U.S. patent application number 13/620214 was filed with the patent office on 2013-03-21 for cold plasma sterilization devices and associated methods.
This patent application is currently assigned to Cold Plasma Medical Technologies, Inc.. The applicant listed for this patent is David J. Jacofsky, Marc C. Jacofsky, Gregory A. Watson. Invention is credited to David J. Jacofsky, Marc C. Jacofsky, Gregory A. Watson.
Application Number | 20130071286 13/620214 |
Document ID | / |
Family ID | 47879451 |
Filed Date | 2013-03-21 |
United States Patent
Application |
20130071286 |
Kind Code |
A1 |
Watson; Gregory A. ; et
al. |
March 21, 2013 |
Cold Plasma Sterilization Devices and Associated Methods
Abstract
A cold plasma sterilization device for sterilization of objects
such as medical instruments. Gas is fed to a plasma chamber where
it is energized by one or more electrodes coupled to a pulse source
to thereby generate a cold plasma inside the plasma chamber. A
dielectric barrier is sandwiched between the gas compartment and
the electrodes to form a dielectric barrier discharge device.
Inside the plasma chamber, one or more conductive stands that are
coupled to ground hold the object to-be-sterilized. The cold plasma
exits the plasma chamber, where it is recirculated for further use
as a plasma source in subsequent cycles. Gases that can be used
include noble gases such as helium, or combinations of noble
gases.
Inventors: |
Watson; Gregory A.;
(Sanford, FL) ; Jacofsky; Marc C.; (Phoenix,
AZ) ; Jacofsky; David J.; (Peoria, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Watson; Gregory A.
Jacofsky; Marc C.
Jacofsky; David J. |
Sanford
Phoenix
Peoria |
FL
AZ
AZ |
US
US
US |
|
|
Assignee: |
Cold Plasma Medical Technologies,
Inc.
Scottsdale
AZ
|
Family ID: |
47879451 |
Appl. No.: |
13/620214 |
Filed: |
September 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61535250 |
Sep 15, 2011 |
|
|
|
Current U.S.
Class: |
422/22 ;
315/111.21 |
Current CPC
Class: |
H05H 1/2406 20130101;
A61M 15/02 20130101; H05H 2001/4682 20130101; H01J 37/3244
20130101; H05H 2240/20 20130101; A61L 2202/11 20130101; A61N 1/44
20130101; H05H 2001/466 20130101; A61L 2/0094 20130101; H01J
37/32348 20130101; A61N 1/40 20130101; A61L 2/00 20130101; A61L
2/14 20130101; H01J 37/321 20130101; H05H 2001/2412 20130101; H05H
2245/1225 20130101; H05H 1/46 20130101; A61M 16/12 20130101; A61L
2/0011 20130101; A61M 2202/0208 20130101; A61M 2202/025 20130101;
A61M 16/06 20130101; H01J 37/3266 20130101; H05H 2277/10
20130101 |
Class at
Publication: |
422/22 ;
315/111.21 |
International
Class: |
A61L 2/08 20060101
A61L002/08; H05H 1/24 20060101 H05H001/24 |
Claims
1. A cold plasma sterilization device comprising: a plasma chamber
comprising a gas input port and a gas output port for throughput of
a gas; one or more dielectric barrier discharge devices attached to
the plasma chamber and configured to generate a cold plasma within
the plasma chamber, wherein each of the one or more dielectric
barrier discharge devices is formed by a dielectric barrier being
sandwiched between a respective electrode and the interior of the
plasma chamber, and wherein each of the electrodes is coupled to a
high voltage electric input; and a conductive stand disposed within
the plasma chamber and configured to accept an object for
sterilization, wherein the conductive stand is coupled to
ground.
2. The cold plasma sterilization device of claim 1, farther
comprising: a gas recirculation system coupled to the gas input
port and the gas output port of the plasma chamber, the gas
recirculation system comprising a recirculating pump configured to
recirculate the gas around the gas recirculation system.
3. The cold plasma sterilization device of claim 2, further
comprising: a fill port for introduction of the gas into the gas
recirculation system; and an exit port for exhaustion of the gas
out of the gas recirculation system.
4. The cold plasma sterilization device of claim 2, wherein the
recirculation pump is a circulation fan.
5. The cold plasma sterilization device of claim 1, wherein the gas
comprises a noble gas.
6. The cold plasma sterilization device of claim 1, wherein the gas
comprises helium.
7. The cold plasma sterilization device of claim 1, wherein the one
or more dielectric barrier discharge devices include a first group
and a second group of dielectric barrier discharge devices, the
first and second group being located on opposing sides of the
plasma chamber.
8. The cold plasma sterilization device of claim 1, wherein the one
or more dielectric barrier discharge devices are distributed evenly
with respect to a center of the conductive stand.
9. The cold plasma sterilization device of claim 1, wherein the
conductive stand comprises two or more conductive stands, each
configured to accept a respective objective for sterilization, and
each coupled to ground.
