A. Michelmore, D.A. Steele, J.D. Whittle, J.W. Bradley, R.D. Short University of South Australia Based upon review article RSC Advances, 2013, 3, 13540-13557 Tutorial on Plasma Polymerization Deposition of Functionalized Films Mawson Institute
A. Michelmore, D.A. Steele, J.D. Whittle, J.W. Bradley,
R.D. Short
University of South Australia Based upon review article
RSC Advances, 2013, 3, 13540-13557
Tutorial on Plasma Polymerization
Deposition of Functionalized Films
Mawson Institute
Tutorial covers
• Introduction – Technological importance of plasma polymers + examples
• The plasma phase
– Plasma – surface interactions
– Mechanisms of deposition
- examines W/F - early stages of film grow - the role of ions
Introduction to Plasma polymerization
• Plasma ignited in organic vapour
– Pure vapour or a mixture of vapours
– Reduced pressure
• Polymer (organic) deposit formed on all surfaces
• Chemistry of deposit often similar to vapour (monomer)
– Polymerisation not dependent on functional group
– Plasma polymers tailored from organic to “inorganic”
General properties of plasma polymers
• Ultra-thin (< 50nm)
• Soluble/Insoluble
• Trapped free radicals
• Adherent
• Conformal
• Pinhole free
• Internal stress – Will crack and flake if too thick
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Plasma polymerization is the ultimate enabling technology
Hydrophobic/Hydrophobic
Functionalized films Chemical Gradients
Responsive “intelligent” surfaces
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Example - Super hydrophobic coatings
• Produced by pulsed plasma polymerization - Highly fluorinated monomers, e.g. TFE • Large amount of conventional PTFE in ‘ribbons’
- Rough surface • In continuous wave mode no ‘ribbons’ on surface
- Ribbons grow in ‘off’ period from activated sites
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Example - Treatment of Burns
• In myskinTM technology a plasma polymerized coating is applied to a bandage to allow the culture of patient’s own cells
• Cells are delivered “off” pp-coated bandage
- Highly effective way of getting cells to patients rapidly
- Used in treatment of severe burns
• Range of potential applications
Haddow et al., Plasma Processes Polym., 2006, 3, 419
Renaissance in plasma polymerization:
• Traditionally, <1990s, scratch resistance, barrier layer, wetting – E.g. Nature, 1966, 209, 769
• Recent-cited applications: - Coating of tissue engineering scaffolds (Adv. Mater., 2006, 18,1406)
- Functionalization of nanotubes for covalent coupling of quantum dots (Adv. Mater., 2007, 19, 4003)
- Fabrication of a microcantilever fast humidity sensor (Adv. Mater., 2007, 19, 4248)
- Micro- and nano-engineering of surface structures (Adv. Mater., 2006, 18, 1406; Adv. Mater., 2007, 19, 1947; Adv. Mater., 2010, 22, ,
1451)
- Surfaces for high-throughput screening devices (Adv. Mater., 2008, 20, 116; Lab on a Chip, 2011, 11, 541)
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Reactor
• Enclosed chamber
- Means to introduce monomer as vapour
- Reduced pressure ~1Pa – 100Pa
- (~0.75 mTorr- 75mTorr)
• Method of excitation DC or AC (RF→MW), CW or pulsed
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RF excitation preferred for plasma polymers
• Electric fields heat electrons, generate plasma
–See Tutorial 2 – The Plasma Phase
• Advantages of RF
–Displacement rather than particle currents
–Stability
–Higher electrons temperature
–Process insulating materials without sputtering at electrodes
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Plasma polymerization:
Plasma Chamber (under vacuum)
Substrate
Gas (Monomer Vapour) Flows into Chamber
Plasma
Radiofrequency Power Applied to System
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(a) Clark and Dilks reactor design 1977 [ref 18] and three decades of reactor design evolution since, illustrating a variety of electrode configurations, power supplies and diagnostic tools (b) Ward 1989 [19] (c) Lopez et al. 1992 [20] (d) O’Toole et al. 1995 [21] (e) Favia et al., 1996 [22] (f) Candan et al. 1998 [23] (g) Alexander et al. 1998 [24] (h) Voronin et al. 2006 [25]
A. Michelmore et al, RSC Advances, 2013, 3, 13540
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Reactor design – Historical Perspective
Gas (Monomer)
Ions Photons Fragments
Electrons
Intact Monomer Atoms Radicals
Oligomers
Metastables
Energy transfer Chemical modification (Deposition Adsorption Grafting)
Desorption Etching
Plasma phase interactions:- Excitation, Ionisation, Relaxation, Ion-Molecule, Radical-Neutral, Fragmentation
Plasma polymerization
Substrate
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