The patterned silk films generated from the latter protocol are generally 40 μm thick. The pattern depth and number of grooves can be modified by changing the grating used to make the PDMS mold. Film thickness can be controlled by changing the concentration of the silk solution, diluting for thinner films or concentrating for thicker films. In addition, pores can be induced within the silk films by mixing various amounts of poly(ethylene oxide) (PEO) into the aqueous silk solution prior to casting. Once the films have been dried and water annealed, the PEO can be removed by immersion in water overnight. For more information please refer to Jin et al.65.