10. The cold plasma sterilization device of claim 1, wherein the
plasma chamber further comprises: a cover having an open position
and a closed position, the open position providing external access
to the conductive stand.
11. A method comprising: placing an object for sterilization on a
conductive stand inside a plasma chamber, wherein the conductive
stand is coupled to ground and configured to accept an object for
sterilization, and wherein the plasma chamber includes a gas input
port and a gas exit port; receiving a gas into the plasma chamber
via a gas input port, with the gas exiting via a gas output port;
and energizing the gas in the plasma chamber to generate a cold
plasma via one or more dielectric barrier discharge devices
attached to the plasma chamber, wherein each of the one or more
dielectric barrier discharge devices is formed by a dielectric
barrier being sandwiched between an electrode and the interior of
the plasma chamber, and wherein each of the electrodes is coupled
to a high voltage electric input.
12. The method of claim 11, further comprising: recirculating, by a
recirculating pump, the gas around a gas recirculation system,
wherein the gas recirculation system is coupled to the gas input
port and the gas output port of the plasma chamber.
13. The method of claim 12, further comprising: introducing gas
into the gas recirculation system via a fill port; and exhausting
the gas out of the gas recirculation system via an exit port.
14. The method of claim 12, wherein the recirculating by a
recirculating pump includes recirculating by a circulation fan.
15. The method of claim 11, wherein the gas comprises a noble
gas.
16. The method of claim 11, wherein the gas comprises helium.
17. The method of claim 11, wherein the energizing includes using a
first group and a second group of dielectric barrier discharge
devices, the first and second group being located on opposing sides
of the plasma chamber.
18. The method of claim 11, wherein the energizing includes using
one or more dielectric barrier discharge devices distributed evenly
with respect to a center of the conductive stand.
19. The method of claim 11, wherein the placing an object for
sterilization on a conductive stand inside a plasma chamber
includes placing two or more objects for sterilization on
respective conductive stands inside the plasma chamber.
20. The method of claim 11, wherein the placing an object for
sterilization on a conductive stand inside a plasma chamber
includes accessing the conductive stand via a cover associated with
the plasma chamber, the cover having an open position and a closed
position, with the open position providing the access to the
conductive stand.
21. The method of claim 12, further comprising: closing flaps in
the plasma chamber to thereby seal the plasma chamber and suspend
gas recirculation; purging the plasma chamber with fresh gas; and
opening the flaps in the plasma chamber to thereby resume gas
circulation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit under 35 U.S.C.
.sctn.119(e) of U.S. Provisional Patent Application No. 61/535,250,
entitled "Harmonic Cold Plasma Devices and Associated Methods",
filed on Sep. 15, 2011, which is hereby expressly incorporated by
reference in its entirety.
[0002] This application is related to U.S. patent application Ser.
No. 13/149,744, filed May 31, 2011, U.S. patent application Ser.
No. 12/638,161, filed Dec. 15, 2009, U.S. patent application Ser.
No. 12/038,159, filed Feb. 27, 2008, and U.S. Provisional
Application No. 60/913,369, filed Apr. 23, 2007, each of which are
herein incorporated by reference in their entireties.
BACKGROUND
[0003] 1. Field of the Art
[0004] The present invention relates to devices and methods for
creating cold plasmas, and, more particularly, to cold plasma
sterilization methods and application devices.
[0005] 2. Background Art
[0006] Atmospheric pressure hot plasmas are known to exist in
nature. For example, lightning is an example of a DC arc (hot)
plasma. Many DC arc plasma applications have been achieved in
various manufacturing processes, for example, for use in forming
surface coatings. Atmospheric pressure cold plasma processes are
also known in the art. Most of the at or near atmospheric pressure
cold plasma processes are known to utilize positive to negative
electrodes in different configurations, which release free
electrons in a noble gas medium.
[0007] Devices that use a positive to negative electrode
configuration to form a cold plasma from noble gases (helium,
argon, etc.) have frequently exhibited electrode degradation and
overheating difficulties through continuous device operation. The
process conditions for enabling a dense cold plasma electron
population without electrode degradation and/or overheating are
difficult and challenging to achieve.
[0008] In another challenging area, autoclaves continue to be used
for sterilization of hospital equipment, particularly surgical
instruments. However, the use of autoclaves poses several
disadvantages that include the following. First, the time needed to
cycle an autoclave system (e.g., up to 45 minutes for a full cycle)
is substantial, and includes the need for significant cool down
time. Second, the repeated temperature swings are rough on
equipment, and the use of steam weathers metals. Third, autoclaves
are large pieces of equipment with high upkeep costs and frequent
downtime. Finally, when a surgical instrument is dropped or
otherwise contaminated in an operating room, it must be "flashed"
in the autoclave. This is a short cycle (e.g. 15-20 minutes) of
high heat and pressure. These surgical instruments come back to the
operating room very hot and therefore must cool prior to their use.
