Rapid Prototype Fabrication of Smooth Microreactor Channel Systems in PMMA by VUV Laser Ablation at 157 NM for Applications in Genome Analysis and Biotechnology

Abstract

A rapid prototyping method for the fabrication of microstructures in polymer substrates has been developed, using a combination of laser direct-write patterning of silicon membrane contact masks and vacuum-ultraviolet (VUV) pulsed laser ablation. The process allows the flexible and rapid prototyping of microreactors and microchannel systems with submicrometer resolution. Thanks to the high photon energy of the VUV (7.9 eV) irradiation, PMMA and also other polymers can be ablated without leaving behind carbonated and/or fluorescent surfaces. Fluences of ≅ 100 mJ/cm2 lead to etch rates of ≅ 140 nm/pulse and result in very smooth surfaces with a roughness in the nanometer range on a micrometer lateral scale. The structured substrates are sealed with a PMMA foil by means of a newly developed low temperature technique without adhesives.

Chemical and Spectroscopic Aspects of Polymer Ablation: Special Features and Novel Directions

“…Atomic force microscope images of the ablated areas yielded surface roughnesses R a < 10 nm for single and multiple pulses. Stuke et al has used 157 nm radiation to form a variety of microstructures (e.g., fluidic microchannel systems for genomic analysis) in PMMA, PC, and PS using a silicone membrane contact mask . More complicated structures, including 6-μm high micro-mesas, were constructed by applying a water-based, microdroplet masking fluid into which air bubbles were injected …”

Interaction of Photons with Polymers: From Surface Modification to Ablation

“…Various other studies supported a dominating photochemical mechanism 5,109. F 2 excimer laser irradiation was applied to create a variety of complex microstructures in PMMA, PC and polystyrene (PS) using a silicone membrane contact mask110 or microdroplets 111…”

Correction of a coherent image during KrF excimer laser ablation using a mask projection

“…The laser fabrication technique is a clean, safe, and convenient process for manufacturing MEMS devices in comparison with other technologies, such as chemical etching, deposition process, and lithography [1]. In particular, the advantage of the excimer laser application is that its non-thermal effects make it suitable for machining plastic, glass, and ceramic crystal [2].…”