GRAVIMETRIC BIOSENSORS BASED ON ACOUSTIC-WAVES IN THIN POLYMER-FILMS

Most gravimetric biosensors use thin piezoelectric quartz crystals, ei ther as resonating crystals (quartz crystal microbalance, QCM), or as bulk/surface acoustic wave (SAW) devices. In the majority of these the mass response is inversely proportional to the crystal thickness whic h, at a limit of about 150 microns, gives inadequate sensitivity. A ne w system is described in which acoustic waves are launched in very thi n (10 microns) tensioned polymer films to produce an oscillatory devic e. A theoretical equation for this system is almost identical to the w ell-known Sauerbrey equation used in the QCM method. Because the polym er films are so thin, a 30-fold increase in sensitivity is predicted a nd verified by adding known surface masses. Temperature sensitivity is a problem so a separate control sensor and careful temperature regula tion are necessary. Preliminary results showing the real time binding of protein (IgG), a step towards immunosensor development, and the use of mass enhancing particles are presented. Inexpensive materials are used so disposable gravimetric biosensors may become feasible.