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Multifunctional Protection of Material Surfaces by Nano Textured Thin Films

Prof. Dr Eva Maria Moser

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Outline

v  Corrosion protection of metallic surfaces

- Nano textured DLC layers

v  Anti-fingerprint and germ inhibiting surfaces:

- Photocatalytically active titania layers

v  Nano-micro structuring of material surfaces

v  Examples of applications

Lotus effect: Transport of pollution

Smooth surface: Gliding water drops

Structured surface: Rolling water drops

www.botanik.uni-bonn.de et www.basf.de

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Plasticiser ESPO

Packaging: Plasticiser diethylhexyladipate (DEHA) or 2-ethylhexanacid (2-EHA)

10 of 11 Alu cans: Bisphenol A

Semicarbazide or epoxidised soja oil (ESBO)

gases, vapour,

germs

waste

information

Envi

ronm

ent chem. and biol.

contamination

taste, aroma

protection Pack

agin

g

Prod

uct

Food Protection against Undesirable Interaction with Packaging

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Production of Thin Coatings using PVD and PE-MOCVD

Processes at Ambient Temperatures

PVD: Reactive dc-sputtering of metallic particles at 10-2 mbar

PE-MOCVD: Evaporation of metal containing precursor in plasma reactor at 10-2 mbar

Production of titania coatings onto flat substrates at atmospheric pressure

Upscaled plasma process: 30 cm

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Pilot R&D plasma web coater at EMPA

Linear microwave discharge and dc-magnetron sputtering discharge

Upscaled deposition of Thin Films

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Sustainable Nano Texturing of DLC Layers: - Durable encapsulation of metallic particles

- Tailoring of wettability

DLC matrix of 70 nm: Diamond Like Carbon layer

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Plasma polymer CHx

Structure of the Plasma Polymer DLC (Diamond Like Carbon), a-C:H

Polyethylene (PE)

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PET-film 12 µm, as received Cluster size: 10 - 20 nm RMS roughness: 0.8 nm

Plasma coating 76 nm on PET-film Cluster size: 25 - 35 nm RMS roughness: 2.0 nm

µm µm

AFM Images of Polyethylene Terephthalate

Topography of the PET surface

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Sustainable Polymer-like DLC Layer as Diffusion Barrier

Polymer-like diffusion barrier layer: Highly cross-linked and inherently flexible

Coated PET / CPP

O2-Perm. 0% r.h. [ml/m2dbar]

O2-Perm. 85% r.h. [ml/m2dbar]

H2O-Permeability 90% r.h. [g/m2d]

Stretch failure [%]

PET: DC/RF /GHz PET: Web coater 1.0 - 1.2 ± .2

0.8 - 2.1 ± .2 0.8 - 0.9 ± .2 0.8 - 2.1 ± .2

0.2 - 0.3 ± .2 0.1 - 0.8 ± .2

2.6 – 3.7 ± .2 3.1 – 5.1 ± .2

hydrophobe / PET phob/phil / PET < 1.0 ± .2

< 1.9 ± .2 < 0.8 ± .2 < 0.7 ± .2

< 0.2 ± .2 < 0.2 ± .2

> 2.5 ± .2 > 4.7 ± .2

hydrophobe / CPP phob/phil / CPP 40 ± .2

27 ± .2 - -

0.4 ± .2 0.8 ± .2

- -

Ref.: PET 12 µm < 123.9 ± .3 < 93.0 ± .3 < 20.4 ± .3 -

Ref.: CPP 75 µm 1000 - 4000 - 4 -

I: diamond-like sp3 > sp2; C > H

II: graphite-like sp3 < sp2; C > H

III: polymer chains sp3 > sp2; C < H

H H

H H

H H H

H H

H

H H

H H H

H H

H H

H H H

H

H

H

H H H

H H H H H

H H

H

H H

H H

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Direct Contact of DLC with Food: No Interaction, no Migration

CPP/PET film plasma treated

3 wt% acetic acid (2h@90°C, 10d@40°C)

95 vol% ethanol (4h@60°C, 10d@40°C)

isooctane (2h@60°C, 2d@20°C)

Ref: CPP/PET < 1 mg/dm2 < 1 mg/dm2 < 4 mg/dm2

wincoat CPP < 1 mg/dm2 < 1 mg/dm2 < 1 mg/dm2

Phil /CPP < 1 mg/dm2 < 1 mg/dm2 < 1 mg/dm2

Phil /CPP < 1 mg/dm2 < 1 mg/dm2 < 1 mg/dm2

Phob /CPP < 1 mg/dm2 < 1 mg/dm2 < 1 mg/dm2

Global Migration according to EU guidelines 2002/72/EG (detection limit: <1 mg/dm2, tolerance limit: <10 mg/dm2)

ESR and fluorescence spectroscopy and polymer-like DLC food for germs (1020 Spins/cm3, g-value: 2.0023 (11 Gauss): à no free radicals in DLC

Hydrophobic DLC

Hydrophilic DLC

Welding-peeling properties:

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storage @ RT storage @ 4°C storage @ 80°C

Ref. Ref. Ref.

wincoat© wincoat© wincoat© printed, wincoat© plasma- treated CPP Folie (75 µm)

Removed tape

wincoat© Plasma Treated Polypropylene is: - wettable, anti-fogging - printable, ready to be coated - sealable, weldable

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Actual Project: DLC Layers and Active Corrosion Protection

Anodic corrosion protection

Reaction: 2 Me + O2 à 2 MeO

Plasma layer: 50 nm

Metallic nano contacts (< 10 mg/m2)

Micro defect Adjustable wettability

Metallic substrate: Aluminium, steel,….

