Carbon Nanotube Reinforced Spider Silk –A Model for the Next Generation of Super Strong and Tough Fibers

摘要

In the never ending search for strong and tough materials we often look to nature forrninspiration. Spider silk, with strength as high as 4 Gpa at a breaking elongation of overrn35%, has long been recognized as the ultimate model of strong and tough material. Howrnever, the practical use of spider silk has eluted us because of the difficulty in domes icingrnspiders.rnThree recent developments have significant implications to addressing the need for strongrnand tough materials. Recent progress in biotechnology, notably by Nexia Biotechnologiesrnthrough transgenic synthesis of spider silk polymer has made large scale manufacturingrnof spider silk a real possibility. In this process, recombinant spider silk, BIOSTEEL BIOSTEELR inrnBELE BELER (Breed Early Lactate Early) goat system were produced in combination withrnpronuclear microinjection and nuclear transfer technologies resulting in a scalablernmanufacturing process for spider silk. While the biotechnology pathway to large scalernmanufacturing of spider silk is promising, the strength of the synthetic silk is far fromrnsatisfactory in spite of it's high level of elongation at break. Another development is thernavailability of carbon nanotube technology. With a Young's modulus of 1 Tpa and arnstrength of 30-60 Gpa at elongation at break ranging from 6-30%, carbon nanotubern(CNT) is an ideal reinforcing material to strengthen the synthetic spider silk. Tornmaximize the reinforcement effect of the CNT the electrospinning process, another recentrndevelopment, has been demonstrated to be an effective means to align carbon nanotube inrna polymer fibril matrix. This simple, non-mechanical fiber spinning process is capable ofrncreating nanoscale fibers in a continuous manner.rnIn this paper, we present recent research activities in our laboratory by combining thesernnew technologies to demonstrate the feasibility of producing super strong and toughrnfibers. Specifically, single walled carbon nanotubes (SWNT) were successfully dispersedrnin transgenic spider silk with various combinations of silk proteins to form spinning dopernfor electrospinning. Nanofibers as small as 10 nm were co-electrospun to form alignedrnand random nanofiber assemblies. Initial tensile testing of the aligned silk compositernshowed a 10X increase in modulus, 5X increase in strength and 3 fold increase inrntoughness with only 1 weight % of SWNT in MaSp1 silk matrix. This early encouragingrnresults has significant implications not only for a broad range of applications includingrntissue engineering scaffolds and ballistic armors but also demonstrating a promisingrnpathway to connect nano tube properties to macro-scale performance.