Feifei Peng: Thermoresponsive colloidal molecules prepared by microfluidics
Place: Kemicentrum, Lecture hall F
A seminar by PhD Student Feifei Peng, Physical Chemistry, Lund University.
Microfluidic systems have recently gained widespread use in soft matter research, particularly for particle synthesis and handling with increased control and sensitivity. The advantage over conventional process stems from the dimensional scaling of microfluidics, and allows to reduce the amount of fluid used in chemical processing and provides accurate manipulation of fluids in a defined geometry on the micron length scale. In my talk, I will present a droplet-based microfluidic approach to fabricate colloidal clusters containing two kinds of thermoresponsive microgels, which exhibit different volume phase transition temperatures (VPTTs). Here we use a microfluidic device to form microgel-containing water-in-oil droplets. The evaporation of the water results in droplet shrinking, forcing the entrapped colloids to form compact molecule-like clusters. The clusters were subsequently crosslinked and redispersed in water in order to create stable colloidal molecules, where the interactions between individual particles on different clusters could be selectively tuned via temperature, and varied from soft repulsive to attractive. This results in molecule-shaped clusters with a well-defined and limited number of temperature-controlled interaction sites. The use of colloids with controlled valences can be expected to lead to new self-assembled structures, inaccessible with simple spheres, and may allow us to copy nature’s successful self-assembly strategy for creating complex structures and functional materials. In addition, I will also discuss our efforts in developing microfluidic devices to sort the clusters according to their sizes, and characterize and manipulate the phase diagram of colloidal clusters as a function of temperature, concentration, mixing ratio and valences of colloidal molecules.