The KSV NIMA Interfacial Shear Rheometer (ISR) is an advanced characterization instrument for studying the viscoelasticity of Langmuir films. It is used for studying phenomena that are controlled by interfacial viscosity and for studying the properties of the films prior to deposition to determine the optimal deposition parameters.

Application overview

Applications controlled by interfacial rheology, including

  • Biological systems such as pulmonary lung surfactant and meibum. Their functionality is largely based on their flow on interphases under stress.
  • Emulsions and foams whose stability is vital for their functionality. Viscoelasticity of an interface can predict the stability of a complex fluid. Micelle/droplet fusion and fission are largely dependent on the interface viscoelasticity.
  • Oil & Gas, Cosmetics, Food products, Biophysics, Pharmaceuticals. Application areas where molecules at interfaces have desired flow properties, such as asphaltenes in oil & gas.

Langmuir monolayer structural studies, including:

  • Phase changes, as the viscoelasticity of the layer is strongly affected by the phase transition.
  • Surface reactions such as crosslinking in real time, as changes in molecular size and shape have typically a strong response in their rheological properties.
  • Aggregation and adsorption, as they typically change the viscoelasticity of the film.
  • Determination of optimal coating parameters prior to the deposition, as the Langmuir-Blodgett coating is based on the flow of the molecules to the solid substrate.

Features & Benefits

  • Simultaneous measuring and controlling of surface pressure due to easy integration with KSV NIMA Langmuir Troughs. This makes it possible to correlate rheological data with monolayer surface pressure and phase transitions that are crucial when working with insoluble surfactants.
  • Extremely high sensitivity — ISR is able to measure very weak elastic and viscous moduli of surfaces and interfaces. The high sensitivity of the method is due to fact that the low inertia hydrophobic probe is moved by magnetic field without mechanical connections.
  • In many applications, such as with biofilms, the long-lasting chemical interactions and film creation kinetics need to be followed in real-time. KSV NIMA ISR does not demand any adjustments to compensate the influence of evaporation as it is based on a unique floating needle technique.
  • Possibility to work with low volumes down to 4.7 mL saves time and cost when working with valuable compounds and subphases.

Product details

The KSV NIMA ISR method is based on interfacial shear rheology. A magnetized probe positioned at the interface is used to create shear deformation on the interface which response can be measured by recording the probe movement optically.

For more information about the technology, see: Interfacial Shear Rheometry

KSV NIMA ISR enables both dynamic and static measurements to define viscoelasticity of the interfacial layers. With dynamic measurement, viscoelastic properties are measured as a function of frequency, time, strain, temperature or surface pressure. Static measurement enables the creep test to be performed and indicates whether the system behaves like an ideal Newtonian liquid (dashpot model) or ideal elastic (spring model). These measurements enable the following parameters to be defined:

  • Elastic (storage) modulus, G’
  • Viscous (loss) modulus, G’’
  • Dynamic interfacial viscosity, μs*
  • Surface/interfacial viscosity, η
  • Relaxation times, τ

Product range

The KSV NIMA ISR can be equipped with either a KSV NIMA Langmuir Trough (or Liquid-Liquid Trough) for simultaneous control of the film packing density or a Low Volume Measurement cell to work with small interfacial areas and reduced subphase volumes.

Both systems enable surface pressure measurement thanks to the integrated highly sensitive Wilhelmy balance. The Langmuir Trough and the Low Volume Measurement Cell are divided into an upper and lower compartment, which can be used to study film viscoelasticity at the liquid-air or liquid-liquid interface.

All the ISR systems have designed hardware solutions for easy injection of the chemicals to enable real-time chemical interactions studies. For example, the low volume cell has two injection ports on each end of the cell to enable easy injection of materials (e.g. proteins, enzymes) in the subphase and allow gradual subphase exchange while measuring.

Technical specifications

Measurement Interfacial Shear Rheometer
Dynamic moduli resolution (mN/m)
0.001
Frequency range (rad/s, Hz)
0.01-10, 0.0016-1.6
Strain range
3·10-4-1

Instrument Dimensions

ISR with Langmuir Trough (L×W×H, cm)
90.8×37.0×70.0
ISR with Low Volume Cell (L×W×H, cm)
19.0×37.0×70.0
* Dimensions exclude the pressure sensor Interface Unit: 15.8×20.9×27.3 cm

Low Volume Measurement Cell (Inner Dimensions)

Lower compartment (heavy phase) (L×W×H, cm)
12.0×1.1×0.65 (volume 4.7 mL)
Upper compartment (light phase) (L×W×H, cm)
12.0×1.96×0.6 (volume 13.9 mL)

Instrument Weight

ISR with Langmuir Trough (kg)
35
ISR with Low Volume Cell (kg)
25

System requirements

Minimum system requirements
  • 1 GHz processor
  • 512 MB RAM
  • 40 GB hard disk drive (20 GB free)
  • 1024×768 resolution
  • 3 x USB2 Port
  • RS-232 Port (for water bath option)
Operating system requirements
  • Windows 8 (64 bit)
  • Windows 7 (64 bit)
  • Windows Vista (32 bit)
  • Windows 10

Application examples

Interfacial viscosity of a protein monolayer

Graph 1 illustrates the evolution of the interfacial viscosity of a protein monolayer (lysozyme) residing between water and decane plotted as a function of time. The surface pressure of the layer is also plotted. The change in surface pressure shows the evolution of the adsorption, interfacial viscosity and the crosslinking of the protein as a viscoelastic ‘skin’ develops at the interface as a function of time. The surface pressure data complements the interfacial rheology data.

ISR Low Volume Measurement

In a KSV NIMA ISR Low Volume Measurement Cell, a 20 mg/mL solution of Lysozyme was injected in the subphase and interfacial viscolelastic properties were monitored (single frequency mode, 0.1 Hz) at an air-water interface (AW) and at an oil-water interface (OW). Graph 2 gives the storage and loss moduli obtained during both experiments. The lyzozyme injection was done at time 0s. The adsorption to the AW interface had only a slight effect on the viscoelastic properties. There was no network formation, the adsorption ended to a plateau and the viscosity dominated during the whole experiment. In the OW experiment the interfacial elasticity clearly developed faster than the interfacial viscosity and a gel point was reached after approximately 11,600 s (3.2 hours).

Phase transition in eicosanol

Graph 3 demonstrates the capability to observe a phase transition in eicosanol by measuring changes in the viscoelastic behavior as a function of surface pressure. The purple crosses show the viscous modulus (surface loss, G’’) that reaches a maximum value at a surface pressure of 5mN/m while nothing is visible on the surface pressure isotherm. The blue crosses show the elastic modulus (surface storage, G’). Both G’ and G’’reach a constant value when the surface pressure reaches approximately 15 mN/m. The value corresponds to a phase transition in the packing of the eicosanol monolayer from tilted liquid to a non-tilted liquid phase. After the phase transition value is reached the film retains some viscous properties while the elasticity is practically zero.