title: Torsional and lateral resonant modes of cantilevers as biosensors: alternatives to bending modes.
abstract: We show here novel cantilever designs that express torsional and lateral modes exhibit excellent mass-change sensitivity to molecular self-assembly on gold (75-135 fg/Hz) which is superior to that of widely investigated bending modes. Lead zirconate titanate (PZT) millimeter-sized cantilevers were designed with two types of anchor asymmetry that induced expression of either torsional or lateral modes in the 0-80 kHz frequency range. Experiments and supporting calculations show that anchor asymmetry enables resonant mode impedance-coupling. The sensitive torsional and lateral modes enabled measurement of self-assembled monolayer formation rate at picomolar levels. The anchor design principle was extended to microcantilevers via finite element simulations, which caused both 97% sensitivity improvement relative to conventional designs, as well as new nonclassical resonant mode shapes.
authors.affiliation: Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Blake N
authors.initials: BN
authors.lastname: Johnson
authors.forename: Harsh
authors.initials: H
authors.lastname: Sharma
authors.forename: Raj
authors.initials: R
authors.lastname: Mutharasan
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D004548:Elasticity; D007854:Lead / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D054159:Torsion, Mechanical; D015040:Zirconium / Q000737:chemistry*
chemical_list: C065536:lead titanate zirconate; D007854:Lead; D015040:Zirconium; D014025:Titanium