Surface microarchitectural design in biomedical applications: preparation of microporous polymer surfaces by an excimer laser ablation technique.

In this report we demonstrate a microprocessing method to prepare microporous polymer films by an excimer laser ablation technique, which may enable the fabrication of functional biomedical devices such as advanced artificial organs. The irradiation of a KrF excimer laser pulses (wave-length 248 nm; fluence 1 J/cm2 pulse) onto several polymer films was achieved by passing a laser pulse through an optical microscope, resulting in the formation of an etched pit on the irradiated surface due to ablative photodecomposition. The number of pulses and the micropositioning of the irradiation were precisely controlled by a computer-aided control unit. Minimal ablation was observed for polyethylene with very small absorption coefficient (alpha) at 248 nm. For polymers which absorbed the laser photons, the etch depth increased linearly with number of pulses. The etch depth per pulse decreased with an increase in alpha values. An excellent structural quality, with micron-order precision of an etched pit, was found for those polymers with larger alpha values, such as polyimide, segmented polyurethane, and polycarbonate.