A microfluidic approach for fabrication of Janus hydrogel particles with magnetic anisotropy is demonstrated. Using this technique, cells and magnetic beads (MBs) can be separately embedded in one hydrogel particle to maintain optical performance, and reduce the contact between cells and magnetic beads (nano- or submicron-particles). Alginate cell capsules prepared by this method can be easily controlled and manipulated by external magnetic fields and require no specific surface modification. Bio-degradability and super-paramagnetic properties of these hydrogel particles were also demonstrated experimentally.

In recent years, a broad range of nanocrystals have been synthesized in droplet-based microfluidic reactors which provide obvious advantages, such as accurate manipulation, better reproducibility and reliable automation. In this review, we initially introduce general concepts of droplet reactors followed by discussions of their main functional regions including droplet generation, mixing of reactants, reaction controlling, in situ monitoring, and reaction quenching. Subsequently, the enhanced mass and heat transport properties are discussed. Next, we focus on research frontiers including sequential multistep synthesis, intelligent synthesis, reliable scale-up synthesis, and interfacial synthesis. Finally, we end with an outlook on droplet reactors, especially highlighting some aspects such as large-scale production, the integrated process of synthesis and post-synthetic treatments, automated droplet reactors with in situ monitoring and optimizing algorithms, and rapidly developing strategies for interfacial synthesis.

Single molecule electrochemistry (SME) has gained much progress in fundamental studies, but it is difficult to use in practice due to its less reliability. We have solved the reliability of single molecule electrochemical detection by integration of digital analysis with efficient signal amplification of enzyme-induced metallization (EIM) together with high-throughput parallelism of microelectrode array (MA), establishing a digital single molecule electrochemical detection method (dSMED). Our dSMED has been successfully used for alkaline phosphatase (ALP) detection in the complex sample of liver cancer cells. Compared to direct measurement of the oxidation current of enzyme products, EIM can enhance signals by about 100 times, achieving signal-to-background ratio high enough for single molecule detection. The integration of digital analysis with SME can further decrease the detection limit of ALP to 1 aM relative to original 50 aM, enabling dSMED to be sensitively, specifically and reliably applied in liver cancer cells. The presented dSMED is enormously promising in exploring physical and chemical properties of single molecules, single biomolecular detection, or single-cell analysis.

Fe-doped CuO (Cu1−xFexO) nanocrystals (NCs) (x=0, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) are prepared by using the urea nitrate combustion method. X-ray diffraction (XRD) analysis confirmed the monoclinic structure of CuO. Single-phase structure is obtained for the 0%–20% Fe-doped CuO, whereas for the 25% and 30% Fe-doped CuO material, secondary phase, α-Fe2O3, is presented. Rietveld refinements of XRD data revealed that with an increase in Fe doping level, there is a monotonic increase in cation vacancies in the Fe-doped samples. X-ray photoelectron spectroscopy measurements on the Cu0.98Fe0.02O sample revealed that the Cu2+ sites are partly substituted by Fe3+ ions. The microstructure is investigated by high-resolution transmission electron microscopy. The magnetic hysteresis loops and the temperature dependence of magnetization of the samples indicated that the samples are mictomagnetic of ferromagnetic domains originated from ferromagnetic coupling between the doping Fe ions in Cu1−xFexO NCs randomly distributed in the antiferromagnetic CuO matrix. The Curie temperature of the ferromagnetic phase is higher than 400 K for all Fe-doped CuO samples. The ferromagnetic behavior of the samples is discussed.

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