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

Abstract

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.

Scalable single-step microfluidic production of single-core double emulsions with ultra-thin shells

“…The main channel width is then tapered from 100 to 20 μm and its height is varied from 30 to 10 μm; this configuration mimics the tip of the injection capillary of a co-flow glass capillary device. 11 We treat the main channel upstream this tip with a solution of 1 vol% perfluorinated trichlorosilane dissolved in HFE 7500 to render its surface fluorophilic, thus preventing wetting of the innermost water phase on the main channel wall. We inject the inner and middle phases at a flow rate of 1 and 0.4 mL h −1 , respectively; under these conditions the innermost aqueous phase forms a stable jet, surrounded by a thin layer of perfluorinated oil, within the main channel.…”

“…The excellent control over the fluid flow afforded by microfluidics enables the production of highly monodisperse double emulsion drops whose composition is well defined. 9,10 However, most often, the fluids that make up the double emulsion drops have different densities and thus, the centers of the inner and outer drops of the double emulsions are off-set; 11 this results in capsules with inhomogeneous shell thicknesses. 12 Capsules with homogeneous shell thicknesses can be made from double emulsion drops with very thin shells as the offset of the centers of the drops is then minimal; this is mainly due to their higher lubrication resistance.…”

“…13 Such double emulsion drops can be produced in a single emulsification step using microfluidic glass capillary devices. 11 Unfortunately, this device is difficult to scale up as every device is aligned manually and is thus unique; even if differences in each device are small, flow rates typically must be adjusted for each device individually. By contrast, devices produced through soft lithography are all much more nearly identical as they are made from masters; this makes their parallelization easier.…”

Patchy colloidosomes – an emerging class of structures

“…decentered core-shell microcapsules are good examples, because the core material can be thermo-triggered and burst-released in a controlled direction [1,51]. In these examples, the direction of release is controlled by an external stimulus.…”

“…Two types of mechanisms trigger the release from a capsule: an internal stimulus (e.g., changes of pH [4] or ionic strength of the solution [44]) or an external stimulus (e.g., light [46], magnetic or electric field [47,48], or ultrasound irradiation [49]). The microcapsule response may be based on either the intrinsic properties of the shell or the content of the capsule, and it is sensitive to the trigger impact [50,51]. The release can be achieved by irreversible shell decomposition (e.g., by melting, degradation, cracking, etc.…”