Microstructured Biomaterials with a Tunable Negative Poisson’s Ratio

The elastic properties of a biomaterial tissue scaffold reflect its ability to handle external loading conditions and must be tailored to match the attributes of the native tissue that it aims to repair. A scaffold’s elastic modulus and Poisson’s ratio describe how it supports and transmits external stresses to the host tissue site. (The Poisson ratio is positive/negative when the material contracts/expands transversally with axial expansion; “auxetic” materials are materials that exhibit negative Poisson ratio.) While the elastic modulus is tunable in scaffolds, the Poisson’s ratio of virtually every porous tissue construct is positive. There have been no reports of solid-phase micro-cellular biomaterials synthesized with a precisely-tuned negative Poisson’s ratio. Others have formed auxetic polyurethane foams by compressing the foams and annealing them while compressed; however, the annealing process renders little practical control over the cellular microstructure comprising the foams, making it very difficult to tune the strain-dependent behavior of Poisson’s ratio. Additionally, the foams have little to no use in biological applications involving the interactions between biomaterials and living tissue (e.g., tissue engineering applications) and other biological applications. University of California, San Diego Office of Innovation and Commercialization licensing@ucsd.edu 858.534.5815