Single and double phosphocholine (DPPC and DSPC) bilayers adsorbed at the s
ilicon-water interface have been prepared and characterised. The second bil
ayer, called "free bilayer", is a novel highly hydrated system floating at
20 to 30 Angstrom above the first one. Robust and reproducible preparation
has been possible thanks to a combination of Langmuir-Blodgett and Langmuir
-Schaeffer techniques. Carefully optimised neutron reflectivity measurement
s have allowed a precise non-destructive characterisation of the structure,
hydration and roughness of the layers. This work opens new possibilities f
or the investigation of the interaction between membrane lipids and soluble
proteins, in particular peptides too small to be Visible with other techni
ques.