The molecularly thin layer of water in direct contact with biomembranes in a physiological environment plays a major role in determining their properties and, in turn, their biological functions. In this context, water is a shorthand notation for “water electrolyte solution”, since almost without exception a variety of ions dissolved in water are needed to ensure the stability of biomembranes. In recent years, the development of compounds of the so-called room-temperature ionic liquid (RTIL) family has enormously expanded the number of ionic systems that could be used to modify the properties of the interfacial water, and thus to affect the behaviour of bio-systems. My study concerns the microscopic mechanisms underlying RTIL effects on biomembranes and their hydration water - and on biosystems generally speaking - and relies on the combination of neutron scattering, molecular dynamics (MD) simulations, and complementary techniques as atomic force microscopy, Raman scattering, and infrared spectroscopy. In my contribution I will briefly review the state of the art in this topic . Then I will show how RTILs diffuse into the hydrophobic portion of lipid biomembranes, enhancing the penetration of water into the bilayer [2,3], slowing down the lipid diffusion, and modifying their elastic properties . Implications in bio-medicine, sensing technology, and material science will be presented.
 Benedetto, A., and Ballone, P. ACS Sust. Chem. Eng. 2016, 4, 392.
 Benedetto, A., Heinrich, F., Gonzalez, M.A., Fragneto, G., Watkins, E., and Ballone, T. J. Phys. Chem. B 2014, 118, 12192.
 Benedetto, A., Bingham, R.J., and Ballone, P. J. Chem. Phys. 2015, 142, 124706.
 Benedetto, A., et al., under preparation.