Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Microfluidic systems capable of generating uniform droplets are gaining attention in food, cosmetics, biochemical, and materials applications. While conventional shear- or interfacial tension-driven nozzle devices can generate highly monodisperse droplets (CV < 5%), their scalability is limited by complex flow designs and clogging. Post-array devices have recently emerged as a high-throughput alternative, producing quasi-monodisperse droplets (CV > 12%) by sequentially breaking larger droplets using micro-post structures. These devices offer shear-dependent tunability of droplet sizes, greater resistance to clogging, and scalability. Notably, droplet size is strongly influenced by the dispersed phase fraction, enabling potential decoupling of droplet size and dispersed phase fraction. This study reviews the principles and performance of post-array devices, compares them with other droplet generation methods, and examines their similarities to droplet splitting in T-junctions and premix membrane emulsification. Challenges such as improving droplet uniformity and miniaturization are also discussed to highlight the potential of post-array systems for practical emulsification applications.

DOI： 10.1063/5.0270507

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Step emulsification (SE) is renowned for its robustness in generating monodisperse emulsion droplets at arrayed nozzles. However, few studies have explored poly(dimethylsiloxane) (PDMS)-based SE devices for producing monodisperse oil-in-water (O/W) droplets and polymeric microspheres with diameters below 20 µm—materials with broad applicability. In this study, we present a PDMS-based microfluidic SE device designed to achieve this goal. Two devices with 264 nozzles each were fabricated, featuring straight and triangular nozzle configurations, both with a height of 4 µm and a minimum width of 10 µm. The devices were rendered hydrophilic via oxygen plasma treatment. A photocurable acrylate monomer served as the dispersed phase, while an aqueous polyvinyl alcohol solution acted as the continuous phase. The straight nozzles produced polydisperse droplets with diameters exceeding 30 µm and coefficient-of-variation (CV) values above 10%. In contrast, the triangular nozzles, with an opening width of 38 µm, consistently generated monodisperse droplets with diameters below 20 µm, CVs below 4%, and a maximum throughput of 0.5 mL h−1. Off-chip photopolymerization of these droplets yielded monodisperse acrylic microspheres. The low-cost, disposable, and scalable PDMS-based SE device offers significant potential for applications spanning from laboratory-scale research to industrial-scale particle manufacturing.

DOI： 10.3390/mi16020132

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.analchem.4c03167

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Step emulsification is a key technique for achieving scalable production of monodisperse emulsion droplets owing to its resilience to flow fluctuations. However, the persistent issue of satellite droplets, an inherent byproduct of main droplets, poses challenges for achieving truly uniform product sizes. In a previous study, we introduced a module with step-emulsifier nozzles upstream and deterministic lateral displacement (DLD) micropillar arrays downstream to generate satellite-free droplets at a low throughput. In this study, we demonstrate an upscaled parallelized setup with ten modules that were designed to produce satellite-free droplets. Each module integrated 100 step-emulsification nozzles in the upstream region with DLD micropillar arrays downstream. We conducted 3D flow simulations to ensure homogeneous distribution of the input fluids. Uniformly supplying an aqueous polyvinyl alcohol solution and an acrylate monomer as continuous and dispersed phases into the ten modules, the nozzles in each module exhibited a production rate of 539.5 ± 28.6 drop/s (n = 10). We successfully isolated the main droplets with a mean diameter of 66 μm and a coefficient of variation of 3.1% from satellite droplets with a mean diameter of 3 μm. The total throughput was 3.0 mL/h. The high yield and contamination-free features of our approach are promising for diverse industrial applications.

DOI： 10.3390/mi15070908

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.iecr.4c00542

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Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

Rapid and reliable on‐site pathogen testing is crucial for diagnosing and managing human health. Nucleic acids (NAs) containing genetic information are valuable target molecules for pathogen testing, and sensitive and rapid detection of NAs using electrochemical approaches has been intensively investigated. Detection approaches for NAs are diverse and compatible with current gene amplification methods and continue to expand with the development of novel functional materials and molecules. The variety of electrochemical sensing devices also continues to expand, and more practical testing is being pursued. This review outlines the latest detection approaches and basic guidelines for NA detection. Furthermore, this review provides an overview of electrochemical sensing devices that utilize novel and unique materials and functions and comprehensively discusses their advantages.

