Systematic study of the roughness of biodegradable polymer surfaces processed by ultrashort laser pulses

Abstract

Polymer-based materials are increasingly common in medical fields, ranging from simple disposable products to complex implants. Polymers have a large variety of physical and chemical properties, fit for use in different medical applications; in particular, biodegradable polymers are interesting for the use as temporary implants - for example in the case of stents, where, after the support phase of a hollow organ the stent can be decomposed by the human body. Roughness of the polymer surfaces is an important parameter for applications. For example, it influences strongly the clinical outcome of stents treatments [1]; as another example, an appropriate surface quality provides a good breeding ground for cell growth [2]. Therefore, precise control over this parameter is desirable. Surface roughness achieved using ultrashort-pulse laser machining depends on processing conditions. The goal of this paper is a systematic investigation of the surface roughness of laser-ablated surfaces as a function of laser processing parameters. To this purpose we machined an array of squares on a sheet of poly(Lactic acid) (PLA) using laser pulses of 350 fs duration at the wavelength of 518 nm. We varied systematically across the array the pulse-to-pulse translation distance, the repetition frequency and the fluence of the laser pulses. We measured the topography of the machined surfaces with a scanning confocal microscope; from the measured surface topography we calculated the standard roughness parameters (arithmetic average) and (root mean square average) [3], obtaining in this way a map of roughness as a function of processing parameters. This map can be used to select appropriate processing parameters for machining surfaces with desired roughness characteristics.Polymer-based materials are increasingly common in medical fields, ranging from simple disposable products to complex implants. Polymers have a large variety of physical and chemical properties, fit for use in different medical applications; in particular, biodegradable polymers are interesting for the use as temporary implants - for example in the case of stents, where, after the support phase of a hollow organ the stent can be decomposed by the human body. Roughness of the polymer surfaces is an important parameter for applications. For example, it influences strongly the clinical outcome of stents treatments [1]; as another example, an appropriate surface quality provides a good breeding ground for cell growth [2]. Therefore, precise control over this parameter is desirable. Surface roughness achieved using ultrashort-pulse laser machining depends on processing conditions. The goal of this paper is a systematic investigation of the surface roughness of laser-ablated surfaces as a function of laser proc...