We consider the sharp interface limit of the Allen-Cahn equation, when a parameter epsilon > 0 that is proportional to the thickness of the di use interface tends to zero, in a two dimensional bounded domain with Neumann boundary conditions. We prove convergence of the solutions of the Allen-Cahn equation to solutions of the sharp interface limit, which is the mean curvature ow with a 90 degree contact angle, provided the limit problem possesses a smooth solution on a certain time interval. To this end we construct a suitable approximation of the Allen-Cahn equation, using three levels of the terms in the formally matched asymptotic calculations, and estimate the dierence with the aid of a suitable spectral estimates of the linearized Allen-Cahn operator. Moreover, we will discuss recent extensions of this results e.g. to the Navier-Stokes/Allen-Cahn system or the Stokes/Cahn-Hilliard system. This is a joint-work with Maximilian Moser.