SEM image of colloidosome, showing the pores that control permeability.
A new approach in exploiting self-assembly to create novel structures with building blocks of lager length scale was created in the work of Weitz and his collaborators, who created structures they call colloidosomes. These structures are made by adsorbing colloidal particles at the interface of an emulsion droplet, gently sintering the particles to stabilize the structure, and the by transferring the larger droplet into a new continuous-phase of fluid which is the same as the inner fluid, thereby resulting in a solid shell with potential utility for encapsulation. An electron micrograph of a colloidosome is show in the Figure. In addition, by looking with higher magnification, the sintered layers between particles are clearly visible, as well as the remaining pores; the size of these pores can be simply controlled by the heating rate, the ripening time and the size of the colloidal particles, providing a simple means of assembling new structures that may prove useful for encapsulation.
Similar objects are already being used to encapsulate drugs to achieve sustained release, and colloidosomes may represent a new structure for such encapsulation.
Reference: “Colloidosomes: Selectively-Permeable Capsules Composed of Colloidal Particles,” A.D. Dinsmore, M F. Hsu, M.G. Nikolaides, A.R. Bausch, M. Marquez, and D.A. Weitz, Science, 298, 1006 (2002).
David A. Weitz (Physics & Applied Physics)
Harvard MRSEC (DMR-0820484)