Active Plasma Sterilizer with Smart Control

Abstract

Active Plasma Sterilizer (APS) system for sterilization / decontamination. [Solution] An active plasma sterilizer (APS) system for sterilization / decontamination includes a sterilization box and multiple small portable plasma reactors (CPPRs) positioned within the sterilization box and configured to generate a surface dielectric barrier discharge (SDBD) for generating and distributing reactive oxygen and nitrogen species (RONS) such as ozone, each of the multiple CPPRs having a reactor panel and a power supply circuit, and the reactor panel having at least one electrode separated by a dielectric medium.

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 417,521, filed October 19, 2022, and U.S. Provisional Application No. 63 / 417,672, filed October 19, 2022, the disclosures of each of which, including any figures, tables, and drawings, are incorporated herein by reference in their entirety. [Background technology]

[0002] The need to prevent interplanetary contamination in space research missions is rooted in two objectives: protecting the target celestial body from terrestrial microbiological contaminants, commonly referred to as "forward contamination," and protecting Earth from potential extraterrestrial life forms, commonly referred to as "backward contamination."

[0003] This important mission coincides with the advancement of the frontiers of space exploration and requires the development of technologies and practices dedicated to maintaining the integrity of scientific research conducted in space. Planetary protection is the protection of Earth from extraterrestrial life (backward contamination) and vice versa (forward contamination), while ensuring the reliability of data collected during space missions.

[0004] While contamination prevention technologies for planetary protection are well established for crewed missions, scientists are exploring technologies for crewed missions. Furthermore, existing technologies approved by the National Aeronautics and Space Administration (NASA) and the European Cooperation for Space Standards (ECSS) for non-crewed missions—dry heat microbial reduction (DHMR), ethylene oxide (EtO), and vapor-phase hydrogen peroxide (VHP)—have certain drawbacks. ECSS reports that DHMR can damage heat-sensitive materials, and VHP can cause harmful material degradation. EtO systems are restricted by regulatory agencies such as OSHA and the EPA due to their long exposure times (2.5–12 hours) and carcinogenic residues. Knowledge gaps regarding VHP's required concentration, delivery mechanism, and material compatibility also hinder its use in space missions. Therefore, alternative technologies are needed that can address microbial reduction for crewed missions while overcoming the drawbacks of currently approved methods for non-crewed missions.

[0005] Researchers have demonstrated that low-temperature plasma (LTP) has the potential to replace traditional decontamination methods used in fields such as planetary protection, food preservation, and surface sterilization. Dielectric barrier discharge (DBD) is a type of LTP that has proven effective against a variety of microorganisms, including bacterial endospores, which are important for planetary protection applications. DBDs are discharges formed when a sufficiently high alternating voltage is applied between two electrodes separated by a dielectric barrier. As the name suggests, surface DBDs (SDBDs) are DBDs formed on surfaces. SDBDs are unique in that they generate reactive species by influencing the surrounding gas flow without using moving parts. DBD decontamination occurs through direct contact with the discharge or indirect contact with reactive species formed by the discharge. Indirect DBD treatment is advantageous for treating hidden surfaces or surfaces relatively large in size. When SDBDs are generated in the air, they produce reactive oxygen and nitrogen species (RONS), which destroy microorganisms such as bacteria, viruses, and fungi. One such species is ozone, which is known to inactivate microorganisms and is the longest-lived species compared to other RONS formed during the production of SDBDs in the air. The mechanism of inactivation of such microorganisms involves a complex series of reactions that lead to cell surface destruction, cell surface leakage, cell component leakage, and cell lysis, ultimately inactivating the microorganisms.

[0006] In line with this vital objective, the Committee on Space Research (COSPAR) develops and regularly updates international policies for planetary protection, with a biennial update cycle. These policies are based on the celestial body and mission type involved. Planetary protection requires the decontamination of assembly cleanroom facilities, space research equipment, and spacecraft components to reduce (disinfect) or eradicate (sterilize) microbial populations.

[0007] Decontamination techniques currently approved for space missions by the National Aeronautics and Space Administration (NASA) and the European Space Cooperation for Standardization (ECSS) include dry heat microbial reduction (DHMR) and vapor phase hydrogen peroxide (VHP). The Viking spacecraft testing era led to the evolution and validation of a decontamination process that combines DHMR with solvent cleaning. Summary of the Invention [Problem to be solved by the invention]

[0008] However, these techniques can be harmful to the advanced materials and electronics used in today's spacecraft development. ECSS reports that the high processing temperatures used in DHMR can lead to damage to heat-sensitive materials, while the hydrogen peroxide used in VHP can lead to harmful material alterations. Furthermore, despite VHP being a NASA-approved technology, knowledge gaps regarding the required concentrations, delivery mechanisms, and material compatibility hinder its use in space missions.

[0009] Therefore, there is an urgent need to explore and develop alternative decontamination technologies that can overcome the inherent deficiencies of currently accepted methodologies in the context of space missions.

[0010] There is a continuing need in the art for improved designs and techniques for space pollution control systems and methods. [Means for solving the problem]

[0011] According to an embodiment of the present invention, an active plasma sterilizer (APS) system for sterilization / decontamination is provided, comprising a sterilization box and a plurality of small portable plasma reactors (CPPRs) disposed within the sterilization box and configured to generate a surface dielectric barrier discharge (SDBD) for generating and distributing reactive oxygen and nitrogen species (RONS). The RONS may also include ozone. The sterilization box is made of polycarbonate. The sterilization box comprises a grid structure disposed within the sterilization box and configured for decontamination measurements. The sterilization box has a plurality of through-holes disposed on the sides of the sterilization box, allowing inoculated sample pieces to be suspended within the sterilization box. Each of the plurality of CPPRs includes a reactor panel and a power supply circuit. The reactor panel includes at least one electrode separated by a dielectric medium. The power supply circuit is configured to convert a low DC voltage to a high AC voltage to generate an SDBD on the surface of the reactor panel. The plurality of CPPRs includes two reactor panels configured to generate different flow operations to better distribute the generated SDBD within the sterilization box. The two reactor panels are a comb reactor panel and a fan reactor panel. The comb reactor panel is configured to generate a two-dimensional (2D) flow distribution dominated by wall jets directed from the shaft of the comb reactor panel toward the tips of the teeth. The fan reactor panel is configured to generate a three-dimensional (3D) flow distribution that forms a swirling flow extending vertically upward and outward from the center of the fan reactor panel. The multiple CPPRs each include three CPPRSs each consisting of a fan reactor panel. The three fan reactor panels are arranged in an equilateral triangular shape on the upper inner surface of the sterilization box. One CPPR having a comb reactor panel is arranged on the bottom surface of the sterilization box, offset by a predetermined distance from the center of the bottom surface. The sterilization box can be, for example, a 3D-printed box using any suitable material (e.g., polycarbonate or any other suitable 3D printing material).

[0012] According to certain embodiments, an ozone decomposition system is provided, comprising: a heating element connected to a power source and configured to decompose ozone by heating ozonated air; a power supply module for supplying power to the heating element; a connecting pipe for providing a path for the ozonated air to flow; and an air pump configured to circulate the generated ozonated air. The ozone decomposition system may further include at least one sensor configured to measure an ozone level or an insulating element for insulating heat generated by the heating element. The power supply module is a standard wall power supply module or a battery-powered module. The power supply module has a feedback loop for supplying power to the heating coil. The power supply module further comprises a power amplifier and a controller configured to control an input voltage to the power amplifier. The input voltage to the power supply module is supplied with a duty cycle. The power supply module further comprises a feedback circuit configured to monitor operating parameters of the load and provide feedback to the controller, and the controller is configured to control operation of the power amplifier based on the provided feedback. The feedback circuit comprises an ozone sensor configured to detect ozone in the airflow.

