Thin films of controlled elastic modulus Were made by photo-cross-linking artificial extracellular matrix (aECM) proteins containing the photosensitive amino acid p-azidophenylalanine (pN(3)Phe). The elastic moduli of the films were calculated from nanoindentation data collected by atomic force microscopy (AFM) using a thin-film Hertz model. The modulus was shown to be tunable in the range 0.3- 1.0 MPa either by controlling the irradiation time or by varying the level of pN3Phe in the protein. Tensile measurements on bulk films of the same proteins and finite-element simulation of the indentation process agreed with the thin-film modulus measurements from AFM. Substrates characterized by spatial variation in elastic modulus were created by local control of the irradiation time.