Seed‐mediated growth of core–shell nanoparticles, which is conventionally performed in a batch reactor, is successfully reproduced in a microfluidic reactor for a facile production of uniform metal core–shell nanoparticles. The proposed microfluidic design is based on the microstructure inversion for achieving multi‐scale homogeneous mixing with uniform nanoparticle residence time. Simulations demonstrate that among the staggered herringbone microstructures investigated in this study, the upper herringbone (UH) structure can rapidly and homogeneously mix multiple‐sized reagents and can also prevent both the irreversible trapping and long residence time of the nanoparticles inside the microfluidic channel. A wide variety of metal core–shell nanoparticles, namely Au@Ag, Au@Pd, and Au@Au with an interior nanogap, are synthesized by using the microfluidic reactor with built‐in UH microstructures. The proposed microfluidic synthesis produces a more uniform shell size than the conventional batch synthesis. This work could significantly expand the practical utility of metal core–shell nanoparticles in a multitude of applications ranging from catalysis to nanomedicine.

The surface hydrophobicity of a microbial cell is known to be one of the important factors in its adhesion to an interface. To date, such property has been altered by either genetic modification or external pH, temperature, and nutrient control. Here we report a new strategy to engineer a microbial cell surface and discover the unique dynamic trapping of hydrophilic cells at an air/water interface via hydrophobicity switching. We demonstrate the surface transformation and hydrophobicity switching of Escherichia coli (E. coli) by metal nanoparticles. By employing real-time dark-field imaging, we directly observe that hydrophobic gold nanoparticle-coated E. coli, unlike its naked counterpart, is irreversibly trapped at the air/water interface because of elevated hydrophobicity. We show that our surface transformation method and resulting dynamic interfacial trapping can be generally extended to Gram-positive bateria, Gram-negative bacteria, and fungi. As the dynamic interfacial trapping allows the preconcentration of microbial cells, high intensity of scattering light, in-plane focusing, and near-field enhancement, we are able to directly quantify E. coli as low as 1.0 × 103 cells/ml by using a smartphone with an image analyzer. We also establish the identification of different microbial cells by the characteristic Raman transitions directly measured from the interfacially trapped cells.

For the first time, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) nanofibrous membrane has been fabricated via electrospinning method. To improve the electrospinnability and reduce the diameter of fibers, the solvent and salt additives were used that affected on the parameters including such as the viscosity and the conductivity of the electrospinning solution for poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). Since the additional salts should be removed, it could be inferred that the co-solvent system was predominant to prepare the nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) membrane. This biodegradable nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) membrane has a great potential to be used in the various application fields such as tissue engineering, implants, packaging materials, agriculture, and so on.

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