[0013] According to another embodiment, an active plasma sterilizer (APS) system for sterilization / decontamination is provided, the APS system including a sterilization box, a plurality of small portable plasma reactors (CPPRs) disposed within the sterilization box and configured to generate a surface dielectric barrier discharge (SDBD) for generating and distributing reactive oxygen and nitrogen species (RONS), an ozone decomposition system including a heating element connected to a power source and configured to decompose ozone by heating ozonated air, a power supply module for supplying power to the heating element, a connecting pipe for providing a path for the ozonated air to flow, and an air pump configured to circulate the generated ozonated air. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic diagram of an APS sterilization box showing decontamination measurement locations, according to an embodiment of the present invention. [Figure 2A] FIG. 1 is a schematic diagram of a plume visualization showing the flow distribution in the reactor that facilitates dispersal of generated ozone, illustrating a comb-shaped reactor with solid and dashed lines representing exposed and grounded electrodes, respectively. [Figure 2B] FIG. 1 shows the characteristic flow of a comb reactor, with arrows indicating three wall jets, including a dominant wall jet directed from the shaft toward the tooth tips. [Figure 2C] FIG. 1 shows a visualization of the plume flow of the comb reactor working flow. [Figure 2D] 1 shows a fan reactor, with colored and gray areas representing exposed and grounded electrodes, respectively. [Figure 2E] FIG. 1 is a diagram showing the characteristic flow of each blade and the center of a fan reactor. [Figure 2F] 1 shows a plume visualization of the operating flow of a fan reactor, in accordance with an embodiment of the present invention, where the fan blades interact to form vortex-like structures, resulting in a generally conical flow projecting upward from the reactor base. [Figure 3] 10A-10C are images illustrating the process of integrating a CPPR and placing it into a sterilization box, according to an embodiment of the present invention. [Figure 4] 1 is a schematic diagram of a measurement grid for decontamination measurements in three planes, according to an embodiment of the present invention. FIG. [Figure 5] FIG. 1 is a schematic diagram illustrating the dimensions of an enclosure constructed for ozone penetration testing, according to an embodiment of the present invention. [Figure 6] 1 shows images of Orthofabric (left) and Kevlar® (right) fabric cells according to embodiments of the present invention. [Figure 7] 1 is a plot of the results of establishing a consistent control with E. coli inoculation, where sample pieces of the same material were inoculated with the same amount of E. coli culture, resulting in a consistent number of bacteria per sample piece, with a maximum variation of 0.3 log (CFU / sample piece), according to an embodiment of the present invention. [Figure 8]1 is a plot of the results of establishing a consistent control with Bacillus subtilis inoculation: sample pieces of the same material were inoculated with the same amount of Bacillus subtilis culture, resulting in a consistent number of bacteria per sample piece, with a maximum variation of 0.3 log (CFU / sample piece), according to an embodiment of the present invention. [Figure 9] Figure 10 is a plot of results showing the log of E. coli CFU / sample piece for exposed sample pieces (average of 11 sample pieces placed inside the APS) and control sample pieces (average of 3 sample pieces placed outside the APS) for four different sample piece materials, each replicated three times. According to an embodiment of the invention, complete kill (4-5 log reduction) was achieved in each case using four CPPRs and a 20-minute exposure (15 minutes CPPR on, 5 minutes CPPR off). [Figure 10] Figure 10 is a plot of results showing the uniform spatial distribution of log reduction of E. coli CFU / sample piece for nine exposed sample pieces placed on the center plane of an APS. According to an embodiment of the invention, complete kill (4-5 log reduction) was achieved at all points using four CPPRs and a 20 minute exposure (15 minutes CPPR on, 5 minutes CPPR off). [Figure 11] Figure 10 is a plot of results showing the log of Bacillus subtilis CFU / sample strip for exposed sample strips (average of 11 sample strips placed within the APS) and control sample strips (average of 3 sample strips placed outside the APS) for four different sample strip materials, each replicated three times. According to an embodiment of the invention, complete kill (4-5 log reduction) was achieved in most cases using six CPPRs and a 30-minute exposure (25 minutes CPPR on, 5 minutes CPPR off). [Figure 12] Figure 10 is a plot of results showing the uniform spatial distribution of log reduction of E. coli CFU / sample piece for nine exposed sample pieces placed on the center plane of an APS. According to an embodiment of the invention, complete kill (4-5 log reduction) was achieved at all points using four CPPRs and a 20 minute exposure (15 minutes CPPR on, 5 minutes CPPR off). [Figure 13A]FIG. 10 is a plot illustrating APS ozone data for four CPPRs and a 20 minute exposure (CPPR 15 minutes on, CPPR 5 minutes off) in accordance with an embodiment of the present invention. [Figure 13B] FIG. 10 is a plot illustrating APS ozone data for six CPPRs and a 30 minute exposure (25 minutes CPPR on, 5 minutes CPPR off) in accordance with an embodiment of the present invention. [Figure 14] FIG. 10 is a plot of results showing ozone concentrations before and after a fabric layer showing ozone penetration without a pump and with a pump, according to an embodiment of the present invention. [Figure 15] 1 shows material compatibility data from SEM analysis of APS exposure on aluminum, polycarbonate, OrthoFabric, and Kevlar®, according to an embodiment of the present invention. [Figure 16] FIG. 1 is a schematic diagram illustrating an embodiment of an ozonolysis module (ODM) for obtaining test results, according to an embodiment of the present invention. [Figure 17] 1 shows the results of an ODM embodiment test for 0 seconds of ODM operation, which represents the natural decay rate of ozone at room temperature according to an embodiment of the present invention. [Figure 18] 10 shows ODM embodiment test results for 30 seconds of ODM operation, according to an embodiment of the present invention. [Figure 19] 10 shows ODM embodiment test results for 60 seconds of ODM operation, according to an embodiment of the present invention. [Figure 20] FIG. 2 is a schematic diagram illustrating details of an ODM according to an embodiment of the present invention. [Figure 21] 1 is a schematic diagram illustrating a high voltage power supply module according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Embodiments of the present invention relate to an active plasma sterilizer (APS) system for surface decontamination in space and terrestrial applications.

[0016] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the invention. As used herein, the term "and / or" includes any and all combinations of at least one of the associated listed items. As used herein, the singular forms "a," "an," and "the" (indefinite and definite articles) are intended to include the plural as well as the singular, unless the context clearly indicates otherwise. Furthermore, as used herein, it will be understood that the terms "comprises" and / or "comprising" specify the presence of stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of at least one other feature, step, operation, element, component, and / or group thereof.

[0017] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention belongs. Furthermore, terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and this disclosure, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such in this specification.

[0018] As used herein, when the term "about" is used in conjunction with a numerical value, it is understood that the value can be within 90% to 110% of the value, i.e., the value can be ±10% of the stated value. For example, "about 1 kg" means 0.90 kg to 1.1 kg.

[0019] It will be understood that in describing the present invention, numerous techniques and steps have been disclosed. Each of these has its own advantages, and each can be used in combination with at least one, and possibly all, of the other disclosed techniques. Accordingly, for the sake of clarity, this specification will refrain from unnecessarily repeating every possible combination of individual steps. Nevertheless, this specification and claims should be read with the understanding that such combinations are fully within the scope of the present invention and claims.

[0020] In embodiments, a non-thermal plasma based active plasma sterilizer (APS) system and method is developed to address shortcomings associated with currently approved methods, such as temperature and material compatibility, while providing a compact, lightweight, safe, fast, and economical decontamination solution.

