Weak compared to covalent bonds and to electrical-charge interactions, charge-fluctuation or van der Waals forces are not usually appreciated for the work they do among membranes and macromolecules. The dominant force that coheres membranes and proteins, source of the powerful surface tension at membrane interfaces, van der Waals forces are again the dominant -- perhaps sole -- attraction that creates membrane multilayers or allows membranes to adhere to artificial surfaces.  van der Waals interactions that are derived from the s.c. Casimir effect are due to fluctuations of electromagnetic field between macroscopic bodies and are in many respects similar to depletion interactions, where the depletion refers to electromagnetic field modes between macroscopic surfaces.

This past year has been a festival of learning to formulate, to measure, and to modify these neglected interactions. The key has been to begin with the elements of physical theory and to relate the polarizability of materials to the fluctuations of charges within them. From this we have been able to design experiments that show how macromolecular organization responds to deliberate changes in solution properties.

	We have been able to see how adding even the simplest salts to water around lipid bilayers will change how these membranes assemble into multilayers. For example, we have seen how the attraction between membranes varies when salts of different ions chloride vs. bromide are dissolved in the intervening water.
	We have reformulated the theory of van der Waals forces in multilamellar systems and have extracted reliable Hamaker coefficients that explicitly depend on the number of multilayers. This allowed us to solve some unsolved problems in the theory of vdW forces. R.Podgornik, P.L. Hansen and V.A. Parsegian, On a reformulation of the theory of Lifshitz - van der Waals interactions in multilayered systems, J. Chem. Phys. 119 (2003) 1070-1077. R.Podgornik and V.A. Parsegian, van der Waals interactions across stratified media, J. Chem. Phys. Volume 120, Issue 7 (2004) pp. 3401-3405.
	One unexpected by-product has been a collaboration with engineers using our equations to design production procedures for thin-film resistors in computer chips.  We expect the collaboration to work to our benefit by providing us with experimental data that are used to compute van der Waals forces.
	Another unexpected result relates to what was known about the friction between an ion and the water through which it moves. Just as there is a charge-water interaction that creates a drag, there is a charge-fluctuation source of drag on a moving particle. V.M. Mkrtchian, V.A. Parsegian, R.Podgornik, W.M. Saslow, Universal Therma Radiation Drag on Neutral Objects, Physical Review Letters 28 November 2003 Phys. Rev. Lett. 91, 220801 (2003).

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