Micromachining of Transparent Biocompatible Polymers Applied in Medicine Using Bursts of Femtosecond Laser Pulses

Abstract

Biocompatible polymers are used for many different purposes (catheters, artificial heart components, dentistry products, etc.). An important field for biocompatible polymers is the production of vision implants known as intraocular lenses or custom-shape contact lenses. Typically, curved surfaces are manufactured by mechanical means such as milling, turning or lathe cutting. The 2.5 D objects/surfaces can also be manufactured by means of laser micromachining; however, due to the nature of light–matter interaction, it is difficult to produce a surface finish with surface roughness values lower than ~1 µm Ra. Therefore, laser micromachining alone can’t produce the final parts with optical-grade quality. Laser machined surfaces may be polished via mechanical methods; however, the process may take up to several days, which makes the production of implants economically challenging. The aim of this study is the investigation of the polishing capabilities of rough (~1 µm Ra) hydrophilic acrylic surfaces using bursts of femtosecond laser pulses. By changing different laser parameters, it was possible to find a regime where the surface roughness can be minimized to 18 nm Ra, while the polishing of the entire part takes a matter of seconds. The produced surface demonstrates a transparent appearance and the process shows great promise towards commercial fabrication of low surface roughness custom-shape optics.

Review on Experimental and Theoretical Investigations of Ultra-Short Pulsed Laser Ablation of Metals with Burst Pulses

“…A surface roughness of 200 nm was measured for processing with the GHz burst in optimal conditions. It should be mentioned that not only metals but also polymers can be polished applying pulse bursts with an intra-burst delay of 400 ps (corresponding to an intra-burst repetition rate of 2.5 GHz) [ 166 ].…”

High-Contrast Marking of Stainless-Steel Using Bursts of Femtosecond Laser Pulses

“…For example, by creation of a periodic sub-micron surface regions that have absorption in the visible optical range and simultaneously generating a Lambertian scattering surface it is possible to make a metal surface to appear grey. Using a single femtosecond pulse, it is typically not possible to initiate surface melting as ablation is the dominating effect, however, if 2 or more pulses within the burst are used, the melting temperature can be easily reached and controlled melting can be achieved [ 39 ].…”

Fabrication of Microfluidic Tesla Valve Employing Femtosecond Bursts

“…It was shown to be a powerful addition to already highly flexible fs laser processing [ 21 ]. It can increase processing throughput [ 22 ] or the quality of the final structure [ 23 ]. As a result, there is a drive to employ this methodology in as many application fields as possible.…”