[0021] Additionally, an ozonated decomposition module (ODM) has been developed, which contains a heating coil, electronics, and piping that provides a path for the ozonated air to flow through. The heating coil heats the ozonated air as it flows through. Heating the air increases the rate at which ozone in the air is decomposed. The electronics power the heating coil, allowing it to operate at a moderately low power. An air pump, such as a fan, is used to force the ozonated air from the ozone generation chamber through the ODM and recirculate it as many times as necessary. The air pump has a flow rate of 10 -3 L / min to 10 6 The flow rate can be in the range of L / min.

[0022] The Active Plasma Sterilizer (APS) system has a central module with a microcontroller and relays to automatically control the frequency and power state of the sub-modules. In addition, the APS system has a series of sensors to find and maintain the most efficient frequency for each sub-module based on the sub-module's feedback voltage and current, as well as the temperature, humidity, and ozone concentration within the sterilization chamber.

[0023] In embodiments, the APS system does not require an inductor. Furthermore, the APS system allows for automatic chamber locking and unlocking once a sterilization cycle is initiated until the chamber reaches an OSHA- and NIOSH-approved gas concentration limit, such as ozone. The system can be configured with a door lock for safe operation of the APS system, which can be an electromagnetic and / or mechanical door lock. The central module has indicators for each connected sub-module and routes power from the main power source to the sub-modules.

[0024] The APS system and method of the present invention is based on surface dielectric barrier discharge (SDBD), a type of non-thermal plasma that generates and distributes reactive oxygen and nitrogen species (RONS), primarily ozone, for decontamination.

[0025] SDBD is produced in a compact reactor such as the compact, lightweight, and energy-efficient Compact Portable Plasma Reactor (CPPR), which employs a fan- and comb-type SDBD configuration capable of generating symmetrical flows and can be strategically integrated into APS systems and methods to achieve uniform spatial sterilization.

[0026] The present invention provides an APS system and method for designing and manufacturing. Results demonstrated that a specific embodiment of the APS can simultaneously reduce pathogenic bacteria, such as E. coli and Bacillus subtilis, on materials including, but not limited to, aluminum, polycarbonate, Kevlar®, and OrthoFabric® at 11 points distributed within the APS by 4-5 logs within 30 minutes, with a maximum ozone concentration x time (CT) requirement of 10,323 ppm / min and a power consumption of 13.2 ± 2.22 W. Spatial distribution of sterilization data at the center surface of the APS demonstrated the ability to uniformly sterilize multiple areas of a contaminated surface within 30 minutes. Ozone penetration into the Kevlar® and OrthoFabric® layers was demonstrated by CPPR, reducing ozone concentrations by up to 16.17% throughout the layer without the use of external penetration aids.

[0027] Furthermore, preliminary material compatibility testing by SEM analysis of the aforementioned materials exposed to the ozone CT values ​​required for sterilization in an APS showed no substantial damage to the materials.

[0028] Therefore, APS technology offers several advantages when applied to planetary protection scenarios, including uniform space decontamination, low processing temperatures, short exposure times, lightweight design without moving parts, ability to decontaminate porous surfaces, and compatibility with materials relevant to space missions.

[0029] According to an embodiment of the present invention, an active plasma sterilizer (APS) system comprises a dry, versatile, reusable, modularly expandable compact portable plasma reactor (CPPR) that generates SDBD using several watts of power across multiple electrodes separated by a dielectric medium. The APS system is based on the concept of achieving spatially distributed decontamination through the synergistic combination of SDBD ozone generation and fluid actuation to distribute and mix the generated ozone without the use of external admixtures. This results in maximized utilization of the generated ozone for rapid decontamination while reducing ozone requirements and residual concentrations. Thus, the APS system is designed to achieve spatially distributed decontamination using the SDBD reactor. APS prototypes are evaluated to determine sterilization efficacy, ozone CT (concentration x time) requirements, power requirements, penetration ability into desired materials, and material compatibility. Testing showed that the APS prototype could achieve complete eradication (4-5 log reduction) of pathogenic bacteria (e.g., E. coli and Bacillus subtilis) in four selected materials—aluminum, polycarbonate, Kevlar®, and OrthoFabric—at 11 simultaneous points within the chamber within 30 minutes at a maximum ozone CTR requirement of 10,323 ppm / min and a total power consumption of 13.2 W. Furthermore, ozone penetration into single and composite fabric layers was successful without the use of external factors. Furthermore, preliminary material compatibility testing using SEM analysis of the four selected materials exposed to the ozone CTR required for sterilization in the APS system revealed no significant damage to the materials.

[0030] Materials and Methods

[0031] APS system design:

[0032] Sterilization Box: Referring to Figure 1, a custom-made polycarbonate box is fabricated with interior dimensions of, for example, 1 ft long, 1 ft wide, and 1 ft high, with walls 0.0065 ft thick. A layer of foam insulating adhesive is placed between the lid and sidewalls of the box to seal it from the external environment. Polycarbonate was selected because it is non-reactive with ozone. To measure the decontamination achieved inside the chamber, holes are drilled in the sidewalls to facilitate suspending inoculated sample pieces inside the box, as shown in Figure 1. In this embodiment, three planes are selected to represent the volume occupied by objects placed inside the box. Plane 1 (P1), Plane 2 (P2), and Plane 3 (P3) are located at d1 = 8 cm, d2 = 11.5 cm, and d3 = 16 cm from the bottom of the box, respectively. The (P,Q,R) coordinate system is used to describe the decontamination measurement grid in a later section. The drilled holes also provided access for measurement probes to collect ozone data inside the box.

[0033] Compact Portable Plasma Reactor (CPPR): The CPPR, integrated into the APS sterilization box, is designed to be compact and portable. The CPPR consists of two components: (a) a reactor panel consisting of two sets of copper electrodes separated by a dielectric medium; and (b) a compact power supply circuit that converts the low DC voltage to the high AC voltage required to generate a surface dielectric barrier discharge on the reactor panel surface. In a specific embodiment, the copper electrode sets are 35 μm thick and separated by a dielectric, such as a 0.76 mm thick hydrocarbon / ceramic (RO4350B) composite with a dielectric constant of 3.48. The CPPR power supply, also known as an active plasma module, is a compact circuit module with a volume of, for example, 48 cubic centimeters and a weight of 55 grams. The CPPR operates on a 25 V DC power supply and consumes an average of 2.2 + 0.37 watts.

[0034] The power supply is housed in an electrically insulating case for enhanced safety. CPPR reactor panels are designed based on their flow-actuated capabilities to distribute the generated ozone. To better distribute the generated ozone within the sterilization box, two reactor panel designs with contrasting flow-actuated capabilities are used: the comb reactor panel and the fan reactor panel. These two panel designs are shown in Figures 2A–2F. The comb reactor panel generates a two-dimensional (2D) flow distribution with a dominant wall jet directed from the shaft toward the tip, while the fan reactor generates a three-dimensional (3D) flow distribution that forms a swirling flow extending vertically upward and outward from the center of the panel. The geometric details of the reactor panels are the same as those used in the ozone study during the development of the SDBD fan configuration.

[0035] As shown in Figure 3, multiple CPPRs (e.g., four) are installed in the sterilization box. The reactor placement and orientation are based on the expected ozone distribution generated by each CPPR reactor panel. Three CPPRs, each equipped with a fan reactor panel, are arranged in an equilateral triangle on the chamber lid. This arrangement is designed to generate a vortex shower of ozone within the chamber volume. An additional CPPR equipped with a comb reactor panel is placed at the bottom of the chamber, offset 2 cm from the center. The comb reactor panel is configured so that the dominant wall jet emanating from the shaft toward the tip of the blades faces upward, ensuring that ozone is transported from the bottom to the top to diffuse the chamber volume. The offset is designed to prevent sample pieces placed at the center points of planes 1, 2, and 3 from blocking the wall jet. The integration of the CPPRs into the sterilization chamber allows for control of the number of CPPRs powered on during an experiment.