During this time period, the patient is under anesthetic and likely
has an opened wound, with resulting increased potential
complications. It is therefore desirable to have an improved method
of rapidly sterilizing surgical instruments without the undesirable
heating effects, exposure to steam and length time periods
associated with autoclaves.
BRIEF SUMMARY OF THE INVENTION
[0009] As noted above, autoclaves have a number of disadvantages in
their use in the sterilization of medical equipment. It is
therefore desirable to have an improved method of rapidly
sterilizing surgical instruments without the undesirable heating
effects and exposure to steam.
[0010] Non-thermal gas plasmas (i.e., cold plasmas) have been shown
to be effective at the destruction of many pathogens. In addition
to their usefulness in the destruction of pathogens, it is also
desirable to recirculate the gas used for cold plasma generation.
Recirculation not only increases the efficiency of a cold plasma
system, but also reduces the operating costs of such a system. In
order to achieve effective sterilization of surfaces, and more
specifically surgical instruments, contact times of several minutes
may be necessary. To effect longer contact times, it is desirable
to have a chamber that can contain one or more instruments and a
volume of plasma. This description embodies the concept, in device
and technique, for creating a plasma sterilization chamber and
recirculating the feed/source specialty gas which would otherwise
be lost to ambient air conditions. The contained CP recirculation
unit shows how a noble gas can be used repeatedly in a cold plasma
reaction chamber by way of electron separation in the reaction
chamber, and electron attraction back to the normal atomic orbit in
the non-energized part of the recirculation unit. This system works
at or near atmospheric pressure levels, requiring no substantial
additional pressure or vacuum.
[0011] An embodiment of a cold plasma sterilization device is
described that includes a plasma chamber having a gas input port
and a gas output port for throughput of a gas. One or more
dielectric barrier discharge devices are attached to the plasma
chamber and are configured to generate a cold plasma within the
plasma chamber. Each of the one or more dielectric barrier
discharge devices is formed by a dielectric barrier being
sandwiched between a respective electrode and the interior of the
plasma chamber. In addition, each of the electrodes is coupled to a
high voltage electric input. A conductive stand is disposed within
the plasma chamber and configured to accept an object for
sterilization, wherein the conductive stand is coupled to ground.
In a further embodiment, recirculation of the gas in the cold
plasma sterilization device is described.
[0012] Another embodiment is described regarding a method of
generating a cold plasma. An object for sterilization is placed on
a conductive stand inside a plasma chamber, where the conductive
stand is coupled to ground and configured to accept the object for
sterilization. The plasma chamber includes a gas input port and a
gas exit port. Gas is received into the plasma chamber via a gas
input port, with the gas exiting via a gas output port. The gas is
energized in the plasma chamber to generate a cold plasma via one
or more dielectric barrier discharge devices attached to the plasma
chamber. A dielectric barrier is sandwiched between an electrode
and the interior of the plasma chamber to form each of the one or
more dielectric barrier discharge devices. Each of the electrodes
is coupled to a high voltage electric input.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0013] FIGS. 1A and 1B are cutaway views of the hand-held
atmospheric harmonic cold plasma device, in accordance with
embodiments of the present invention.
[0014] FIGS. 2A and 2B illustrate an embodiment of the cold plasma
device without magnets, in accordance with embodiments of the
present invention.
[0015] FIG. 3 is an exemplary circuit diagram of the power supply
of a cold plasma device, in accordance with embodiments of the
present invention.
[0016] FIG. 4 illustrates the generation of cold plasma resulting
using a dielectric barrier discharge principle, in accordance with
embodiments of the present invention.
[0017] FIG. 5 illustrates a cold plasma sterilization device, in
accordance with an embodiment of the present invention.
[0018] FIG. 6 illustrates a recirculating cold plasma sterilization
device, in accordance with an embodiment of the present
invention.
[0019] FIG. 7 illustrates a plasma chamber of a recirculating cold
plasma sterilization device, in accordance with an embodiment of
the present invention.
[0020] FIG. 8 illustrates the cold plasma emanating from a cold
plasma sterilization device, in accordance with an embodiment of
the present invention.
[0021] FIG. 9 illustrates the cold plasma emanating from a cold
plasma sterilization device, in accordance with an embodiment of
the present invention.
[0022] FIG. 10 illustrates a method of sterilizing an object using
a cold plasma sterilization device, in accordance with an
embodiment of the present invention.
[0023] FIG. 11 illustrates a method of sterilizing an object using
a cold plasma sterilization device that uses plasma chamber
purging, in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Cold temperature atmospheric pressure plasmas have attracted
a great deal of enthusiasm and interest by virtue of their
provision of plasmas at relatively low gas temperatures. The
provision of a plasma at such a temperature is of interest to a
variety of applications, including wound healing, anti-bacterial
processes, various other medical therapies and sterilization.
