Mean first-passage time of surface-mediated diffusion in spherical   domains
  We present an exact calculation of the mean first-passage time to a target on the surface of a 2D or 3D spherical domain, for a molecule alternating phases of surface diffusion on the domain boundary and phases of bulk diffusion. The presented approach is based on an integral equation which can be solved analytically. Numerically validated approximation schemes, which provide more tractable expressions of the mean first-passage time are also proposed. In the framework of this minimal model of surface-mediated reactions, we show analytically that the mean reaction time can be minimized as a function of the desorption rate from the surface. 
O. B\'enichou, D. S. Grebenkov, P. E. Levitz, C. Loverdo and R.   Voituriez
cond-mat.stat-mech