Recommendations for Future Work - Conclusion and Recommendations for Future Study

Chapter 8. Conclusion and Recommendations for Future Study

8.2 Recommendations for Future Work

(1) The fluid modeling coupled with a neutral flow solver using detailed plasma chemistry should be conducted to help elucidate the observed physical phenomena, which are otherwise very difficult to understand only based on measurements.

(2) Further tailor of the properties of nitrogen- and air-based discharges using a realistic pulse-based power source with the help of fluid modeling should be conducted to enhance the applicability of the proposed discharges.

(3) For CF₄/Air DBD APPJ OES measurement, try to enlarge the relative CFx/F line peak intensity of OES spectrum compare with background (without plasma) CF4/Air. To presume plasma chemistry of the possible existence of CFx/F line peak in discharge region of CF4/Air DBD APPJ.

(4) For CF₄/Air DBD APPJ post-discharge region, try to use FTIR measuring reactive F species (as CFx fragment and CF2O) IR spectrum. To presume plasma chemistry of the possible existence of relative F species in post-discharge region of CF4/Air DBD APPJ.

(5) Using ATR-FTIR analysis the bacteria (E. coli and B. subtilis)/B. subtilis spore of surface chemical composition after DBD plasma untreated/treated to explain the cell wall variation of C1s/O1s chemical bonding energy.

(6) For B. subtilis spore sterilization mechanism presuming of CF4/Air DBD APPJ, to study relative references about low pressure CF₄/O₂ plasma remove photo-resistance mechanism. And try to search the optimum concentration of CF4/Air for B. subtilis spore sterilization.

(7) To use air DBD APPJ treated the similar cell membrane material (liposome bilayers) and compare the SEM of liposome bilayers and E. coli. It can help to

understand plasma chemistry of E. coli outer cell wall.

(8) For PP film treated by nitrogen-based DBD APPJ, the XPS data of chemical composition C and O atom concentration are different with C1s peak curve fitting C-O, C-C, C=O, COO concentration. To discuss with equipment technician about the calculating rules and verify again.

(9) For PP film non-stationary treated by nitrogen-based DBD APPJ case, try to normalize the equation of non-stationary speeds and treatment distances in fixed O2/N2

ratio. It can help to presume PP film contact angle variation in application.

(10) More studies are required to clarify qualitatively and quantitatively what kinds of reactive species for the sterilization of B. subtilis spore using the CF₄/air DBD APPJ.

(11) We can possibly apply an enlarged enclosure to cover the post-discharge jet region to form a region of abundant metastable region for some specific applications.

(12) As demonstrated in the present thesis, we have shown that the nitrogen- and air-based DBD APPJ system is very effective with a reduced cost in improving hydrophilic properties and sterilization/inactivation of a polymer surface. It is thus highly promising to apply this APPJ system to improve the cell attachment or bio-compatibility of some bio-materials, for example, PLA ((C6H8O4)n) as the skeleton of artificial vascular graft and PDMS ((C₂H₆OSi)_n) as the microfluidic channels, in a totally dry approach, unlike the conventional chitosan coating ((C6H11NO4)n), which is notoriously time-consuming and very tedious.

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Appendix A.

Removal of the 2nd Order Radiation in OES Spectra

We have used two long-pass filters (280 and 400 nm) to measure the OES spectra (Fig. A-1 and A-2) to remove the 2^nd order radiation caused by the grating system of the OES. We used the 280 nm long-pass filter for removing the NO-γpeak emission lines (215, 226.9, 237, 247 nm) to verify if our originally measured spectra in the range of 430-500 nm in the post-discharge region (N2 + 0.06% O2) contained the 2nd order NO-γemission lines. We have observed that the corresponding 2nd order of NO-γpeak emission lines (430, 453.8, 474, 494 nm) disappeared. Similarly, the use of 400 nm long-pass filter have made the 674.2 nm emission (2nd order of 337.1 nm) disappeared in the post-discharge region (pure N2). For reference, Fig. A-3 (below) shows the detailed classification of the originally unfiltered observed OES lines. The above verified that the originally measured OES spectra without optical filters require some proper modifications by removing these 2nd order emission lines, as now shown in the new Figs. A-4(a) and A-4(b). As shown in the new Fig. A-4(b), the N2 1st positive emission line (580 nm) was clearly observed, especially as 0.06% of O₂ was added into the N2.

