Date of Award

Fall 2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Micro and Nanoscale Systems

First Advisor

Hai-Feng Ji

Abstract

One focus of the microcantilever (MCL) sensing area is to develop a novel surface modification approach to increase the microcantilever bending amplitudes and thus further improve sensitivities. In this dissertation, enzyme incorporated using the Layer by-Layer (LbL) process, LbL deposition of micro-, nano-hydrogel particles and electrophoretic deposition (EPD) of micro-, nano-hydrogel particles were applied to prepare a multilayer or thin hydrogel films on the surface of microcantilevers. Prior to applying to the microcantilevers, LbL and electrophoretic deposition techniques were also applied to gold coated silicon wafer surfaces to investigate the feasibility and deposition behavior using these techniques. The multilayers prepared through self-assembling of poly(styrenesulfonate) (PSS), poly(ethylenimine) (PEI), and organophosphorus hydrolase (OPH), responded to organic phosphorus compounds such as paraoxon, parathion, and dimethyl phosphate at different bending amplitudes and bending rates. The bending mechanism investigation suggested that the conformational change of the OPH might be the primary contributor of the MCL bending. The micro-, nano- hydrogel particle deposition on the silicon wafer and microcantilever through LbL process was investigated and discussed based on the observation and characterization using optical microscope, SEM and AFM techniques. A pseudo-3D mechanism was promoted to explain the hydrogel particle deposition process. The research on the EPD demonstrated that the technique was a convenient and reliable approach to deposit a uniform and continuous hydrogel thin film on the microcantilever devices. The bending responses of hydrogel coated microcantilever correlated with changes in environmental pH, demonstrating the feasibility of this hydrogel film for micro-sensor development.

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