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   Technology Profile#150    6/14/2000
Related TechUpdate Article(s):
High Energy-Density Thin-Film Capacitor


In the mid-1980s, BMDO funded Maxwell Laboratories, Inc., to develop a high energy-density thin-film capacitor for a then-classified project called Mile Run. Since then, derivatives of this technology are being applied in pulsed-power devices to purify water, sterilize medical products, preserve food, and power heart defibrillators. The newly renamed Maxwell Technologies is currently selling film capacitor-based products for all these applications.

Technology Description:

In the mid-1980s, Maxwell Laboratories developed a high energy-density metalized film dielectric capacitor. A capacitor is a device that stores and discharges energy. In general, it is two electrodes separated by a dielectric layer, which acts as an insulator. Maxwell’s capacitor was constructed by evaporating and condensing a metal, usually aluminum, onto a thin layer on both sides of a polymer film, usually polypropylene. The layers of aluminum, each a few angstroms thick, act as electrodes; the polymer film, which is a few microns thick, forms the dielectric layer. The resulting film is then tightly wound many times to form a cylindrical shape, which is then inserted into a cylindrical container. The operating parameters depend on the application; however, the capacitor typically can provide 100 to 400 joules of energy per discharge at a voltage of 2 to 3 kilovolts.

A useful feature of Maxwell’s capacitor is that the electrode is designed to be “self-healing,” which means that if a short circuit develops in a small area of the dielectric layer, the electrodes in that region would vaporize, rendering that area of the film inactive. This capability allows the capacitor to continue functioning, although at diminished capacity (much like a hard disk drive with bad sectors) while degrading gracefully during the span of its design lifetime. Without this feature, the capacitor would suddenly become totally inoperable whenever a short circuit developed between the electrodes, which frequently can happen in such thin dielectric films.

MDA Origins:

BMDO’s predecessor, the Strategic Defense Initiative Organization, partially funded development of this capacitor to produce a compact, lightweight device that could provide pulsed power for space-based lasers and accelerators. Funding was provided through two Science and Technology contracts under a then-classified project called Mile Run.

Spinoff Applications:

The high energy-density thin-film capacitor technology could be used in sterilization, preservation, and portable heart defibrillator products. In a sterilization system, the capacitor generates high voltage, high current pulses which energize one or more inert gas lamps. The spectrum of light emitted by the lamp is generally similar to the spectrum of sunlight hitting the earth’s surface, but is 20,000 times more intense. This light kills resistant micro-organisms in both water and air in a fraction of second.

The capacitor-based sterilization system offers a strong line of defense against micro-organisms, including water-borne Cryptosporidium, which is always a concern in developing countries, where the drinking water can often be contaminated by it. This parasite is also a concern in the United States, where, for example, it sickened about 400 people in the Milwaukee area during the summer of 1993. Unfortunately, filtering and dosing with chlorine at U.S. water treatment plants does not remove or kill this micro-organism. In some outbreaks, all that municipal water utilities could do was recommend that people boil water for at least one minute before drinking it.

In a preservation system, the capacitor generates high voltage, high current pulses which are applied for a few microseconds to two electrodes in a housing chamber. Liquids and pumpable foods are passed through the chamber where the pulsed energy kills spoilage organisms and pathogens on the surface of the products without affecting their taste or color. This preservation technology can be applied to meet critical needs of the fresh juice industry.

In a portable heart defibrillator, an electric high-voltage power source charges the capacitor. This stored energy is then discharged into the patient. The process is called defibrillation and its goal is to shock a patient’s heart so that the normal beating pattern can be restored. Most patients that require defibrillation are experiencing ventricular fibrillation (VF) caused by sudden cardiac arrest. VF is an ineffective quivering of the heart muscle that makes it unable to pump blood through the body. Once the blood stops circulating, a person quickly loses consciousness and the ability to breathe, and will die without effective treatment. The chance of survival drops about 10 percent with each passing minute.

At present, it is estimated that fewer than one-third of ambulances are equipped with defibrillators and about 15 percent of fire department emergency response vehicles carry these life-saving devices. Equipping more emergency personnel with capacitor-based portable heart defibrillators could make a difference in terms of saving lives.


Maxwell is commercializing capacitor-based pulsed-power sterilization and preservation equipment as well as capacitor-based portable heart defibrillators:

Pulse Power Technologies: In 1988, Maxwell spun off a subsidiary called PurePulse Technologies. This business unit has since developed two proprietary sterilization and preservation processes—PureBright® and CoolPure®—that can be applied to a wide variety of products in several markets.

PureBright: PureBright technology effectively purifies water and air, sterilizes medical and pharmaceutical products, and reduces bacteria levels on the surface of foods and packaging materials. It uses concentrated energy in short, high-intensity pulses to kill micro-organisms without using heat, chemicals, or ionizing radiation. High peak power pulses of electrical energy are used to produce intense pulses of light that kill resistant micro-organisms. In September 1996, Maxwell’s PureBright technology received FDA clearance for killing bacteria on food.

PureBright is highly effective in killing micro-organisms such as vegetative bacteria, yeasts, molds, bacterial spores, and viruses. Its kill rate is 10 to 10,000 times that of traditional ultraviolet light treatments such as high-power mercury lamps. Although PureBright’s light does not penetrate opaque materials, it is transmitted through many types of clear packaging materials, fluids, and air. PureBright's extremely short exposure time greatly reduces the potential for material degradation. The treatment is a clean process, leaving no chemical residues and requiring no evacuation steps.

