A nanocell for quartz crystal microbalance and quartz crystal microbalance with dissipation-monitoring sensing

Abstract

A novel device for nanometer-confinement of soft matter in one dimension (1D) is presented. This nanocell, with very large (up to 10(6):1) cell-radius to cell-height ratio, is tailored as an accessory for quartz crystal microbalance (QCM) and QCM with dissipation-monitoring (QCM-D) sensing to study internal and interfacial energy dissipation phenomena in highly confined (in 1D) soft matter and fluid films (patent pending). The cell consists of two macroscopic plates (diameter of 9 mm), a top (the "lid") and a bottom (the QCM-D sensor), separated by appropriate spacers with heights ranging from below 100 nm up to 10 microm. The surfaces of both the lid and the bottom plate can be mechanically or/and chemically modified, prior to cell assembly, in order to tailor desired interfacial properties for the experiment. The cell is mounted on a standard QCM-D sensor, an AT-cut quartz crystal (the quartz crystal is cut at an angle of 35 degrees from its ZX-plane), forming the bottom plate. We illustrate theoretically and experimentally, as application examples, the use of this device for studies of dynamic mass loading and internal energy dissipation processes in thin films of ethylene glycol respective thin liquid crystal films around the nematic-isotropic phase transition.

A miniaturized flow reaction chamber for use in combination with QCM-D sensing

“…When the height of the chamber is reduced to such small values as in this work, there is an increasing risk to get interferences due to acoustic waves that might be emitted from the sensing crystal (Edvardsson et al 2007;Kanazawa and Gordon 1985;Ohlsson et al 2009) to the opposite chamber surface confining the chamber. It is well known that the penetration depth, d, of the shear wave depends on the viscosity, g, the density, q, and the oscillation frequency, x, as…”

“…Smaller volumes also give faster response when heating and cooling the sample. This was recently demonstrated for QCM-D, in a study where the phase transition of liquid crystals was monitored by QCM-D in nanoliter volumes (Ohlsson et al 2009). In the latter experiment, the QCM-D crystal defines, together with an enclosing wall and a lid, a very small volume.…”

“…Factors that had to be considered were the extinction depth of the acoustic shear wave of the QCM-D sensor in the liquid compared to the chamber height, and also when and if depletion of reactants would be an issue due to the increased domination of the boundary layers near the liquid-solid interfaces. Based on these considerations, the present flow chamber was constructed after the same principles as the previously developed nanoliter chamber (Ohlsson et al 2009) primarily for more static situations than in the present work. In this work, the concept is extended to suit systems where rapid sample exchanges are required, especially for the determination of chemical reaction rates and other time-dependent processes.…”

“…The typical chamber volume was about 3 ll. This volume could have been made even smaller by reducing the chamber height (in principle down to 3 nl for a 50 nm high chamber working under static conditions, (Ohlsson et al 2009)). As the volume (height) is decreased, flow resistance successively will be an issue of increasing importance, eventually preventing flow mode measurements with reasonable time resolution.…”

“…However, for the present application a few microliters chamber volume was aimed for. Another potential issue, specific for the QCM-D technique, is related to interference phenomena of the acoustic waves emitted from the sensor surface into the measurement chamber (Ohlsson et al 2009;Lin and Ward 1995). The miniaturized flow chamber was first characterized with respect to liquid exchange and flow characteristics, and thereafter its performance in a biomolecular application example was demonstrated; namely the formation of SLBs on a SiO 2 surface.…”