Microreactor Technology Research Articles

Cell Lysis and Detoxification of Cyanotoxins Using a Novel Combination of Microbubble Generation and Plasma Microreactor Technology for Ozonation.

There has been a steady rise in the incidences of algal blooms globally, and worryingly, there is increasing evidence that changes in the global climate are leading to a shift toward cyanobacterial blooms. Many cyanobacterial genera are harmful, producing several potent toxins, including microcystins, for which there are over 90 described analogues. There are a wide range of negative effects associated with these toxins including gastroenteritis, cytotoxicity, hepatotoxicity and neurotoxicity. Although a variety of oxidation based treatment methods have been described, ozonation and advanced oxidation are acknowledged as most effective as they readily oxidise microcystins to non-toxic degradation products. However, most ozonation technologies have challenges for scale up including high costs and sub-optimum efficiencies, hence, a low cost and scalable ozonation technology is needed. Here we designed a low temperature plasma dielectric barrier discharge (DBD) reactor with an incorporated fluidic oscillator for microbubble delivery of ozone. Both technologies have the potential to drastically reduce the costs of ozonation at scale. Mass spectrometry analysis revealed very rapid (<2 min) destruction of two pure microcystins (MC-LR and MC-RR), together with removal of by-products even at low flow rate 1 L min−1 where bubble size was 0.56–0.6 mm and the ozone concentration within the liquid was 20 ppm. Toxicity levels were calculated through protein phosphatase inhibition assays and indicated loss of toxicity as well as confirming the by-products were also non-toxic. Finally, treatment of whole Microcystis aeruginosa cells showed that even at these very low ozone levels, cells can be killed and toxins (MC-LR and Desmethyl MC-LR) removed. Little change was observed in the first 20 min of treatment followed by rapid increase in extracellular toxins, indicating cell lysis, with most significant release at the higher 3 L min−1 flow rate compared to 1 L min−1. This lab-scale investigation demonstrates the potential of the novel plasma micro reactor with applications for in situ treatment of harmful algal blooms and cyanotoxins.

Easy-to-perform and cost-effective fabrication of continuous-flow reactors and their application for nanomaterials synthesis

The translation of continuous-flow microreactor technology to the industrial environment has been limited by cost and complexity of the fabrication procedures and the requirement for specialised infrastructure. In the present study, we have developed a significantly more cost-effective and easy-to-perform fabrication method for the generation of optically transparent, continuous-flow reactors. The method combines 3D printing of master moulds with sealing of the PDMS channels’ replica using a pressure-sensitive adhesive tape. Morphological characterisation of the 3D printed moulds was performed and reactors were fabricated with an approximately square-shaped cross-section of 1 mm2. Notably, they were tested for operation over a wide range of volumetric flow rates, up to 20 ml/min. Moreover, the fabrication time (i.e., from design to the finished product) was <1 day, at an average material cost of ∼£5. The flow reactors have been applied to the production of both inorganic nanoparticles (silver nanospheres) and organic vesicular systems (liposomes), and their performance compared with reactors produced using more laborious fabrication methods. Numerical simulations were performed to characterise the transport of fluids and chemical species within the devices. The developed fabrication method is suitable for scaled-up fabrication of continuous-flow reactors, with potential for application in biotechnology and nanomedicine.

Synergy of Microtechnology and Biotechnology: Microreactors as an Effective Tool for Biotransformation Processes§: §The paper was presented at European Biotechnology Congress, 25-27 May 2017, Dubrovnik, Croatia.

SUMMARYDespite the fact that microreactors have been present for more than 40 years now and that their potential has been extensively exploited in chemical synthesis, analytics and screening, to date very few biocatalytic processes have been explored in microreactors. It is claimed that enzymatic microreactor technology is exactly in the same place where chemical microreactors were 15 years ago. However, general opinion is that the efforts devoted to the research of micro-enzymatic reactors will inaugurate a new breakthrough in bio-based processing. The aim of this review is to explore the synergy between microtechnology, mainly microreactors, and biotechnology, and to assess its potential, opportunities, challenges and future application in biotechnology.

