Induced grating is a new method to measure the size and distribution of nanoparticles in a substance. In induced grating, electrodes are connected to a group of nanoparticles. When a voltage is applied to the electrodes, the nanoparticles move due to the attractive and repulsive forces. The nanoparticles distribute themselves into some configuration based on the charges of the electrodes. This distribution can be obtained by passing light through the substance and observing the diffraction pattern of the light as it passes through the nanoparticles. Once this distribution is recorded, the voltages are turned off. The nanoparticles will once again disperse due to the change in attractive and repulsive forces. However, different nanoparticles will move at different rates. Heavier nanoparticles will take longer to move than lighter particles. By observing the light diffraction pattern as the nanoparticles disperse, you can obtain a measurement of the size and distribution of nanoparticles. This method works for nanoparticles ranging from 0.5-500 nanometers and allows for simultaneous measurement of small and large nanoparticles.
References: Canter, Neil "Measuring nanoparticles". Tribology & Lubrication Technology. FindArticles.com. 15 Feb, 2011. http://findarticles.com/p/articles/mi_qa5322/is_201001/ai_n49421435/