Cold Plasma Application Device
[0025] To achieve a cold plasma, a cold plasma device typically
takes as input a source of appropriate gas and a source of high
voltage electrical energy, and outputs a plasma plume. FIG. 1A
illustrates such a cold plasma device. Previous work by the
inventors in this research area has been described in U.S.
Provisional Patent Application No. 60/913,369, U.S. Non-provisional
application Ser. No. 12/038,159 (that has issued as U.S. Pat. No.
7,633,231) and the subsequent continuation applications
(collectively "the '369 application family"). The following
paragraphs discuss further the subject matter from this application
family further, as well as additional developments in this
field.
[0026] The '369 application family describes a cold plasma device
that is supplied with helium gas, connected to a high voltage
energy source, and which results in the output of a cold plasma.
The temperature of the cold plasma is approximately 65-120 degrees
F. (preferably 65-99 degrees F.), and details of the electrode,
induction grid and magnet structures are described. The voltage
waveforms in the device are illustrated at a typical operating
point in '369 application family.
[0027] In a further embodiment to that described in the '369
application, plasma is generated using an apparatus without
magnets, as illustrated in FIGS. 2A and 2B. In this magnet-free
environment, the plasma generated by the action of the electrodes
61 is carried with the fluid flow downstream towards the nozzle 68.
FIG. 2A illustrates a magnet-free embodiment in which no induction
grid is used. FIG. 2B illustrates a magnet-free embodiment in which
induction grid 66 is used. FIG. 1B illustrates the same embodiment
as illustrated FIG. 2B, but from a different view. Although these
embodiments illustrate the cold plasma is generated from electrode
12, other embodiments do not power the cold plasma device using
electrode 12, but instead power the cold plasma device using
induction grid 66.
[0028] In both a magnet and a magnet-free embodiment, the
inductance grid 66 is optional. When inductance grid 66 is present,
it provides ionization energy to the gas as the gas passes by.
Thus, although the inductance grid 66 is optional, its presence
enriches the resulting plasma.
[0029] As noted above, the inductance grid 66 is optional. When
absent, the plasma will nevertheless transit the cold plasma device
and exit at the nozzle 68, although in this case, there will be no
additional ionization energy supplied to the gas as it transits the
latter stage of the cold plasma device.
[0030] As noted with respect to other embodiments, magnetic fields
can be used in conjunction with the production of cold plasmas.
Where present, magnetic fields act, at least at some level, to
constrain the plasma and to guide it through the device. In
general, electrically charged particles tend to move along magnetic
field lines in spiral trajectories. As noted elsewhere, other
embodiments can comprise magnets configured and arranged to produce
various magnetic field configurations to suit various design
considerations. For example, in one embodiment as described in the
previously filed '369 application family, a pair of magnets may be
configured to give rise to magnetic fields with opposing directions
that act to confine the plasma near the inductance grid.
Cold Plasma Unipolar High Voltage Power Supply
[0031] The '369 application family also illustrates an embodiment
of the unipolar high voltage power supply architecture and
components used therein. The circuit architecture is reproduced
here as FIG. 3, and this universal power unit provides electrical
power for a variety of embodiments described further below. The
architecture of this universal power unit includes a low voltage
timer, followed by a preamplifier that feeds a lower step-up
voltage transformer. The lower step-up voltage transformer in turn
feeds a high frequency resonant inductor-capacitor (LC) circuit
that is input to an upper step-up voltage transformer. The output
of the upper step-up voltage transformer provides the output from
the unipolar high voltage power supply.
[0032] FIG. 3 also illustrates an exemplary implementation of the
unipolar high voltage power supply 310 architecture. In this
implementation, a timer integrated circuit such as a 555 timer 320
provides a low voltage pulsed source with a frequency that is
tunable over a frequency range centered at approximately 1 kHz. The
output of the 555 timer 320 is fed into a preamplifier that is
formed from a common emitter bipolar transistor 330 whose load is
the primary winding of the lower step-up voltage transformer 340.
The collector voltage of the transistor forms the output voltage
that is input into the lower step-up voltage transformer. The lower
step-up transformer provides a magnification of the voltage to the
secondary windings. In turn, the output voltage of the lower
step-up voltage transformer is forwarded to a series combination of
a high voltage rectifier diode 350, a quenching gap 360 and finally
to a series LC resonant circuit 370. As the voltage waveform rises,
the rectifier diode conducts, but the quench gap voltage will not
have exceeded its breakdown voltage. Accordingly, the quench gap is
an open circuit, and therefore the capacitor in the series LC
resonant circuit will charge up. Eventually, as the input voltage
waveform increases, the voltage across the quench gap exceeds its
breakdown voltage, and it arcs over and becomes a short circuit. At
this time, the capacitor stops charging and begins to discharge.
The energy stored in the capacitor is discharged via the tank
circuit formed by the series LC connection.
