Adhesion of Membranes: A Theoretical Perspective

We theoretically study (i) a large membrane segment and (ii) a closed membrane surface or vesicle that adhere to another surface. The membrane segment can undergo unbinding transitions as a result of thermally excited shape fluctuations. These transitions are studied by renormalization group methods and by Monte Carlo simulations. The shape of a bound vesicle is determined by the interplay of bending and adhesion energies. This interplay leads to adhesion transitions from a free to a bound vesicle state even in the absence of shape fluctuations. Our theory helps to clarify the notion of a contact angle for membranes.