[0036] High-voltage power supply module

[0037] As shown in Figure 21, the high-voltage power supply module of the APS system is a programmable microprocessor-based system. The control logic of the high-voltage power supply module is configured for initial system tuning at power-on and continuous real-time monitoring based on advanced adaptive control methods for optimal plasma generation for various loads.

[0038] During initial setup of the system, the microprocessor is configured to determine the resonant frequency of the reactor and transformer without generating a plasma. In this condition, the gate pulse is selected to be short enough to suppress plasma emission.

[0039] The microprocessor is then configured to scan the system from frequency f1 to frequency f2. At the end of the scan, the microprocessor is configured to determine the frequency corresponding to the maximum voltage across coil L3. This frequency is then used to trigger plasma generation. The gate pulse is then varied accordingly depending on the total gate charge of the MOSFET.

[0040] During the ozone generation process, the program controls the L3 voltage and the rate of ozone concentration rise. When the rate of ozone concentration rise begins to change due to changes in the load on the reactor, the microprocessor enters an active tuning mode that changes the resonant frequency, gradually bringing ozone production to the optimum level.

[0041] In an embodiment, the high voltage power supply module can power at least one load. In another embodiment, it can power multiple loads. The Wi-Fi chip can be connected via I2C communication, as can the sensor.

[0042] In FIG. 21, C1 represents a current maintaining capacitor for a MOSFET transistor (Q1), D1 and D2 represent drain protection for the MOSFET transistor, L1, L2, and L3 represent the primary, secondary, and tertiary windings of a transformer (Tr1), respectively, Q1 represents a power MOSFET transistor, R1 represents a gate resistor, R2 and R3 represent voltage dividers, T1 represents a MOSFET temperature sensor, U1 represents a microprocessor, +24V represents built-in short circuit protection, +5V represents the microprocessor power supply, and sensors include sensors configured to measure humidity, temperature, and ozone levels, respectively.

[0043] Evaluation of sterilization effect of target contaminants using APS

[0044] Experiments were conducted to test the sterilization effectiveness of the APS system, including tests conducted for (a) 11 measurement points within the sterilization box, (b) two test microorganisms commonly used in sterilization testing, (c) four materials commonly used in spacecraft applications, (d) up to six CPPRs to determine the minimum number of CPPRs required to obtain sterilization within 30 minutes, and (e) seven exposure time points. Each of these tests is described below, followed by a description of the experimental procedure.

[0045] Measurement grid: 11 measurement points are selected in the internal volume of the prototype to simulate distributed decontamination of various points on the surface of an object placed in the box, including 9 points on plane P2 (the central plane) and the centers of planes P1 and P3, as shown in Figure 4. To suspend the sample piece in the chamber within the measurement grid, a sterile Teflon-coated string (e.g., 0.1 mm in diameter) is used to suppress ozone loss, since Teflon does not react with ozone.

[0046] Test microorganisms: Escherichia coli and Bacillus subtilis

[0047] Escherichia coli (ATCC 11775) NCTC 9001 Escherichia coli (Migula) Castellani and Chalmers, Serovar O1:K1:H7, type strain. ATCC 11775 (BSL 2 level): Escherichia coli is a Gram-negative, rod-shaped, facultative anaerobic bacterium that is capable of replicating under adverse conditions, making it suitable for evaluating decontamination technologies.

[0048] Bacillus subtilis (ATCC 6051) (Ehrenberg) Cohn, type strain, bacteriophage host (BSL 1 level): Bacillus subtilis (B. subtilis) is a spore-forming, Gram-positive, aerobic bacterium commonly found in soil and vegetation. While nonpathogenic, it can contaminate food and be pathogenic to immunocompromised individuals. This bacterial species was chosen because of its widespread use in disinfection studies using traditional disinfection methods. Furthermore, its spore-forming ability makes this species interesting for evaluating decontamination technologies for planetary protection.

[0049] Test Materials: Four materials that play an important role in space missions are selected for testing. These materials are cut into 1 inch square sample pieces and are shown in the table below with referenced use cases.

[0050] Table 1: Materials selected for testing:

[0051] [Table 1]

[0052] Number of CPPRs and exposure time: Exposure time refers to the time the inoculated sample piece is placed in the APS prototype. Combinations of the number of CPPRs and exposure time (CPPR on + CPPR off time) were repeatedly tested to determine the number of CPPRs required to completely kill the selected bacterial species.

[0053] 3 CPPR: 10 minutes (on throughout). 4 CPPR: 5 minutes (on throughout). 4 CPPR: 15 minutes (10 minutes on + 5 minutes off) 4 CPPR: 20 minutes (15 minutes on + 5 minutes off) 4 CPPR: 25 minutes (20 minutes on + 5 minutes off) 4 CPPR: 30 minutes (15 minutes on + 5 minutes off + 5 minutes on + 5 minutes off) 6 CPPR-30 minutes (25 minutes on + 5 minutes off)

[0054] Culture preparation: E. coli and B. subtilis strains are stored at -80°C in Luria-Bertani (LB) broth and nutrient broth supplemented with 30% glycerol, respectively. Frozen stocks of E. coli and B. subtilis are grown overnight in LB broth at 37°C and nutrient broth at 30°C, respectively. Use a spectrophotometer to estimate the bacterial concentration in fresh LB or nutrient broth cultures, diluting as necessary to obtain a concentration of approximately 5 x 10 7 Obtain a concentration of CFU (colony forming units) / ml. Next, use 10 μl of these broth cultures to inoculate 4-5 logs of E. coli and B. subtilis.

[0055] Pretreatment of the sample specimens and the APS box: Autoclave sterilization at 121°C using a dry autoclave cycle. At the beginning of each experiment, the box and all components inside were wiped down with 70% isopropyl alcohol to prevent external contamination. Furthermore, the lid was left open to allow free air circulation within the box for at least 30 minutes to ensure that the ozone concentration inside the box matched the room level before the experiment. This step was performed by placing the chamber in a ducted BYPASS fume hood (Phoenix Controls Corporation, 100 lfm). All experiments were performed within this fume hood for safety reasons. The box was sealed during the experiment to prevent interference with the fume hood.

[0056] Post-processing of sample pieces and APS boxes: For post-processing experiments, sample pieces are mixed in 15 ml of PBS solution using a Fisher Scientific Mini Vortexer lab mixer. 100 μl of this mixture (for exposed sample pieces) or a dilution (for unexposed sample pieces) is plated onto agar plates (LB agar for E. coli and nutrient agar for B. subtilis) and incubated at 37°C (E. coli) or 30°C (B. subtilis) for 24 hours. Plate counts are performed to quantify the number of bacterial colonies present on the sample pieces. All post-processing is performed in a Class II, Type A2 Microbiological Safety Cabinet (BSC) to prevent external contamination and maintain safety protocols.

[0057] Control experiment: A control experiment is performed to accurately quantify bacterial inactivation by the APS and to exclude inactivation due to environmental factors related to the experimental setup or procedure. In this step, a fixed bacterial concentration is maintained on a sterile sample piece inoculated with a fixed amount of bacterial culture medium. During the experiment, the inoculated sample piece is left in the APS for a period of time consistent with the exposure time without the CPPRS power on, and then post-processed. This experiment is repeated at least three times.

