Graduation Year

2022

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Engineering

Major Professor

Nurettin Sahiner, Ph.D.

Co-Major Professor

Venkat R. Bhethanabotla, Ph.D.

Committee Member

Ramesh R. Ayyala, M.D.

Abstract

In this thesis, polycarbonate (PC) and acrylic (PMMA) surfaces were treated with carbon tetrafluoride (CF4), oxygen (O2), and air plasmas with a low-pressure plasma method in order to change their surface properties such as surface free energy and wettability. Moreover, different pattern sized, line, triangular and square shaped surface patterns were used to determine the shape and size-dependent changes. The characteristics of untreated and plasma treated surfaces were examined via contact angle (CA) measurements with distilled (DI) water, against plasma treatment number. Moreover, surface free energy (SFE) calculations of the PC and PMMA surfaces were carried out from sessile drop CA measurements using the OWRK/Fowkers method. From the obtained results, it was observed that untreated PC and PMMA surfaces showed 70.18°±0.47° and 77.32°±0.80° CA degrees respectively. After treated with CF4 plasma, both of the surfaces became more hydrophobic with CA values for PC surfaces 109.04°±0.35° while 105.76°±0.61° for PMMA. Besides, O2 and air gas plasma-treated surfaces became more hydrophilic, in contrast to untreated and CF4 plasma treated surfaces. Moreover, CF4 plasma treated PC and PMMA surfaces SFE values decreased to 10.23±0.63 mN/m. and 12.11±1.53 mN/m. respectively while it was increased for air plasma treatment with the value of 57.58±1.12 mN/m. for PC and 62.13 ± 1.15 mN/m for PMMA surfaces. Slide-off angle of each treated surface was examined by surface tilting method. Untreated PC surface’s, advancing and receding CA were found as 101.48°±0.33° and 65.60°±0.11° respectively for 34.77°±0.50° slide-off angles. Moreover, advancing and receding CA for untreated PMMA were found as 93°±0.64° and 61.60°±1.19° respectively for 24.49°±1.14° slide-off angle. Slide-off angle were observed at smaller degrees for Air and O2 plasma treatedsurfaces while it was found bigger degrees after being treated with CF4, for both of the surfaces. X-ray Photoelectron Spectroscopy (XPS) analysis results showed the surface functionalization of both PC and PMMA surfaces. Sequential plasma treatment applied PC and PMMA surfaces with CF4 and Air, Air and CF4, O2 and CF4, and CF4 and O2 plasmas. PC and PMMA surfaces' contact angle values were decreased to 10.62°±0.88° and 14.96°±0.2°, respectively, after several treatments.

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