A Parametric Study on Selective Ultrasonic Foaming of Porous Polymer for Biomedical Applications

A selective ultrasonic foaming (SUF) process was developed to fabricate porous polymer for biomedical applications. The method employs a high intensity focused ultrasound (HIFU) transducer to selectively heat and implode gas-impregnated polymers. This acoustic method is solvent-free and capable of creating interconnected pores that have various topographical features at different length scales. In this paper, we investigate the effects of major process parameters of the SUF process, including the ultrasound power, scanning speed, and the specimen gas concentration. The pore size and interconnectivity of the porous structure were analyzed. The microstructures were characterized using the scanning electron microscopy (SEM) and a dye penetration test. It was found that the scanning speed of the ultrasound had a significant effect on the pore size control, and that low gas concentration was a necessary condition for interconnected porous structures.