Apparatus for Surface Lipid Film Studies

Since Langmuir reported monolayer studies, a great many instruments (commercial) have been designed about this method. The clean surface of water shows no change in surface tension if one moves a barrier across it. However, if a surface-active agent is present, then the latter molecules will be compressed, and this will give rise to a decrease in snrface tension. 

Monolayer systems are composed of only a monomolecnlar lipid film on water surface. The aim in these systems is to study the properties of a monomolecnlar thin lipid film spread on the surface of water, which is not possible by any other techniqne. Lately, it has been shown that such lipid films are useful membrane models for biological membranes strnctnre and function studies. The modem methods have allowed one to measure the monolayer properties in mnch detail than earlier. No other method exists through which one can obtain any direct information about the molecular packing or interactions (forces acting in two dimensions). 

The film balance (also called Langmuir trough) consists of a teflon (or teflon lined) rectangular trough (typically 20 cm x 10 cm x 1 cm). Teflon poly(tetraflouroethylene) (PTFE) allows one to keep the apparatus clean. A barrier of teflon is placed on one end of the trough, which is used as a barrier to compress the lipid molecules. Currently, there are many commercially available film balances. 

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