Application Of Microreactors Research Articles

Liquid marbles: review of recent progress in physical properties, formation techniques, and lab-in-a-marble applications in microreactors and biosensors.

Liquid marbles (LMs) are nonsticking droplets whose surfaces are covered with low-wettability particles. Owing to their high mobility, shape reconfigurability, and widely accessible liquid/particle possibilities, the research on LMs has flourished since 2001. Their physical properties, fabrication mechanisms, and functionalisation capabilities indicate their potential for various applications. This review summarises the fundamental properties of LMs, the recent advances (mainly works published in 2020-2023) in the concept of LMs, physical properties, formation methods, LM-templated material design, and biochemical applications. Finally, the potential development and variations of LMs are discussed.

Droplet Tweezers Based on the Hydrophilic-Hydrophobic Interface Structure and Their Biological Application.

Droplet controllable operation has wide applications in microfluidics, biomedicine, microreactors, and other fields. Droplets can spontaneously transfer from a high-energy state to a low-energy state, but how to reverse transfer the droplets is a difficult task. In this article, we use a special hydrophilic-hydrophobic interphase structure (HHIS) to achieve this reverse transfer. We specifically study the critical conditions under which droplet transfer can be achieved. The length of the hydrophilic surface in this structure and the hydrophilic/hydrophobic properties of the surface must be in the appropriate range. Based on this, an optimized structure used to transfer droplets was designed. Finally, we carried out research on biological applications and successfully achieved the transfer of droplets from zebrafish eggs and zebrafish larvae. This unique method is low-cost, biofriendly, and highly applicable to various surfaces, illustrating the great potential in chemical and biological analysis.

Hierarchically Structured, All-Aqueous-Coated Hydrophobic Surfaces with pH-Selective Droplet Transfer Capability.

Often inspired by nature, techniques for precise droplet manipulation have found applications in microfluidics, microreactors, and water harvesting. However, a widely applicable strategy for surface modification combining simultaneous hydrophobicity and pH-sensitivity has not yet been achieved by employing environmentally friendly assembly conditions. The introduction of pH-responsive groups to an otherwise fluorinated polyphosphazene (PPZ) unlocks pH-selective droplet capture and transfer. Here, an all-aqueous layer-by-layer (LbL) deposition of polyelectrolytes is used to create unique hydrophobic coatings, endowing surfaces with the ability to sense environmental pH. The high hydrophobicity of these coatings (ultimately reaching a contact angle >120° on flat surfaces) is enabled by the formation of hydrophobic nanoscale domains and controllable by the degree of fluorination of PPZs, polyamine-binding partners, deposition pH, and coating thickness. Inspired by the hierarchical structure of rose petals, these versatile coatings reach a contact angle >150° when deposited on structured surfaces while introducing a tunable adhesivity that enables precise droplet manipulation. The films exhibited a strongly pronounced parahydrophobic rose petal behavior characterized through the contact angle hysteresis. Depositing as few as five bilayers (∼25 nm) on microstructured rather than smooth substrates resulted in superhydrophobicity with water contact angles >150° and the attenuation of the contact angle hysteresis, enabling highly controlled transfer of aqueous droplets. The pH-selective droplet transfer was achieved between surfaces with either the same microstructure and LbL film building blocks, which were assembled at different pH, or between surfaces with different microstructures coated with identical films. The demonstrated capability of these hydrophobic LbL films to endow surfaces with controlled hydrophobicity through adsorption from aqueous solutions and control the adhesion and transfer of water droplets between surfaces can be used in droplet-based microfluidics applications and water collection/harvesting.

Mechanism and modeling of Taylor bubble generation in viscous liquids via the vertical squeezing route

Bubble formation routes are vital to the application of microreactors, but a systematic understanding of the vertical squeezing remains lacking. Accordingly, this study focuses on the vertical squeezing bubble generation mechanism in viscous liquids in a T-junction microchannel. The results show there are the retraction, expansion, shrinking, and necking formation stages in the vertical squeezing route. A new formation stage, the retraction stage, is seen compared with horizontal squeezing. The influence of operating conditions on the generation mechanism was investigated from the gas–liquid interface behavior and force analysis, and the different formation mechanisms of satellite bubbles in the necking stage for two different squeezing routes were revealed. In addition, the complex bubble generation frequency rules were unified using a dimensionless frequency parameter. Finally, models for the generation frequency and bubble size were proposed. This work could provide some choice and design for the fundamentals of microreactors.

