Knowledge of the mechanical properties of electrospun fibers is Important for their successful application in tissue engineering, material composites, filtration and drug delivery In particular, electrospun collagen has great potential for biomedical applications due to its biocompatibility and promotion of cell growth and adhesion. Using a combined atomic force microscopy (AFM)/optical microscopy technique, the single fiber mechanical properties of dry, electrospun collagen type I were determined. The fibers were electrospun from a 80 mg ml(-1) collagen solution in 1,1,1,3,3,3-hexafluro-2-propanol and collected on a striated surface suitable for lateral force manipulation by AFM The small strain modulus, calculated from three-point bending analysis, was 2.82 GPa. The modulus showed significant softening as the strain increased. The average extensibility of the fibers was 33% of their initial length, and the average maximum stress (rupture stress) was 25 MPa The fibers displayed significant energy loss and permanent deformations above 2% strain (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved.