Author: Elif Kaya, University of Ege Department of Bioengineering
Microfluidic devices are high technology products that consist of one or more microchannels less than 1 mm in size. These devices pave the way for engineering applications in macro systems. One of the branches of this technology is microreactors. These are platforms with very low reservoir volumes and operated in continuous flow mode. It can be used to improve various processes and reactions at the micro level. It also provides a new perspective to both industrial applications, chemical, and biological analysis in terms of their working capacities and functionality. This technology is productive and safe systems with high potential outputs and low-cost production facilities. Fluid flow, thermal and chemical kinetic behavior, their size and energy flow are observed in this system. These features make this technology useful in various application areas.
Advantages of Microreactors
They have many advantages that provide high-efficiency performance and repeatability. The miniaturization of reactors and the ability to connect with different components provide new capabilities against other conventional methods. These miniature reactors provide potentially high-efficiency and low-cost . The small size, which is one of its advantages, allows the reactions to reach higher heat and mass transfer rates. These high heat transfer rates perform reactions under more uniform temperature conditions. Additionally, the advantage of the smaller size ensures a short residence time in the reactors . In microchannel, devices have a large surface and interface areas. These systems generate a laminar flow that provides good control of the reaction conditions and time . Due to their small size, the small volume of the required reagents minimizes the number of expensive reagents thus reduces the cost. Furthermore, the possibility of sensor integration increases the reliability of micro-reactors . All these advantages allow new reaction paths that are inaccessible for conventional reactions with micro-sized reactors.
The formation of microreactor devices is considerably complex. Its design requires a lot of information about material choice, production methods, transport rates, coating and loading, and placement of sensors. The design parameter is divided into two concepts; thermal and fluid design. The aim of the thermal design is the optimization of parameters such as flow rate, microchannel shape, pressure drop, reaction temperature and yield. In fluidic design, the minimization of the distribution of the residence time in the reactor and the optimization of the microchannel number is important. The flow in this technology is mainly laminar due to the small hydraulic diameter of the channels. With the laminar flow profile, microchannel residence time distribution is highly dependent on the diffusion coefficients and channel dimensions of the species . Microreactors are produced using a variety of materials such as polymers, silicon, metals, stainless steel, glass, and ceramics. The common fabrication techniques are stereolithography, photolithography, soft lithography, wet and dry etching, or micromachining depending on the material to be used . Each material has its own advantages and disadvantages. In addition to the specific properties of the materials, operating conditions, cost, and ease of production are also considered for the reaction as selection criteria. During high-temperature reactions, for example, silicon is a good choice with its low heat loss and chemical resistance properties but the cost of production is relatively high. Thermoplastics are good candidates for cheap and fast development of processes or for single use options. However, it is incompatible with organic solvents and not suitable for temperatures and pressures .
Microreactors are defined as a minimum unit that can be used to improve various unit operations and reactions in the microstructure. In recent years, this technology has shown many advantages as mentioned above. High-throughput screening, biological analysis of cells and proteins, reaction kinetics and mechanism studies are some of the uses . Microfluidic systems are a valuable tool in drug discovery. Compared to equivalent reactors, the reactions inside the microvolume reactors produce more pure products in a shorter time. In addition, there are many proven reactions that show better reactivity, yield, and selectivity . Microreactor devices are divided into two types: chip and microcapillary. Chip-type reactors offer advantages like easy control of fluids and the integration of many processes into a single reaction device . The most important application of the lab-on-a-chip system is high-throughput screening. This application is used in the diagnosis of biological agents and infectious disease, microbial recognition and rapid DNA replication . In summary, the benefits of this new technology have a vital impact on the chemical and the pharmaceutical industry. There are also crucial effects on medicine, life science, clinical and environmental diagnosis.
Microreactor technology has been growing rapidly in recent years. In addition to the many advantages they provide, there are some common challenges, such as connection, fluidics, and parallel control and monitoring of reaction conditions . Researchers should be directed to design optimization and marketable technology in order to overcome all these challenges in the future. Considering its advantages and benefits, it is predicted that this technology will be indispensable in micro and chemical process technology.
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