[0058] Exposure experiments: In each exposure experiment, approximately 10 7 10 μl of bacterial culture containing CFU / ml is inoculated onto 14 sample pieces of one material. A 10 μl inoculum is approximately 10 5 The concentration of CFU / sample piece is selected. Next, 11 sample pieces are placed inside the APS at the 11 measurement points shown in Figure 4 and exposed for the selected time. The remaining 3 sample pieces are placed outside the chamber for the same time as the control. After the exposure period, all 14 sample pieces are post-processed and the concentration of CFU / sample piece is determined. The following formula is used to calculate CFU / sample piece:

[0059] CFU / sample piece = CFU / ml*V1=Dx*10 x *V1

[0060] where V1 = the volume (ml) of PBS used to mix the sample pieces in post-treatment, and Dx = the CFU counted in the xth dilution plate.

[0061] The reduction in microbial colonies per sample piece at each measurement point is determined from the difference in CFU / sample piece between exposed and control (unexposed) sample pieces.

[0062] Ozone measurement

[0063] A 2B Technologies Model 106-6 Ozone Monitor, which operates based on UV absorption between 180 nm and 280 nm, preferably 254 nm, is used to measure ozone in the APS prototype chamber. The monitor's accuracy is 0.01 ppm or 2% of the reading. Ozone measurements are taken at the center of the sterilization box, using the exposure time determined in the sterilization efficacy test, the corresponding CPPR on and off times.

[0064] Ozone penetration test

[0065] To evaluate the permeability of ozone generated by a CPPR into a fabric layer with and without the assistance of an external factor such as a pump, an enclosure was constructed. As shown in Figure 5, the enclosure includes: 1) a CPPR support tab for holding the CPPR; 2, 3) top and bottom measurement holes located above and below the fabric layer, respectively, for accessing the data collection probe; 4) an air outlet hole connected to the pump or left open based on the experiment; and 5) a fabric sample holder for holding a fabric sample or cell. A CPPR with a fan reactor panel was used for the test. The fabric sample holder had a rectangular cutout with Velcro® to which the Velcro® at the border of the fabric sample was attached. Ozone concentrations were measured above and below the fabric layer for 5 minutes, starting 10 seconds after powering on the CPPR, to measure ozone permeability. The measurements were averaged over the final minute of the measurement period, allowing the ozone concentration to stabilize. Measurements at the top and bottom were taken separately to minimize the influence of the measurements on data collection. The top and bottom of the enclosure were blocked to prevent the generated ozone from escaping. Before every experiment, ensure that the ozone level inside the enclosure is the same as the ambient ozone level. Three replicates are performed for each fabric sample type, with and without the use of a pump for forced penetration.

[0066] Three different fabrics were tested: Kevlar®, OrthoFabric, and a composite layer of Kevlar® and OrthoFabric. Velocity and ozone data were collected before and after the fabric layer, with and without the pump. Sample dimensions were 4 cm x 5 cm, with thicknesses of 1 mm, 2 mm, and 3 mm for the OrthoFabric, Kevlar®, and composite samples, respectively. The Kevlar® fabric was 2 mm thick, while the OrthoFabric was 1 mm thick. As shown in Figure 6, the samples were placed in "cells" made of Velcro® to hold the fabric in place and maintain a uniform shape.

[0067] Ozone is measured using a 2B Technologies Model 106-6 Ozone Monitor as previously described. Velocity and temperature are measured using a Testo 405i Smart Probe Hotwire Anemometer with an accuracy of ±0.1 m / s +5% for velocity and ±0.5°C for temperature.

[0068] Prior to testing, the temperature, humidity, and air velocity through the chamber were measured without powering the CPPR, both with and without the pump. Upstream and downstream air velocities refer to the air velocity above and below the fabric layer, respectively. A total of five measurements were taken for each measurement, and the average values ​​were calculated as follows: Temperature = 24.4°C, Humidity = 62.70%, Upstream air velocity with pump = Vpu = 0.08 m / s ± 0.02 m / s, Downstream air velocity with pump = Vpd = 0.15 m / s ± 0.03 m / s, Upstream air velocity without pump = Vnu = 0.03 m / s ± 0.01 m / s, Downstream air velocity without pump = Vnu = 0.02 m / s ± 0.01 m / s.

[0069] Preliminary Material Compatibility Testing

[0070] Four materials were selected: aluminum, polycarbonate, Kevlar®, and OrthoFabric. Exposure to the APS resulted in complete kill of E. coli and B. subtilis. These exposure conditions correspond to equivalent ozone CT (concentration x time) values ​​required for sterilization (4-5 log reduction) of the two test species. All four materials were examined for visible surface degradation and changes in material composition using standard SEM analysis. A Hitachi S 3000 SEM at the University of Florida's Nanoscale Research Facility (NRF) was used for these tests.

[0071] Results and Discussion

[0072] Evaluation of sterilization effectiveness of contaminants by APS:

[0073] Control experiments: To establish consistent bacterial concentrations for sterilized sample pieces of different materials inoculated with 5-6 log of E. coli and B. subtilis CFU, the results are shown in Figures 7 and 8, with error bars based on the standard deviation of triplicates. This data shows that when sample pieces of the same size and material are inoculated with the same volume of culture medium, the number of bacteria per sample piece is consistent, with a maximum variation of 0.3 log. 10 (CFU / sample piece). This data also validates the post-processing method for recovering the microbial population from the inoculated sample piece.

[0074] Exposure Experiments: As described in the Materials and Methods section, a total of 37 replicate exposure experiments were conducted using two test microorganisms, seven exposure times, and four selected materials. The replicate experiments were designed to find the optimal combination of the number of CPPRs and exposure time required to completely kill each test microorganism within 30 minutes for all selected materials. As a result, for control counts of 4–5 log CFU / sample, complete kill of E. coli was achieved within 20 minutes with four CPPRs. The same results were obtained for B. subtilis within 30 minutes with six CPPRs. Figures 9 and 10 show the overall sterilization results (average reduction over 11 measurements) and the spatial distribution of the achieved log reduction for E. coli and B. subtilis contaminated specimens exposed to APS for (a) 20 minutes with four CPPRs (15 minutes on + 5 minutes off) and (b) 30 minutes with six CPPRs (25 minutes on + 5 minutes off).

[0075] Referring to Figures 9 and 10, results obtained for surfaces contaminated with E. coli showed that APS achieved complete kill or a 4-5 log reduction of E. coli on aluminum, polycarbonate, OrthoFabric, and Kevlar® at 11 points within the chamber, with four CPPRs activated for 15 minutes, with a minimum exposure time of 20 minutes.

[0076] Similarly, Figures 11 and 12 show that APS completely killed B. subtilis on aluminum, polycarbonate, OrthoFabric, and Kevlar® at 11 points within the chamber. The increased CPPR and exposure time required to completely kill B. subtilis compared to E. coli can be explained by the fact that B. subtilis is a Gram-positive bacterium with a protective outer cell wall, a cytoplasmic membrane, and a thick cell wall. Furthermore, the selected B. subtilis is a spore-forming bacterium, which is able to form resistant, durable protective spores and withstand extreme environmental conditions.

[0077] The sterilization results demonstrate the potential of APS to uniformly sterilize aluminum, OrthoFabric, polycarbonate, and Kevlar® objects contaminated with pathogens such as E. coli and Bacillus subtilis at 4-5 logs per square inch of surface within 30 minutes. Furthermore, the successful sterilization of the four materials demonstrates that APS can sterilize both solid and porous surfaces without the need for external admixtures or dispersants.

