Because of the rapid decay in the enhancement penetration depth, the solvent absorption is minimized. This allows for direct study of specific regions in the membrane with the resolved intrinsic vibrational probes in the lipid membrane. SEIRAS is useful for studying interfacial properties, such as water structure near a supported lipid bilayer (95-97), with very low penetration depth into the bulk. Lipid membranes have large potentials because of concentration or pH gradients, and SEIRAS enables studying the effects of fields and potentials in biological systems using vibrational probes to measure the local electrostatic environments. Additionally, SEIRAS provides the ability to rapidly change sample conditions such as pH or ion concentrations and the ability to measure kinetics on the timescale of seconds to hours (98). In typical SEIRAS measurements, a lipid vesicle solution is prepared and deposited on the metal surface. A spacer of adsorbed molecules can be used to form "floating" lipid bilayers , mitigating any effects from the metal surface on the membrane properties. The vesicles rupture and self-assemble as an ordered monolayer on the surface, eventually forming a bilayer .