Advances in electro- and sono-microreactors for chemical synthesis.

The anatomy of electrochemical flow microreactors is important to safely perform chemical reactions in order to obtain pure and high yielding substances in a controlled and precise way that excludes the use of supporting electrolytes. Flow microreactors are advantageous in handling unstable intermediates compared to batch techniques and have efficient heat/mass transfer. Electrode nature (cathode and anode) and their available exposed surface area to the reaction mixture, parameters of the spacer, flow rate and direction greatly affects the efficiency of the electrochemical reactor. Solid formation during reactions may result in a blockage and consequently decrease the overall yield, thus limiting the use of microreactors in the field of electrosynthesis. This problem could certainly be overcome by application of ultrasound to break the solids for consistent flow. In this review, we discuss in detail the aforementioned issues, the advances in microreactor technology for chemical synthesis, with possible application of sonochemistry to deal with solid formations. Various examples of flow methods for electrosynthesis through microreactors have been explained in this review, which would definitely help to meet future demands for efficient synthesis and production of various pharmaceuticals and fine chemicals.

Microreactor technology for biodiesel production: a review

Due to a rise in global demand for energy and an increase in greenhouse gases, biodiesel has been accepted as an alternative fuel because of its biodegradability, low environment detrimental effect, better quality of exhaust gas emission, and renewability. Biodiesel is a mixture of monoalkyl esters of long-chain fatty acids also known as fatty acid methyl esters. Transesterification is the most commonly adopted technique for the production process. But the conventional biodiesel technology has its own disadvantages. Process intensification technologies can overcome these drawbacks. Some novel reactors such as microchannel reactor, static mixers, oscillatory flow reactors, and spinning tube reactors have been developed so as to improve mass transfer and mixing. These technologies can achieve rapid and high reaction rates due to the high surface area/volume ratio and short diffusion distance thus intensifying the transesterification process. Various factors such as alcohol to triglyceride molar ratio, microchannel size, residence time, reaction temperature, mixing mechanism, and catalyst affect the production process. Although biodiesel production has been commercialized in several countries, it still requires a clean, effective, and environment-friendly technology to make it cost-effective and increase its competency against conventional fossil fuels. Microreactor technology, however, has proved to be a benchmark to serve this purpose. The current review paper provides an overview about different types of microreactors used in biodiesel production and the parameters affecting biodiesel production in microreactors. The microreactor technology discussed in this paper aims to improve the production process by decreasing the reaction time from hours to minutes.

Analyzing mixing quality in a T-shaped micromixer for different fluids properties through numerical simulation

Microreaction engineering enables new strategies in process intensification. A precise analysis of local mass transfer and hydrodynamics in micromixers for different flow regimes are strongly needed for a complete understanding the processes occurring. One of the simplest in the manufacture, but at the same time, quite effective T-shaped micromixer was used for numerical investigation and analyzing the mixing quality and flow regimes as well as the influence of different fluids properties on this parameters. It was numerically revealed that the viscosities and the densities, as well as the initial temperatures and the rheology of mixing fluids have significant effects on the flow regimes and the mixing efficiency of two fluids. In this study viscosities and densities ratios of mixing fluids ranged from 1 to 2; the coefficient n in power-law model of non-Newtonian fluids ranged from 0.3 to 1; the initial temperatures difference of two fluids was varied up to 40°C. Mixture components concentration as well as pressure and velocity fields distribution in the micromixer was obtained. The dependence of fluids mixing efficiency and the pressure drop, as well as a map of flow regimes and mixing modes on the Reynolds number and properties of miscible fluids was numerically established.

Novel approach to investigation of semiconductor MOCVD by microreactor technology

Metal-Organic Chemical Vapour Deposition is a very complex technology that requires further investigation and optimization. We propose to apply microreactors to (1) replace multiple expensive time-consuming macroscale experiments by just one microreactor deposition with many points on one substrate; (2) to derive chemical reaction rates from individual deposition profiles using theoretical analytical solution. In this paper we also present the analytical solution of a simplified equation describing the deposition rate dependency on temperature. It allows to solve an inverse problem and to obtain detailed information about chemical reaction mechanism of MOCVD process.

