The RHEOLASER MASTER, an optical microrheometer (Diffusing Wave Spectroscopy instrument), is designed for conducting optical microrheology analysis. Microrheology is a new branch within the field of rheology, primarily focused on analyzing the viscoelastic properties of soft matter at the micron scale. By measuring the displacement of particles in soft materials (such as gels, polymers, emulsions, dispersants, etc.) due to thermal energy (Brownian motion), their inherent viscoelastic characteristics can be determined. The motion trajectory of particles can reflect the structure of the material.

Different parameters can be derived from the root mean square curve of particle displacement, such as:

- Elasticity Index
- Viscosity Index
- Solid-Liquid Balance Point
- Viscoelastic Modulus
- Gel Point

The advantages of the optical microrheometer (Diffusing Wave Spectroscopy instrument) include:
- Measurements are conducted entirely under static conditions: The process involves no mechanical shear forces, allowing for the analysis of particularly fragile samples like weak gels, yogurt, cream, etc., and yields unaltered, original viscoelastic results.
- Non-contact measurement: Samples are placed in a 20ml glass sample cell for testing. It enables monitoring changes in the viscoelasticity of the same sample over aging time: stability analysis, recovery tests, etc.
- Microstructural analysis: Measurements are performed at the micron scale, facilitating the analysis of the material's microstructure.
Particle motion (Brownian motion) is measured using multi-speckle diffusing wave spectroscopy. The measurement unit consists of a light source that generates a coherent laser beam and a detector that receives backscattered interference waves. This interference pattern, known as the speckle image, is detected by a multi-pixel detector. The patented speckle image processing technology can measure:
- Photon mean free path
- Root mean square distance of particle motion

From these raw data, relevant rheological parameters can be calculated, such as:
- Elasticity Index
- Viscosity Index
- Solid-Liquid Balance Point
- Viscoelastic Modulus
- Gel Point