Production of anisotropic polymer microparticles by microfluidic routes

Polymeric microparticles with anisotropies of composition, shape and functionality are highly attractive systems by virtue of the properties they exhibit in relation to their isotropic counterparts. For example:

• for composition, anisotropic particles with different compartments, containing smaller particles (organic or inorganic) or different molecules, can be used in a wide range of applications such as vectorization and controlled release of active ingredients, catalytic systems, sensors, water purification, digital displays, structural materials, etc. ;

• in terms of shape, the maximum compactness of non-spherical particles is greater than that of spherical particles. Compared with spherical particles, shape anisotropy results in different electrical, magnetic, optical and hydrodynamic properties;

• for functionality, particles with a differentiated distribution of functionalities on their surface, such as functional groups, can exhibit a propensity for self-assembly and thus generate new properties.

However, the conventional preparation of such anisotropic particles requires the use of very specific processes, which are often discontinuous, complicated, multi-step and offer little reproducibility.

The aim of this review article is to give an overview of recent developments using continuous flow techniques based on microfluidic systems for the manufacture of anisotropic polymer microparticles, including microfibers, and to mention their most noteworthy applications.