Multiphase flow processing in microreactors combined with heterogeneous catalysis for efficient and sustainable chemical synthesis

The convergence of continuous flow chemistry and microreactor technology creates numerous possibilities towards the development of an efficient and sustainable chemical synthesis. In this field, the combination of heterogeneous catalysis and multiphase flow processing in microreactors represents an important approach. This review presents a summary of the recent progress on the utilization of wall-coated and packed-bed microreactors for carrying out heterogeneously catalyzed gas-liquid and liquid-liquid reactions, with a focus on the microreactor operation principles and selected reaction examples with promising application potential. Finally, an outlook on the future development trends is provided.

Novel Smart Microreactors Equipped with Responsive Catalytic Nanoparticles on Microchannels.

Nowadays efficient and reliable control of highly exothermic reactions to effectively prevent overheating or even explosions still remains a challenging task, although newly developed microreactor technology has shown promise. Here, we report a novel smart microreactor system equipped with responsive catalytic nanoparticles on microchannels for self-regulated control over highly exothermic reactions by responding to the reaction-generated heat. On the basis of shrinking/swelling behaviors of polymeric networks in the responsive catalytic nanoparticles, the smart microreactor could respond to the change of reaction temperature to tune the catalysis activity of catalytic particles in a thermo-feedback process. As a breakthrough result, highly exothermic reactions carried out in such a microreactor can be well-controlled in a self-regulation process without any manual assistance, efficiently ensuring the safety of the reaction. Such smart responsive catalytic systems have high potential and are attractive as a new generation of efficient tools that feature a self-regulation property for highly exothermic catalytic reactions.

Applications of Flow Microreactors in Electrosynthetic Processes.

The fundamental advantages and potential benefits of flow microreactor technology include extremely large surface-to-volume ratios, precise control over temperature and residence time, extremely fast molecular diffusion, and increased safety during reactive processes. These advantages and benefits can be applied to a wide range of electrosynthetic techniques, and so the integration of flow microreactors with electrosynthesis has received significant research interest from both academia and industry. This review presents an up-to-date overview of electrosynthetic processes in continuous-flow microreactors. In addition, the advantages of continuous-flow electrochemistry are discussed, along with a thorough comparison of microreactor-based processes and conventional batch reaction systems.

A comparative discussion of different designs of passive micromixers: specific sensitivities of mixing efficiency on Reynolds numbers and fluid properties

Fluid mixing enhancement is an important topic of microfluidics and microreactor technologies. Though many micromixers based on different mechanisms have been reported so far, most investigations were conducted case by case due to the diversity of applications. For a more comprehensive understanding of the problem, this paper presents a comparative discussion of five different passive micromixers, including a planar spiral mixer, a planar split-and-recombine (SAR) mixer, a 3D serpentine mixer, a 3D SAR mixer, and a 3D mixer with divergent geometries. The involved mixing mechanisms include Dean flow/secondary flow, SAR process and viscous interfacial instabilities. From a geometric perspective, this study compares (i) planar and fully 3D structures, (ii) single channels whose cross section preserve connectedness and interconnected multiple sub-channels, (iii) microchannels with and without divergent structures. Key characteristics of the designs are highlighted. The influence of Reynolds number, fluid viscosity and viscosity ratio are also discussed. As the discussed micromixers cover a wide range of fluid mixing conditions, it also serves as a mini-review, providing useful reference on the selection of optimum design for different applications.

Biotransformations in Microflow Systems: Bridging the Gap between Academia and Industry

