Micromechanical resonant sensors for detection and characterization of biological entities
Abstract
Micromechanical sensors can be developed that have the sensitivity to detect single, individual biological entities such as bacteria, spores, viruses and so on. In the present study, cantilever beams are used as resonance-detector based mass sensors for biological entities. Microsized cantilever beams were used to detect the mass of Listeria innocua bacteria by applying increasing concentration of bacteria suspension in fluid on the same cantilever beam and measuring the resonant frequency changes in air. Cantilever beams have also been used to detect the mass of adsorbed antibodies, following which they were used to demonstrate the capture of bacterial cells on the cantilever beam surface. In order to detect smaller masses such as those of virus particles, it is necessary to scale down the dimensions of the cantilever beams in order to achieve the required mass sensitivity. Cantilever beams with dimensions in the range of 4-5 μm length, 1-2 μm width and 20-30 nm thickness, have been fabricated using silicon-on-insulator wafers. These cantilever beams have been used to detect the mass of a single vaccinia virus (dry) particle under ambient conditions. Resonator mass-detection capability can also be improved by externally driving the cantilever beams, using a piezoelectric layer below the cantilever chip. Towards the goal of obtaining selectivity of capture, antibodies and protein layers were attached on the cantilever surface. The mechanical properties of the composite cantilever structure change upon the attachment of the proteins. This work will also describe the phenomenon of the attached protein thickness varying with the available area of the microsized cantilever beam.
Degree
Ph.D.
Advisors
Bashir, Purdue University.
Subject Area
Electrical engineering|Biomedical research
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