[0078] Ozone data and CT (concentration x time) requirements:

[0079] Based on the number of CPPRs required to completely kill E. coli and B. subtilis by 4-5 logs on 11 sample pieces in the APS chamber and the corresponding exposure time, ozone data were collected in the APS at the center of the central plane (P2) for the following operating conditions. Based on the B. subtilis concentrations on the 11 sample pieces in the APS chamber, ozone data were collected in the APS at the center of the central plane (P2) for the following operating conditions: (a) four CPPRs and 20 minutes (15 minutes CPPR on, 5 minutes CPPR off) and (b) six CPPRs and 30 minutes (25 minutes CPPR on, 5 minutes CPPR off). These measurements were performed separately from the decontamination experiment to (a) prevent erroneous measurements due to the loss of measured concentrations due to the use of ozone for decontamination and (b) prevent contamination of the ozone monitor. The results are shown in Figures 13A and 13B, where the orange line represents the time when the CPPR was off. For statistical reliability, three replicates were performed for each exposure time, and the standard deviation observed across the replicates was used for the error bars on the graphs.

[0080] Figure 13A shows that when four CPPRs are energized for 20 minutes (CPPRs on for 15 minutes, CPPRs off for 5 minutes), the ozone concentration in the center of the APS peaks at approximately 500 ppm after 15 minutes and then gradually decreases. Meanwhile, Figure 13B shows that when six CPPRs are energized for 30 minutes (CPPRs on for 25 minutes, CPPRs off for 5 minutes), the ozone concentration in the center of the APS converges to approximately 420 ppm after 15 minutes and stabilizes there until the CPPRs are turned off. While this seems counterintuitive, possible explanations for this difference include: (a) the distribution of ozone generated by the six CPPRs results in more ozone mixing within the APS, which is beneficial for decontaminating a larger volume but may affect ozone measurements or result in faster ozone decomposition; and (b) the interaction of the flow structures generated by the six CPPRs may result in more mixing and vortex structures, which may shift the peak concentration in the center of the APS to a different point. Furthermore, increasing the power of the six CPPRs in the APS was observed to result in larger concentration deviations, which could be attributed to increased mixing and unstable flow structures.

[0081] It should be noted that the evaluation of the spatial ozone distribution within the APS was outside the scope of this study, mainly due to time constraints, and the focus of this study was on investigating the spatial distribution of decontamination within the APS.

[0082] The ozone CT requirement is calculated using the following formula to account for differences in CPPR on and off times during exposure:

[0083] CT value = Sum (C i t s )

[0084] where C i is the reading of the i-th sample by the ozone monitor, t s where is the sampling time of the ozone monitor, and n is the total number of samples collected during a particular exposure time. The calculated CT values, along with the maximum ozone concentration achieved at each exposure time, are shown in Table 2. Table 2: Ozone CT (concentration x time) values ​​recorded on the APS.

[0085] [Table 2]

[0086] Power consumption:

[0087] Based on sterilization efficacy testing, the six CPPRs used in certain embodiments of the APS can completely kill pathogenic bacteria on various surfaces within 30 minutes with the six CPPRs active for 25 minutes. The power requirement for a single CPPR is 2.2 ± 0.37 watts, while the power requirement for the CPPRs in the APS reaches 13.2 ± 2.22 watts.

[0088] Ozone penetration:

[0089] Average ozone data from five replicate measurements above (upstream) and below (downstream) the fabric layer with and without the pump are shown in Table 3 below and Figure 14. Without the pump, the percent reduction in ozone concentration from the top of the fabric layer (the side where the CPPR was installed) to the bottom of the fabric sample was 7.59% for Kevlar®, 16.17% for OrthoFabric, and 13.90% for the Kevlar® and OrthoFabric composite layer. This result indicates that ozone generated by the CPPR can penetrate the fabric layers within the enclosure without the aid of external factors. Data collected with the pump showed much lower ozone concentrations. This is likely due to the rapid displacement of the generated ozone by the suction power of the air pump used. With the pump, the percent reduction in ozone was 66.52% for Kevlar®, 28.72% for OrthoFabric, and 68.30% for the composite of both fabrics. The higher ozone reduction observed when the pump was used is likely due to the very low ozone concentrations measured before penetration. Therefore, this data indicates that a pressure-based mechanism is not required for CPPR-generated ozone to penetrate the fabric layers. Combined with the Kevlar® and OrthoFabric decontamination data, this indicates that APS does not require additional components to penetrate ozone into fabrics like Kevlar® and OrthoFabric. Table 3: Ozone penetration data for different fabric layers with and without the pump.

[0090] [Table 3]

[0091] Material Compatibility:

[0092] A single sample piece from each of four materials—aluminum, polycarbonate, Kevlar®, and OrthoFabric—was placed in an APS sterilization chamber and subjected to two sterilization conditions, each designed to completely kill E. coli and B. subtilis: (a) APS Exposure 1: 20 minutes (15 minutes on + 5 minutes off) with four CPPRs; (b) APS Exposure 2: 30 minutes (15 minutes on + 5 minutes off) with six CPPRs. All four materials were visually examined for surface degradation and changes in material composition by standard SEM analysis and comparison with a control sample piece not exposed to APS. The results are shown in Figure 15. Data from the control (unexposed) material sample are compared with samples that underwent APS Exposure 1 and APS Exposure 2. Visual analysis of the SEM images at the 50-200 micron scale revealed no material degradation. Comparing the material compositions, APS Exposure 1 resulted in an increase in oxygen content of approximately 3% for aluminum, 0% for polycarbonate, and 1% for Kevlar®. APS exposure 2 resulted in an increase of approximately 6% for aluminum, approximately 2% for polycarbonate, and approximately 5% for Kevlar®. These preliminary results suggest that the APS exposure required for sterilization does not result in significant degradation of aluminum, polycarbonate, OrthoFabric, or Kevlar® materials. Further SEM analysis with detailed compositional studies is possible for APS.

[0093] Active Plasma Sterilizer (APS) Effects:

[0094] This compact, energy-efficient sterilization system, with built-in ozone generation and mixing capabilities, is provided for planetary protection-related sterilization. The design of the APS prototype sterilization box and the incorporation of a CPPR for ozone generation and distribution are described. The CPPR is integrated based on the strategic selection and placement of SDBD reactor panel designs (fan reactor configuration and comb reactor configuration) to ensure uniform distribution of generated ozone within the sterilization box. Spatially distributed decontamination is achieved based on the synergistic combination of fluid actuation to distribute and mix SDBD ozone generation and DBD-generated ozone without the use of external mixing agents or moving parts. The APS prototype was evaluated by (a) contaminating sample pieces made of four different materials (aluminum, polycarbonate, Kevlar®, and OrthoFabric) with two test microorganisms (E. coli and Bacillus subtilis) at 4-5 log levels and testing their sterilization effectiveness. (b) We determined the number of CPPRs required to completely kill selected microorganisms within 30 minutes, (c) determined the corresponding ozone CT (concentration × time) and power requirements, (d) tested ozone penetration into selected fabric materials, and (e) conducted preliminary material compatibility testing by SEM analysis. Results revealed that the APS was capable of simultaneously achieving a 4-5 log reduction of pathogenic bacteria, such as E. coli and Bacillus subtilis, on materials including (but not limited to) aluminum, polycarbonate, Kevlar®, and OrthoFabric at 11 points within the chamber, with a maximum ozone CT requirement of 10,323 ppm / min and a total power consumption of 13.2 W within 30 minutes. Ozone generated by the CPPR successfully penetrated single and composite fabric layers, reducing ozone concentrations by up to 16.17% through the fabric layers without the use of external factors to promote penetration. Preliminary material compatibility testing by SEM analysis of four selected materials exposed to the ozone CT values ​​required for sterilization by the APS revealed no significant damage to the materials. With advantages such as uniform spatial decontamination, low processing temperature, short exposure time, light weight due to the absence of moving parts, ability to decontaminate porous surfaces, and compatibility with related materials, APS has demonstrated its potential as a sterilization technology applicable to planetary protection.

