NANO-flex Nanoparticle Measurement Device for Particle Size Distribution with 180° DLS Dynamic Light Scattering




System for characterization of colloids by dynamic light scattering within a size range of 0.8 nm to 6.5 µm. Suitable for material systems with concentrations from ppm up to 40% vol., depending on substance type. Minimum is 1 droplet.

Particle Size Distribution

The NANO-flex 180° DLS System measures size distributions in the range of 0.8 nm to 6.5 µm. The applied heterodyne 180° back scattering principle of the Nanotrac® is characterised by its high selectivity in the nano-range and is therefore also suitable for samples with broad size distribution. Highly concentrated samples are measured without interfering multiple scattering.

The applied Nanotrac® back scattering in the NANO-flex is designed as a flexible measuring probe with 8 mm ø. Thus, it can be used in many ways, even in-situ and in the measuring cylinder of the Stabino®!

The 180° DLS–Method

NANO-flex measurement principle
Figure 3:
The described 180° DLS-method.

The laser is focused to the sample via an optical fiber and a sapphire window. The window reflects a part of the incoming laser light. Both, laser reflection and scattered light interfere at the detector diode. Due to the excellent signal/noise ratio, there is no need for an expensive detection system.

The fluctuating part of the signal is modulated by the Brownian diffusion of particles and transformed by Fast Fourier into a power spectrum which is referenced by the laser frequency. Without assumption on any distribution model, the size distribution is derived from the power spectrum.

Molecular weight determination according to Debye

Further to the DLS size, a Debye plot feature with automatic dn/dc determination provides molecular weight.


DLS applications with the NANO-flex module are nearly unlimited, provided the viscosity of the sample is in the Newtonian range, a condition for the free Brownian movement in the fluid and for the accurate calculation of the size. The liquid medium of the particles can be of organic or aqueous nature.
The critical coagulation point of a dispersion can be determined by measurement of size and potential inside Stabino®. For this purpose, the NANO-flex size sensor is dipped into the Stabino® measuring cylinder.