Controllable Directional Liquid Transport in Open Channel

AbstractDirectional liquid transport has gradually drawn worldwide attention due to its diverse potential applications in precision medicine, microfluidics, and microreactors. However, previous directional liquid control usually resorts to complex hierarchical micro‐nano structures, heterogeneous wettability, or external driving fields, which inevitably limits the flexibility and applicability of liquid manipulation. Here, a novel open channel surface is presented, which exhibits an on‐demand directional transport performance via a shifting mechanism of weak area on liquid precursor. The coupling effect of sidewall wettability and bottom hydrophobic barrier patterns redistributes the surface pressure from the front and rear meniscus of liquid precursor, which determine the position of weak area and transport direction. The impacts of wettability and various barrier patterns on anisotropic liquid transport ability are made clear, and the design principle of unidirectional open channels without complex microstructure is validated. Smart directional transport can also be easily built by use of various stimulus materials, such as thermal responsive polymer. This controllable directional liquid transport can introduce ways for various on‐demand liquid manipulations.

An aquatic microrobot for microscale flow manipulation

Microrobots have been developed and extensively employed for performing the variety tasks with various applications. However, the intricate fabrication and actuation processes employed for microrobots further restrict their multitudinous applicability as well as the controllability in high accuracy. As an alternative, in this work an aquatic microrobot was developed using a distinctive concept of the building block technique where the microrobot was built based on the block to block design. An in-house electromagnetic system as well as the control algorithm were developed to achieve the precise real-time dynamics of the microrobot for extensive applications. In addition, pivotal control parameters of the microrobot including the actuating waveforms together with the operational parameters were verified and discussed in conjunction with the magnetic intensity simulation. A mixing task was performed with high efficiency based on the trajectory planning and rotation control of the microrobot to demonstrate its capability in flow manipulation which can be advantageous for microreactor applications down the load. Aside from it, a dissolution test was further conducted to provide an on-demand flow agitation function of the microrobot for the next level of lab chip applications. The presented work with detail dynamic analysis is envisaged to provide a new look of microrobot control and functions from the engineering perspective with profoundly potential applications.

Bubble dynamics and mass transfer enhancement in split–and–recombine (SAR) microreactor with rapid chemical reaction

In this study, a split–and–recombine (SAR) microreactor which is composed of convergent–divergent arc channel and rectangular obstacles was designed, and its enhancement characteristics in gas–liquid rapid chemical absorption system were explored. In the SAR microreactor, the deformation, splitting, stretching and breakup of bubbles are monitored by a high–speed camera. Accordingly, the bubble velocity pulsation caused by SAR structure is analyzed. The squeezing mechanism for bubble breakup located on the front surface of the obstacle is revealed. Two breakup patterns, namely complete and partial breakup, are observed, and the mass transfer performance is highly related to them. The mass transfer enhancement factor (Eka) of SAR structure increases with gas/liquid flow rate in complete breakup pattern while decreases in partial breakup pattern. The increase of gas–liquid flow rates and the number of SAR units, or slower reaction rate strengthens the velocity fluctuation and bubble breakup, resulting in an increase in Eka, with a maximum value of 2.74. Overall, the SAR microreactor performs comparable to Corning Advanced Flow Reactor in term of mass transfer energy efficiency. This work guides the application of SAR microreactor in rapid gas–liquid chemical reaction system.

Magnetic response Janus emulsions stabilized by Mangeto-surfactant

Magnetic response emulsions, with regulated motion of droplets by magnetic fields, provide opportunities in system design. Research in Janus emulsion is blooming attributed to excellent multiple chambers, diverse interfaces, and advanced structures. Responsive Janus emulsions are prepared, using two immiscible oils of dimethyl phthalate (DMP)/vegetable oil (VO) and small molecules of magneto-surfactants ([H-G-C16]FeCl4) as stabilizer, in batch-scale by traditional vortex mixing. The composition of emulsion, the concentration of surfactant, and the emulsification energy are applied to control the topology of the structured fluid, and more importantly achieve the quantitative regulation of magnetic response. Janus droplets with clear inner interfaces are successfully constructed solely by magneto-surfactant, and the strategy is universal and even extended to Cerberus emulsions composed of three separated compartments. The magnetic response is visualized by directed moving against gravity and saturated magnetization. The responsivity is enhanced about 44.5%-54.5% accompany with VO lobe transformation from “waxing crescent” to “full moon with a hole”. The magnetic response is increased as high as 80.0% by decreasing the droplet size. Delicate calculations reveal that the ordered arrangement of [H-G-C16]FeCl4 at the interfaces, mainly contributes to the magnetic response compared with aggregates in the continuous phase. The adsorption on the VO/aq interface dominates the overall response due to the higher affinity of the surfactant to the VO phase. The findings open an avenue in the production of magneto-responsive multiple emulsions, which would push forward future application in smart microreactors, intelligent fluids, and responsive delivery systems.