PureBright has been highly successful in the treatment of water and air. Testing shows PureBright effectively eliminates highly resistant organisms such as Cryptosporidium oocysts and viruses in water. The treatment is also effective in eliminating bacteria, spores, and viruses in air ducts. PureBright's extremely short treatment time also maintains high flow rates in water treatment applications.

Other commercial activities include the following:

•PurePulse teamed with Tetra Pak, a large international food packaging and food equipment company, to commercialize the PureBright process for food packaging applications. Tetra Pak is Maxwell’s primary strategic partner in this application and owns a 5-percent stake in PurePulse.

•In December 1995, PurePulse signed a 7-year, exclusive licensing agreement for PureBright systems to be incorporated into equipment manufactured by Automatic Liquid Packaging, Inc. (Woodstock, IL). PureBright systems will be used for sterilizing pharmaceutical products. Under the licensing agreement, PurePulse will receive revenues from the sale of PureBright systems and royalties based on product throughput.

•In June 1997, PurePulse licensed its PureBright technology to a major manufacturer and marketer in the health care field. The agreement involves technology rights and the $2 million purchase of several PureBright systems over the next several years. Options to extend the license and purchase additional systems would increase the total value of the agreement to more than $5 million.

•In October 1997, PurePulse signed an agreement to supply PureBright water treatment systems to a major international restaurant chain. Currently, PurePulse has installed prototype systems in Mexico and the United States.

PurePulse has been working closely with the customer to develop a compact water treatment system to purify water for drinking and for making ice cubes, coffee, teas, hot chocolate, and fountain-dispensed soft drinks. The water purifier offers a flow-through rate of 4 gallons per minute and easily fits into commercial kitchens. PurePulse intends
to market this system, called the PBW4, to restaurants as soon as field testing is completed.

•In early 1998, PurePulse signed an agreement with Pall Corporation, which could lead to the commercialization of its PureBright technology for producing high-purity water for the semiconductor industry. According to industry sources, the annual market for ultra-pure water for semiconductor manufacturing and other industrial scientific applications is estimated to be over $200 million.

CoolPure: CoolPure technology effectively preserves food without using ionizing radiation or chemicals. It uses pulses of high-intensity electric fields to kill spoilage organisms and pathogens in pumpable liquid products. In July 1995, the U.S. Food and Drug Administration (FDA) cleared CoolPure for preserving liquid foods.

CoolPure avoids the high temperatures and accompanying thermal damage that occur with heat pasteurization. The process kills high levels of vegetative micro-organisms through massive electroporation, or rupturing, of microbial cell membranes. It has no effect on the taste, chemistry, or functionality of the food or liquid. Treatment costs are usually less than $0.04 per liter.

While CoolPure technology is still being refined for high-capacity commercial applications, PurePulse currently offers a low-capacity system (a flow-through rate of 10 liters per hour) for laboratory and research communities. PurePulse is working with U.S. military organizations and industry groups to further research and develop advanced preservation applications for this technology.

Heart Defibrillators: Maxwell says its largest capacitor market is hospitals, but it is expecting the public gatherings market—sports stadiums, office buildings, health clubs, and shopping malls—to grow substantially in the next few years. The company has developed four types of capacitors, and annually sells about 20,000 of these devices to 10 original equipment manufacturers.

For example, Zoll Medical Corporation (Burlington, MA) uses Maxwell capacitors in all of its portable and hospital defibrillators. Consider this success story: Two years ago, Robert Rowland collapsed and stopped breathing when he suddenly experienced a cardiac arrest, which often can be fatal. Bystanders quickly called 911 and began administering cardiopulmonary resuscitation to keep him alive. The local fire department soon arrived and, fortunately, the firefighters were equipped with a Zoll portable heart defibrillator. This medical device successfully delivered a shock to Mr. Rowland’s heart, restarting it. Later, he was transported to a nearby hospital where doctors were able to care for him properly.

Company Profile:

The newly renamed Maxwell Technologies develops, manufactures, and markets products and services involving purification systems, information technologies, and power conversion systems and components. The company's advanced technology solutions are used in utilities, food processing and packaging, health care, industrial computer manufacturing, transportation, mining, and information technology markets as well as Federal and local governments.

Historically, a significant portion of the company's revenues have been through sales directly to the Federal government or resellers to the Federal government. In the past several years, the company has devoted substantial resources to develop commercial markets for its products.

The company's business segments are defined as follows:

•Energy products: Energy storage and discharge products, power conditioning components and electromagnetic interference filters for the health care, wireless communications, power quality, transportation, and government markets.

•PurePulse technologies: Advanced sterilization and decontamination products for medical, pharmaceutical, restaurant, and food packaging markets.

•Systems division: Scientific research; computer simulation and analysis; design, development, and integration of major pulsed power systems; and operation and maintenance of test facilities, primarily to the government. Also, state-of-the-art software products and services for management information and integrated information systems, as well as educational products and applications for the Internet and for wide-area and local-area networks.

•I-Bus: Design and manufacture of custom and standard computer solutions for original equipment manufacturers.

Maxwell’s stock is publicly traded on NASDAQ, under the symbol MXWL.

Contact Information:

Maxwell Technologies
Corporate Office
9275 Sky Park Court
San Diego CA 92123
web: http://www.maxwell.com

Tracy Perry, Vice President (corporate office contact)

Dr. Joel Ennis (principal investigator, high energy-density film capacitors)
email: ennis@maxwell.com

Ed Blank (principal investigator, supercapacitors and high energy-density film capacitors)
email: blank@maxwell.com

Jon Williams (director of sales, energy products division)
email: jonw@maxwell.com

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