Development of a flexural plate-wave (FPW) immunoglobulin-E (IgE) allergy bio-sensing microsystem

Utilizing self-assembled monolayer (SAM) nanotechnology, microelectromechanical systems (MEMS) and integrated circuit (IC) technologies, a flexural plate-wave (FPW) based immunoglobulin-E (IgE) bio-sensing microsystem which is capable of small test sample volume (5 μl), short operation time (<10 min), small physical size (<15 cm × 9 cm × 1 cm) and at low cost (<30 USD/test) is developed and tested. This system consists of a pair of FPW microsensors (one measurement sensor and one reference sensor) and a frequency-shift readout IC microchip. In the sensors, two 3 μm-thick aluminum (Al) reflection grating electrodes (RGE) are fabricated beside the two-port chrome/gold (Cr/Au) interdigital transducers (IDTs) to effectively reduce the high insertion loss of conventional FPW microsensors, achieved a very low insertion loss (−9.2 dB) and high mass sensitivity of human IgE antigen (−6.08 × 109 cm2 g−1) at center frequency of 6.6 MHz. A frequency-shift readout IC with high sampling resolution (31.25 kHz) has also been developed for the signal processing of the FPW biosensors. The frequency shift caused by various immobilized IgE concentrations can be accurately read out in less than 10 min which is much faster than the commercial enzyme-linked immunosorbent assay (ELISA) analysis system (>60 min).