Microfluidic preparation of flexible micro-grippers with precise delivery function.

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.

Smart Amphiphilic Janus Microparticles: One-Step Synthesis and Self-Assembly.

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.

Multi-functional micromotor: microfluidic fabrication and water treatment application.

Micromotors are important for a wide variety of applications. Here, we develop a microfluidic approach for one-step fabrication of a Janus self-propelled micromotor with multiple functions. By fine tuning the fabrication parameters and loading functional nanoparticles, our micromotor reaches a high speed and achieves an oriented function to promote the water purification efficiency and recycling process.

Four reversible and reconfigurable structures for three-phase emulsions: extended morphologies and applications.

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.

Water-oil Janus emulsions: microfluidic synthesis and morphology design.

In this work we developed a facile method to prepare water-oil Janus emulsions in situ with tunable morphologies by using a double-bore capillary microfluidic device. In addition, by combining the theory model and our liquids' properties, we propose a method to design the morphology of water-oil Janus emulsions. To systematically research Janus morphologies we combined the theory model and the fluids' properties. Under the model guidance, we carefully selected the liquids system where only the interfacial tension between the water phase and the continuous phase changed while keeping the other two interfacial tensions unchanged. Thus we could adjust the Janus morphology by changing the surfactant mass fraction in the continuous phase. In addition, with the double-bore capillary, we prepared water-oil Janus emulsions with a large flow ratio range. By adjusting the flow ratio and the surfactant mass fraction, we successfully prepared Janus emulsions with gradual morphology changes, which would be meaningful in fields that have a high demand for morphology designing of amphiphilic Janus particles.

Controlled stimulation-burst targeted release by smart decentered core-shell microcapsules in gravity and magnetic field.

By combining gravity and magnetic force, we have developed a versatile and facile microfluidic method for forming magnetic decentered core-shell microcapsules in which the directions of the oil core and the magnetic nanoparticles are either opposed or the same. When the temperature rises above the LCST of the PNIPAm, the shell shrinks rapidly and the core targets burst release towards the converse or the same direction as the magnet. By adjusting the direction of the magnet, the release direction of the active substance could be correspondingly accurately controlled.