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SURFACE MODIFICATION OF POLYCARBONATE BY
RADIO FREQUENCY PLASMA FOR ANTIMICROBIAL
APPLICATIONS
Ajoy Kumar ChandaResearch Scholar
Department of Chemical Engineering
IIT Kharagpur
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Presentation outline
Introduction
Introduction of plasma
Objective of Current WorkMaterials and methods
Results and discussion
Conclusion
Future Work
References
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IntroductionAdherence of bacteria to a polymer surface results in bio film
formation.
Antibacterial agent is coated on medical polymers to prevent biofilm formation
To obtain the antimicrobial properties, the substrate is usually
impregnated or compounded with an antimicrobial agent.
Surface modification of medical polymers or devices is a
relatively simple and effective strategy to create a desirable
surface.
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PolycarbonatePolycarbonates, which are long-chain linear polyesters
of carbonic acid and dihydric phenols such as Bisphenol-A
It is naturally transparent , extraordinary heat and chemicalresistance with excellent toughness properties .
It has a low surface energy, which leads to poor adhesion
They have a broad range of applications for automobileheadlamps,corrective lenses, compact discs, syringes,and medicaldevices.
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Plasma
Energy Energy Energy
Solid Liquid Gas Plasma
Plasma a quasi neutral gas, referred to as fourth state of matter
Collection of particles consisting of electrons, ions and excitedatoms and molecules
Moves in random directions
Electrically neutral
Ionization of neutrals sustains the plasma in the steady state
Natural Plasma Lightning, all stars including sun
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Schematic Diagram of CCP Reactor
Plasma
Substrate
Atoms/Molecules
Photons
Metastables
Ions
Electrons
Gas
Vacuum
Powered
electrode
Power
SupplyFree radicals
Active species in
plasma
Grounded
electrode
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Objective of current work
Surface modification of polycarbonate by RF plasma treatment
To enhance the antimicrobial properties.
To study the effect of concentration of colloidal silver on
antimicrobial properties.
To study the effect of process variables on surface energy.
To study the effect of plasma treatment on wettability.
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Materials
Polycarbonate(2.5 cm x 1.6 cm)
Silver purum, colloidal.
Escherichia coli MTCC 1302Culture media(nutrient agar)
Nutrient broth
The low pressure plasma reactor.
Incubator
Autoclave
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Experimental Procedure
Schematic diagram of PECVD
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Range of process parameter used
Treatment time --- 2 to 10 min
RF power supply--- 20 to 150 W
Argon gas flow rate --- 5 to 20 SCCMOxygen gas flow rate--- 3 to 14 SCCM
Frequency is 13.56 M Hz
Pressure is 150 mTorr
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Digital photograph of the plasma reactor
1
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Preparation of Liquid culture media and agar
plateNutrient broth:
0.65grams of powdered nutrient broth was suspended in a
conical flask containing 50ml of distilled water.
autoclave for steam sterilization. Operating conditions of the
autoclave was:
Temperature: 1210
CPressure: 15 Psi
Time: 15-20 min
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ContinueAgar plate:
5.6 grams of powdered nutrients agar was suspended in a
conical flask containing 200ml of distilled water.
autoclave for steam sterilization.
Prepare 10 Petri dishes once in presence of laminar air flow.
placed in incubator for 24 hours.
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Preparation of colloidal silver solutionFor 100 ppm concentration of colloidal silver solution
The 100ml deionized water with 0.010gm of silver powder was
stirred in magnetic stirrer at room temperature.
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Coating technique
(i) Spin coating (ii) Dip coating
During the first stage , a small puddle of the colloidal solution
was dropped at the center of the sample loaded.
Coating was accelerated to 1000 and 3000 rpm for 1 min.
During the last stage, the coated film was dried in a hot air
oven at 4050o
C for 1 h for complete removal of thesolvent.
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Surface characterizationSurface energy analysis(using goniometer)
Surface chemistry analysis (using FTIR Spectroscopy)
Surface morphology(using scanning electron microscope)
Thickness analysis ( using surface profilometer)
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Surface energy calculation
Surface energy Polar and dispersive components
Ks = Ksp + Ks
d
Fowkes approximation method
[(1+ cosU)/2][ Kl/(Kld)1/2] = (Ks
p)1/2 (Klp/Kl
d)1/2 + (Ksd)1/2
U - contact angle of liquid on solid surface, measured by sessile
drop method .
