Toward the Fabrication of Hierarchically-Structured Porous Polymers for Tissue Engineering Scaffords

Hierarchically-structured porous polymers play an important role in scaffold-based tissue engineering. However, the fabrication of these polymers presents a significant challenge because of the requirements of controllable pore size, distribution and interconnectivity. In this work, we report on a novel porous polymer fabrication method using high-intensity focused ultrasound (HIFU). The measurements of both spatial and temporal temperature field are reported for biocompatible PMMA (polymethyl methacrylate) samples insonated with a 1.1 MHz/3.3 MHz HIFU transducer. The acoustic power and insonation duration were both varied. The results have shown that HIFU has a dramatic heating effect on polymers: the temperature increasing rate can exceed 20°C/second and the final temperature can be higher than 120°C. This rapid, localized heating effect is exploited to foam CO2 saturated PMMA samples selectively and generate hierarchical microstructures. The created microstructures were characterized using the scanning electron microscopy (SEM). The results have shown that the amount and rate of acoustic energy dissipation during the HIFU insonation directly affect the polymer foaming process. Preliminary theoretical modeling of the acoustic field and heat transfer behavior in the porous polymers are also presented.Copyright © 2005 by ASME