MEMS for Drug Screening Applications
Jia Zhou, Shayne Zurn, David Markus, Sue Mantell , and Dennis Polla
University of Minnesota, US
Keywords: microbeam, resonant frequency, fluorescent dye, avidin, biotin
MEMs offer a quick, low cost method for screening new drugs. In this MEMs application, microbeams were designed such that an affinity between the beam surface (coated with a biomolecule) and a second biomolecule (simulating a potential drug) created a shift in the beam resonant frequency.
Cantilever and bridge microbeams were fabricated and tested in both air and liquid. Avidin and Biotin were attached to the microbeams following protocols developed at Affymax and the University of Minnesota. The beams were excited by applying AC voltage to one PZT layer. The other PZT layer was used to monitor the beam response. Changes in the resonant frequency and quality factor were recorded and compared for each beam. Over 50 cantilever microbeams and 168 bridge microbeams (Figure 1) were tested. A drop in resonant frequency was consistently noted after the biotin molecule was introduced (the frequency shift relative to a beam with avidin only).To verify that the frequency shift could be attributed to the added mass of biotin a biotin molecule with fluorescien dye was introduced. A direct correlation between fluorescent intensity and resonant frequency shift was observed (Figure 2). Limited tests were also conducted in liquids. These tests showed that the resonant frequency shifts and the quality factor drop when the structure is immersed in a liquid. The bridges were modeled as a thin plate. The effect of adding a small mass on resonant frequency was modeled and compared to the experimental results. The model indicates the effects of scaling beam size on beam response In this paper, the beam design, fabrication will be described. Data will also be presented which demonstrate the effectiveness of this screening method.
NSTI Nanotech 2003 Conference Technical Program Abstract