We present two novel approaches to 2D optical strain sensing in thin polymer foils that allow for mass-production by MEMS production techniques. The sensor principles are based on purely optical methods: the sensitive detection of either wavelength or intensity transfer functions in specifically designed planar waveguide structures. The goal is to develop 2D strain sensor arrays that are easy to integrate in flexible polymer foils and which can be applied to a wide range of measurement applications in research and technology. We discuss the sensor concepts and analyze their performance under optimal conditions.