Development of an acoustic-wave MEMS biosensing device

We are developing an acoustic-wave biosensor based on MEMS technology that promises high sensitivity without the need for molecular tagging and external components.; Our development efforts have focused on the following key areas: (1) The computer-aided design layout and validation of the MEMS chip is described in Chapter 3. Here we outline the key design variables and give a description of the micromechanical sensing structures and the embedded electronic circuitry. We then explain the CAD layout validation process which ensures the successful fabrication of the designed MEMS chip. (2) The characterization and testing of the MEMS chip in regards to both the electronic components and mechanical structures is then presented in Chapter 4. The vibration behavior of the membrane structures is compared, characterized, and modeled as a plate-like structure with elasticity being the main restoring force. (3) The modification of the membrane structure is next presented in Chapter 5. The modification scheme first involves deposition of a polystyrene layer. This polystyrene film coats the membrane forming a conformal composite structure. The polystyrene layer serves as the basis for subsequent receptor immobilization. The membrane surface is then modified to specifically and selectively detect the target analyte of interest. The functionalization chemistry used to modify the membrane involves photochernically activating the polystyrene surface and immobilizing biomolecular binding species capable of exploiting ligand-ligate specificity. The immobilization which makes use of the avidin-biotin interaction is demonstrated optically via fluorescence microscopy and gravimetrically using a macroscopic quartz crystal microbalance (QCM). (4) The design of an acrylic-based sample reservoir is presented in Chapter 6. The clamshell design is fabricated via a laser engraving technique to etch flow channels and a reservoir well into air acrylic plastic substrate. (5) In chapter 7 we integrate the MEMS device with the surface modification chemistry to develop our MEMS based acoustic wave sensor. We illustrate the feasible of the sensor by detecting fluorescent-labeled avidin molecules conjugated to 1 mu diameter polystyrene beads. We demonstrate that our device functions properly both gravimetrically and optically. (6) Finally, we propose areas for future research and development in this biosensor design. (Abstract shortened by UMI.)...