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Surface-tension-confined droplet microfluidics

“…Huang et al [61] took advantages of the ferrofluid-molding strategy to successfully generate microcone structures with different inclination angle by regulating the direction of external magnetic field applied to the ferrofluid. In a nutshell, 3 µL of water-based ferrofluid containing 10-nm magnetic nanoparticles was firstly divided into microdroplets owing to magnetic hydrodynamic instability and arrays of droplets formed a hexagonal pattern under the control of magnetic disks.…”

“…To flexibly control the movement of liquids on the surface, various micro/nanoscale topographic structures were fabricated via molding combined with metal deposition and other methods. [54,55,60,61,65,66] The mechanism of liquid movement on asymmetrically patterned substrates was studied by Chamakos et al [67] As presented in above articles, a droplet on such a (super-)hydrophobic surface patterned with micro/nanoscale rods or pillars behaved like a "liquid sphere" which could easily move in direction which was generally decided by the direction of slanted or bended rods and pillars. It has been proved that the direction that a liquid droplet tends to move in was basically influenced by the unbalanced capillary retention force at the contact line and in cases where the capillary effect was weakened, the anisotropic friction behavior fades.…”