200 300 400 500

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W Frequency : 60 kHz

z : 4 (mm)

(b)

Fig. A-1 The OES spectra (a) without filter; (b) w/280 nm longpass filter

200 300 400 500

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W Frequency : 60 kHz

z : 4 (mm)

(b)

Fig. A-2 The OES spectra (a) 200-500 nm w/480 nm filter; (b) 500-900 nm w/400 nm filter.

180 220 260 300 340 380 420 460 500

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

180 220 260 300 340 380 420 460 500

Wavelength (nm)

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

Dielectric material: Quartz 1mm Plasma absorbed power : 175 W

Fig. A-3 OES in the (a) 180-500 nm; (b) 500-900 nm for the post-discharge plasma (60 kHz, 50 SLM, absorbed power=175W).

180 220 260 300 340 380 420 460 500

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

180 220 260 300 340 380 420 460 500

Wavelength (nm)

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

Dielectric material: Quartz 1mm Plasma absorbed power : 175 W

Dielectric material: Quartz 1mm Plasma absorbed power : 175 W Frequency : 60 kHz

z : 4 (mm)

(b)

Fig. A-4 Optical emission spectra for the post-discharge plasma: (a) 180-500 nm; (b) 500-900 nm (60 kHz, 50 SLM, absorbed power=175W).

Table A-1 Major reaction channels in a nitrogen/oxygen discharge.

Appendix B.

3D-table min. scale 0.05 mm Z=2mm tolerance= 0.05 / 2

100 1.25%

± 2 × = ±

3. Output power from power supply Quasi-pulsed power min. scale 10W

Nitrogen-based DBD APPJ 500 W tolerance= 10 / 2

100 1%

± 500 × = ± Air-based DBD APPJ 300 W tolerance= 10 / 2

100 1.67%

± 300 × = ±

4. Frequency

Quasi-pulsed power min. scale 0.01 kHz

Nitrogen-based DBD APPJ 60 kHz tolerance= 0.01/ 2

100 0.01%

± 60 × = ±

Air-based DBD APPJ 30 kHz tolerance= 0.01/ 2

100 0.02%

± 30 × = ±

5. Contact angle

CAs are obtained by averaging over three to five measurements over a region of a ITO glass/PP film with ±3°.

PP film CA (23°) tolerance= 3

100 13.04%

±23× = ±

6. AFM Roughness (nm)

Surface roughness are obtained by averaging over three to five measurements over a region of a ITO glass/PP film with ±0.05 nm.

ITO glass untreated roughness 0.68 nm tolerance= 0.05

100 7.35%

±0.68× = ±

Table 1-1 Breakdown voltages of the plasma discharge [Schutze et al., 1998]

Table 1-2 Densities of charge species in the plasma discharge [Schutze et al., 1998]

Table 1-3 Densities of oxygen species in the discharges [Schutze et al., 1998]

Table 1-4 Main plasma reaction [Eliasson, B., 1991]

Table 2-1 Summary of the DBD-APPJ system.

Item Description Model Specification

1 Planar DBD APPJ

APPL Designed (1) Two parallel copper electrodes 50 × 50 × 8 mm

APPL Designed (1) The inlet cooling temperature control was 20 ± 2℃

(2) The water pressure control was 1.6 ± 0.1 kg/cm²

(3) The diameter of the cooling pipe was 1/4”

(2) frequency converter (0~60Hz) 6 Non-Stationary

Stage

U-S1-D0-H080378 (Unice E-O Service

Inc.)

(1) Maximum traveling distance 20 cm

Table 2-2 Summary of the instrumentation.

Ite m

Description Model Specification

1 (1) Thermocouple on the surface using a micropipette

(3) The values of the static contact angle were obtained using Laplace-Young curve fitting to measure the 10 average values

8 AFM D5000 (Veeco) (1) Surface Profile measurement

(2) Max. horizontal scan area: 80×80μm²

(2) Electron voltage: 5kV (3) Amplification factor: respect to the PP film surface was 45°,

(2) Imaging exposure time:

0.2 sec for 1 mm-side view, 2 sec for 50 mm-front view

(post-discharge region) (3) Imaging exposure time:

0.2 sec for bottom view (discharge region)

Table 2-3 Element peak line information of NO (220-280 nm)

Table 2-4 Test conditions of planar DBD APPJ in PP film modification application.