Metallic nano contacts: ∅ 5 nm in DLC permanently immobilised

DLC: Diamond Like Carbon Plasma thin film (50 nm): Highly crosslinked plasma polymer as durable matrix

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Excellent Corrosion Protection by Metallic Nano Contacts

Corrosion tests performed at EMPA, Dr Markus Faller: -  Pore test according to Verpackungsrundschau 11/1976 -  Determination of electrochemical parameters (impedance-spectroscopy) -  Salt spray test (DIN EN ISO 9227 NSS): Storage for 3 days at 35 °C -  Condensed water test climate (DIN EN ISO 6270-2 AHT: 7 days with 2 cycles at 100% rel. humidity (8 h at 40°C and 16 h at 23°C)

Pure DLC layer deposited onto Al- foil with poor protection; many pores are visible

Metal-doped DLC layer onto Al-foil with good protection; without pores

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Al-foils after 27 days condensed water test: left: Hydrophobic, metal-doped DLC right: Chemically cleaned Al-foil, without coating

Excellent Corrosion Protection by Metallic Nano Contacts

Corrosion tests performed at EMPA, Dr Markus Faller: -  Pore test according to Verpackungsrundschau 11/1976 -  Determination of electrochemical parameters (impedance-spectroscopy) -  Salt spray test (DIN EN ISO 9227 NSS): Storage for 3 days at 35 °C -  Condensed water test climate (DIN EN ISO 6270-2 AHT: 7 days with 2 cycles at 100% rel. humidity (8 h at 40°C and 16 h at 23°C)

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v  Corrosion protection of metallic surfaces

v  Anti-fingerprint and germ inhibiting surfaces:

- Photocatalytically active titania layers

v  Nano-micro structuring of material surfaces

v  Examples of applications

no illumination illumination for 1 day illumination for 6 days

AFM images of E. coli on the TiO2 surface: Kayano Sunada et al., Journal of Photochemistry and Photobiology A: Chemistry 156 (2003) 227–233

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Benefits of Photo-induced Titaniumdioxid (Titania, TiO2)

disinfection

UV-protection

selective diffusion barrier

biocompatibility bioactivity

detoxification

active self-cleaning

anti-fogging

decontamination

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Activation of titania layers at 365 nm (UV light)*

Bleaching of a 0.05 mmol solution of methylene blue by titania

Tests for Photo-induced Catalytic Activity at Humid Conditions

Activation of titania layers at 428 nm (visible blue light)

Activation of titania under visible light at 625 nm

*CIF = 1.0 corresponds to bleaching of 1.7 mmol/m2⋅d of methylene blue by a PVD-TiO2 ref. layer (50 nm, on a glass slide) according to ISO 10678:2010

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H2O

CO2 H2O

O2- Ti4+

CHx

O2

TiO2 (anatase) hν ≥ Eg Titania TiO2

O2-

OH*

H2O

h+

Photocatalyst reaction TiO2 à electron + hole

e- Reactions

Redox potential

3.2 eV

CB

VB

Organic compound + Mineral acid

Photocatalytic Reactions at Titania Surfaces

O2

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19 HRTEM-image of the 192 nm sputtered pure PVD TiO2 layer, ref. A:

Crystalline domains of anatase [110] in amorphous matrix

Crystallinity of PVD Titania Layers

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Destruction of Stearic Acid: Fingerprints and Germs

Roughness [nm]: 14.9 7.2 4.7 5.4 3.5

AFM-Images: ∼ 200 nm thick PVD-TiO2

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5

10

15

20

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0 1 2 3 4 5 6 7 24 32 48

Concen

tra)

on  of  stearic  acid    [m

ol⋅10-­‐

3 ]  

Time  of  irradia)on  [h,  @  365  nm]  

PVD-b 1000 nm PVD-b 200 nm PVD 1000 nm PVD 200 nm PECVD-c 130 nm

1 h 1 h 1 h

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RODAC plates contaminated with E. coli à 428 nm for 16 h à  Red colour: No growth of bacteria (negative) à  Yellow colour: Colonies of bacteria (positive)

Sample 10

0.00E+00

5.00E+07

1.00E+08

1.50E+08

2.00E+08

2.50E+08

3.00E+08

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Time [h]

Conc

entra

tion

[bac

t/ml]

TiO2 Optical testBlank Optical testTiO2 Viability testBlank Viability test

The destruction of Escherichia coli cells as well as the released endotoxin has been investigated using a modified form of the ISO/DIN 22196.

