Optical manipulation of a dielectric particle along polygonal closed-loop geometries within a single water droplet

This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korea government (MSIT) (No. 2019R1A2C2011293) and the UK Engineering and Physical Sciences Research Council (Grant EP/P030017/1).We report a new method to optically manipulate a single dielectric particle along closed-loop polygonal trajectories by crossing a suite of all-fiber Bessel-like beams within a single water droplet. Exploiting optical radiation pressure, this method demonstrates the circulation of a single polystyrene bead in both a triangular and a rectangle geometry enabling the trapped particle to undergo multiple circulations successfully. The crossing of the Bessel-like beams creates polygonal corners where the trapped particles successfully make abrupt turns with acute angles, which is a novel capability in microfluidics. This offers an optofluidic paradigm for particle transport overcoming turbulences in conventional microfluidic chips.Publisher PDFPeer reviewe

Functionalization of Pyridinium Derivatives with 1,4-Dihydropyridines Enabled by Photoinduced Charge Transfer

© 2020 American Chemical Society. By exploiting electron donor-acceptor (EDA) complexes between 1,4-dihydropyridines and N-amidopyridinium salts under visible light irradiation, we discovered that photoinduced intermolecular charge transfer induces a single-electron transfer event without requiring a photocatalyst for the facile functionalization of pyridines. The generality of this method is amenable to various types of 1,4-dihydropyridines radical precursors to generate structurally different radicals such as alkyl, acyl, and carbamoyl radicals, ultimately providing facile access to synthetically valuable C4-functionalized pyridines. A broad range of functional groups are well accommodated under mild and metal-free conditions, and the synthetic utility of the present method is showcased by the late-stage functionalization of a variety of biologically relevant pyridine-based compounds, pharmaceuticals, and peptide feedstocks11Nsciescopu

A Rail-Temperature-Prediction Model Based on Machine Learning: Warning of Train-Speed Restrictions Using Weather Forecasting

Predicting the rail temperature of a railway system is important for establishing a rail management plan against railway derailment caused by orbital buckling. The rail temperature, which is directly responsible for track buckling, is closely related to air temperature, which continuously increases due to global warming effects. Moreover, railway systems are increasingly installed with continuous welded rails (CWRs) to reduce train vibration and noise. Unfortunately, CWRs are prone to buckling. This study develops a reliable and highly accurate novel model that can predict rail temperature using a machine learning method. To predict rail temperature over the entire network with high-prediction performance, the weather effect and solar effect features are used. These features originate from the analysis of the thermal environment around the rail. Precisely, the presented model has a higher performance for predicting high rail temperature than other models. As a convenient structural health-monitoring application, the train-speed-limit alarm-map (TSLAM) was also proposed, which visually maps the predicted rail-temperature deviations over the entire network for railway safety officers. Combined with TSLAM, our rail-temperature prediction model is expected to improve track safety and train timeliness

PDMS shielding 을 이용한 크랙 기반 습도 제어 및 신축성 인장 센서 개발

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Visible-Light-Driven C4-Selective Alkylation of Pyridinium Derivatives with Alkyl Bromides

ⓒ 2020 American Chemical Society Reported herein is a general strategy for the photochemical cross-coupling between N-amidopyridinium salts and various alkyl bromides under photocatalyst-free conditions, granting facile access to various C4-alkylated pyridines. This approach exploits the intriguing photochemical activity of electron donor-acceptor (EDA) complexes between N-amidopyridinium salts and bromide, which provides a photoactive handle capable of generating silyl radicals and driving the alkylation process. The robustness of this protocol was further demonstrated by the late-stage functionalization of complex compounds under mild and metal-free conditions11sci

Development of electrodes with resistance to tension through structural shape control

Interest in healthcare and wearable devices has been increasing recently. A strain sensor is required in various wearable devices. With respect to such devices, studies on resistance changes in strain sensors using flexible materials are in progress. However, the resistance of the rest area in a strain sensor should not change according to the applied strain. So, an electrode with resistance to stretching, bending, and torsion is required in such strain sensors. Tension, bending, and torsion can be realized through structural shape control, rather than by using flexible materials. Further, such an electrode that maintains electrical properties has been developed and manufactured. This electrode can be used in various applications such as foldable devices, e-papers, batteries, and multifunctional wearable devices.22Nkc