Preparing Langmuir-Blodgett layers or lipid multilayers for neutron reflectometry experiments

D17 is neutron reflectometer designed to be as flexible as possible offering a wide range of resolutions and several modes of operation. The large multidetector allows both specular and off-specular reflectivity to be measured sumultaneously. The instrument is suitable for studying surface structures on solids and solid/liquid interfaces.
One of its main application is the study of biological membranes and especially the cell wall.

The cell wall is a phospho-lipid bi-layer which incorporates active proteins. This formidably complex system is essential for life because it provides the a local environment for the cell constituents; the membrane offers protection from external aggression by filtering through useful molecules and rejecting waste.
Neutrons are particularly prized for the study of biological membranes since these consist of hydrogenated materials in a watery medium. Neutron reflectivity profiles are extremely sensitive to selectively exchanging hydrogen with deuterium in specific molecules. The study of the cell membrane generally amounts to the study of simple model systems (Langmuir-Blodgett layers or lipid multilayers). In addition, research on biological membranes ranges from bio-sensors to drug-targeting.

The movie below shows how samples of model biological membranes suitable for neutron experiments are prepared.

Ref. Stacks of model membranes in control humidity:
  T. Salditt, C. Münster, U. Mennicke, C. Ollinger, G. Fragneto (2003) Langmuir, 19, 7703-7711.
Ref. Fluid floatting bilayers:
  G. Fragneto, T. Charitat, F. Graner, K. Mecke, L. Perino-Gallice, E. Bellet-Amalric (2001) Europhys. Lett., 53, 100-106.