Ks, Kl - surface energy of the solid, liquid.
Klp , Kl
d polar and dispersive components of liquid surface
energy.
Ksp, Ks
dpolar and dispersive components of solid surface energy
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Surface free energies of test liquids used
Test liquids Klp Kl
d Kl
Water 51.0 21.8 72.8
Formamide 38.5 19.0 57.5
Diiodomethane 2.3 48.5 50.8
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Overview of Static contact angle
measurements
1
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Assessment of antimicrobial activityThe samples were subjected to Agar Diffusion test which
is based on zone of inhibition.
The zone of inhibition is simply the area on the agar platethat remains free from microbial growth.
A microbial suspension was spread over the face of a
sterile agar plate.
Coated sample was placed on agar plate.Incubated for an18-24 hours.
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Sl.No. Power(W)Flow
rate(sccm)Time(min)
Ksp
mN m-1
Ksd
mN m-1
Ks
mN m-1
1 20 10 6 6.3 34.5 40.8
2 60 10 6 6.1 31.9 38.0
3 100 10 6 4.8 31.5 36.3
4 150 10 6 4.5 30.2 34.7
5 60 10 2 7.9 29.8 37.8
6 60 10 8 6.5 32.3 38.8
7 60 10 10 5.0 33.4 38.4
8 60 5 6 4.5 33.0 37.5
9 60 15 6 8.1 32.0 40.1
10 60 20 6 4.8 33.9 38.7
Results and discussion1(a) Surface energy analysis after Ar plasma treatment
untreated polycarbonate: Ksp = 1.3 mN m-1 , Ksd= 31.8 mN m-1 ,Ks =33.1mN m-1
1
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Effect of surface energy with RF power
0 20 40 60 80 100 120 140 160
34
35
36
37
38
39
40
41
42
Surfaceenergy(mN/m)
Power(W)
Time= 6 min, Flow rate=10sccm
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Effect of Surface energy with time
0 2 4 6 8 10 1 2
30
32
34
36
38
40
42
44
Surfaceenergy(mN/m)
Time(min.)
RF power= 60W,Flow rate= 10sccm
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1(b)FTIR analysis
1
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Details of different peaks in FTIR spectra
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1(c)Agar diffusion test
The productionofa high concentrationofchemically active speciesin
the plasma phase may cause the increase ofthe antimicrobial
propertiesofcolloidal silver
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2(a) Surface energy analysis after oxygen plasma treatment
(i) Variation of surface energy with RF power
U of untreated PC with water- 79.51o U of treated PC- 28.58o
20 40 60 80 100 120 140 160
50
52
54
56
58
60
62
64
66
68
Surfaceenergy(mN/m)
Power(W)
After1 hr
After24hrs
Flow rate = 14 sccm, ExposureTime= 6 min
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(ii) Variationofsurface energy with time
0 2 4 6 8 10
60.0
60.5
61.0
61.5
62.0
62.5
63.0
63.5
64.0
64.5
65.0
surfaceenergy(mN/m
)
Exposure Time(min.)
After1 hr.
After24 hrs.
Flow rate=14sccm,Power= 120W
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(iii)Variation of surface energy vs flow rate
0 2 4 6 8 10 12 1450
52
54
56
58
60
62
64
66
68
70
SurfaceEnergy(mN/m)
Flow rate(sccm)
After1hr.
After24hrs.
RF Power=120W, Exposure Time=6 min
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2(b) FTIR analysis
1
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2(c) SEM analysis
SEM image of untreated
polycarbonate
SEM image of uncoated PC treated
by oxygen plasma at 50W
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SEM Pictures of Dip coating by Colloidal silver on 50W Oxygen plasma treated
Polycarbonate on at (a) 100ppm (b) 400ppm
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Sem image of spin coating by 400ppm Conc. Of colloidal silver on 50W oxygen
plasma treated Polycarbonate
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2(d) Film thickness analysisFilm thickness of untreated PC at 400 ppm -191nm
Results:-additional colloidal silver particles coordinated with new
functional groups formed on the surface.
