Text

theses

This thesis presents the design, fabrication, and characterization of polymer-based cantilever probes for atomic force microscopes (AFMs), in order to enable biological research requiring non-destructive high-speed high-resolution topographical imaging and nanomechanical characterizations of sub-cellular and cellular samples. A reliable low-cost surfacemicromachining process is developed for the rapid prototyping of bio-compatible polymer-based V-shaped AFM probes. The physical properties of fabricated prototypes, such as effective spring constant, resonant frequency, and quality factor, are determined experimentally via thermal noise method and analytically via finite element and parallel-beam approximation methods. Using a prototype, AFM nanoindentation measurements are performed on live mammalian cells— human cervical epithelial cancer cells (called “HeLa”) in a liquid culture medium. Experimental results are compared to those obtained using a commercial Si-based probe; when the prototype probe is used, the deformation and/or distortion of the cell membrane are reduced significantly albeit repeated indentations on the cell surface. For further AFM-based biological studies, the design and fabrication process of the prototype probe are fine-tuned; a reasonably straight cantilever with a strain gradient as low as 10-4 μm-1 is achieved via corrugating the optical reflection coating or confining it to the tip region, and a sharp tip with a radius of curvature as small as ~40 nm, which is comparable to that of a Si-based probe, is achieved via sequential depositions of low- and high-viscosity acrylic polymers.

ETD_7426

M.S.

Includes bibliographical references

by Fangzhou Yu

doi:10.7282/T3TT4T8V

ETD graduate

The author owns the copyright to this work.