Temporal super-resolution differential dynamics microscopy for detecting fast dynamics*

We introduce dual-color differential dynamic microscopy (DDM) for detecting fast dynamics. DDM has been used extensively to measure the diffusive or ballistic motion of small particles, macromolecules and bacteria. Rather than localizing and tracking individual particles, DDM works by measuring the intensity fluctuations in images across a range of detectable spatial frequencies and provides data similar to that provided by dynamic light scattering. However, DDM is limited by the camera frame rate. Fast dynamics can be measured with high-speed cameras but those are typically expensive. We have developed a dual-color imaging setup which allows us to detect dynamics faster than the camera’s frame rate. We trigger blue and red light at well-defined times within a single image exposure. By analyzing each color channel separately and in combination we detect dynamics that are several times faster than the camera frame rate.