Integration of excimer laser micromachining in a biomedical sensor microfabrication process

In the frame of the Interreg IV project “MICROBIOMED”, the Centre Spatial de Liège (CSL) participated to the development of an original concept of plasmonic-related instrumentation platform dedicated to diagnostic biosensing tests out of the laboratory. The developed instrumental platform includes both disposable one-use microfluidic affinity biochip and compact optical readout device for biochip monitoring involving mobile Internet devices for data processing and communication. The biochip includes both microfluidic and optical coupling structures formed into a single plastic slab (see Fig. 1). The microfluidic path of the biochip operates in passive capillary pumping mode. The optical detection part involves Surface Plasmon Resonance phenomenon. An essential advantage of the developed biochip is that its implementation involves conventional hot embossing and thin film deposition process, perfectly suited for mass production of low-cost microfluidic biochip for biochemical applications. In this presentation we focus on the fabrication of the fluidic channels and capillary structures with a commercial excimer laser mask projection system working at 193 nm. Micro-pillars of 25μm width for the capillary pump as in Fig. 1 have been ablated in the PMMA master slab used for the replication chain of the biochip prototype. By simply changing the pattern on the motorized mask, micro-pillars from 10µm to 50 µm diameter have been also machined successfully in PMMA and even glass. The mask is made of a structured metallic thin layer deposited on a quartz substrate and prepared at CSL by direct writing laser technique. The excimer laser mask projection technique allows ablating several tens of µpillars per second in the field of view of the laser beam. The entire micro-pillars area of the biochip master is then performed by a simple step and repeat laser process. The topography and dimensions of the µstructures have been measured by SEM and interferometric optical profilometry. The dynamic hydrophilic behavior of a liquid drop on the micro-pillars structure has been monitored with the camera of a contact angle instrument.