Assessment of Screen-Covered Grooved Sodium Heat Pipes for Microreactor Applications

New nuclear reactor designs that incorporate heat pipes are being investigated for possible near-term deployment in terrestrial applications. This study explores the use of screen-covered axially grooved sodium heat pipes and their applicability for providing heat removal for microreactors. A sodium working fluid is appropriate for microreactors operating in the 5 to 20 MW(thermal) range at approximately 650°C. HTPIPE, a legacy software code, was validated for the case of screen-covered grooves and used to perform steady-state analyses to determine the performance limits of a proposed heat pipe design. The performance limits of a sodium heat pipe with a screen-covered square grooved wick structure is compared to that of an equivalent heat pipe with an annular wick. In a horizontal orientation at an operating temperature of 650°C,the performance limits for the heat pipe with an annular wick configuration are 15% higher than for the screen-covered grooved wick. At operating temperatures below 777°C, the annular wick outperforms the screen-covered grooved wick, and at temperatures above 777°C, the screen-covered grooved wick outperforms the annular wick. However, the marginal performance gain at higher temperatures may not justify the use of heat pipes with a screen-covered grooved wick structure due to increased manufacturing costs.

Internal Radiation Dose Evaluation for an Unruptured Post Release Tristructural Istropic Fuel Particle for Advanced and Micro-reactor Applications: Erratum.

Internal Radiation Dose Evaluation for an Unruptured Post Release Tristructural Istropic Fuel Particle for Advanced and Micro-reactor Applications: Erratum.

Concentration measurement of a mixture using an infrared transceiver

Microreaction technologies are employed in various applications like space propulsion, atomization, drug delivery and in lab-on-chip applications. Mixing index measurement in micro reactors is essential to assess the performance of the proposed micro mixer. A major roadblock in the design of a micromixer is its assessment and determination of mixing index during the operation due to the complex flow characteristics and mass transfer that occur during the mixing of fluids or reactants. Sensor design is thus vital in analyzing the performance of micro mixers during operation. Infrared sensing is a versatile flow visualization technique which has been effectively used previously to characterize two phase flows in conventional macro channels. The present work develops a robust multiphysics simulation framework and provides a comprehensive characterization of an infrared sensor to perform online assessment of micromixers during their operation. This study considers the case of an optimized passive micromixer described in several literatures and models the microfluidic mixing between silica nanoparticles and distilled water at various concentrations. Further coupling was done by applying the physics of ray optics to understand the performance of an infrared sensor. The variation in infrared sensor output with the mixing index is presented based on the multiphysics coupling. With this analysis, the characteristic output of an infrared sensor can be inferred for any practical microfluidic mixing and microreactor application, thus helping the instrumentation design for online performance assessment of micromixers.

Visible-light photooxidation of benzene to phenol in continuous-flow microreactors

• Phenol was efficiently prepared via the benzene photooxidation in a microreactor. • The influencing factors were optimized to achieve a high phenol yield. • The photomicroreactor with LEDs greatly shortened the reaction time and saved energy. • A kinetic model was obtained with the photooxidation mechanism understanding. In this work, phenol was synthesized by the photooxidation of benzene in the continuous-flow microreactor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as the oxidant and water as the oxygen source under 450 nm LEDs irradiation. The effects of the molar ratio of H 2 O to benzene, the molar ratio of DDQ to benzene, the concentration of benzene, the residence time, solvent type and reaction environment on the reaction performance were systematically studied. Under the optimized condition, the yield of phenol reached a high value (i.e., 94%) and the selectivity was over 99%. The photomicroreactor with the blue-LEDs as an eco-friendly light source significantly reduced the reaction time, and largely improved the light utilization efficiency and process efficiency for the synthesis of phenol from benzene compared to the batch reactor. Moreover, the reaction kinetic model was established based on a plug flow model, and the reaction order with respect to benzene and DDQ was found to be two and one in this photooxidation process, respectively. Such establishment of a reaction kinetics was beneficial for further understanding the photooxidation mechanism. This work demonstrates that the application of microreactors in combination with LEDs provides a promising and efficient strategy for the photooxidation of benzene to phenol and for the deep understanding on its photooxidation mechanism.

