ABSTRACT
We used microfluidic technology for preparing gas-liquid Janus emulsions; we firstly proposed a one-step preparation method of micro-grippers and then characterized the function of oriented and precise delivery behavior. Because of the enrichment of Fe3O4 nanoparticles, the micro-gripper can reach a speed of 1.5 mm s-1 driven by a magnetic field. The micro-gripper's body is made of a poly(N-isopropylacrylamide) hydrogel, a reversible temperature-responsive polymer. The thermo-sensitivity of hydrogels offers the function of grasping, to closely integrate with the target carried, ensuring the stability of the carrying process. The reversible variation of the hydrogel allows the micro-gripper to be reusable and have a long shelf life.
ABSTRACT
Self-assembly is the process to form ordered compound structures. Theories and experiments involving nanosized Janus particles have proved that the assembled cluster structures are related to the unit number. Micrometer-sized amphiphilic Janus particles could also act as surfactants to stabilize droplets and aggregate to form clusters. When the scale order increases to the millimeter size, particles are usually connected under shape-match mechanism, which means that the assembled structure is related to the particular particle morphology rather than the particle number. Similar to millimeter-sized particles, sub-millimeter-sized particles are larger and heavier such that their gravity cannot be ignored, whereas their Brownian motion could be neglected. To investigate the self-assembly behavior of sub-millimeter-sized Janus particles, we synthesize smart amphiphilic Janus microparticles directly from water-oil Janus droplets in one step by using a double-core capillary device. We find that the amphiphilic Janus particles could also be distributed directionally between the sides of the water-oil interface. When in oil solutions with several water droplets, the particles self-assemble into micelle-like structures to cover the water droplets with the hydrophilic phase inside. After evaporation, structures with a hydrophilic concave and a hydrophobic convex are formed. This paper demonstrates that sub-millimeter-sized amphiphilic Janus particles exhibit similar ability to nano-sized Janus particles to aggregate into clusters with ordered structures.
ABSTRACT
Here in this article, we classify and conclude the four morphologies of three-phase emulsions. Remarkably, we achieve the reversible transformations between every shape. Through theoretical analysis, we choose four liquid systems to form these four morphologies. Then monodispersed droplets with these four morphologies are formed through a microfluidic device and captured in a petri-dish. By replacing their ambient solution of the captured emulsions, in-situ morphology transformations between each shape are achieved. The process is well recorded through photographs and videos and they are systematical and reversible. Finally, we use the droplets structure to form an on-off switch to start and shut off the evaporation of one volatile phase to achieve the process monitoring. This could be used to initiate and quench a reaction, which offers a novel idea to achieve the switchable and reversible reaction control in multiple-phase reactions.