[0033] Continuing to refer to FIG. 3, the inductor also forms the
primary winding of the upper step-up voltage transformer 340. Thus,
the voltage across the inductor of the LC circuit will resonate at
the resonant frequency of the LC circuit 370, and in turn will be
further stepped-up at the secondary winding of the upper step-up
voltage transformer. The resonant frequency of the LC circuit 370
can be set to in the high kHz-low MHz range. The voltage at the
secondary winding of the upper step-up transformer is connected to
the output of the power supply unit for delivery to the cold plasma
device. The typical output voltage is in the 10-150 kV voltage
range. Thus, voltage pulses having a frequency in the high kHz-low
MHz range can be generated with an adjustable repetition frequency
in the 1 kHz range. The output waveform is shaped similar to the
acoustic waveform generated by an impulse such as a bell is struck
with a hammer. Here, the impulse is provided when the spark gap (or
SCR) fires and produces the voltage pulse which causes the resonant
circuits in the primary and secondary sides of the transformer to
resonate at their specific resonant frequencies. The resonant
frequencies of the primary and the secondary windings are
different. As a result, the two signals mix and produce the unique
`harmonic` waveform seen in the transformer output. The net result
of the unipolar high voltage power supply is the production of a
high voltage waveform with a novel "electrical signature," which
when combined with a noble gas or other suitable gas, produces a
unique harmonic cold plasma that provides advantageous results in
wound healing, bacterial removal and other applications.
[0034] The quenching gap 360 is a component of the unipolar high
voltage power supply 310. It modulates the push/pull of electrical
energy between the capacitance banks, with the resulting generation
of electrical energy that is rich in harmonic content. The
quenching gap can be accomplished in a number of different ways,
including a sealed spark gap and an unsealed spark gap. The sealed
spark gap is not adjustable, while unsealed spark gaps can be
adjustable. A sealed spark gap can be realized using, for example,
a DECI-ARC 3000 V gas tube from Reynolds Industries, Inc.
Adjustable spark gaps provide the opportunity to adjust the output
of the unipolar high voltage power supply and the intensity of the
cold plasma device to which it is connected. In a further
embodiment of the present invention that incorporates a sealed (and
therefore non-adjustable) spark gap, thereby ensuring a stable
plasma intensity.
[0035] In an exemplary embodiment of the unipolar high voltage
power supply, a 555 timer 320 is used to provide a pulse repetition
frequency of approximately 150-600 Hz. As discussed above, the
unipolar high voltage power supply produces a series of spark gap
discharge pulses based on the pulse repetition frequency. The spark
gap discharge pulses have a very narrow pulse width due to the
extremely rapid discharge of capacitive stored energy across the
spark gap. Initial assessments of the pulse width of the spark gap
discharge pulses indicate that the pulse width is approximately 1
nsec. The spark gap discharge pulse train can be described or
modeled as a filtered pulse train. In particular, a simple
resistor-inductor-capacitor (RLC) filter can be used to model the
capacitor, high voltage coil and series resistance of the unipolar
high voltage power supply. In one embodiment of the invention, the
spark gap discharge pulse train can be modeled as a simple modeled
RLC frequency response centered in the range of around 100 MHz.
Based on the pulse repetition frequency of 192 Hz, straightforward
signal analysis indicates that there would be approximately
2,000,000 individual harmonic components between DC and 400
MHz.
[0036] In another embodiment of the unipolar high voltage power
supply described above, a 556 timer or any timer circuit can be
used in place of the 555 timer 320. In comparison with the 555
timer, the 556 timer provides a wider frequency tuning range that
results in greater stability and improved cadence of the unipolar
high voltage power supply when used in conjunction with the cold
plasma device.
Cold Plasma Sterilization Device
[0037] Devices, other than the cold plasma device illustrated above
in FIG. 1, can also generate cold plasma. For example, cold plasma
can also be generated by a dielectric barrier discharge device,
which relies on a different process to generate the cold plasma. As
FIG. 4 illustrates, a dielectric barrier discharge (DBD) device 400
contains one metal electrode 410 covered by a dielectric layer 420.
The electrical return path 430 is formed by the ground 440 that can
be provided by the substrate undergoing the cold plasma treatment.
Energy for the dielectric barrier discharge device 400 can be
provided by a power supply 450, such as that described above and
illustrated in FIG. 2. More generally, energy is input to the
dielectric barrier discharge device in the form of pulsed
electrical voltage to form the plasma discharge. By virtue of the
dielectric layer, the discharge is separated from the metal
electrode and electrode etching is reduced. The pulsed electrical
voltage can be varied in amplitude and frequency to achieve varying
regimes of operation.
