Abstract:

1. The Placement of Hydrophobic Coatings Using Atmospheric Plasma ProcessesPresented by:Marisa Scofield

2. Abstract: A practical atmospheric plasma treatment process has been developed in order to deposit stable hydrophobic coatings on different types of materials. Seong Kim at Pennsylvania State University uses a methane-helium/argon mixture in a process in which the hydrocarbon layer can be placed on different types of substrates. The substrates can be both metallic and insulating and the end result yields a product with good and durable hydrophobicity not dependent on the substrate. The coatings are made via self assembled monolayers (SAM). These hydrophobic coatings can be used in a variety of ways including corrosion prevention, micro-device lubrication, and barrier coatings in biomedical systems.

3. Outline: • Introduction to application process treatment • Drawbacks to the atmospheric plasma process • Benefits to the atmospheric plasma process • Introduction to self assembled monolayer (SAM) • Proposed mechanism for self assembled monolayer formation • Sample mechanism for applying the SAM to the substrate • Potential uses in corrosion prevention, self-lubrication of microelectromechanical systems (MEMS) and barrier coatings in biomedical devices • Conclusion • References

4. Introduction to application process treatment • Atmospheric Plasma: • An electric discharge is a plasma, which in turn is ionized gas. There has to be a continuous source of energy to maintain the plasma. One type is Atmospheric Pressure Glow Discharge (APGD).7 • Ways to cause ionization include collisions of energetic particles or ionizing radiation. • An electromagnetic field may be used to excite the plasma medium and generate a constant source of energy 1. J-H Kim, G Liu and S H Kim (2006) J. Mater. Chem. 16: 977-981

5. Potential drawbacks and benefits with atmospheric plasma application process: Drawbacks6 • The chemical nature of the molecules can be altered by the plasma • The optical property of the base material could be severely impaired • Substrate samples had a high risk of being damaged by the plasma source Benefits1 • Generally does not produce chemical waste • Can be fully automated • Since it is operated in the glow discharge area, it can be applied to both metallic and insulating substrates • Suitable for continuous in-line processing

6. Introduction to hydrophobic coating: • Self Assembled Monolayers (SAM)5 • Well organized organic monolayers that are formed spontaneously upon exposure of a substrate surface to a solution of assembling molecules possessing reactive functionalities. • Some examples include long-chain hydrocarbons and fluorocarbon molecules. • Works best when the surface of the substrate has been modified to include NH2 and OH terminal groups.

7. This sample condensation reaction occurred on the substrate surface after it had been hydroxylated and dried in a vacuum. It is a condensation reaction because two separate molecules have bonded to eachother by the concurrent loss of two methyl groups and the H attached to the hydroxyl group. This is an example of a way to lubricate a microelectromechanical system in order to prevent excessive corrosion. A proposed mechanism for self assembled monolayer formation: Rymuza, Z. (1999) Microsystem Technologies 5: 173 - 180

8. Once the monolayer has been formed: • There is a liquid-phase application and hydrolysis • Then adsorption occurs in which the monolayer accumulates on the surface of the substrate through the formation of Si-O-Si bonds • Finally the molecules are cross-linked through covalent bonding Rymuza, Z. (1999) Microsystem Technologies 5: 173 - 180

9. Application and its use in corrosion prevention and barrier coatings in biomedical devices: • A thin hydrophobic layer can be applied to biomedical devices in order to prevent corrosion as well as maintaining the mechanical efficiency and properties of the device. • The device may be subject to some sort of mechanical movement, or it may be an electronic device that needs protection from the surrounding bodily fluids. McNamara, Brian, “Form and Function: the quest to design biomedical devices which replicate and facilitate nature’s way.” (15 April 2006) <www.physics.dcu.ie/.../mcnamarabs.html>

10. Conclusion: • There are several ongoing investigations into the best method for applying a hydrophobic coating to a particular substrate. While there are drawbacks to using the atmospheric plasma method, it can be widely used for continuous in-line processing among other benefits. This process is used for many different reasons including corrosion prevention, micro-device lubrication, and barrier coatings in biomedical systems.s

11. References: 1. J-H Kim, G Liu and S H Kim. Deposition of stable hydrophobic coatings with in line CH4 atmospheric rf plasma (2006) J. Mater. Chem. 16: 977-981 2. Mauritz, Kenneth, “Sol Gel Research” Feb. 2004. Mauritz Resarch Group. (15 April 2006) http://www.psrc.usm.edu/mauritz/index.html 3. McNamara, Brian, “Form and Function: the quest to design biomedical devices which replicate and facilitate nature’s way.” (15 April 2006) <www.physics.dcu.ie/.../mcnamarabs.html> 4. Moore, Caroline A. "Hydrophobic Coatings with Atmospheric Plasma." RSC Publishing. 21 Feb. 2006. 15 Apr. 2006 <http://www.rsc.org/Publishing/ChemTech/Volume/2006/3/Hydrophobic_coatings.asp>. 5. Rymuza, Z. (1999) Microsystem Technologies 5: 173 - 180 6. Wang, Anfeng, Jeff Chinn, Xuemei Liang, Ting Cao, Haiying Tang, Steven O. Salley, Gregory W. Auner, and K.y. Simon Ng, comps. Preparation of Hydrophobic Multilayers on Solid Surfaces. 1 Nov. 2005. Dept. of Chemical Engineering and Materials Science at Wayne State University. 15 Apr. 2006 <http://aiche.confex.com/aiche/2005/techprogram/P15483.HTM>. Wang, Anfeng (2005) 7. Wikipedia: the free encyclopedia. 6 April 2006. MediaWiki. (15 April 2006) <http://en.wikipedia.org/wiki/Main_Page>