Quartz Crystal Microbalance with Integrated Surface Plasmon Grating Coupler

We have integrated a surface plasmon grating coupler into a quartz crystal microbalance (QCM) for studying surface association/dissociation reactions. In the integrated system only QCM measurement is needed to record both the optical and the acoustic signals in the same association/dissociation reaction. This integration considerably simplifies a conventional combination instrument of a grating-coupled surface plasmon resonance (SPR) spectrometer and a quartz crystal microbalance by eliminating a number of SPR components. Moreover, in the integrated system detection of the light reflections is not needed by which one bypasses the interference problem caused by two coherent light reflections off the glass window used to seal the fluid sample and off the sensor surface. The utility of the integrated system is demonstrated using a layer-by-layer polyelectrolyte multilayer deposition protocol, in which the complete features of a conventional grating-coupled SPR/QCM combination instrument are retained, including detection of optical and acoustic changes, as well as monitoring of adsorption kinetics.