Flexible Microplasma Devices: Phototherapeutic Bandages

1
Flexible Microplasma Devices Phototherapeutic
Bandages

• Senior Design Final Presentation
• December 1st, 2005
• Kate Tobin and Jason Readle, Group 13
• TA Alexander Spektor

2
Outline

• Introduction
• Objectives
• Original Design
• Fabrication
• Challenges and Design Decisions
• Testing
• Performance
• Safety
• Recommendations

3
Introduction

• Devices consist of two treated flexible aluminum
  strips
• Plasma forms in the gap between strips and
  cavities
• Gas selection determines output spectrum
• Flexible light-emitting devices such as these
  have many potential medical applications

4
Objectives

1. Fabricate devices to operate in vacuum chamber
2. Also develop a packaging to allow the devices to
   work outside the chamber
3. Test and characterize device performance
4. Evaluate safety of device for medical use

5
Wavelengths for Phototherapy

• Irradiation devices with output from 400-500nm
  have been effective against eczema1
• UVA (340-400nm) has been successfully used to
  treat sclerosing skin diseases2
• A wide range of wavelengths have been used in
  tandem with photosensitizers for photodynamic
  therapy, with many new sensitizers with strong
  absorbance at 650-850nm 3,4
• Time interval between sensitizer administration
  and light treatment can often be several days3
• Dosage required varies, 3 J/cm2 500 J/cm2 4

• J. Krutmann, K. Medve-Koenigs, T. Ruzicka, U.
  Ranft, J. H. Wilkens, Ultraviolet-free
  phototherapy, Photodermatology Photoimmunology
  Photomedicine, vol. 21, pp. 59-61, 2005
• M. Brenner, T. Herzinger, C. Berking, G. Plewig,
  K. Degitz, Phototherapy and photochemotherapy of
  sclerosing skin diseases, Photodermatology
  Photoimmunology Photomedicine, vol. 21, pp.
  157-165, 2005
• D. Dolmans, D. Fukumura, R. K. Jain,
  Photodynamic therapy for cancer, Nature Reviews
  Cancer, vol. 3, pp. 380-387, 2003
• 4 T. J. Dougherty, C. J. Gomer, B. W. Henderson,
  G. Jori, D. Kessel, M. Korbelik, J. Moan, Q.
  Peng, Photodynamic therapy review, Journal of
  the National Cancer Institute, vol. 90, pp.
  889-905, 1998

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Photodynamic Cancer Treatment
D. Dolmans, D. Fukumura, R. K. Jain, Photodynamic
therapy for cancer, Nature Reviews Cancer, vol.
3, pp. 380-387, 2003
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Original Design
(Proprietary information deleted)
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Original Design

• Al2O3 as dielectric barrier on strips
• Acts as barrier to sputtering caused by AC plasma
• Protect against shorting out/breakdown
• Supports electric field to excite gas
• Glass paste to enhance durability and dielectric
  strength

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Fabrication
10
Fabrication
Untreated Sample
Anodization
Glass Paste
Baking
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Vacuum Chamber Devices
Polyimide Tape
Wire Attachment
Vacuum Chamber Device
Vacuum Chamber Device
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Packaged Devices
(Proprietary information deleted)
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Challenges and Design Decisions

• Thickness of Al2O3 layer
• Too thick higher operating voltages
• Too thin risk of breakdown greater
• First vacuum chamber device may have experienced
  breakdown due to thinner layer
• Glass paste consistency
• Protects devices from wrinkling easily and
  increases dielectric strength, but can make
  device stiff if too thick

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Challenges and Design Decisions

• Gas selection
• He, Ne, and N2 all have emission lines favorable
  to certain medical applications
• He has much lower intensity, difficult to
  generate N2 plasma without raising voltage too
  high
• Focused testing on Ne
• Lengthy fabrication process
• Out of 35 strips cut, only 3 devices (6 strips)
  survived for demonstration (2 vacuum chamber
  devices, 1 packaged device)

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Challenges and Design Decisions
(Proprietary information deleted)
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Successes
17
TestingPerformance and Safety
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Tests Performed

• L-I (chamber only) and I-V by adjusting supply
  voltage and measuring output light (cd/m2) and
  supply current, derived resistance and efficiency
  from this
• Output spectrum and uniformity using CCD camera
• Tested leakage in packaged device using pressure
  transducer
• Measured temperature and conductivity of packaged
  device with thermocouple and multimeter

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Vacuum System Setup
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Test Setup
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L-I-V, Flat Device
Turn on
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L-I-V, Bent Device
Turn on
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I-V, Packaged Device
(Proprietary information deleted)
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Uniformity

• Measured Luminance (cd/m2) at 9 points on Flat
  Device with constant voltage and pressure, during
  best operation we could achieve

Non-uniformity (lower is better) Standard Deviation 100s/µ 100(Max-Min)/(2µ)
700 Torr Neon, 308 Vrms 5.44 8.99
400 Torr Helium, 263 Vrms 8.44 12.14
As a reference, commercial flat lamp for
backlighting has non-uniformity of 20
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Efficiency, Flat Device
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Efficiency, Bent Device
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Differential Resistance
Most plasma devices have negative differential
resistance
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706 nm
390 nm
427 nm
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(No Transcript)
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585 nm
702 nm
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Packaging Test
(Proprietary information deleted)
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Safety
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Resistance of Packaging

• Multimeter was unable to read anything but open
  during testing, and is rated to go up to 20 M?
• Only discharge array would be exposed in final
  product

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Operating Temperature

• After device had been running 30 minutes,
  temperature stabilized at 38 C (100 F)
• Negative temperature effects do not begin until
  43 C (restricted blood flow)
• Packaging was exposed to up to 80 C over the
  course of an hour without comprising its integrity

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Range of Operating Voltages

• Wide operating range turn-on voltage and
  breakdown
• Table corresponds to tests with Neon at 700 T
• This will permit the use of a fixed-voltage power
  supply, i.e. 230 Vrms, so that users cannot harm
  themselves adjusting voltage

Turn-On (Vrms) Upper Limit Tested (Vrms)
Vacuum Flat 153 317
Vacuum Bent 164 266
Packaged 195 249
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Recommendations

• Automated and standardized fabrication process to
  improve device uniformity
• Improved uniformity would allow for higher
  applied voltages
• Greater output intensity without breakdown
• Use of more difficult gases such as N2
• Bulk production roll to roll process (to reduce
  costs)
• Sealing packaging in desired gas environment
• (Proprietary information deleted)

37
Thanks

• Dr. Sung-Jin Park Visiting Professor, Mentor
• Alex Spektor ECE 445 T.A.
• Dr. J. Gary Eden Director of Laboratory for
  Optical Physics and Engineering
• Kwang Soo Kim Graduate Student