title: Greatly increased toughness of infiltrated spider silk.
abstract: In nature, tiny amounts of inorganic impurities, such as metals, are incorporated in the protein structures of some biomaterials and lead to unusual mechanical properties of those materials. A desire to produce these biomimicking new materials has stimulated materials scientists, and diverse approaches have been attempted. In contrast, research to improve the mechanical properties of biomaterials themselves by direct metal incorporation into inner protein structures has rarely been tried because of the difficulty of developing a method that can infiltrate metals into biomaterials, resulting in a metal-incorporated protein matrix. We demonstrated that metals can be intentionally infiltrated into inner protein structures of biomaterials through multiple pulsed vapor-phase infiltration performed with equipment conventionally used for atomic layer deposition (ALD). We infiltrated zinc (Zn), titanium (Ti), or aluminum (Al), combined with water from corresponding ALD precursors, into spider dragline silks and observed greatly improved toughness of the resulting silks. The presence of the infiltrated metals such as Al or Ti was verified by energy-dispersive x-ray (EDX) and nuclear magnetic resonance spectra measured inside the treated silks. This result of enhanced toughness of spider silk could potentially serve as a model for a more general approach to enhance the strength and toughness of other biomaterials.
authors.affiliation: Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany. smlee@mpi-halle.de
authors.forename: Seung-Mo
authors.initials: SM
authors.lastname: Lee
authors.forename: Eckhard
authors.initials: E
authors.lastname: Pippel
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gösele
authors.forename: Christian
authors.initials: C
authors.lastname: Dresbach
authors.forename: Yong
authors.initials: Y
authors.lastname: Qin
authors.forename: C Vinod
authors.initials: CV
authors.lastname: Chandran
authors.forename: Thomas
authors.initials: T
authors.lastname: Bräuniger
authors.forename: Gerd
authors.initials: G
authors.lastname: Hause
authors.forename: Mato
authors.initials: M
authors.lastname: Knez
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D000818:Animals; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D008422:Materials Testing; D047011:Silk / Q000737:chemistry* / Q000648:ultrastructure; D013112:Spiders; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D047011:Silk; D014867:Water; D000535:Aluminum; D014025:Titanium; D015032:Zinc