| Abstract
| - Microscale fish bowls, hollow particles with engineered holes in their surfaces, were prepared using two differentmethods. In the first method, commercial latex beads suspended in water were swollen with a good solvent of thepolymer, followed by freezing with liquid nitrogen and evaporation of the solvent below 0 °C. While one big holewas generated when the amount of solvent used for the swelling was relatively low, small holes could be producedin the outer surface of each bowl by increasing the degree of swelling. The porosity and pore structure show a similardependence on the degree of swelling for both amorphous and semicrystalline polymers even though they are supposedto exhibit different phase behaviors during the freezing and solvent evaporation processes. In the second method, apolymer emulsion in water was prepared and then frozen with liquid nitrogen, followed by solvent evaporation below0 °C. The porosity and pore structure could be controlled by adjusting the concentration of the polymer solution usedto prepare the emulsion. As for encapsulation, the bowl-shaped particles could be transformed back into solid beadsvia thermal annealing at a temperature near the glass transition temperature of the polymer or by adding a good solventof the polymer to the colloidal suspension. In a proof-of-concept experiment, microscale fish bowls were fabricatedfrom poly(caprolactone), quickly loaded with a fluorescent dye, and sealed through thermal annealing. The encapsulateddye could then be slowly released in a phosphate buffered saline, suggesting their potential use as a new class ofmicroscale capsules for drug delivery.
|