[0095] According to embodiments of the present invention, a safe, compact, and energy-efficient sterilization system, an active plasma sterilizer, incorporating an ozone mixing system and a residual ozone removal system is provided for sterilization of spacecraft facilities related to planetary protection. Accordingly, a compact, lightweight, non-thermal, safe, cost-competitive, and rapid decontamination system and method have been developed and integrated into spacecraft and platform subsystems. Potential applications include sterilization of spacecraft components and ground-based contamination control for test operations and cross-contamination control of onboard components. Some example applications include pre- and post-launch sterilization of sample collection devices (e.g., drills), surfaces, and spacesuits. Embodiments of the present invention extend sterilization modalities beyond time and temperature constraints to include cleaning of adhesive surfaces and refine cleaning protocols beyond the use of alcohol and bleach, as described in the recent 2020 NASA Technology Taxonomy report.

[0096] The following technical achievements will be achieved: (i) The first Active Plasma Sterilizer (APS) system and method with an integrated Compact Portable Plasma Reactor (CPPR) for testing will be developed; (ii) Aluminum, polycarbonate, Kevlar, and OrthoFabric sample pieces contaminated with E. coli and B. subtilis will be sterilized (4-5 log reduction) within 20-30 minutes at 11 locations simultaneously within the prototype; (iii) The number of CPPRs within the APS required for sterilization within 30 minutes will be determined to be six; (iv) The ozone CT values ​​required for sterilization of E. coli and B. subtilis will be determined to be 6789.02 ppm / min and 10323 ppm / min, respectively.

[0097] In the embodiment, the volume of the APS prototype is determined to be 30 L, although the size of the APS is scalable.

[0098] A total of 37 replicate exposure experiments were performed using two test microorganisms, seven exposure time points, and four selected materials to determine the optimal combination of the number of CPPRs and minimum exposure time required for complete kill of each test microorganism for all selected materials.

[0099] Experimental results show that, at a control count of 4-5 logs of CFU / sample, complete kill of E. coli is achieved within 20 minutes with four CPPRs. For B. subtilis, the same results are achieved within 30 minutes with six CPPRs.

[0100] The overall sterilization results and spatial distribution of the achieved log reduction, along with the associated ozone data, are shown for materials contaminated with E. coli and B. subtilis, exposed to APS exposures equivalent to (a) a 20-minute exposure time with four CPPRs activated for 15 minutes, and (b) a 30-minute exposure time with six CPPRs activated for 25 minutes. Additionally, the associated ozone data for these experiments is also provided.

[0101] The APS system and method has great potential for commercialization due to its wide range of applications, from room disinfection in hospitals and businesses to its versatile applicability in preserving and decontaminating agricultural products. It also has the ability to decontaminate everyday items such as children's toys, clothing, bags, and shoes. Once the product undergoes technical validation, market drivers will likely be the demand for larger equipment and the ability to safely and efficiently decontaminate large volumes.

[0102] According to embodiments of the present invention, an APS system and method are designed for rapid decontamination that is lightweight, low-cost, non-thermal, and potentially integrated into spacecraft or platform subsystems. This addresses shortcomings associated with existing methods for space missions, such as high processing temperatures and material incompatibility. Furthermore, the APS may be used to achieve microbial reduction during crewed missions. Compared to existing large, power-hungry DBD ozone generation systems, the APS offers advantages including, but not limited to, (a) a small, lightweight, and low-energy power source; and (b) ozone mixing via SDBD flow actuation, enabling rapid decontamination with lower ozone demand and low residual ozone. Potential applications include sterilization of spacecraft components and subsystems, ground-based contamination control for test runs, and in-flight component cross-contamination control. Specific applications include pre- and post-launch sterilization of sample collection devices (e.g., drills), surfaces, and spacesuits.

[0103] Ozone Decomposition Module (ODM)

[0104] Ozone is a powerful antimicrobial agent. It destroys microorganisms by reacting with oxidizable cellular components, particularly those containing double bonds, sulfhydryl groups, and phenolic rings. Ozone thus targets membrane phospholipids, intracellular enzymes, and genomic material, resulting in cell damage and microbial death. Ozone has many advantages as a sterilizing and disinfecting gas, and its strong oxidizing properties (E = 2.076) make it a highly efficient sterilizing agent. Therefore, ozone is widely used for sterilizing aseptic packaging containers, decontaminating fresh produce, and preserving food in refrigerated warehouses.

[0105] However, ozone is an inherently unstable gas and cannot be stored; it must be generated on-site, making it impractical for use in many environments. Furthermore, ozone decomposes into harmless oxygen after a few hours. However, practical ozone applications require the ability to decompose at a faster rate once the sterilization activity is complete. OSHA regulations state that ozone concentrations must not exceed 0.1 ppm during an 8-hour exposure period, a concentration significantly lower than is typically required for most ozone-based applications. The ability to rapidly decompose ozone into harmless oxygen offers numerous advantages to ozone-based technologies, significantly reducing standby times after use.

[0106] According to an embodiment of the present invention, an ozonation decomposition module (ODM) includes a heating coil, electronics, and piping that provides a path for ozonated air to flow through. The heating coil heats the ozonated air as it flows through. Heating the air increases the rate at which ozone in the air is decomposed. The electronics power the heating coil, allowing it to operate at a reasonably low power. An air pump, such as a fan, is used to force the ozonated air from the ozone generation chamber through the ODM and recirculate it as many times as necessary. The air pump has a flow rate of 10 -3 L / min to 10 6 The flow rate can be in the range of L / min.

[0107] An embodiment of the subject innovation demonstrated that, for 5 L containing 100 ppm ozone, an ODM operating at 400°C and a flow rate of 250 L / min can reduce the ozone concentration in the chamber to less than 0.1 ppm within 60 seconds. The electrical circuit for the heating element in the current ODM uses an induction coil with a ZVS driver. Results from the same setup show that the ozone in the chamber is reduced to approximately 1 ppm after 30 seconds.

[0108] Embodiments of the present invention may include systems such as induced airflow (e.g., through the use of a fan), temperature adjustment within a heat coil to vary ozone concentration levels, measurement of ozone within the flow path to automatically adjust usage levels, or other suitable means.

[0109] An initial test setup was developed as shown in Figure 16. For testing, an ozone generator was placed in the chamber to generate 100 ppm ozone in a 5 L volume. The test procedure is as follows:

[0110] 1. Set up the ozone monitor to measure the initial ozone in the chamber.

[0111] 2. Turn on the CPPR for 6 minutes to achieve a chamber concentration of approximately 100 ppm. During this time, record the chamber ozone concentration every 10 seconds using an ozone monitor.

[0112] 3. Turn off the CPPR and run the ODM for 0 seconds. During this time, pressure changes may cause problems with the ozone monitor, so the ozone monitor should be removed or switched off.

[0113] 4. After the allotted time has elapsed, turn off the ODM and turn the ozone monitor back on. Record the ozone level in the chamber for 10 minutes.

[0114] 5. Open the chamber and allow the ozone level to equilibrate with the room level.

[0115] 6. Once the ozone concentration is below 0.1 ppm, seal the chamber.

[0116] 7. Repeat steps 1 to 6 for ODMs with 30 and 60 second startup times.

