Technology

How Dynamic Light Scattering Works

Dynamic light scattering (DLS) uses the principles of Brownian motion and Doppler shift to determine the size and number of particles in a suspension. A laser light is positioned so it shines through the suspension, and a special light detector called a photon counter is positioned at an angle with respect to the laser.

The particles in the suspension undergo Brownian motion (random movement). As the particles move through the suspension, they pass through the beam of laser light, which causes some of the light to scatter in all directions. Because the particles are moving, the scattered light undergoes a Doppler shift, which is to say that there is a very slight change in the scattered light compared to the unscattered light. Larger particles move slowly, and exhibit a small Doppler shift, whereas small particles move quickly and exhibit a large Doppler shift.

The photon counter is able to detect the light scattered in its direction, and measures the fluctuations in light intensity that result from the Doppler shift. The intensity fluctuations are measured for a period of time and the data is processed into a correlation function — a mathematical function that identifies the patterns in the data.

A secondary mathematical analysis, called a polydispersity analysis, is performed on the correlation function in order to identify the size of particles in the suspension and the relative number of particles of each size.

ThromboLUX® uses DLS to determine the size and distribution of particles that are in a platelet sample.