Film bulk acoustic resonators (FBARs) have been evaluated for use as biosensors because of their high sensitivity and small size. This study fabricated a novel human IgE biosensor using shear-mode FBAR devices with c-axis 23°-tilted AlN thin films. Off-axis radio frequency (RF) magnetron sputtering method was used for deposition of c-axis 23°-tilted AlN thin films. The deposition parameters were adopted as working pressure of 5 mTorr, substrate temperature of 300°C, sputtering power of 250 W, and 50 mm distance between off-axis and on-axis. The characteristics of the AlN thin films were investigated by X-ray diffraction and scanning electron microscopy. The frequency response was measured with an HP8720 network analyzer with a CASCADE probe station. The X-ray diffraction revealed (002) preferred wurtzite structure, and the cross-sectional image showed columnar structure with 23°-tilted AlN thin films. In the biosensor, an Au/Cr layer in the FBAR backside cavity was used as the detection layer and the Au surface was modified using self-assembly monolayers (SAMs) method. Then, the antigen and antibody were coated on biosensor through their high specificity property. Finally, the shear-mode FBAR device with kt2 of 3.18% was obtained, and the average sensitivity for human IgE detection of about 1.425 × 105 cm2/g was achieved.

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This paper describes design and implementation of a digitally controlled single-inductor dual-output (SIDO) buck converter operating in discontinuous conduction mode. This converter adopts time-multiplexing control in providing two independent output voltages using only an inductor. The design issues of the digital controller are discussed, including static and dynamic characteristics. Implementation of the controller, a modified hybrid digital pulse width modulator and a single look-up table are developed. The digital controller was implemented on a field-programmable gate array-based control board. Experimental results demonstrating system validity are presented for a SIDO buck converter with nominal 3.6 V input voltage, and the outputs are regulated at 1.8 and 2.2 V.

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