title: Utilizing a high fundamental frequency quartz crystal resonator as a biosensor in a digital microfluidic platform.
abstract: We demonstrate the operation of a digital microfluidic lab-on-a-chip system utilizing Electro Wetting on Dielectrics (EWOD) as the actuation principle and a High Fundamental Frequency (HFF; 50 MHz) quartz crystal microbalance (QCM) resonator as a mass-sensitive sensor. In a first experiment we have tested the reversible formation of a phosphor-lipid monolayer of phospholipid vesicles out of an aqueous buffer suspension onto a bio-functionalized integrated QCM sensor. A binding of bio-molecules results in an altered mass load of the resonant sensor and a shift of the resonance frequency can be measured. In the second part of the experiment, the formation of a protein multilayer composed of the biomolecule streptavidin and biotinylated immunoglobulin G was monitored. Additionally, the macroscopic contact angle was optically measured in order to verify the bio-specific binding and to test the implications onto the balance of the surface tensions. Using these sample applications, we were able to demonstrate and to verify the feasibility of integrating a mass-sensitive QCM sensor into a digital microfluidic chip.
authors.affiliation: Institute for Microelectronics and Microsensors, Johannes Kepler University, Linz, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lederer
authors.forename: Brigitte P
authors.initials: BP
authors.lastname: Stehrer
authors.forename: Siegfried
authors.initials: S
authors.lastname: Bauer
authors.forename: Bernhard
authors.initials: B
authors.lastname: Jakoby
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hilber