The model was recreated in SolidWorks version 2018 (Dassault Systèmes, Vélizy-Villacoublay, France) and used throughout the simulation and design study. Figure 1a–c shows the details of the microchannel geometry and microchannel dimensions.
Computational modeling of thermal characteristics of hybrid nanofluid in micro-pin fin heat sink for electronic cooling
Published in International Journal of Green Energy, 2021
Nuraini Binti Sukhor, Alhassan Salami Tijani, Jeeventh Kubenthiran, Ibrahim Kolawole Muritala
There is a large volume of published studies describing the role of heat sinks and microchannel in the thermal management of electronic components (Agrawal et al. 2015; Ganatra et al. 2018; Haghighi, Goshayeshi, and Reza 2018; Ibrahim et al. 2018; Maradiya, Vadher, and Agarwal 2018; Sajid, Ali, and Bicer 2020; Sajid et al. 2019; Zaretabar, Asadian, and Ganji 2018). Conventional pin-fin heat sinks are commonly used in industrial applications such as transformers, nuclear energy, and CPU. Tuckerman and Pease were the first to discover an effective cooling technique for electronic cooling by introducing microchannel heat sink (Tuckerman and Pease 1981. There are two types of microchannel systems; a microchannel heat sink that absorbs heat energy from a hot surface and cools it down, and a microchannel heat exchanger where heat is transferred between cold and hot medium (Silvério et al. 2015; Soudagar et al. 2020; Usman Sajid* and Bicer 2020b). Table 1 shows the overview of various nanofluids and their application. It can be observed from the table that large number of authors use nanofluid for thermal management of different devices such as heat pipes, heat sinks, solar thermal systems and electronic cooling, etc.