Aerosol generation and handling in microchannels

The application of T-shaped micromixers is demonstrated for the generation of nanoscale aerosols by the mixing of hot vapor–gas-mixtures with cold gas. The fast mixing within micromixers leads to high supersaturation of the vapor and to homogeneous nucleation. After nucleation, the particles grow to their final size until the vapor is saturated. Different mixing ratios and gas temperatures have been investigated. Special attention was paid to thermal insulation and particle deposition at the channel walls. Experimental results for particle deposition (prefabricated NaCl nanoparticles in a nitrogen carrier stream) and aerosol generation (vitamin E droplets in nitrogen) are presented. High temperature gradients up to 10^6 K/s lead to a rapid condensation and formation of nanosized droplets with a mean diameter of 20–50 nm and a narrow size distribution. First experimental results for the two-phase flow in a separation chip indicate the suitability for mixing and further improvements for phase separation.