Recent remarkable progress in understanding and engineering enzymes and whole cells as highly selective and environment-friendly catalysts enabling novel routes for the production of pharmaceuticals, fine and platform chemicals, and biofuels has spurred the quest for fast biocatalyst screening and development of efficient processes with long-term biocatalyst use. Besides this, current efforts towards more sustainable production systems and bio-based products have triggered an intense research on chemo-enzymatic cascades and establishment of continuous end-to-end processing. Microreaction technology, which has in the last two decades changed the paradigm in the laboratory and production scale organic synthesis, is recently gaining attention also in the field of applied biocatalysis. Based on the trends highlighted within this article, microfluidic systems linked with appropriate monitoring and feedback control can greatly contribute to successful implementation of biocatalysis in industrial production. Microflow-based droplets facilitate ultrahigh-throughput biocatalyst engineering, screening at various operational conditions, and very fast collection of data on reaction kinetics using minute amounts of time and reagents. Harnessing the benefits of microflow devices results in faster and cheaper selection of substrate(s) and media, and development of suitable immobilization methods for continuous biocatalyst use. Furthermore, the use of highly efficient reactor designs integrated with downstream processing enabling also faster and more reliable scale-up can bridge the gap between the academic research and industrial use of biocatalysts.

Hierarchically structured particles for micro flow catalysis

This work introduces the investigation of three-layered metal/polymer/polymer hierarchically structured composite particles, prepared by a microfluidic synthesis method combined with layer-by-layer (LBL) technology. Composite particles made of multiple length scales ranging from nanometer to sub-micrometer and submilimeter, and their potential application in catalysis is shown. In the first part, with the advantage of microreaction technology, platinum nanoparticles of a precise size were synthesized and electrostatically combined to oppositely charged surface-active polymer nanoparticles. After controlling the nanoparticles ratio and metal density on the polymer surface, nanocomposite particles of high specific surface to volume ratio were immobilized on the surface of microfluidically prepared polyacrylamide hydrogel particles, in second part. Platinum nanoparticles offer the possibility to be used as potential catalysts. For further study, the catalytic activity of the obtained hierarchical metal-polymer composite particles was evaluated by bleaching an azo-dye (Cochenille Red) with sodium borohydride. Different experiments have been conducted in the absence as well as in the presence of the composite particles. It has been found that a significant enhancement of the bleaching rate was realized in case of platinum containing composite particles.

Exploring the Fundamentals of Microreactor Technology with Multidisciplinary Lab Experiments Combining the Synthesis and Characterization of Inorganic Nanoparticles

Multidisciplinary lab experiments combining microfluidics, nanoparticle synthesis, and characterization are presented. These experiments rely on the implementation of affordable yet efficient microfluidic setups based on perfluoroalkoxyalkane (PFA) capillary coils and standard HPLC connectors in upper undergraduate chemistry laboratories. Fundamental principles and concepts as well as practical tips for the rapid deployment of microfluidics are presented. In-line membrane separation, the segmented-flow regime, high-temperature experiments, and in-line analytical techniques are illustrated by the preparation of inorganic nanoparticles (silver, gold, and cadmium selenide or telluride) in microreactors. Besides microfluidics, analytical techniques for nanoparticle analysis are also illustrated.

Computational Fluid Dynamic Simulation of Mixing in Circular Cross Sectional Microchannel

The application of process intensification has been catching up with the trend already observed in the chemical engineering area, where the use of microfluidic devices has already been elevated to production scale. Microreactor technology, an element of process intensification, offers potential benefits to the future of chemical engineering for its well-defined high specific interfacial area available for heat and mass transfer resulting in higher transfer rates and enhances safety due to its low hold-ups. In relation to the time-scale of chemical kinetics, diffusive transport in micro-devices is faster than in conventional mixers. Since mixing has a crucial impact on the overall performance of micro reaction processes, the need for measuring and comparing mixing performance have also increased. To exploit the resulting potential, the mixing behaviour of flow mixers on micro-scales need to be further investigated. In this work, three-dimensional Computational Fluid Dynamics (CFD) model with circular cross section micro channel has been developed instead of rectangular cross section done by other researchers as circular micro channel can withstand large pressure difference without undergoing any significant distortion where non-circular cannot. The CFD simulation was carried out using COMSOL Multiphysics 4.2a software to investigate the effects of “T” and “Y” micro channel configurations, inlet velocity and diffusion coefficient towards the mixing quality in the micro reactor. The results demonstrated that inlet velocity and diffusion coefficient has significant effects on mixing performance where low inlet velocity and high diffusion coefficient value resulted in better mixing performance. It was found that “Y”-shaped micro channel showed complete mixing at a shorter distance as compared to “T”-shaped micro channel and the minimum mixing length of micro channel needed for complete mixing is 20 mm.

