Graphene and Carbon Nanotube Auxetic Rubber Bionic Composites with Negative Variation of the Electrical Resistance and Comparison with Their Nonbionic Counterparts. (21st April 2017)

• Record Type: Journal Article
• Authors: Valentini, Luca; Bittolo Bon, Silvia; Pugno, Nicola M.
• Is Part Of: Advanced functional materials. Volume 27:Number 24(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-04-21
• Subjects: bionic composites -- electrical properties -- graphene -- mechanical properties; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201606526
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : Microorganism metabolic activity can facilitate the formation of cellular material systems that have unusual mechanical and physical properties. In the living world microorganisms are commonly used for preparing porous food by fermentation; here carbon nanotubes, graphene nanoplatelets, and a mix of them are dispersed in liquid silicone rubber with single‐cell fungi of commercial beer yeast. The fermentation of such microorganisms during the gelling of the silicone matrix results in bionic composites with buckled/collapsed cells that infer, as rationalized with an analytical model and excluded in a abiotic experimental comparison, auxetic properties. During stretching it is found that the Poisson's ratio of such composites changes sign, from negative to positive, and the variation of the electrical resistance is negative. In addition to the conductivity increment, a general increment of the stretchability and damage resistance with respect to the composites prepared by abiotic process is observed. Bionic composites, even if in their infancy, can thus be multifunctional and superior to their traditional/abiotic counterparts. Abstract : Isotropic linear elastic materials such as silicone rubber are transformed in materials with auxetic behavior (i.e., negative Poisson's ratio) through microorganism digestion. Additionally, these bionic composites offer negative electrical resistance change under strain with superior toughness even if they are less dense. Through such unexpected multifunctional material properties, superior stretchablity and damage resistance, these composites pave the way for extreme applications.