Improving sensitivity, accuracy and efficiency of piezoelectric sensors for detecting biomolecules is important to the development of sensitive and reliable assays in the healthcare field for early detection and prevention of diseases. To achieve sub-femtomolar sensitivity, Drexel’s researchers have developed a piezoelectric plate sensor (PEPS) capable of in-solution detection of biomolecules with zeptomolar or higher sensitivity.

PEPS is a new type of piezoelectric sensor consisting of a PMN-PT freestanding film 8 μm in thickness, less than 1mm2 in size, thinly coated with gold electrodes on the two major surfaces and encapsulated with a thin electrical insulation to enable immersion in water solutions. Receptor specific to a biomarker is immobilized on the surface of the electrical insulation layer. Binding of the target biomarker to the receptor on the PEPS surface shifts the PEPS length-extension-mode (LEM) or width-extension-mode (WEM) resonance peak frequency, f. Detection of a target protein or DNA marker is achieved by directly immersing a PEPS in the biological fluid and monitoring the LEM or WEM resonance frequency shift, Δf, in real time. Detection sensitivity, Δf/f, varied by several parameters such as PMN-PT grain size and the applied direct current bias electric field, has been enhanced a 1000-fold as compared to that of purely mass detection, resulting in DNA detection at the level of 1.6x10-18 molar. This detection was achieved at room temperature in PBS, without sample isolation, concentration or amplification within 30 minutes. Combinations with other detection techniques, such secondary tags for the target molecule, can further enhance sensitivity to a zeptomolar level. Arrays of PEPS can be used for simultaneous detection of multiple biomarkers in the same sample.