Silica Nanoparticle Dispersion Size Measurement Using Dielectrophoresis on a Microfabricated Electrode Array

摘要

In this article, we report a technique that uses dielectrophoresis to measure particle size distribution information of silica nanoparticle dispersions using a microfabricated periodic interdigitated electrode array. An AC voltage is applied to the electrode array, producing a non-uniform electric field. Depending on their relative permittivity with respect to the dispersion solution, nanoparticles aggregate at either electric field maxima or minima due to dielectrophoresis, forming a periodic density grating. We probe the nanoparticle density grating with a laser beam to generate a diffraction pattern, and then monitor how fast the nanoparticle density grating decays due to diffusion after the electric field is turned off. Particle size information is derived from the diffusion rate. The advantages of the technique include: a) able to operate over a wide range of concentrations and purity levels, b) relatively insensitive to outlier particles in the tail ends of the size distribution, and c) relatively fast (on the order of seconds) measurement response. These characteristics make the method suitable for industrial samples and real time process monitoring.