Nanoscale three-point bend test of a single polymeric nanofiber

Abstract

Biodegradable polymers in the form of highly porous nanofibrous scaffolds are ideal for tissue engineering because they contain nanoscale fibers that can simulate those found in extracellular matrix. However, because of their size, the structural integrity of the scaffolds may be compromised and needs to be examined. To do this, individual nanofibers are mechanically characterized so that accurate mechanical properties of these nanofibrous scaffolds can be evaluated. To date, little is done in this area due to extreme difficulty in manipulating ultrafine fibers and measuring the small forces and deformations induced. To overcome this, the atomic force microscope (AFM) which is capable of probing forces and displacements at the nanoscale, is used for investigating the structural and mechanical properties of single strand nanofibers. A poly L-lactic acid (PLLA) nanofibrous scaffold is first fabricated from polymer solution using the phase separation method. The surface structure and elastic properties of individual nanofibers are investigated. The elastic modulus is obtained by performing a three-point bend test on a portion of nanofiber suspended over a microscale groove using an AFM tip. The elastic modulus is found to be 1.0±0.2GPa for fibers less than 350nm but decreases with increase in fiber diameter in excess of 350nm. This is due to the effect of shear deformation which becomes more significant as length to diameter ratio decreases. © 2004 Materials Research Society.