A new PZT piezoelectric sensor for gravimetric applications using the resonance-frequency detection

Piezoelectric sensors made of quartz, Pb(Zr,Ti)O3, Pb(La,Zr,Ti)O3, or Pb(Zr,Ti,Sn)Oy have rapidly been developed recently because of the potential applications in devices such as biosensors, accelerometers, pressure sensors, and ultrasonic transducers. However, the development of devices with reduced size but with improved sensitivity is highly important. With this idea, the study aims to develop a lead zironate titanate (PZT) chip as a novel gravimetric biosensor using the resonance feature in biomolecule detection. The PZT thin film characterized by the X-ray diffractometer (XRD) has a perovskite structure. The fabricated PZT sensor was designed with 250 μm × 250 μm-sensing areas of electrodes, determined by the measured impedance at 98.5 MHz frequency. The morphology and cross-section of scanning electron microscope (SEM) images show that the thickness of the spin-on PZT layer was about 500 nm and the crystal grain size was less than 50 nm. Moreover, an evaluation circuit consisted of a resonance circuit and a frequency-to-voltage circuit was established to detect bovine serum albumin (BSA) protein. The PZT sensor, combined with evaluation circuit, showed a high sensitivity of 62.8 Hz cm2/ng. The detection sensitivity was enhanced by 300 folds than that of traditional quartz crystal microbalance (QCM).