175 W Plasma absorbed power

2 – 20 mm Treatment distance

60 kHz, 500 W, power density (Large) Output power from

Non-stationary speed: 0.5 - 8 cm/s ITO glass treatment

60 kHz, 500 W, power density (Large) Output power from

Non-stationary speed: 0.5 - 8 cm/s ITO glass treatment

60 kHz, 500 W, power density (Large) Output power from

Non-stationary speed: 1 - 9 cm/s ITO glass treatment

60 kHz, 500 W, power density (Large) Output power from

Non-stationary speed: 1 - 9 cm/s ITO glass treatment

50 slm (16.5 m/s) Flow rate

N₂(99.99%)、O2 /N₂(0.004~1.6%) Discharge gas

Table 2-6 Test conditions of planar DBD APPJ in E. coli and B. subtilis sterilization.

30 kHz, 300 W, power density (Large) Output power from

Table 2-7 Test conditions of planar DBD APPJ in B. subtilis spore sterilization.

Non-stationary speed: 1 cm/s

30 kHz, 300 W, power density (Large) Output power from

power supply

B. subtilisspore (10⁵、10⁶、10⁷spore/mL) Treatment bacterial cell

Compressed air 、CF4/air (2%) Discharge gas

30 kHz, 300 W, power density (Large) Output power from

power supply

B. subtilisspore (10⁵、10⁶、10⁷spore/mL) Treatment bacterial cell

Compressed air 、CF4/air (2%) Discharge gas

Table 3-1 FTIR measured absorption peak value of 1055 cm^-1 for ozone in the post-discharge region for N2, compressed air, and O2 discharges in z distance 4-20mm.

0.0152

Table 4-1 Measured contact angles of non-stationary PP film at different O₂/N₂ ratios after plasma treatment (z=2 mm, v= 0.5 cm/s)

O₂/N₂ (%) Contact angle (^o)

0 75

0.002 74

0.004 73

0.006 72

0.008 70

0.01 77

0.012 77

0.014 76

0.016 74

0.019 73

0.021 73

0.06 26

0.2 27

0.4 33

0.8 39

1.6 77

Table 4-2 Measured contact angles of non-stationary PP film at four typical O₂/N₂ ratios after plasma treatment (Z=2 mm, v= 0.5-8 cm/s)

V (cm/s) O₂/N₂ (%)

0.06 0.20 0.40 0.80

0.5 26 27 33 39

1 33 45 50 72

2 80 82 94 94

4 97 91 101 98

8 100 97 103 103

Table 4-3 RMS roughness of PP film at different treating distances measured by AFM

z (mm) RMS roughness (nm)

Untreated 40.4

2 19.6

6 17.8

20 28.6

Table 4-4 Atomic percent concentration and ratio and percentage peak area of XPS C1s core level spectra of untreated PP and atmospheric- pressure plasma treated PP

Table 5-1 XPS measured chemical composition of ITO glass after planar-DBD APPJ

Table 6-1 Summary of survival rates under different treatment distances for E. coli bacteria (10⁷ CFU/mL) on petri dishes for different gas discharges. Other discharge parameters: gas flow rate=10 slm, stage moving speed=1cm/sec, output power from power supply=300 W, gap=1 mm, and Z=20 mm.

89/20/3/1/0

Table 6-2 Summary of survival rates under different treatment distances for B. subtilis bacteria (10⁷ CFU/mL) on petri dishes for different gas discharges. Other discharge parameters: gas flow rate=10 slm, stage moving speed=1cm/sec, output power from power supply=300 W, gap=1 mm, and z= 20 mm.

80/61/18/3/0

Table 7-1 Chemical composition of PP film after planar-DBD APPJ treatment (30 kHz, output power from power supply=300 W)

CF₄/air

Table 7-2 Summary of survival rates under different bacterial number treatments for B.

subtilis spore bacteria on petri dishes for air discharges. Other discharge parameters: gas flow rate=5 slm, stage moving speed=1cm/sec, output power from power supply=300 W, gap=1 mm, and Z=14 mm.

