Introduction

Negative Poisson Ratio or "auxetic" Materials (Materials which expand in the y direction when pulled in the x direction) gain their properties from structure rather than composition[4].  Auxetic structures can be manufactured a number of ways at a variety of scales [1],[2]. Since the goal here was to provide a classroom demonstration, the material's cell design was manufactured with a relatively large feature size using a Laser Cutter[3]. However, the approach can be used to create structures at a resolution of 600 dpi given the described manufacturing technology.  A 2011 blog post [5] mentions an article on both applications [6] and synthetic origins [7] of auxetic materials.  CMU reports on a design tool used to make things like shoes from auxetic materials [8].

Bibliography

  1. "Making and characterizing negative Poisson's ratio materials" R. S. LAKES and R. WITT, International Journal of Mechanical Engineering Education Vol 30 No 1 August 2000 - pdf
  2. "Making Negative Poisson's Ratio Microstructures by Soft Lithography" Bing Xu, Francisco Arias, Scott T. Brittain, Xiao-Mei Zhao, Bartosz Grzybowski, Salvatore Torquato, and George M. Whitesides, Adv. Mater. 1999, 11, No. 14 - pdf
  3. LASER SERIES: Laser Cutting and Etching Safety and Basic Use - techshop - pdf
  4. imechanica.org Journal Club April 2010: Negative Poisson's ratio materials - html
  5. Gaddeswarup's blog "Stretching without wrinkles" Wednesday, September 28, 2011 - html
  6. "Stretch, but without the wrinkles" by Marianne Freiberger - html
  7. "Foam structures with a negative Poisson's ratio" - html
  8. Computational Design Tool Transforms Flat Materials Into 3D Shapes - html