DWS RheoLab

Advanced optical rheology
Brand: 
LS Instruments
Category: 
Diffusing Wave Spectroscopy

The DWS RheoLab is an optical rheometer. It provides information and data on the viscoelastic properties of the sample and allows the study of consistencies and microstructures while requiring only small sample volumes (150 µL). The measurements are non-contact and non-destructive: the use of a hermetically sealed cuvette enables stability or shelf-life studies over long periods, even on highly viscoelastic and fragile microstructures.

It can measure viscosity, elasticity, mean square displacement, and particle size. This means that one of its key advantages is combining multiple instruments in one: both a rheometer and a particle analyzer, capable of measuring highly viscous samples and characterizing fragile microstructures.

Based on the powerful DWS Microrheology technique, the RheoLab is ideal for a wide range of viscoelastic samples, including polymers, microgels, protein solutions, emulsions, particle suspensions, dairy products, and cosmetics.

Info Request

Videos

Webinar - An introduction to the DWS RheoLab

Files

AttachmentSize
PDF icon Brochure2.15 MB
PDF icon Specifications199.22 KB

News, events, promotions, webinars

14/11/2022
Webinar - LS Instruments - DWS Microrheology: Fundamentals & Applications
09/05/2022
SICC course: How to improve and evaluate the cosmetic stability - LS Instruments DWS and X-Rite Color Spectrophotometry presentations
22/10/2021
Publication: "Lysozyme amyloid fibrils can be used as natural bio-flocculants to precipitate contaminants in water"
27/04/2021
Webinar, 29 april 2021: Applications of DWS to Pharmaceutical Formulation Technology
03/08/2020
Inhaled effervescent antibiotic to combat lung infections. DWS RheoLab played a crucial role.

Application Fields

Nanoparticles
Polymers and Composites
Nano-Bio Sciences - Nanobiotechnology
Nanopharma & Nanomedicine
Extract the viscoelastic properties without damaging the sample

Microrheology is a method that utilizes the Brownian motion of tracer particles embedded in the sample. Since the viscoelastic properties of the surrounding environment influence the particle's movement, microrheology can extract these properties without applying any external force. The RheoLab employs Diffusing Wave Spectroscopy (DWS) technology to detect particle motion.

The DWS technique offers unmatched sensitivity and range, far exceeding particle tracking, DLS, or camera-based microrheology.

 

Diffusing Wave Spectroscopy
 

Diffusing Wave Spectroscopy (DWS) is an advanced light scattering technology used to measure the Brownian motion of tracer particles embedded in the sample. Similar to DLS, DWS analyzes the temporal fluctuations of the light intensity scattered by the particles. The statistics of these fluctuations are reflected in the measured correlation function, from which the mean square displacement of the tracer particles can be calculated.

Unlike DLS, DWS amplifies the scattered light, increasing the sensitivity of each scattering event. This makes DWS the most suitable technique for microrheology.

Smart approach to study microstructure

Most soft materials exhibit viscoelastic behavior, meaning their mechanical properties lie between those of a purely elastic solid and those of a viscous liquid. DWS microrheology can quantify both the viscous and elastic properties of a material over a wide range of time scales; this makes it an invaluable tool for understanding the microstructure and relaxation times of many soft materials.

Extends limits of rheology

DWS RheoLab harnesses the patented Echo technique that allows rapid measurements of slowly relaxing samples equivalent to ordinary multi-speckle DWS (MS-DWS). The Echo-DWS technique also enables the measurement of high frequencies due to the fast detectors which give access to an unmatched frequency range, much larger than MS-DWS. Since Echo-DWS has a significantly higher tracer motion sensitivity than MS-DWS and DLS, it also allows the measurement of large moduli in samples such as firm gels and concentrated polymer solutions.

Technical Features

  • Fully automated DWS Microrheology
  • Applicable to all homogeneous transparent or opaque samples
  • Fluid with a large range of viscosities from 0.1 mPa∙s to 1000 Pa∙s can be measured
  • Storage and loss moduli G'(ω), G''(ω) in a frequency spectrum 0.1 Hz to 1 MHz (0.1Hz to10MHz with pseudo cross-correlation upgrade)
  • Elasticity range from 1 Pa to 50 kPa
  • Computes the mean square displacement (MSD) of particles
  • Contact-free. No mechanical force applied to the sample: ideal for stability or shelf life studies
  • Monitors time-dependent processes
  • Regulated sample temperature from 4°C to 90°C
  • Temperature stability < 0.02°C
  • Compact and robust design
  • Several cuvette sizes available
  • Sample quantity down to 150 μl (for 1 mm thick sample cell)
  • Several options available
  • Particle sizing at high concentrations
  • Online support forum for all customers

Technology

Diffusing Wave Spectroscopy with Echo Technology (EU Patent)

Scattering geometry

Transmission (backscattering optional)

Viscosity range

0.1 m Pa · s to 1000 Pa · s

Storage (G’) & loss (G’’) moduli

1 Pa to 50 kPa

Frequency range

0.5 rad/s to 105 rad/s (106 rad/s with extended frequency upgrade)  

Particle sizing** (radius)

0.1 to 1 µm (accuracy of ±5% in the turbid range)

Cuvette sizes

1 x 10 mm, 2 x 10 mm, 5 x 10 mm, 10 x 10 mm

Sample volume

150 µL to 1.5 mL, depending on cuvette used

Temperature range    

4 to 100 °C (optional: 4 to 180 °C) with stability better than ±0.02 °C

Laser class

1

Laser

685 nm with 45 mW

Detector

High sensitive APD, QE > 65%

Detection

Single mode fiber with integrated optics

Correlator

Two channel multiple tau, 12.5 ns to 1 h
Two channel linear tau with selectable lag time

Software

Including microrheological analysis

Laboratory requirements

< 60 % relative humidity and T = 17 to 26 °C

Size

38 x 31 x 24 cm

Weight

Approx. 14 kg

* The maximum range is sample dependent.

** Requires backscattering mode.

*** A climate controlled room at or below 23 °C required to meet these specifications, for temperatures below the dew point a dry air source is required. (optional: 4 to 180 °C)

Info Request