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In microfluidic chips applications, the monitoring of the rate and the direction of a microfluidic flow is very important. Here, we demonstrate a liquid flow rate and a direction sensor using a partially gold-coated tilted fiber Bragg grating (TFBG) as the sensing element. Wavelength shifts and amplitude changes of the TFBG transmission resonances in the near infrared reveal the direction of the liquid flowing along the fiber axis in the vicinity of the TFBG due to a nanoscale gold layer over part of the TFBG. For a device length of 10 mm (and a diameter of 125 µm for easy insertion into microfluidic channels), the flow rates and the direction can be detectable unequivocally. The TFBG waveguiding properties allow such devices to function in liquids with refractive indices ranging from 1.33 to about 1.40. In addition, the proposed sensor can be made inherently temperature-insensitive by referencing all wavelengths to the wavelength of the core mode resonance of the grating, which is isolated from the fiber surroundings.
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http://dx.doi.org/10.1364/OL.392511 | DOI Listing |
Anal Sci
September 2025
Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
Surface-enhanced Raman scattering (SERS) is a powerful analytical technique; however, its quantitative application has been limited by the instability of substrates and significant signal fluctuations. In this study, we demonstrated that 4-aminobenzenethiol (4-ATP) can be quantitatively detected through statistical analysis of SERS signal intensity distributions obtained using citrate-stabilized AuNPs, biotin-functionalized AuNPs, and gold nanoparticle (AuNP)-bound polystyrene (PS) microparticles. Raman spectra obtained in bulk aqueous solution under static conditions showed that the detection sensitivity of 4-ATP using AuNP-bound PS microparticles was approximately twice that achieved with citrate-stabilized AuNPs or biotin-modified AuNPs.
View Article and Find Full Text PDFNat Commun
September 2025
Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Institute of Science Tokyo, Nagatsuta-cho, Midori-ku, Yokohama, Japan.
The research and implementation of portable and low-cost analytical devices that possess high reproducibility and ease of operation is still a challenging task, and a growing field of importance, within the analytical research. Herein, we report the concept, design and optimization of a microfluidic device based on electrochemiluminescence (ECL) detection that can be potentially operated without electricity for analytical purposes. The device functions exploiting the concept of streaming potential-driven bipolar electrochemistry, where a potential difference, generated from the flow of an electrolyte through a microchannel under the influence of a pressure gradient, is the driving force for redox reactions.
View Article and Find Full Text PDFLab Chip
September 2025
Department of Engineering Design, Indian Institute of Technology Madras, India.
Microfluidic devices offer more accurate fluid flow control and lower reagent use for uniform nanoparticle synthesis than batch synthesis. Here, we propose a microfluidic device that synthesizes uniform iron oxide nanoparticles (IONPs) for highly efficient intracellular delivery. The 3D-printed device was fabricated, comprising two inlets in the T-shaped channel with an inner diameter of 2 mm, followed by a helical mixing channel with a single outlet.
View Article and Find Full Text PDFSoft Matter
September 2025
Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA.
Advances in fluidic droplet generation both necessitate and enable accessible, high throughput methods to optimize formulations by measuring surface tension. One fluidic approach involves creating extensional flow using constrictions. Droplets deform within a constriction, and then experience extensional flow upon exiting into a wider channel.
View Article and Find Full Text PDFSoft Matter
September 2025
Department of Mechanical Engineering, Clemson University, Clemson, SC 29634-0905, USA.
Pores scale flows through contractions and expansions are relevant in geoengineering, microfluidics and material processing These flows experience shearing and extensional kinematics near constrictions, where polymer solutions may demonstrate instabilities that arise from the fluid's nonlinear rheological characteristics even in creeping flows. The relative effect of shearing and extension can be controlled by the flow geometry. Following our earlier reports on the constriction length (M.
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