Table 7-3 Summary of survival rates under different bacterial number treatments for B.

subtilis spore bacteria on petri dishes for CF₄/air (2%) discharges. Other discharge parameters: gas flow rate=5 slm, stage moving speed=1cm/sec, output power from power supply=300 W, gap=1 mm, and Z=14 mm.

96/9/0/0/0

(a) (b)

Fig. 1-1 Types of atmospheric-pressure plasma: (a) transferred arc; (b) plasma jet; (c) corona discharge; and (d) dielectric barrier discharge. [Schutze et al., 1998].

(a)

(b) (c)

Fig. 1-2 Typical electrode arrangements of barrier discharges: (a) planar reactor; (b) cylindrical reactor; and (c) pin-to-plate discharge. [Wagner, et al., 2003 and Lee, et al., 2005]

Power supply

Fig. 2-1 Schematic sketch of a planar DBD APPJ

Fig. 2-2 Image of the venting chamber.

-12 -8 -4 0 4 8 12 Voltage (kV)

-500 -400 -300 -200 -100 0 100 200 300 400 500

Charge (nC)

*Gas: N₂

Flow rate: 50 (slm) Power: 500 (W) Frequency: 60 (kHz) Discharge gap: 1 (mm) Dielectric: Quartz 1 (mm)

(a)

(b)

Fig. 2-3 Typical Lissajous figure for a parallel-plate DBD APPJ: (a) distorted-sinusoidal voltage power supply; and (b) AC power supply [Wagner et al. 2003].

PMT

Fig. 2-4 Schematic sketch of a planar DBD APPJ with OES measurement.

Fig. 2-5 Line identification of O₂/N₂ DBD plasma OES spectrum (180-280 nm).

245 246 247 248 249

λ (µm)

0 2 4 6 8 10

Intensity (a.u.)

exp

sim (360 K)

*Gas: N₂

Flow rate: 50 (slm) Frequency: 60 (kHz) Dischage gap: 1 (mm) Dielectric: Quartz 1 (mm) Specrum: NO-r

=0.01 nm

Position: Discharge

Fig. 2-6 Observed and simulation emission spectra of NO-γ. The gas temperature in the calculated spectrum was 360 K (∆λ=0.01 nm, output power from power supply= 500W).

3600 3200 2800 2400 2000 1600 1200 800

Wavenumber (cm-1)

0 0.03 0.06 0.09 0.12 0.15

Absorbance (a.u.)

* Gas : Air

Flow rate : 10 (slm)

Dielectric : ceramic (2mm) Gap : 1 (mm)

Input power : 300 (W) Frequency : 30 (kHz) Z : 16 (mm)

CO₂

H₂O

O₃

Fig. 2-7 Air DBD plasma infrared spectrum in 800-3600 cm^-1 (air plasma) (output power from power supply=300 W).

(a)

(b)

Fig. 3-1 Images of post-discharge region of APPJ with discharge gases consisting of (a) N2, and (b) N2+0.06% O2 (output power from power supply=500 W).

Fig. 3-2 Bottom view of discharge region for N2, compressed air and O2 discharges. Other discharge parameters: gas flow rate=10 slm; output power from power supply=300 W;

and gap=1 mm.

N

₂

Compressed air O

₂

1.5 cm

N

₂

Compressed air O

₂

1.5 cm

Fig. 3-3 Side view of post-discharge region for N₂, compressed air and O₂ discharges.

Other discharge parameters: gas flow rate=10 slm; output power from power supply=300 W; and gap=1 mm.

0 5 10 15

Time (µs)

-12 -8 -4 0 4 8 12

Voltage (kV)

-2.5 2.5 7.5 12.5 17.5

-600 -400 -200 0 200 400 600

Current (mA)

*Gas: N₂

Flow rate: 50 SLM Gap: 1 (mm)

Dielectric material: Quartz 1 mm Plasma absorbed power: 175 W Frequency: 60 kHz

Fig. 3-4 Typical current and voltage waveforms for N₂ discharge (60 kHz).

-10 0 10 20 30 40 50

Dielectric: Ceramic 2 (mm) Power: 300 (W)

-10 0 10 20 30 40 50

Fig. 3-5 Typical current and voltage waveforms for various gas discharges: (a) N₂; (b) O₂; and (c) compressed air (output power from power supply=300 W).