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis.

Microreactor technology and flow chemistry could play an important role in the development of green and sustainable synthetic processes. In this review, some recent relevant examples in the field of flash chemistry, catalysis, hazardous chemistry and continuous flow processing are described. Selected examples highlight the role that flow chemistry could play in the near future for a sustainable development.

Continuous synthesis of UiO-66 in microreactor: Pursuing the optimum between intensified production and structural properties

The increasing demand for MOFs can only be satisfied by establishing robust and reproducible synthesis routes which allow a profitable scale-up of the requested materials while preserving their textural properties and stability. A scalable MOF synthesis may provide a technology platform for the further development and modification of the product, from both a chemical and an engineering perspective. And, above all, MOFs could be delivered to the market at a substantially reduced price.In this work UiO-66 was synthesized continuously by employing micro reactors and the concept of flow chemistry. The microreaction technology (MRT) process turned out to be a viable alternative to the time and energy consuming conventional synthesis processes, as significantly faster reaction rates could be achieved compared to the conventional batch processes (Zhou et al., 2014; Frameworks for Commercial Success, 2016). Microreactors are characterized in particular by high surface-to-volume ratios and channel dimensions in the submillimeter range, which offer a significant enhancement of heat and mass transfer within the reactor, additionally the chemical reactions can be accelerated by orders of magnitude and can thus be processed close to their kinetic optimum conditions.Different reaction parameters were studied in order to elucidate their influence on the product properties. All synthesized MOF crystals were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and nitrogen adsorption measurements.The MRT approach allowed the continuous fabrication of MOF crystals with distinct morphological characteristics in a time-efficient manner. The obtained results represent a faster and energy-efficient route to continuously produce UiO-66, compared to the standard synthetic protocols. The materials prepared in this work have a lower coordination of the Zr sites in comparison to the UiO-66 that can be produced in batch (Cavka et al. 2008); nevertheless the presence of coordinative unsaturated sites is a preferred feature of MOFs for some specific application such as catalysis (Shearer et al., 2014).

Flow chemistry—Microreaction technology comes of age

Over the past two decades, microreaction technology has matured from early devices and concepts to encompass a wide range of commercial equipment and applications. This evolution has been aided by the confluence of microreactor development and adoption of continuous flow technology in organic chemistry. This Perspective summarizes the current state‐of‐the art with focus on enabling technologies for reaction and separation equipment. Automation and optimization are highlighted as promising applications of microreactor technology. The move towards continuous processing in pharmaceutical manufacturing underscores increasing industrial interest in the technology. As an example, end‐to‐end fabrication of pharmaceuticals in a compact reconfigurable system illustrates the development of on‐demand manufacturing units based on microreactors. The final section provides an outlook for the technology, including implementation challenges and integration with computational tools. AIChE J, 2017 © 2016 American Institute of Chemical Engineers AIChE J, 63: 858–869, 2017

4th International Conference Implementation of Microreactor Technology in Biotechnology (IMTB 2017), Bled, Slovenia, April 23–26, 2017

4th International Conference <i>Implementation of Microreactor Technology in Biotechnology</i> (IMTB 2017), Bled, Slovenia, April 23–26, 2017

Organic electrosynthesis in flow microreactor

Recently, microreactor technology has received significant research interest from both academia and industry. Fundamental advantages and potential benefits of microreactor technology are an extremely large surface-to-volume ratio, precise temperature control, precise residence time control, strict laminar flow control, extremely fast molecular diffusion, and improvement of reaction process safety. These advantages and benefits can be applied to a wide range of organic synthesis and organic mass production processes. Electron transfer is one of the most common driving factors for organic reactions, and organic electrosynthesis serves as a straightforward and powerful method of organic electron-transfer processes. The integrated use of microreactor technology with organic electrosynthesis is one of the most sophisticated processes in organic chemistry. In addition, novel systems that are realized only by using electrochemical microflow reactors have been developed recently. This review summarizes recent advances in organic electrosynthesis using flow microreactors.