Just enjoy this really nice video that Clyde Midelet made about his experiments on modulating the extinction spectrum of a microfluidic sample of gold nanoparticles using the power of dielectrophoresis. The sample is a colloidal solution of 80 nm spherical gold nanoparticles in water.
The details of the experiments (why, how, …) can be found in our publication in the journal Particle & Particle Systems Characterization.