4.1 KiB
| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Differential dynamic microscopy | 3/3 | https://en.wikipedia.org/wiki/Differential_dynamic_microscopy | reference | science, encyclopedia | 2026-05-05T10:04:12.670972+00:00 | kb-cron |
== Applications == DDM was initially used to characterize the dynamics of colloidal particles undergoing Brownian motion in dilute and concentrated suspensions, extracting diffusion coefficients and other hydrodynamic parameters from the wavevector dependence of decorrelation rates. DDM has been extended to measure dynamics in complex fluids, including aggregation processes of nanoparticles and dynamics of anisotropic colloids. DDM has been widely applied to quantify bacterial motion and motility, providing ensemble-averaged parameters such as population swim speed, diffusivity, and run–tumble statistics without single-particle tracking. Confocal and fluorescence implementations further enable measurements in fluorescent and optically challenging samples, including concentrated and multiply scattering systems. Selected application areas include: Particle sizing and size distributions: DDM can be used for particle sizing by extracting diffusion coefficients and converting them to hydrodynamic sizes via the Stokes–Einstein equation. This can be extended to multimodal size distributions and mixtures, where DDM provides size information even when individual particles are not resolved. Protein sizing and macromolecular characterization: DDM has been extended to characterize proteins at dilute concentrations of a few milligrams per milliliter, achieving hydrodynamic radius measurements in excellent agreement with commercial DLS instruments while requiring only microliters of sample. Turbid and concentrated suspensions: DDM has been used to probe dynamics in turbid suspensions over wide ranges of concentration and optical thickness, enabling analysis of samples challenging for conventional light scattering measurements. Microrheology and viscometry: Tracking-free microrheology and microliter viscometry variants have been developed using DDM analysis of tracer fluctuations, enabling determination of viscosity or viscoelastic moduli from small sample volumes. Biological and cytoskeletal network dynamics: DDM has been applied to quantify dynamics in biopolymer and cytoskeletal networks, where it provides a Fourier-space view of relaxation and rearrangement dynamics in microscopy image sequences. Liquid crystal phase transitions and orientational ordering: DDM has been applied to probe orientational dynamics and pretransitional fluctuations in liquid crystalline systems. In confined nematic cells, DDM captures changes in director fluctuations and dynamic correlations near phase boundaries, providing insights into collective orientational relaxation and anisotropic dynamics in the nematic regime. Active and non-equilibrium materials: DDM is increasingly used to quantify multiscale dynamics in active and out-of-equilibrium soft materials, including gels and dynamically heterogeneous systems with multiple relaxation regimes. Related reciprocal-space approaches have been applied to glassy colloids to characterize multiscale heterogeneous dynamics in two-dimensional systems, and to investigate Brownian yet non-Gaussian diffusion of tracer particles in hard-sphere glasses. In biological active matter, DDM-derived methods have enabled tracking-free quantification of collective cell dynamics, including single-cell displacements and division rates in confluent monolayers, and have been used to dissect active diffusion and advection driven by cytoskeletal activity in the Drosophila ooplasm.
== Relationship with other imaging-based scattering methods == Scattering-based DDM belongs to the so-called near-field (or deep Fresnel) scattering family, a family of imaging-based scattering methods. Near field is used here in a similar way to what is used for near field speckles i.e. as a particular case of Fresnel region as opposed to the far field or Fraunhofer region. The near field scattering family includes also quantitative shadowgraphy and Schlieren.
== References ==