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Microfluidic devices are composed of microchannels with a diameter ranging from ten to a few hundred micrometers. Thus, quite a small (10 ^−9 –10 ^−18 l) amount of liquid can be manipulated by such a precise system. In the past three decades, significant progress in materials science, microfabrication, and various applications has boosted the development of promising functional microfluidic devices. In this review, the recent progress on novel microfluidic devices with various functions and applications is presented. First, the theory and numerical methods for studying the performance of microfluidic devices are briefly introduced. Then, materials and fabrication methods of functional microfluidic devices are summarized. Next, the recent significant advances in applications of microfluidic devices are highlighted, including heat sinks, clean water production, chemical reactions, sensors, biomedicine, capillaric circuits, wearable electronic devices, and microrobotics. Finally, perspectives on the challenges and future developments of functional microfluidic devices are presented. This review aims to inspire researchers from various fields—engineering, materials, chemistry, mathematics, physics, and more—to collaborate and drive forward the development and applications of functional microfluidic devices, specifically for achieving carbon neutrality.

The present work was aimed at preparing a thermosensitive nanoreactor system which could adjust its dispersion/aggregation status according to external temperature change to achieve the switchable catalysis. The mesoporous silica nanoparticle (MSNP) was selected as the framework material of the nanoreactor, and Ag nanoparticles were encapsulated in the mesoporous silica by an in situ reaction. Dodecyl groups were introduced onto MSNP surface, which could transform reversibly between complexation and disassociation with α-cyclodextrin (CD) cavity upon temperature change. It was found that the nanoreactors aggregated and the catalysis was effectively switched ‘off’ in the presence of CD polymers at low temperature (20 °C). However, when the temperature increased to 50 °C, the nanoreactors redispersed and catalysis successfully switched ‘on’. [ABSTRACT FROM AUTHOR]

In the present work, a thermoresponsive nanorattle with a Ag nanoparticle (NP) core (one catalyst in the nanorattle), and a poly(N-isopropylacrylamide) shell was developed. An imidazole group was grafted on the polymer shell by copolymerization as the other catalyst. Owing to the catalytic activities of the imidazole group and Ag NP with regards to hydrolysis and reduction, respectively, this nanorattle exhibited tandem-reaction catalytic abilities. In addition, because of the shrinkage of the poly(N-isopropylacrylamide) shell at high temperatures, the tandem reaction could be controlled to stop at the first reaction step. That is to say, only the hydrolysis reaction was catalyzed by the imidazole group being grafted on the surface of the shell. The reduction step in the tandem reaction catalyzed by the Ag particle, however, was switched off by the shrinkage of the poly(N-isopropylacrylamide) shell. This protocol opens up an opportunity to develop controllable catalysts for complicated chemical processes. [ABSTRACT FROM AUTHOR]