Sample Power( in W) Concentrati
on
Film thickness
(in nm)
1 40 400 ppm 244
2 80 400 ppm 282
3 120 400 ppm 315
4 150 400 ppm 346
5 150 1 mg/ ml 2220
40 60 80 100 120 140 160
240
260
280
300
320
340
360
Filmt
hickness(innm)
Power(in W)
Concentration=400
ppm
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continueAntimicrobial effect of colloidal silver is evident from agar
diffusion test.
SEM study supported the increased surface energy results by
exhibiting increased roughness.
From the results of profilometer, It may be concluded that afterplasma treatment on sample, adhesion property of PC
increases.
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Future workSurface modification of polycarbonate by Helium and Nitrogen
plasma treatment of improvement of antibacterial properties.
Study the effect of process variable of plasma treatment onantimicrobial properties.
Extension of this work for gram-positive bacteria like
Staphylococcus aureus (S.aureus).
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References1. Wei Zhang, Paul K. Chu, Junhui Ji, Yihe Zhang. Plasma surface modification of poly vinyl
chloride for improvement of antibacterial properties. Biomaterials 27 (2006) 4451.
2. .K. Vaideki, S. Jayakumar, R. Rajendran. Investigation on the effect of RF air plasma and
neem leaf extract treatment on the surface modification and antimicrobial activity of cotton
fabric. Applied Surface Science 254 (2008) 24722478.
3. Sumin Kim, Hyun-Joong Kim. Anti-bacterial performance of colloidal silver-treated
laminate wood flooring. International Biodeterioration & Biodegradation 57 (2006) 155162.
4. Der-Chi Tien, Kuo-Hsiung Tseng, Chih-Yu Liao. Colloidal silver fabrication using the
spark discharge system and its antimicrobial effect on Staphylococcus aureus. MedicalEngineering & Physics 30 (2008) 948952.
5. N. Gomathi, C. Eswaraiah, Sudarsan Neogi. Surface Modification of Polycarbonate by
Radio-Frequency Plasma and Optimization of the Process Variables with Response Surface
Methodology. Journal of Applied Polymer Science, Vol. 114, 15571566 (2009).
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6. Gomathi, N., Sureshkumar, A., Sudarsan Neogi, 2008. RF plasma treated polymers
for biomedical applications. Current Science 94, 1478-1486.
7. Petica, S. Gavriliu, M. Lungu, N. Buruntea. Colloidal silver solutions with
antimicrobial properties. Materials Science and Engineering B 152 (2008) 2227.
8. Victor Torres, Monica Popa, Daniel Crespo. Silver nanoprism coatings on optical
glass substrates. Microelectronic Engineering 84 (2007) 1665-1668.
9. Wei Zhang, Paul K. Chu, Junhui Ji. Antibacterial properties of plasma-modified and
triclosan or bronopol coated polyethylene. Polymer 47 (2006) 931936.
10.Jaleh, B.; Parvin, P.; Wanichapichart, P.; Saffar, A.P.; Reyhani, A. Induced super
hydrophilicity due to surface modication of polypropylene membrane treated by
O2plasma. Applied Surface Science Vol. 257 (2010), 16551659.
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Thank You
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Fourier transform infra-red spectroscopic
(FTIR)It deals with the infrared region of the electromagnetic
spectra
The infrared spectrum of a sample is recorded by passing abeam of infrared light through the sample. Examination of
the transmitted light reveals how much energy was
absorbed at each wavelength.
Analysis of these absorption characteristics reveals detailsabout the molecular structure of the sample. When the
frequency of the IR is the same as the vibration frequency
of a bond, absorption occurs.
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Scanning Electron Microscope (SEM)
(SEM) is a type of electron microscope that images a sample by scanning
it with a high-energy beam of electrons in a raster scan pattern.
The electrons interact with the atoms that make up the sample producingsignals that contain information about the sample's surface topography,
composition, and other properties such as electrical conductivity.
SEM can produce very high-resolution images of a sample surface,
revealing details about less than 1 to 5 nm in size.Due to the very narrow electron beam, SEM micrographs have a large
depth of field yielding a characteristic three-dimensional appearance
useful for understanding the surface structure of a sample.
1