Overcoming Limitations in Surface Geometry‐Driven Bubble Transport: Bidirectional and Unrestricted Movement of an Underwater Gas Bubble Using a Magnetocontrollable Nonwetting Surface

AbstractThe movement of underwater gas bubbles significantly affects the core processes of a variety of applications in water electrolysis, heat transfer, optofluidics, and other fields. To maneuver the motion of bubbles, surface geometry‐driven transport is widely applied by employing asymmetric nonwetting surfaces, which induce Laplace pressure based on the bubble radius differences in confined states. Although this method has successfully demonstrated bubble manipulations in various geometries, it has inevitably shown some critical limitations; gas bubbles move unidirectionally from tip to root direction and cease their movements upon reaching unconfined states. This unidirectional and local bubble transport restrains the method's applicability to many fields, and overcoming this obstacle still remains an enormous challenge. Herein, a magnetocontrollable lubricant‐infused surface (MCLIS) is introduced as a key solution to this issue. MCLISs manipulate the adhesion of gas bubbles by controlling magneto‐responsive microwire alignments and rendering two reversible adhesion states, sticky (upright) and slippery (laying wires). This unique characteristic of MCLISs enables the bidirectional and geometry‐unrestricted transportation of bubbles by the wire geometry‐gradient force (Fwgg) generated at sticky–slippery interfaces. Furthermore, this novel magnetic responsive surface supports anti‐buoyancy transport and presents promising applications in microreactors and optical laser shutters in aqueous media.

An application of continuous flow microreactor in the synthesis and extraction of rabeprazole

Abstract The oxidation of rabeprazole sulfide is a key step in the synthesis of rabeprazole, a drug for the treatment of stomach acid-related disorders. The current rabeprazole production process adopts one pot batch process, which has low reaction efficiency and poor stability. A continuous process can greatly improve the production efficiency and solve the above problems. Therefore, the reaction parameters of rabeprazole in microreactor were explored through laboratory experiments to explore the possibility of continuous production of rabeprazole. Rabeprazole sodium was synthesized by using rabeprazole thioether as a raw material and sodium hypochlorite solution as the oxidant. Oxidation, quenching, acid-base regulation and extraction were completed continuously in the microreactor. Rabeprazole solution with a purity of 98.78% (±0.13%) can be obtained continuously in 56 s, whereas intermittent production lasted for at least 2 h. Thus, the microreactor can effectively improve the oxidation synthesis efficiency of rabeprazole, and provide reference for the realization of other reactions in the microreactor.

3D-Printed Bioinspired Cassie-Baxter Wettability for Controllable Microdroplet Manipulation.

It is a great challenge to fabricate a surface with Cassie-Baxter wettability that can be continuously adjusted from hydrophilicity to superhydrophobicity by changing of geometric parameters. In this paper, we propose and demonstrate a bioinspired surface fabricated by using a projection micro-stereolithography (PμSL) based 3D printing technique to address the challenge. Independent of materials, the bioinspired textured surface has a maximum contact angle (CA) of 171°, which is even higher than that of the omniphobic springtail skin we try to imitate. Most significantly, we are able to control the CA of the bioinspired surface in the range of 55-171° and the adhesion force from 71 to 99 μN continuously by only changing the geometric parameters of the bioinspired microstructures. The underlying mechanisms of the CA control of our bioinspired surface are also revealed by using a multi-phase lattice Boltzmann model. Furthermore, we demonstrate potential applications in droplet-based microreactors, nonloss water transportation, and coalescence of water droplets by employing our 3D-printed bioinspired structures with their remarkable precise Cassie-Baxter wettability control and petal effects. The present results potentially pave a new way for designing next generation functional surfaces for microdroplet manipulation, droplet-based biodetection, antifouling surfaces, and cell culture.

Internal Radiation Dose Evaluation for an Unruptured Post Release Tristructural Istropic Fuel Particle for Advanced and Micro-reactor Applications.

