Date on Master's Thesis/Doctoral Dissertation

5-2011

Document Type

Master's Thesis

Degree Name

M.S.

Department

Mechanical Engineering

Committee Chair

Panchapakesan, Balaji

Author's Keywords

Carbon nanotube; Microgripper; Self-assemble; Nano-electrode; Nanoneedle; Electrical measurement

Subject

Microelectromechanical systems; Nanotubes

Abstract

In this thesis self-assembled growth of Ag2Ga nano-needles on batch fabricated micro-grippers are reported. The room temperature growth of Ag2Ga nano-needles have been recently developed as stylus for Atomic Force Microscopy (AFM). Integration of such nano-needles onto batch fabricated micro-grippers can potentially lead to the development of nano-grippers for nano-manipulation of materials, measurement of electrical properties of nanostructures and finally measurement of electrochemical properties of cells. We explored the growth process of nano-needles on batch fabricated microgrippers. Micro-grippers were first batch fabricated using carbon nanotube/SU8 process at the University of Louisville's clean room facility. Following the gripper fabrication, 20 nm chromium and 100 nm silver were selectively deposited onto the arms of the grippers using shadow masking techniques. Each silver coated arm was selectively dipped onto liquid gallium and retracted for the formation of Ag2Ga eutectic nano-needles at room temperature in ambient environment. The length and diameter of nano-needles can be controlled by the thickness of silver and volume of gallium liquid. Scanning Electron Microscope (SEM) characterization revealed nano-needles of 100 -120 nm in diameter and 7-15 µm long on each gripper. Following the nano-needle growth on the grippers, the grippers were packaged onto a ceramic chip carrier and wire bonded. Following wire bonding, 100 nm of parylene was coated everywhere besides the surface of gripper/needles to enable electrical insulation in liquid environments, and then the tips of nano-needles are exposed. I-V measurements revealed an open circuit resistance of 120 Giga-ohms showing the versatility of the grippers integrated with the needles as electrodes for measurement of electrical properties of nano-materials and in liquids. Preliminary measurements on a small carbon nanotube film when brought into contact with the needle revealed six to eight orders of magnitude change in the resistance showing that these needles are highly sensitive for electrical property measurement on nano-materials. Finally, the needles were tested inside phosphate buffered saline and performed linear sweep voltammetry to investigate reduction-oxidation reactions on the surface of the nano-needle.

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