Over the past decade, microfluidic technology has developed rapidly due to the fact that it can achieve precise control of fluids on a small scale and also possesses many advantages, such as a steady and controllable generation process and low consumption of raw materials. Therefore, microfluidic technology has significant applications in various fields, such as materials science, chemical engineering, cosmetics production, and food technology.

With decreasing scale, the effects of the surface/interface on fluid behavior become more important, and these play a significant role in the manipulation efficiency and quality of the fluids. Recently, there have been several experimental and numerical works focused on surface and interface science in microfluidic systems. However, the detailed mechanisms underlying fluid flow and surface/interface effects in microfluidic systems are yet to be fully understood. In addition, the manipulation theories and methods for the surface/interface during fluid manipulation in microfluidic systems are still to be further developed to improve the efficiency of the microfluidic systems.

This special issue aims to highlight methods and emerging challenges for microfluidic techniques, with a special emphasis on surface and interface science in microfluidic systems. We invite original research articles and reviews focused on all aspects of droplet microfluidics, along with the properties or applications of droplets/particles relating to chemical engineering and biomedical engineering.

Potential topics include but are not limited to the following:

• Gas-liquid interface, liquid-liquid interface, solid-liquid interface, and gas-solid interface
• Heat, mass transfer and fluid flow in microsystems
• Hydrodynamics of droplets/particles
• Viscous, inertial, and interfacial tension effect
• Applications in microreactors, bioassays, micro fuel cells, etc.
• Electrophoresis, electroosmosis, diffusiophoresis, and diffusioosmosis