ABSTRACT
A novel integrated bio-sensor technology based on thin-film bulk acoustic wave resonators on silicon is presented and the feasibility of detecting DNA and protein molecules proofed. The detection principle of these sensors is label-free and relies on a resonance frequency shift caused by mass loading of an acoustic resonator, a principle very well known from quartz crystal micro balances. Integrated ZnO bulk acoustic wave resonators with resonance frequencies around 2 GHz have been fabricated, employing an acoustic mirror for isolation from the silicon substrate. DNA oligos have been thiol-coupled to the gold electrode by on-wafer dispensing. In a further step, samples have either been hybridised or alternatively a protein has been coupled to the receptor. The measurement results show the new bio-sensor being capable of both, detecting proteins as well as the DNA hybridisation without using a label. Due to the substantially higher oscillation frequency, these sensors already show much higher sensitivity and resolution comparable to quartz crystal micro balances. The potential for these sensors and sensors arrays as well as technological challenges will be discussed in detail.
Subject(s)
Biosensing Techniques/instrumentation , DNA/analysis , Electrochemistry/instrumentation , In Situ Hybridization/instrumentation , Protein Array Analysis/instrumentation , Proteins/analysis , Biosensing Techniques/methods , Coated Materials, Biocompatible/chemical synthesis , Coated Materials, Biocompatible/chemistry , Electrodes , Equipment Design , Equipment Failure Analysis , Feasibility Studies , Gravitation , In Situ Hybridization/methods , Pilot Projects , Protein Array Analysis/methods , Reproducibility of Results , Sensitivity and Specificity , Staining and Labeling , Streptavidin/analysis , Stress, Mechanical , Systems IntegrationABSTRACT
Experimental and theoretical investigations of the electromechanical anisotropy of ceramics modified with Ca, Ni-Nb, and Mn are presented. It is demonstrated that the large anisotropy of these ceramics is neither a bulk property of the PbTiO(3)-crystallites nor a domain wall effect. The anisotropy is caused by the statistical orientation of the crystallites in the ceramics and by the material properties due to this orientation. The ratio of electrostrictive coefficients and the ratio of single-crystal permittivities in these ceramics also play a decisive role. The result enables one to comprehend easily the dependence of the ceramic's electromechanical anisotropy on the material composition, the degree of poling, and the temperature.
