Fabrication of Pill-Shaped Polyimide Aerogel Particles Using Microfluidic Flows

This work focuses on the fabrication and organic dye adsorption capacity of pill-shaped polyimide aerogel microparticles of diameter approximately 200 μm and length approximately 1000 μm. First, spherical polyimide sol droplets suspended in silicone oil are generated in a microfluidic droplet generator. Second, these droplets are guided into a contraction flow channel to deform them into pill-shaped droplets. Third, the pill-shaped droplets undergo sol–gel transition in a heated section of the flow channel and turn into particles. Finally, the pill-shaped aerogel microparticles are recovered via solvent exchange and supercritical drying and characterized. The data indicate that the flow rates of polyimide sol and silicone oil strongly influence the length of the microparticles while surfactants, although not necessary to obtain pill-shaped particles, exert strong influence on the aspect ratio of the particles. The aspect ratio of particles and the internal morphology are discussed using hydrodynamic and interfacial forces. The ionic dye adsorption capacity of these pill-shaped particles is determined and compared with that of spherical gel microparticles.