Mechanical BioMEMS Technologies for Advanced Label-free Sensing of Biomolecular Species in Microfluidic Channels

The aim of this PhD project is to investigate alternative sensing methodologies that can possibly improve the sensing performances of lab-on-chip (LOC) designed for biochemical applications. Suspended microchannel resonator (SMR) for bio-mechanical sensing applications have become very popular as detection of weigths of chemicals integrated in LOC. They exploit laser doppler vibrometry (LDV) for dynamic mode detection. In this thesis two different SMRs designs have been investigated, involving either technological challenges - the use of polymers as material and processing techniques based on laser micromachining - and different sensing phenomena - the use of the parametric resonance rather than the standard harmonic resonance response. The flexibility of two-photon direct laser writing is exploited to optimize a highly- versatile fabrication strategy based on a shell-writing procedure with the aim to reduce fabrication time of big inlet/outlet sections compatible with most microfluidic systems for LOCs. With respect to standard microfabrication techniques, requiring several technological steps to obtain suspended hollow structures, this method allows to fabricate complex SMR sensors in only one fabrication step, by virtue of its intrinsically three- dimensional nature. A SMR fixed-fixed beam has been fabricated and characterized by LDV. A different sensing mechanism based on the parametric resonance instead of the harmonic resonance has been investigated to develop a novel platform for the characterization of biomolecules in free-flow with unique specificity, sensitivity, and speed: to this purpose a PDMS based device was realized by laser machining, a rapid prototype fabrication technique; beside to it, a commercial fused silica capillary tubing was also employed in the realization of a prototype for this sensing mechanism, and both solutions were tested through LD