DOI： 10.1002/elsa.202400005

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Deterministic lateral displacement (DLD) is a promising technology that allows for the continuous and the size-based separation of suspended particles at a high resolution through periodically arrayed micropillars. In conventional DLD, the critical diameter (D_c), which determines the migration mode of a particle of a particular size, is fixed by the device geometry. Here, we propose a novel DLD that uses the pillars of a thermo-responsive hydrogel, poly(N-isopropylacrylamide) (PNIPAM) to flexibly tune the D_c value. Upon heating and cooling, the PNIPAM pillars in the aqueous solution shrink and swell because of their hydrophobic-hydrophilic phase transitions as the temperature varies. Using the PNIPAM pillars confined in a poly(dimethylsiloxane) microchannel, we demonstrate continuous switching of particle (7-μm beads) trajectories (displacement or zigzag mode) by adjusting the D_c through temperature control of the device on a Peltier element. Further, we perform on/off operation of the particle separation (7-μm and 2-μm beads) by adjusting the D_c values.

DOI： 10.1038/s41598-023-32233-z

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Other Link： https://www.nature.com/articles/s41598-023-32233-z

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Step emulsification, which uses a geometry-dependent mechanism for generating uniformly sized droplets, has recently gained considerable attention because of its robustness against flow fluctuations. However, like shear-based droplet generation, step emulsification is susceptible to impurities caused by satellite droplets. Herein, we demonstrate the integration of deterministic lateral displacement (DLD) to separate the main and satellite droplets produced during step emulsification. Step-emulsification nozzles (16 μm deep) in the upstream region of the proposed device were arrayed on the sidewalls of the main channel (91 μm deep). In the downstream region, the DLD micropillars were arrayed periodically with a critical diameter (cut-off value for size-based separation) of 37 μm. When an acrylate monomer and aqueous polyvinyl alcohol solution were infused as the dispersed and continuous phases, respectively, the nozzles produced monodisperse main droplets in the dripping regime, with an average diameter of ~60 μm, coefficient of variation (CV) value below 3%, and satellite droplets of ~3 μm. Upon entering the DLD region near the sidewall, these main and satellite droplets were gradually separated through the pillars based on their sizes. Finally, off-chip photopolymerization yielded monodisperse polymeric microspheres with an average diameter of 55 μm and a CV value of 2.9% (n = 202).

DOI： 10.3390/mi14030622

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

We found the power-law correlation for microfluidic droplet splitting can describe the mean droplet diameter generated in post-array devices.

DOI： 10.1039/d3lc00573a

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Authorship：Last author,　Corresponding author   Language：English  

DOI： 10.3390/mi13030482

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

Microparticles with uniform anisotropic structures are widely used in physical, chemical, and biological fields owing to their ability to combine multiple functions on a micro-scale. Here, a microfluidic emulsion-based external gelation method was demonstrated for the first time to produce monodisperse Janus calcium alginate (Ca-alginate) hydrogel microparticles consisting of two compartments. This approach provided a fast reaction condition under which we could prepare magnetic Janus Ca-alginate microparticles with diameters ranging from 148 to 179 μm and a coefficient of variation (CV) less than 4%. Moreover, the boundaries between the two compartments were clear. In addition, the volume fraction of each compartment could be adjusted by varying the flow rate ratio between two dispersed phases. Next, we produced fluorescent Janus beads and magnetic-fluorescent Janus beads with an average diameter of ∼150 μm (CV < 4.0%). The magnetic Janus hydrogel microparticles we produced could be manipulated by applying a magnetic field to achieve self-assembly, rotation, and accumulation. Magnetic Janus hydrogel microparticles are also capable of mammalian cell encapsulation with good cell viability. This article presents a simple and stable approach for producing monodisperse bi-compartmental Janus hydrogel microparticles that could have great potential for application in physical, biochemical, and biomedical fields.