[0117] The test results are shown in Figures 17, 18, and 19. The 0-second test, as shown in Figure 17, demonstrates the natural decay rate of ozone in the chamber. After 10 minutes, the ozone concentration in the chamber stabilized at approximately 3.4 ppm, highlighting the critical role of the Ozone Destruction Module (ODM). Without the ODM, the APS would rely on natural ozone decay, significantly extending its operating time. The results for ODM operation times of 30 and 60 seconds are plotted in Figures 18 and 19, respectively, and show that the ozone in the chamber decreased by an order of magnitude as the ODM operation time increased.

[0118] 20, in an embodiment, the ODM has a casing 1 with an inlet port 2 and an outlet port 3, a heating element 4, an ozone sensor 5, a power circuit 6, and insulation 7. The heating element can be internally disposed as a coil, wire mesh, or other suitable form that can be connected to an electrical source for Joule-type heating, or can be used as a collector for an external heat source such as radiation or an electron beam.

[0119] In one embodiment, the ODM includes a heating element connected to a power source and configured to decompose ozone by heating ozonated air, a power module providing power to the heating element, a connecting pipe providing a path for the ozonated air to flow, and an air pump configured to circulate the generated ozonated air. The ODM may further include at least one sensor configured to measure ozone levels or an insulating element for insulating against heat generated by the heating element. The power module is a standard wall power module or a battery-powered module. The power module further includes a feedback loop for providing power to the heating coil. The power module may further include a power amplifier and a controller configured to control an input voltage to the power amplifier. The input voltage to the power module is provided in a duty cycle. The power module may further include a feedback circuit configured to monitor operating parameters of the load and provide feedback to the controller, and the controller is configured to control operation of the power amplifier based on the provided feedback. The feedback circuit includes an ozone sensor configured to detect ozone in the airflow.

[0120] In an embodiment, ozone levels are measured based on UV light absorption in the range of 180 nm to 280 nm, preferably 254 nm, in an ozone depletion module (ODM) (e.g., at least one sensor configured to measure ozone levels).

[0121] In an embodiment, the heating element is an induction heating mesh / coil.

[0122] In embodiments, water or other liquid solvents are employed to facilitate pumping and removal of contaminated air, thereby promoting rapid absorption of reactive oxygen and nitrogen species (RONS).

[0123] ODM Test Data

[0124] [Table 4-1]

[0125] [Table 4-2]

[0126] [Table 4-3]

[0127] [Table 4-4]

[0128] [Table 4-5]

[0129] [Table 4-6]

[0130] It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof may be suggested to those skilled in the art and are within the spirit and scope of the present application.

[0131] All patents, patent applications, provisional applications, and publications mentioned or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent not inconsistent with the explicit teachings of this specification.

Claims

1. 1. An active plasma sterilizer (APS) system for sterilization / decontamination, comprising: Sterilization box, a plurality of small portable plasma reactors (CPPRs) disposed within the sterilization box and configured to generate a surface dielectric barrier discharge (SDBD) for generating and distributing reactive oxygen and nitrogen species (RONS); An APS system comprising:

2. 10. The APS system of claim 1, The sterilization box is made of polycarbonate. APS system.

3. 10. The APS system of claim 1, The sterilization box includes a grid structure disposed within the sterilization box and configured for decontamination measurements. APS system.

4. 10. The APS system of claim 1, The sterilization box has a plurality of through-holes arranged on the side of the sterilization box, and the inoculated sample pieces can be suspended in the sterilization box. APS system.

5. 10. The APS system of claim 1, RONS contains ozone APS system.

6. 10. The APS system of claim 1, Each of the plurality of CPPRs has a reactor panel and a power supply circuit. APS system.

7. 7. The APS system of claim 6, The reactor panel has at least one electrode separated by a dielectric medium. APS system.

8. 7. The APS system of claim 6, The power supply circuit is configured to convert a low DC voltage to a high AC voltage to generate an SDBD on the surface of the reactor panel. APS system.

9. 7. The APS system of claim 6, The plurality of CPPRs have two reactor panels configured to generate different flow operations to better distribute the generated SDBD within the sterilization box. APS system.

10. 10. The APS system of claim 9, the two reactor panels are a comb reactor panel and a fan reactor panel; the comb reactor panel is configured to generate a two-dimensional (2D) flow distribution dominated by wall jets directed from the shaft of the comb reactor panel toward the tips of the teeth; The fan reactor panel is configured to generate a three-dimensional (3D) flow distribution that forms a swirl flow that extends vertically upward and outward from the center of the fan reactor panel. APS system.

11. 11. The APS system of claim 10, the plurality of CPPRs includes three CPPRSs, each CPPRS consisting of a fan reactor panel; The three fan reactor panels are arranged in an equilateral triangle on the upper inner surface of the sterilization box; One CPPR having a comb-shaped reactor panel is positioned on the bottom surface of the sterilization box, offset a predetermined distance from the center of the bottom surface. APS system.

12. 10. The APS system of claim 1, further comprising at least one sensor and feedback circuit configured to monitor a voltage or operating parameter of the load and provide feedback to the controller for voltage control or current overload prevention; The controller is configured to control operation of the power amplifier based on the provided feedback. APS system.

13. 10. The APS system of claim 1, At least one sensor for measuring the temperature, humidity, and / or ozone content of the air for optimizing operation The APS system further comprises:

14. 10. The APS system of claim 1, A door lock is further provided for safety of the operation of the APS system. The door lock is an electromagnetic door lock, a mechanical door lock, or an electromagnetic and mechanical door lock. APS system.

15. 10. The APS system of claim 1, Wireless or wired link devices for data logging The APS system further comprises:

16. a heating element connected to a power source and configured to heat the ozonated air and thereby decompose the ozone; a power supply module for supplying power to the heating element; a connecting pipe providing a path through which the ozonated air flows; an air pump configured to circulate the generated ozonated air; An ozone decomposition system comprising:

17. and further comprising at least one sensor configured to measure ozone levels.

17. The ozonolysis system of claim 16.

18. 18. The ozonolysis system of claim 17, The at least one sensor is configured to measure the ozone level based on UV light absorption in the range of 180 nm to 280 nm. Ozone decomposition system.

19. 17. The ozonolysis system of claim 16, an insulating element for insulating the heat generated by said heating element; 10. The ozone decomposition system according to claim 1, further comprising:

20. 17. The ozonolysis system of claim 16, The power module can be a standard wall power module or a battery-powered module. Ozone decomposition system.

21. 17. The ozonolysis system of claim 16, The power supply module has a feedback loop for supplying power to the heating coil. Ozone decomposition system.

22. 17. The ozonolysis system of claim 16, The power supply module further includes a power amplifier and a controller configured to control an input voltage to the power amplifier. Ozone decomposition system.

23. 17. The ozonolysis system of claim 16, The input voltage of the power supply module is supplied with a duty cycle Ozone decomposition system.

24. 17. The ozonolysis system of claim 16, the power supply module further comprising a feedback circuit configured to monitor an operating parameter of the load and provide feedback to the controller; The controller is configured to control operation of the power amplifier based on the provided feedback. Ozone decomposition system.

25. 17. The ozonolysis system of claim 16, The heating element is an induction heating mesh / coil Ozone decomposition system.

26. 1. An active plasma sterilizer (APS) system for sterilization / decontamination, comprising: Sterilization box, a plurality of small portable plasma reactors (CPPRs) disposed within the sterilization box and configured to generate a surface dielectric barrier discharge (SDBD) for generating and distributing reactive oxygen and nitrogen species (RONS); The ozone decomposition system according to any one of claims 16 to 25. An APS system comprising:

27. 27. The active plasma sterilizer (APS) system of claim 26, If the ozonated air becomes contaminated, the contaminated air is removed by a liquid solvent to enhance the absorption of reactive oxygen and nitrogen species (RONS). Active Plasma Sterilizer (APS) System.

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