[0038] In an exemplary embodiment of the present invention, a
sterilization device is provided as shown in FIG. 5. Cold plasma
sterilization device 500 has plasma chamber 510 through which gas
flow occurs. Gas enters at gas input 540 and exits at gas output
550. Plasma chamber 510 is surrounded by electrodes 520 which are
connected to electrical input line 530. Separating plasma chamber
510 from electrodes 520 is a dielectric barrier 560. In order to
ensure a gas-tight seal, one or more gaskets 570 can be used. This
device has an elongated insulating structure surrounded by a
conductor. Plasma chamber 510 can be made of insulating material,
including acrylic, plastic, ceramic and the like. Similarly,
dielectric barrier 560 can be made of any suitable dielectric
material sufficient to withstand the high voltages applied to the
electrodes. For example, dielectric barrier 560 can be made of a
suitable dielectric material, such as ceramic,
polytetrafluoroethylene (PTFE), quartz and the like. Plasma chamber
510 can be any shape including a cylinder. Electrical input line
530 is configured to be connected to a pulsed power supply (not
shown). Pulsed power supply provides a source of pulsed electrical
source of appropriate voltage and frequency.
[0039] As noted above, plasma chamber 510 is a chamber in which gas
of an appropriate composition can be presented for gas flow through
to an output orifice, such as gas output 550. In a typical example,
the gas is helium. Other gases include a helium-oxygen gas
combination, although other gases and gas combinations can be used.
When electrical energy is applied to device, a cold plasma is
formed in the gas. Stray capacitance in plasma chamber 510 will
flow to ground to complete the electrical circuit and result in the
formation of ionized gas or plasma (albeit somewhat diffuse). A
target object (e.g., an object to be sterilized) can be placed in
an object holder within plasma chamber 510. If the object holder
has a connection, or a suitable capacitance, to ground, such a
connection will result in a greater intensity of the plasma. The
cold plasma can be visual in that a non-transparent color will
become evident upon the provision of energy to the gas. This type
of cold plasma device can be used for the sterilization of surgical
implants and instruments, where a small size model is suitable for
use in operating room, laboratory, medical office, etc., and a
large size model is suitable for central sterilization processing
in a hospital, medical supply or manufacturing facility.
[0040] Gas can be used once and released. Alternatively, the gas
can be re-used or recycled (i.e., recirculated). Advantages
obtained by recirculating the gas include the following. First,
gases, and in particular noble gases such as helium, are expensive.
Second, power utilization can be reduced. Fresh gas that enters the
system for the first time requires high energy levels to achieve
ionization, while returning gas in a recirculation system retains
an elevated energy level when it returns to the plasma chamber.
Consequently, recirculation allows for potentially a lower power
consumption. Third, certain working environments do not permit
large volumes of gas (e.g., noble gas) in a contained occupied
space such as an operating room due to the risk of potential
suffocation. Furthermore, when an ionized noble gas mixes with
ambient air, reactive molecules such as ozone are produced, which
are potential irritants. Finally, a recirculation process causes
turbulence that ensures the cold plasma is well distributed in the
treatment chamber, and therefore reaches into the inner lumina of
tools (e.g., cannulated drill bits, laparoscopy tools).
[0041] In an exemplary embodiment of the present invention, a low
gas consumption embodiment 600 of the cold plasma device is
illustrated in FIG. 6. Any appropriate gas can be used, with helium
being a possible gas. Gas is input to the recirculatory system via
an fill port 650. Gas can be released from the recirculatory system
via exit port 660. A recirculate pump 610, such as a circulation
fan, forces the gas in a clockwise direction from the fill port 650
to a plasma chamber 620, where the gas encounters one or more
dielectric barrier device structures of the type illustrated in
FIG. 5. These dielectric barrier device structures are coupled to
one or more appropriate high voltage pulsed power sources of the
type illustrated in FIG. 2 and described above. Gas exits from
plasma chamber 620 to rejoin the recirculation loop in a clockwise
fashion. Motion of the gas in a counter-clockwise fashion also
falls within the scope of embodiments of the present invention. In
the recirculatory system, the plasma-carrying gas can exit through
an exit port 660 for possible external application to a treatment
area of interest. Recirculate pump 610, such as a circulation fan,
can also control the degree of ionization of the resulting plasma,
as well as the timing of the sterilization of the treatment area.
View tubes 640 can be optionally added to provide the ability to
visually examine the gas flow, and presence of the cold plasma.
Pressure gauge 630 can be optionally added to provide additional
control and measurements of the performance of the cold plasma
recirculatory system 600.
[0042] A typical use model of the cold plasma sterilization system
600 is described below. An object, such as a medical instrument, to
be sterilized is placed into plasma chamber 620. A suitable gas
source, such as a noble gas source is connected to the fill port
650 and both the fill port 650 and exit port 660 are opened until
plasma chamber 620 contains only noble gas. At this point, fill
port 650 and exit port 660 are both closed. The electrical energy
is next provided to electrical input 680, which is coupled to
electrodes similar to electrodes 520 illustrated in FIG. 5. The
electrical energy causes cold plasma to form in plasma chamber 620.
Recirculate pump 610, such as a recirculation fan, is turned on.
The action of recirculate pump 610 draws some of the ionized gas
out of plasma chamber 620 to the left, as illustrated in FIG. 6.