Escherichia coli

Bacteria without/with damaged hard shell

Inactivation of the Viability of Bacteria and their Destruction

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*Tests were performed according to ISO 22196: Sterilisation if <1 of 1 mio germs after 24 hours

Antibacterial activity under visible light

Tests according to ISO 22196: Growth reduction efficacy [log cfu]

PVD TiO2-b 13.8.3.0047-1 (300 nm, CIF = 7.0/1.7 RMS = 5.2 nm, hydrophilic)

E. coli: 0.75 (slight) S. aureus: 0.62 (slight)

PE-MOCVD TiO2-c 13.8.3.0047-2 (200 nm, CIF = 7.3/3.1 RMS = 1.0 nm, hydrophobic)

E.coli: 2.35 (significant) S. aureus: 2.46 (significant) E. coli do not stick well to the titania surface and can be removed easily

PVD TiO2 black 13.8.3.0047-3 (1.4 µm, CIF = 10.1/1.3 RMS = 5.0 nm, hydrophilic)

E. coli: > 5.52 (strong) à 20 of 1 mio germs S. aureus: > 3.68 (strong)

Germ-Inhibiting Features of Titania

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TiO2 coatings Indenter type : Berkovich

Nano Hardness

[GPa]

Elastic Modulus [GPa]

Vickers [HV]

(f = 94.5)

PVD titania invisible 2012 2.8 86.2 265

PVD titania black 2012 3.4 29.5 321

PE-MOCVD titania invisible 2012 1.5 42.4 142

Nano hardness of titania layers has been improved up to > 15 GPa ! Hardness testing results are en route ! Tests have been performed according to ISO 14577 at CSEM Neuchâtel + VH = 0.0945 MPa

Nano Hardness of Titania Monolayers

24 Adhesion Improvement and Anti-fogging Effect

Anti-fogging effect Easy-to-clean effect

v  Corrosion protection of metallic surfaces

- Nano textured DLC layers

v  Anti-fingerprint and germ inhibiting surfaces:

- Photocatalytically active titania layers

v  Nano-micro structuring of material surfaces

v  Examples of applications

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Micro Structuring of Polymeric Surfaces at PSI

PSI: HEX03 technical data: - max. Press force 200 kN - Permissible thickness of the emboss sandwich max. 20 mm - Vacuum / chamber <1 mbar - Max. embossing area 120 mm - Max. temperature 320° C

PSI: Specac technical data: - Max. Press force 40 kN - Permissible thickness of the emboss sandwich max. 80 mm - Vacuum / chamber none - Max. embossing area 100 mm - Max. temperature 280° C

The hot embossed CPP film is lifted from the structured master wafer

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Hydrophilic surfaces •  sustainable (no interaction) •  super-polar, anti-fogging •  stretchable •  chemically resistent •  printable, good adhesion •  weldable

Hydrophobic surfaces •  sustainable (no fluor) •  super-hydrophobic •  stretchable •  water repellent, „LOTUS“ •  chemically resistent •  weldable PCT WO 2008/08122133_A1 and PCT WO 1998/58117

Sustainable Nano – Micro Structures on Polyolephins

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wincoat© treated surface: 6°

Untreated surface Cast-polypropylene: 97°

wincoat© treated surface: 146°

Anti-fogging effect Water repellency

à “Easy-to-clean” surfaces à  Complete emptying of content (packaging)

PCT WO 2008/08122133_A1

Controlled Condensation of Water due to Plasma Treatment of Polymeric Surfaces

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The surfaces “easy-to-clean” are distinguished by their surface energies and the micro-nano structures of the surfaces. (Θ = water contact angle)

DLC phob flat or with micro structure super-hydrophobic

Θ >120° surface with very weak polarity

hydrophobic 120 °

80°< Θ <120° surface with weak polarity

hydrophilic 20°

10°< Θ <80° surface with high polarity

super-hydrophilic Θ < 10° surface with very high polarity

DLC and polymeres (-C-H, Si-C-, F-Si-,)

DLC phil SiO2, TiO2

TiO2* and

micro structure

DLC phil SiO2 , TiO2

Passive, not interacting surfaces

Active, interacting surfaces

TiO2* flat or with

micro structure

TiO2* smooth

or nano structure

TiO2* smooth

or nano structure

Combination of Micro-nano Structures and Functional Layers

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29 Transparent PE-MOCVD TiO2 layer on chromated sample

Black PVD TiO2 layer on chromated sample

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Functionalisation

Structuring Doping

Tailored manipulation at material surfaces using plasma technology

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Merci – Grazie – Danke - Thank you

Die Neigung des Menschen, kleine Dinge wichtig zu nehmen, hat sehr viel Grosses hervorgebracht. The human tendency to regard little things as important has produced very many great things. Georg Christoph Lichtenberg (1742-1799)

R&D projects Nr. 7960.2, 10778.1, 10747.2 PFNM-NM have been funded by CTI

Several patents are hold for the presented thin films and deposition processes.

Dr Eva Maria Moser HESSO hepia eva.moser@sunrise.ch +41 76 321 21 59