DOI： 10.1063/5.0077916

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Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsami.1c08662

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Janus droplets can function as excellent templates for fabricating physically and chemically anisotropic particles. Here, we report new surfactant-laden Janus droplets with curvature controllability and enhanced stability against coalescence, suitable for fabricating shape-anisotropic polymer microparticles. Using a microfluidic flow-focusing device on a glass chip, nanoliter-sized biphasic droplets, comprising an acrylate monomer segment and a silicone-oil (SO) segment containing a surfactant, were produced in a co-flowing aqueous polyvinyl alcohol (PVA) solution. At equilibrium, the droplets formed a Janus geometry based on the minimization of interfacial energy, and each of the two Janus segments were uniform in size with coefficient-of-variation values below 3%. By varying the concentration of the surfactant in the SO phase, the curvature of the interface between the two lobes could be shifted among concave, planar, and convex shapes. In addition, the Janus droplets exhibited significantly improved stability against coalescence compared with previously reported Janus droplets carrying no surfactant that coalesced rapidly. Finally, via off-chip photopolymerization, concave-convex, planar-convex, and biconvex lens-shaped particles were fabricated.

DOI： 10.3390/mi12010029

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acsomega.0c02971

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Society of Chemical Engineers, Japan  

DOI： 10.1252/jcej.19we160

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

The separation and sorting of micro- and nano-sized particles is an important step in chemical, biological, and medical analyses [...]

DOI： 10.3390/mi11060602

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Scopus

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>We propose sheath-free microfluidic deterministic lateral displacement devices with inertially focused single straight input.</p>

DOI： 10.1039/d0lc00354a

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.analchem.8b05587

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Authorship：Last author,　Corresponding author  

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier B.V.  

DOI： 10.1016/j.snb.2018.01.112

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/c8ra01491d

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Scopus

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Scopus

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Scopus

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Scopus

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Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical and Electronics Engineers Inc.  

DOI： 10.1109/TRANSDUCERS.2017.7994480

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c7ra05852g

Web of Science

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Authorship：Lead author,　Last author,　Corresponding author  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.snb.2015.09.085

Web of Science

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Publishing type：Research paper (international conference proceedings)  

Scopus

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Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.11522/pscjspe.2016S.0_327

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Publishing type：Research paper (international conference proceedings)  

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Publishing type：Research paper (international conference proceedings)  

Scopus

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.sna.2015.10.011

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

DOI： 10.3390/mi6101428

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/smll.201401269

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c3an01314f

Web of Science

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Precision Engineering  

DOI： 10.2493/jjspe.79.460

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Language：Japanese   Publisher：The Japan Society for Precision Engineering  

DOI： 10.11522/pscjspe.2013A.0.917.0

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c2lc40245a

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Publisher：The Japan Society for Precision Engineering  

DOI： 10.11522/pscjspe.2011A.0.385.0

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/08927020903193812

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Authorship：Lead author,　Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

The preparation of multiple emulsions with controlled droplet sizes and internal structures has been a challenge for a long time. However, in recent years, a major breakthrough has been achieved in the preparation of monodisperse single emulsions by small‐scale fluid processing, which has enabled the formation of multiple emulsions with the desired droplet sizes, structures, and compositions. This review deals with the preparation of controlled multiple emulsions in various microstructured devices. The four preparation pathways are discussed individually. They are (a) membrane emulsification, (b) microchannel emulsification, (c) the use of a two‐dimensional microfluidic device, and (d) the use of a three‐dimensional coaxial microcapillary device. The applications of the prepared multiple emulsions to a novel class of materials are also discussed.

DOI： 10.1002/ceat.200800119

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

DOI： 10.1039/b713141k

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/adma.200700272

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Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/adma.200502431

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/b501972a

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Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/la0480336

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.cej.2003.11.019

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Royal Society of Chemistry  

DOI： 10.1039/b108740c

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Language：Japanese   Publisher：Institute of Electrical Engineers of Japan  

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Authorship：Lead author,　Last author,　Corresponding author   Language：Japanese  

CiNii Books

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Authorship：Last author,　Corresponding author  

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Authorship：Lead author  

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Presentation type：Poster presentation  

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Presentation type：Poster presentation  

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Country：Japan

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