Some ionized gas may be visible in the left most view tube 640
shown above. The plasma is returning to its ground state with
increasing distance from plasma chamber 620. The reconstituted
noble gas passes by recirculate pump 610 (i.e., recirculation fan,
or other suitable pumping mechanism), and returns to plasma chamber
620 to be ionized again. This creates a continuous flow of cold
plasma through plasma chamber 620 which serves to increase contact
between the plasma and object to be sterilized (e.g., medical
instrument), particularly in the inner spaces of the
to-be-sterilized object, while maintaining cool temperatures. In an
embodiment, the recirculate pump 610 can be variable speed in order
to provide a variety of operating regimes commensurate with
different gas flow speeds.
[0043] Referring to FIG. 7, which shows further details of plasma
chamber 620, there are six electrodes 720 placed on either side of
this ionization chamber 710, for a total of twelve electrodes 20.
In other embodiments, electrodes 720 can be completely on one side
of plasma chamber 620, or divided into two or more groups of
electrodes distributed either randomly inside plasma chamber 620 or
in distributed in a non-random fashion inside plasma chamber 620.
There are two metallic conductive stands 740 in the center of
plasma chamber to receive the object to be sterilized. These
metallic conductive stands 740 are coupled to a ground path. In
other embodiments, electrodes 720 can be positioned equally about
the center of metallic conductive stand 740, or center of metallic
conductive stands 740, when multiple metallic conductive stands 740
are in use. When plasma chamber 620 is filled with gas via gas port
750 (gas port 760 would provide the exit port for the gas) and the
energy is activated via electrical wires 730, the energy flows
through the gas toward the object to-be-sterilized to return to
ground. In doing so, the energy ionizes the gas within plasma
chamber 620 and bathes the object to-be-sterilized (e.g., medical
instrument) in plasma thereby sanitizing its surfaces.
[0044] Referring to both FIGS. 6 and 7, in an exemplary embodiment
of plasma chamber 610, plasma chamber 610 can be fitted with an
acrylic top cover 770 (e.g., seal plate), and a series of fasteners
670 that maintain cover 770 in place during operation. For example,
the thickness of the acrylic top cover 770 can be 0.75'', with a
series of 5/16''.times.6'' bolts used as fasteners. Fasteners 670
(e.g,, bolts) are present to allow access to plasma chamber 610,
but maintain positive pressure when plasma chamber 610 is being
purged of room air and filled with the required gas, e.g., noble
gas. A suitable hinge and latch system, studs and nuts or other
equivalent mechanisms can be used to implement fasteners 670.
[0045] FIG. 8 illustrates the internal environment of plasma
chamber showing the distal end of a cannulated acorn reamer 820,
the object undergoing sterilization. Two electrodes 810 are visible
in the upper portion of the illustration. One of the ground stands
830 holding the cannulated acorn reamer 820 is visible to the right
side of FIG. 8. The iridescent balls of light are focal energy flow
from the plasma to the cannulated acorn reamer 820, which are
likely due to fine scale surface irregularities.
[0046] FIG. 9 illustrates a lateral view of the entire cannulated
acorn reamer 920 in plasma chamber 610 during system recirculation
mode. The six electrodes 910 on one side of plasma chamber 610 are
clearly visible. The more intense ionization is noted at the ground
stands 930, while a fine plasma covers the whole of plasma chamber
610. Without the circulating air flow due to, for example,
recirculate pump 610, the distribution of the cold plasma would be
more coarse and uneven.
[0047] In a further embodiment, plasma chambers 610 can be
configured in series to allow multiple simultaneous objects to be
sterilized in a row of chambers, all connected to the same
recirculatory gas system. A bypass port and valve assembly could
accompany each chamber so that if one chamber were to be opened,
the power is cut, and gas is bypassed so that the other chambers
remain unaffected. Once closed again, the individual chamber is
purged with fresh noble gas, valves opened, and it is returned to
the series. Such a multiple plasma chamber configuration would be
useful for high throughput applications.
[0048] In a still further embodiment, plasma chamber 510 can
include doors or flaps at the gas input 540 and gas output 550.
Before accessing plasma chamber 510, the doors or flaps can be
closed on the inflow and outflow tubes of plasma chamber 510 in
order to seal off the rest of the system from the ambient
environment. After the next item is loaded in plasma chamber 510,
the chamber is purged with fresh gas, and the doors or flaps are
then reopened. Using the doors or flaps, only plasma chamber 510
needs to be purged and refilled with the gas, rather than the whole
system. Alternatively, fill port 650 and exit port 660 can be
located anywhere in the system, including at the plasma chamber
510. Therefore, instead of doors or flaps, fill port 650 and exit
port 660 can be used to purge plasma chamber 510. For example, a
gas cartridge can be connected to fill port 650 to refill plasma
chamber 510. Using this approach, the gas in the remainder of the
system (i.e., the gas that is "walled off") would take a
substantial amount of time to become sufficiently contaminated as
to adversely affect the cold plasma generation process, and thereby
require more extensive purging. Using the doors or flaps thereby
reduces gas consumption. In a hospital sterilization setting, small
gas cartridges can be used rather than large gas cylinders to
supply gas to the cold plasma sterilization system.
