The KSV NIMA Surface Potential Sensor (SPOT) is used for determining molecular orientation changes in Langmuir films. Together with the surface pressure sensor included in all KSV NIMA Langmuir and Langmuir-Blodgett Troughs, it gives an in-depth view of the Langmuir monolayer interactions.

Application overview

  • Determining molecular orientation: The SPOT provides information about molecular orientation by observing changes in surface potential and combining the data with surface pressure information.
  • In-depth view of Langmuir layer interactions: Surface pressure isotherm alone is unable to separate the reasons for surface pressure changes. Combined with the SPOT, the data gathered from the layer is doubled, giving an in-depth understanding of the layer.
  • Determining effective dipole moments: The sensor can be used to determine effective dipole moments through simple surface potential measurements of a compressed film.
  • Film electronic structure characterization: Small changes in the electronic structure of molecules can be detected by measuring the change in surface potential.
  • Molecular structure characterization: Quantify the effects of changes to molecular structure through positional offsets and peak values of the surface potential plots.
  • Complex formation monitoring: Observe and follow complex formations between monolayers, sub-phase species or adsorbates.

Features & benefits

  • Double the amount of data – all in one software: The KSV NIMA Surface Potential Sensor is operated with KSV NIMA LB Software and does not require any additional software. Both the surface pressure and surface potential are automatically plotted in the same graph for simple comparison.
  • Accurate and reproducible measurements: The non-contact and non-destructive vibrating plate capacitor method ensures excellent accuracy and reproducibility.
  • Easy set up: The KSV NIMA Surface Potential Sensor connects directly to the KSV NIMA Interface Unit used with KSV NIMA L and LB Troughs. It is easily installed with a simple plug-and-play operation. The sensor has a flexible stand allowing rapid and easy integration with a trough. Furthermore, the sensor is factory calibrated for a quick start-up

Product details

The KSV NIMA Surface Potential Sensor measures the potential difference above and below the film and is sensitive to the sum of all the individual dipole moments. The changes in surface potential are measured by detecting the potential difference between the vibrating plate, which is placed above the monolayer, and the counter electrode, which is immersed in the sub-phase below the monolayer.

The sensor allows complementing data from surface pressure—area isotherm measurements obtained from a Langmuir and Langmuir-Blodgett Trough. It allows the determination of monolayer composition, molecular orientation, degree of molecular dissociation and molecular interactions at the interface.


The KSV NIMA Surface Potential Sensor is recommended for use with a KSV NIMA Langmuir, Langmuir-Blodgett or  Microscopy Trough to enable combined surface pressure and surface potential measurements. The SPOT can also be used with other troughs together with a KSV NIMA Interface Unit.

Application Examples

The interaction of an antiparasitic peptide with cell membrane models

In drug discovery the permeation of the drug into cells through cell walls and the reaction of the drug within the cell membrane are important factors for drug efficiency. In this example, a drug candidate for the Human African Sleeping Sickness (HAT) was studied in vitro in a model cell membrane.

The oligopeptide-based drug S-(2,4-dinitrophenyl) glutathione di-2-propyl ester, has shown activity in the treatment of HAT and was studied in Langmuir monolayer model membrane of DPPC (dipalmitoyl phosphorylcholine), an abundant lipid in the protozoan membrane. The monolayer properties of the drug itself and its interactions with DPPC monolayers were studied with Langmuir equipment with a surface potential meter and polarization modulation surface infrared reflection absorption spectrometer. 

Surface pressure-area and surface potential-area isotherms of a HAT-drug monolayer at air-buffer interface.

For more information see Resources tab.

Application Note  — Interactions of Biomolecules in Cell Membrane Models


  1. Pascholati et al., ‘Colloids and Surfaces B: Biointerfaces’ 74 (2009) 504–510
  2. Kim et al., ‘J of American Chemical Society’ (2010), 132, pp. 8180-8186