Coplanar waveguide devices: Surveying nanocolloid dynamics

Dutu, Constantin Augustin [UCL] Vlad, Alexandru [UCL] Roda Neve, Cesar [IMEC, Belgium] Avram, Ionel [UCL] Sandu, Georgiana [UCL] Raskin, Jean-Pierre [UCL] Melinte, Sorin [UCL]

We present a novel class of biosensing devices, based on coplanar waveguides fabricated onto thin glass and working in the frequency interval from 40 MHz to 40 GHz. Specifically, polystyrene beads of different diameters were first studied to establish a robust methodology for surveying the sedimentation dynamics of colloidal aqueous solutions. The relative variation of the transmission parameter with respect to water was monitored over the operational frequency range and for a broad interval of concentrations. The careful comparison between the sedimentation dynamics of polystyrene particles in water and in NaCl aqueous solutions was tackled. A decrease in the sedimentation time, consistent with the screening of an electrical charge at the surface of the colloids, was observed for the saline solutions and quantitatively assessed. Considering the observed variation of the transmission parameter with the particles’ size, the technique was further employed to survey the clustering between biotin and streptavidin-coated nanocolloids. Compared to the reference solutions with biotin-modified beads, the sedimentation rate displayed a 50% increase for mixtures containing 9 volumes of biotin and 1 volume of streptavidin-modified beads [4.5 ng/μL of streptavidin] and reached a 400% increase when equal volumes of biotin and streptavidincoated nanobeads were mixed [22.5 ng/μL of streptavidin]. We’ll discuss the integration within lab-on-chip technologies and the exploitation of these devices for enhanced real-time monitoring of target analytes as well as for surveying soft matter self-assembly in various microfluidic environments.