Cold Plasma Sterilization Usage Methods
[0049] FIG. 10 provides a flowchart of an exemplary method 1000 to
generate a cold plasma using a cold plasma treatment device,
according to an embodiment of the present invention.
[0050] The process begins at step 1010. In step 1010, an object for
sterilization is placed on a metal stand inside a plasma chamber,
wherein the conductive stand is coupled to ground and configured to
accept an object for sterilization, and wherein the plasma chamber
includes a gas input port and a gas exit port. In an embodiment, an
object 820 is placed on a conductive stand 740 in a plasma chamber
710, having gas input and output ports 750, 760.
[0051] In step 1020, gas is received into a plasma chamber. In an
embodiment, a gas is received into plasma chamber 710.
[0052] In step 1030, the received gas is energized in the plasma
chamber to form a cold plasma via one or more dielectric barrier
discharge devices attached to the plasma chamber, wherein each of
the one or more dielectric barrier discharge devices is formed by a
dielectric barrier being sandwiched between an electrode and the
interior of the plasma chamber, and wherein each of the electrodes
is coupled to a high voltage electric input. In an embodiment, the
received gas is energized in plasma chamber 710 using energy from
electrodes 720 that is in turn received from electrical input 730.
Dielectric barrier 560 is sandwiched between electrode 520 and
plasma chamber 510.
[0053] At step 1040, method 1000 ends.
[0054] FIG. 11 provides a flowchart of an exemplary method 1100 to
generate a cold plasma including recirculation, using a cold plasma
treatment device, according to an embodiment of the present
invention.
[0055] The process begins at step 1110. In step 1110, an object for
sterilization is placed on a metal stand inside a plasma chamber,
wherein the conductive stand is coupled to ground and configured to
accept an object for sterilization, and wherein the plasma chamber
includes a gas input port and a gas exit port. In an embodiment, an
object 820 is placed on a conductive stand 740 in a plasma chamber
710, having gas input and output ports 750, 760.
[0056] In step 1120, gas is received into a plasma chamber. In an
embodiment, a gas is received into plasma chamber 710.
[0057] In step 1130, the received gas is energized in the plasma
chamber to form a cold plasma via one or more dielectric barrier
discharge devices attached to the plasma chamber, wherein each of
the one or more dielectric barrier discharge devices is formed by a
dielectric barrier being sandwiched between an electrode and the
interior of the plasma chamber, and wherein each of the electrodes
is coupled to a high voltage electric input. In an embodiment, the
received gas is energized in plasma chamber 710 using energy from
electrodes 720 that is in turn received from electrical input 730.
Dielectric barrier 560 is sandwiched between electrode 520 and
plasma chamber 510.
[0058] In step 1140, flaps in the plasma chamber are closed to seal
the plasma chamber.
[0059] In an embodiment, flaps in plasma chamber 710 are closed to
thereby suspend gas recirculation.
[0060] In step 1150, the plasma chamber is purged with fresh gas.
In an embodiment, plasma chamber 710 is purged with fresh gas with,
for example, the use of a gas cartridge to provide the required
amount of gas.
[0061] In step 1160, the flaps in the plasma chamber are reopened.
In an embodiment, flaps in plasma chamber 710 are reopened to
thereby resume gas recirculation.
[0062] In step 1170, method 1100 ends.
[0063] It is to be appreciated that the Detailed Description
section, and not the Summary and Abstract sections, is intended to
be used to interpret the claims. The Summary and Abstract sections
may set forth one or more but not all exemplary embodiments of the
present invention as contemplated by the inventor(s), and thus, are
not intended to limit the present invention and the appended claims
in any way.
[0064] The present invention has been described above with the aid
of functional building blocks illustrating the implementation of
specified functions and relationships thereof. The boundaries of
these functional building blocks have been arbitrarily defined
herein for the convenience of the description. Alternate boundaries
can be defined so long as the specified functions and relationships
thereof are appropriately performed.
[0065] The foregoing description of the specific embodiments will
so fully reveal the general nature of the invention that others
can, by applying knowledge within the skill of the art, readily
modify and/or adapt for various applications such specific
embodiments, without undue experimentation, without departing from
the general concept of the present invention. Therefore, such
adaptations and modifications are intended to be within the meaning
and range of equivalents of the disclosed embodiments, based on the
teaching and guidance presented herein. It is to be understood that
the phraseology or terminology herein is for the purpose of
description and not of limitation, such that the terminology or
phraseology of the present specification is to be interpreted by
the skilled artisan in light of the teachings and guidance.
[0066] The breadth and scope of the present invention should not be
limited by any of the above-described exemplary embodiments, but
should be defined only in accordance with the following claims and
their equivalents.
* * * * *