There are unique benefits from advanced/micro-reactor designs and fuel types that offer safety features in the case of an accident that may reduce environmental consequences compared to conventional reactors and fuels. Tristructural isotropic (TRISO) fuel particles are a robust advanced nuclear fuel type that leads to the unique question of how unruptured, activated TRISO particles will interact with humans. TRISO particles are 900 μm in size, and that particle size restricts internal dose assessment to the ingestion pathway. Activity of the TRISO particle was established by High Temperature Engineering Test Reactor simulations. The TRISO particle encapsulation was assumed to be perfect; exploration of internal dose contribution from radionuclides released from encapsulation was not included. The TRISO particle was assumed to be mixed actively within each alimentary tract compartment such that homogenous distribution could be assumed according to the International Commission on Radiological Protection publication 133. The dose assessment results indicate that the rectosigmoid colon had the highest internal organ dose for both reference male (2.1 Sv) and female (2.3 Sv). The internal dose from ingestion of the scenario-specific TRISO particle was 0.25 Sv for the reference male and 0.29 Sv for the reference female, which exceeds the annual occupational effective dose limit of 0.05 Sv in the Code of Federal Regulations, 10 CFR Part 20 Subpart C. Similarly, the annual occupational limit of 0.5 Sv to any one organ would be exceeded for the left colon, right colon, and rectosigmoid colon for both the reference male and female.

Synthesis of N-vinyl pyrrolidone by acetylene process in a microreactor

Vinylation reaction of 2-pyrrolidone with acetylene to synthesize N-vinyl pyrrolidone was successfully implemented in a microreactor. The application of microreactor not only avoided the safety issue caused by acetylene decomposition and explosion, but also intensified gas-liquid mass transfer and improves the selectivity of N-vinyl pyrrolidone to 100%. The catalyst and reaction performance of vinylation reaction were investigated in detail. First of all, potassium salt, the homogeneous catalyst for this reaction was prepared and potassium pyrrolidone was identified to be the catalytic active species through comparison among different precursors. In addition, the catalyst was confirmed to have pretty good stability. Then the effects of the reaction conditions were clarified such as gas-liquid ratio, reaction pressure and the catalyst content. Both pressurization and higher KOH content were beneficial to convert more reactants. Finally, to realize the efficient transformation of the reactants, the liquid phase was recycled to obtain the sufficient gas-liquid contact time. After four-round cycling liquid phase, the conversion of 2-pyrrolidone was up to 45.3%.

Three-dimensional CFD modelling of a photocatalytic parallel-channel microreactor

This paper presents the estimation of adsorption rate and apparent kinetic rate constants for photodegradation of 4-nitrophenol in a recirculating and single-pass photocatalytic microreactor using simulated solar radiation. The effect of changing initial concentration (Co) of 4-nitrophenol in a recirculation mode was predicted by employing a dynamic transport model with kinetics (momentum and mole transports) using COMSOL Multiphysics. Adsorption and kinetic rate constants were estimated by fitting 3D model to experimental data. The estimated monolayer (m) and multilayer (n) adsorption–desorption rate constants were 1.77x104 m3 mol-1 h−1 (kads,m), 0.0252 h−1 (kdes,m), 1.77x104 m3 mol-1 h−1 (kads,n) and 0.0126 h−1 (kdes,n) respectively; and apparent kinetic constant (kapp) was 2.16 h−1. Results from the single pass model showed that a rise in Co produces an increase in initial degradation rate. Moreover, decreasing flow rate (Q), increasing microchannel length (L) and decreasing microchannel height (h) boost the overall conversion of 4-nitrophenol in solution. This work demonstrates the promising application of microreactors in heterogeneous photocatalysis as tertiary stage technology for wastewater treatment, especially for the photodegradation of recalcitrant pollutant.

Design, Fundamental Principles of Fabrication and Applications of Microreactors

This study highlights the development of small-scale reactors, in the form of microstructures with microchannel networking. Microreactors have achieved an impressive reputation, regarding chemical synthesis ability and their applications in the engineering, pharmaceutical, and biological fields. This review elaborates on the fabrication, construction, and schematic fundamentals in the design of the microreactors and microchannels. The materials used in the fabrication or construction of the microreactors include silicon, polymer, and glass. A general review of the application of microreactors in medical, biological, and engineering fields is carried out and significant improvements in these areas are reported. Finally, we highlight the flow patterns, mixing, and scaling-up of multiphase microreactor developments, with emphasis on the more significant industrial applications.

Two-Phase Flow in a Coiled Flow Inverter: Process Development from Batch to Continuous Flow

The transfer of batch processes to continuous flow is a major driver for the application of microreactors. Here, we present a methodology for the transfer of (bio-)chemical reactions in batch mode ...