title: A strategy for chemical sensing based on frequency tunable acoustic devices.
abstract: A new acoustic sensor geometry, the magnetic acoustic resonant sensor (MARS), is described. The device comprises a circular 0.5-mm-thick resonant plate fabricated from a wide variety of nonpiezoelectric materials and coated on the underside with a 2.5-microm-thick aluminum film. Harmonic radial shear waves over at least a 2 orders of magnitude frequency range can be induced in the resonant plate by enhanced magnetic direct generation using a noncontacting rf coil and NdFeB magnet. Mass loading with adherent aluminum films produced frequency changes of 106 Hz/nm (40.8 Hz/ng-mm(-2)), while contact with viscous fluids resulted in maximum changes of 15 446 Hz/cP. At an operating frequency of 50 MHz, the device detected viscosity changes as low as 0.0006 cP. The adsorption of proteins such as human IgG and the binding of a complementary antigen, goat anti-human IgG, on the upper nonmetallized surface of the device has been monitored with a detection limit of approximately 75 ng/mL. The binding of substrates and allosteric effectors to glycogen phosphorylase b has provided evidence that the device is very sensitive to viscoelastic changes in adsorbed proteins. The MARS device generates radial shear acoustic waves over a broad bandwidth that are unaffected by the conductivity of the solution. These results suggest that simple metal, glass, crystalline, or polycrystalline plates can be used as a new type of tunable acoustic immunosensor.
authors.affiliation: Institute of Biotechnology, University of Cambridge, UK.
authors.forename: H S
authors.initials: HS
authors.lastname: Sindi
authors.forename: A C
authors.initials: AC
authors.lastname: Stevenson
authors.forename: C R
authors.initials: CR
authors.lastname: Lowe
mesh_terms: D000162:Acoustics; D015374:Biosensing Techniques / Q000379:methods*; D002138:Calibration; D055590:Electromagnetic Phenomena; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D010763:Phosphorylase b / Q000032:analysis; D011506:Proteins / Q000032:analysis*; D012822:Silicon Dioxide
chemical_list: D007074:Immunoglobulin G; D011506:Proteins; D012822:Silicon Dioxide; D010763:Phosphorylase b