The Physics Behind And Biosensing Applications Of Resonant Micro- And Nanomechanical Sensors
The research presented herein focuses on the use of micro- and nanoelectromechanical systems (MEMS/NEMS) as mechanical resonators employed as sensors. The thesis describes the physical mechanisms underlying their use as sensors and demonstrates their utility in biosensing applications. This field is developing in the wake of the inception and widespread propagation of MEMS devices and scanned probe microscopies like atomic force or scanning tunneling microscopy. Recently there has been growing interest in their application to biological systems and the detection of low concentrations of biomolecules, where they could enable novel or deeper understandings of these systems or the onset and progression of disease. In order to push the limits of sensitivity to such levels, a full understanding of the sensing mechanisms is needed which, once attained, will shed light on appropriate sensor design parameters, materials, functional pattering, and the use of higher resonant modes. Two key themes that emerge from this work are the effect of device geometry and device optimization for use as biosensors. Especially important are the demonstrated applications of non-cantilever geometries and the results suggesting that these devices are also more sensitive and quantitative than cantilevers when the number of bound analytes on a device becomes very small. For biosensing applications, a "secondary mass labeling" technique has been developed that greatly improves device sensitivity to lightweight biomolecules specifically bound to the resonant sensors by effectively amplifying the mass of the analyte. After motivating the use of these sensors and providing a detailed discussion of the technology in general in Chapters 1 and 2, the experimental details of device fabrication and use are described in Chapter 3. Chapter 4 features in-depth discussion of the mathematical derivations and physics underlying the operation of these devices as sensors. Then in Chapter 5, the preparation of these devices for biosensing is described, and two realistic examples are demonstrated for the detection of prion proteins and prostate specific antigen. Together with the high device yield and rapid readout of devices, the results presented herein show great promise for real applications of this technology in medicine or other applications.
Dissertation or Thesis