UV Laser Machined Polymer Substrates for the Development of Microdiagnostic Systems

TLDR

Liquid‑handling capability is essential for micro‑total analysis systems and chemical diagnostics, motivating the development of new fabrication methods. This study reports a UV laser photoablation technique to fabricate miniaturized liquid‑handling systems on polymer substrate chips. Using 200‑mJ UV excimer laser pulses in computer‑controlled patterns, the authors ablate channels and reservoirs on polystyrene, polycarbonate, cellulose acetate, and PET, then seal them with low‑cost film lamination. The resulting high‑aspect‑ratio, hydrophilic, and rough channels enable electroosmotic flow that scales with electric field, pH, and ionic strength, while protein coatings markedly reduce this flow.

Abstract

This report describes a UV laser photoablation method for the production of miniaturized liquid-handling systems on polymer substrate chips. The fabrication of fluid channel and reservoir networks is accomplished by firing 200 mJ pulses from an UV excimer laser at substrates moving in predefined computer-controlled patterns. This method was used for producing channels in polystyrene, polycarbonate, cellulose acetate, and poly(ethylene terephthalate). Efficient sealing of the resulting photoablated polymer channels was accomplished using a low-cost film lamination technique. After fabrication, the ablated structures were observed to be well defined, i.e., possessing high aspect ratios, as seen by light, scanning electron, and atomic force microscopy. Relative to the original polymer samples, photoablated surfaces showed an increase in their hydrophilicity and rugosity as a group, yet differences were noted between the polymers studied. These surface characteristics demonstrate the capability of generating electroosmotic flow in the cathodic direction, which is characterized here as a function of applied electric field, pH, and ionic strength of common electrophoretic buffer systems. These results show a correlation between the ablative changes in surface conditions and the resulting electroosmotic flow. The effect of protein coatings on ablated surfaces is also demonstrated to significantly dampen the electroosmotic flow for all polymers. All of these results are discussed in terms of developing liquid-handling capability, which is an essential part of many μ-TAS and chemical diagnostic systems.