-12 -8 -4 0 4 8 12

Voltage (kV)

-500 -400 -300 -200 -100 0 100 200 300 400 500

Charge (nC)

*Gas: N₂

Flow rate: 50 (slm) Power: 500 (W) Frequency: 60 (kHz) Discharge gap: 1 (mm) Dielectric: Quartz 1 (mm)

Fig. 3-6 Typical Lissajous figure for a parallel-plate DBD APPJ of N₂ discharge (output power from power supply=500 W).

-10 -8 -6 -4 -2 0 2 4 6 8 10

Voltage (kV)

-600 -400 -200 0 200 400 600

Charge (nC)

*Gas: Compressed air Flow rate: 10 (slm) Gap: 1 (mm)

Dielectric: Ceramic 2 (mm) Power: 300 (W)

Frequency: 30 (kHz)

(c)

Fig. 3-7 Lissajous figure for a parallel-plate DBD APPJ for various gas discharges driven by a distorted sinusoidal voltage power supply (30 kHz, output power from power supply=300 W): (a) N₂; (b) O₂; and (c) compressed air.

180 220 260 300 340 380 420 460 500

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

180 220 260 300 340 380 420 460 500

Wavelength (nm)

Dielectric material : Quartz 1mm Plasma absorbed power : 175 W

Dielectric material: Quartz 1mm Plasma absorbed power : 175 W

Dielectric material: Quartz 1mm Plasma absorbed power : 175 W Frequency : 60 kHz

z : 4 (mm)

(b)

Fig. 3-8 Optical emission spectra in (a) 180-500 nm; and (b) 500-900 nm for post-discharge plasma (60 kHz, 50 SLM)

O

₂

/N

₂

(%)

Z d is ta n ce (m m )

0.2 0.4 0.6 0.8 1

5 10 15 20

1E+06 900000 800000 700000 600000 500000 400000 300000 200000 100000 90000 80000 70000 60000 50000 40000 30000 20000 10000

Fig. 3-9 Distributions of typical NO-γ UV emission intensity (236.6 nm, photon energy:

5.2 eV) as functions of downstream distance and O₂/N₂ (%) in post-discharge region (60 kHz, 50 SLM, output power from power supply=500 W)

180 200 220 240 260 280 300 320 340 360 380 400

400 500 600 700 800 900

Wavelength (nm) post-discharge plasma (output power from power supply=300 W).

180 200 220 240 260 280 300 320 340 360 380

Wavelength (nm)

In te n si ty ( a. u .)

Air

Air+ 2% CF₄

* Flow rate: 5 (slm) Power: 300 (W) Frequency: 30 (kHz) Discharge gap: 1 (mm) Dielectric: Ceramic 2 (mm)

Fig. 3-11 Optical emission spectrum in 180-380 nm for the discharge plasma (output power from power supply=300 W).

0 4 8 12 16 20

z (mm)

20 30 40 50 60 70 80

T em p er at u re (

C )

Compressed Air O2

* Flow rate: 10 (slm) Power: 300 (W) Frequency: 30 (kHz) Discharge gap: 1 (mm) Dielectric: Ceramic 2 (mm)

Fig. 3-12 Temperature distributions in the post-discharge jet region of N2, compressed air and O₂ discharges (output power from power supply=300 W).

O₂/N₂(%)

Fig. 3-13 Distributions of O₃ concentration (ppm) as functions of downstream distance and O2/N2 (%) in post-discharge region (60 kHz, 50 SLM, output power from power supply=500 W).

3600 3200 2800 2400 2000 1600 1200 800

Wavenumber (cm^-1)

A b so rb an ce ( a. u .)

N₂

Compressed air O₂

O₃ O₃ O₃

* Z = 4 (mm)

Fig. 3-14 Infrared spectra of post-discharge region for N2, compressed air, and O2

discharges in the 800-3600 cm^-1 (30 kHz, 10 SLM, output power from power supply=300 W).

O₂/N₂(%)

Z d is ta n ce (m m )

0.5 1 1.5

5 10 15 20

100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 Degree (o)

Fig. 4-1 Distribution of measured contact angles as a function of downstream distance

在文檔中脈衝式電源之平板型介電質常壓電漿束特性分析及利用其後放電區域的應用研究 (頁 77-148)