Controlled Self-Assembly of Quantum Dots and Block Copolymers in a Microfluidic Device

Abstract

The controlled self-assembly of polymer-stabilized quantum dots (QDs) into mesoscale aqueous spherical assemblies using microfluidics is described. In a flow-focusing configuration, self-assembly is initiated by the addition of water to a blended solution of polystyrene-coated QDs and amphiphilic polystyrene-block-poly(acrylic acid) stabilizing chains and terminated in a downstream quench step. The on-chip evolution of assemblies is monitored through fluorescence microscopy, and particle size distributions are determined off-chip by transmission electron microscopy. On-chip size control of the assemblies is demonstrated via both the average water concentration in the channel and the flow rate.

Facile preparation of fluorescence-encoded microspheres based on microfluidic system

“…Microfluidic techniques are widely applied in the preparation of microcapsules and monodispersed microspheres. Through this method, various shapes and morphologies polymer particles such as truncated spheres and hemispheres can be obtained [17][18][19][20][21][22][23][24][25][26][27][28]. Especially, Xia et al successfully prepared PCL microspheres for cell culture applications by using the microfluidic device [17,18] and Yang et al reported multi-functional PCL microcapsules for drug delivery by microfluidic chip method [19].…”

Particles in Microfluidic Systems

“…This approach was instrumental in enabling the encapsulation of fluorescent and magnetic nanoparticles within the larger polymer particles. 3,22 The inclusion of cadmium sulfide quantum dots (QDs) into stabilized block copolymer particles was also demonstrated in a microfluidic device. 3,20 While a similar T-junction strategy was used, the reaction mechanism was substantially different from the spherical hydrogels just discussed.…”

“…3,22 The inclusion of cadmium sulfide quantum dots (QDs) into stabilized block copolymer particles was also demonstrated in a microfluidic device. 3,20 While a similar T-junction strategy was used, the reaction mechanism was substantially different from the spherical hydrogels just discussed. This effort involved a selfassembly process that was monitored fluorescently such that the process could be quenched with water at an optimal point in the reaction.…”

“…Particle sizes from this self-assembly process ranged between 50 and 100 nm. 3 In related work, a multiphase gas-liquid microfluidic reactor was used to create microplugs of liquid within which the particle polymerization occurred. Serpentine channels were used to increase mixing within the dispersed droplets followed by a post-formation channel.…”

“…These attributes are advantageous for self-assembly, reaction, and precipitation conditions leading to particle formation or particle property alteration. 3,4 Microfluidic confinement of particles in combination with forces from optical fields, electrical fields, magnetic fields, chemical interactions, and pressure will be discussed.…”