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Nonporous corundum powder, known as an abrasive material in the industry, was functionalized covalently with protein binders to isolate and enrich specific proteins from complex matrices. The materials based on corundum were characterized by TEM, ESEM, BET, DLS, EDS, and zeta potential measurements. The strong Al-O-P bonds between the corundum surface and amino phosphonic acids were used to introduce functional groups for further conjugations. The common crosslinker glutaraldehyde was compared with a hyperbranched polyglycerol (PG) of around 10 kDa. The latter was oxidized with periodate to generate aldehyde groups that can covalently react with the amines of the surface and the amino groups from the protein via a reductive amination process. The amount of bound protein was quantified via aromatic amino acid analysis (AAAA). This work shows that oxidized polyglycerol can be used as an alternative to glutaraldehyde. With polyglycerol, more of the model protein bovine serum albumin (BSA) could be attached to the surface under the same conditions, and lower non-specific binding (NSB) was observed. As a proof of concept, IgG was extracted with protein A from crude human plasma. The purity of the product was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A binding capacity of 1.8 mg IgG per gram of corundum powder was achieved. The advantages of corundum include the very low price, extremely high physical and chemical stability, pressure resistance, favorable binding kinetics, convenient handling, and flexible application.

This paper introduces an active electrical technique for dynamic tuning of MEMS resonators. The proposed technique is based on using the resonator output current to generate displacement or acceleration signals by integration or differentiation operations, respectively. The resulting signal is then scaled to generate an appropriate tuning signal. When applied to the resonator through additional signal ports, the tuning signal electrically modifies the equivalent mechanical stiffness or mass of the resonator, thereby tuning the resonance frequency in a bidirectional fashion depending on the polarity of the scaling. This tuning scheme has been applied to a piezoelectric AlN-on-Si BAW square resonator to tune its 14.2 MHz resonance frequency by 22 kHz, equivalent to 1550 ppm. The proposed tuning technique can be applied to a wide range of MEMS resonators and resonant sensors, e.g., to compensate for temperature or process-induced variations in their resonance frequencies. [ABSTRACT FROM AUTHOR]

This letter reports, for the first time, on a high-frequency resonant square micro-gyroscope using piezoelectric transduction. Degenerate pairs of orthogonal flexural resonance modes are used to provide energy exchange paths for the Coriolis-based resonant gyroscope in response to z-axis rotation. Aluminum nitride thin films have been used to provide highly efficient electromechanical transduction for drive and sense modes without requiring any dc polarization voltage for operation. A proof-of-concept design consisting of a 300 \mum\times\,300 \mum square gyro shows linear rate sensitivity of 20.38 \muV/^\circ/s when operating in its first flexural mode at \sim11~MHz. [ABSTRACT FROM AUTHOR]