Masters Theses


"This thesis investigates two materials, SU8 photoresist and RuO₂, for possible incorporation into a self-calibrating microfluidic biosensor. The negative, epoxy based photoresist SU8 has been widely used in the fabrication of micro-electro-mechanical systems (MEMS) devices. This is due to its many desirable features that make it a suitable material for a wide variety of MEMS applications. The effects cross-linking (exposure dose) and bonding time have on bond strength and plasma modification of the SU8 surface were investigated as well as the bond strength of etched SU8. It was shown that adhesive bonding was an effective method of bonding, with bond strengths of 1500 psi possible. Plasma etching of SU8 was shown to significantly modify the surface while having a detrimental effect on bond strength. High oxygen plasma etching produced a hydrophilic SU8 surface, while CF₄ etching produced a hydrophobic surface. In both cases, the surface modification was shown to be temporary. Another important aspect of the biosensor is the electrode material. Ruthenium oxide (RuO₂) was examined because it has been shown to have much potential for use as an electrode. The resistivity, crystallinity and adhesion of reactively sputter deposited RuO₂ thin films to SU8 as a function of oxygen in the sputtering gas was investigated. It was found that both a change from Ru to RuO₂ films and a transition in preferred crystal orientation of RuO₂ in the films occurred as oxygen content in the film increased. It was shown that resistivity of RuO₂ is related to the amount of oxygen in the film. Film stress was shown to have a large impact on adhesion to SU8 and for this reason films produced in a moderate oxygen environment are suggested for use as an electrode material"--Abstract, page iv.


OKeefe, Matt

Committee Member(s)

Miller, F. Scott, 1956-
Kim, Chang-Soo


Materials Science and Engineering

Degree Name

M.S. in Materials Science and Engineering


National Institutes of Health (U.S.)


Missouri University of Science and Technology

Publication Date

Summer 2008

Journal article titles appearing in thesis/dissertation

  • Effect of UV-exposure, bond time and plasma treatment on bond strength of SU8
  • Influence of oxygen of reactive sputtering of ruthenium oxide


ix, 55 pages

Note about bibliography

Includes bibliographical references.


© 2008 Margaret T. Audrain, All rights reserved.

Document Type

Thesis - Open Access

File Type




Subject Headings

Photoresists -- Materials

Thesis Number

T 9398

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Electronic OCLC #