One of our most modern artifacts is the recent, extraordinary gift from Dr. Adir Jacob: the prototype of his invention that revolutionized the sterilization of medical and dental instruments. No, it's not much to look at aesthetically—not many prototypes of engineering breakthroughs are very attractive to the uneducated eye—but it proved his transformative concept magnificently. And Johnson & Johnson, after it bought Dr. Jacob's patents, gave his brilliant idea a great deal of polish and then delivered it to the world - to great mutual benefit.

Below is a discussion of the science and technology of the invention, followed by video excerpts of an interview with the inventor, Dr. Adir Jacob.

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Dr. Adir Jacob explains the low temperature plasma sterilization process and the general function of his prototype sterilization unit. 

Sterilization of medical and dental instruments is a crucial function for the healthcare industry.  Up until the very early 1990's, the predominant means for sterilization were heat, typically high pressure steam or dry air, and poisonous gases, for which Ethylene Oxide (ETO) was widely used.

Both means have significant drawbacks. High temperature sterilization will damage delicate instruments (e.g. endoscopes and other electro/optical devices), as well as instruments with non-metallic plastic components of low melting point temperature.

Likewise, ETO is a highly toxic and carcinogenic gas, requiring extreme caution for safe use and a very long (fifteen hours) post-sterilization purging cycle to ensure that all residuals of the gas and its by products have been removed.

An alternative sterilization technology, based on the use of a gas plasma (such as found inside a neon sign) was being investigated at the time, but had its own setbacks. Most notably, since a plasma contains both electrically charged and electrically neutral active species (e.g. elements in an atomic and ionic state) the exposure of the sterilization load to the plasma resulted in pitting and abrasion of metallic and non-metallic surfaces and was otherwise damaging to delicate instruments.

In the late 1980's, Dr. Adir Jacob – a chemical physicistwith extensive experience in developing gas plasma etching and deposition systems for the semiconductor industry – patented an innovative low temperature gas plasma technology for the safe and quick sterilization of medical instruments and devices. This exhibit displays his patent model or prototype, explains how the technique works, and highlights the technology's successful transition to a commercial product in widespread use in today's global healthcare industry.

Motivation for the Invention

By the mid – 1980s, Dr. Jacob had spent sixteen years heavily involved in the evolution of plasma etching and deposition systems for the manufacture of semiconductor devices. In those years the semiconductor industry was associated with a highly cyclical marketplace, which created severe economic dislocations in down years (for example, see the figure below).

Looking for more stable and commercially rewarding applications he came to focus on the medical field and its positive growth over time.  While reviewing the process technologies used in the medical devices industry, he identified the prevailing hazardous and expensive technology used for the low temperature sterilization of medical devices and materials employed by the healthcare industry worldwide.

Unique Claim of the Invention

Low Temperature Plasma - A partially ionized and very reactive gas or vapor, overallelectrically neutral (see Figure below), wherein the electron temperature is quite high and that of the neutral components is near ambient temperature. The components of the plasma give off a characteristic glow when electrically discharged at low pressure.

Although the art of plasma generation has been known for decades, its previous applications to sterilization were unsuccessful and never commercialized.  The main reason for this failure was the direct exposure of the sterilization load to the plasma glow discharge itself and its associated electrons, ions and neutral active species. 

The exposure to electrically charged active particles resulted in surface modification of the sterilization load, including erosion, pitting and resultant melting, thus rendering the load useless.

The purpose of this invention was not only the exposure of the sterilization load to a nontoxic processing gas, but also to a glowless and electrical field-free sterilization zone, thereby isolating it from the deleterious effect of the electrically charged particles and exposing it to the electrically neutral active particles preferentially, as claimed in Claim 1 of the Jacob US4801427 Patent:

"…creating a gas plasma, having a substantially field-free and glowless volume within the perforated electrode containing said device and materials, whereby said devices and materials are contacted by substantially electrically neutral active species at a temperature below that which would be detrimental to said devices and materials “.

Operation of  Low Temperature, Low Temperature Plasma Sterilizer

Broadly speaking, the sterilization process of this invention begins with the placement of commercial pouches containing medical devices and materials to be sterilized within a sterilization zone, electrically isolated from the electrically grounded chamber enclosure.

The figure below illustrates an RF sterilizer, constructed within a rectangular outer enclosure having an electrical connection to the grounded side of the RF generator. 

An inner, perforated structure (electrode) is concentric with the outer enclosure, and is connected to the ungrounded (hot) side of the RF generator.

The inner surface of the outer enclosure is roughened, as by sand blasting.

Both the outer shell and the perforated inner structure (electrode) may be heated or cooled by flowing a suitable heat exchange fluid through the coils surrounding these elements.

The entire enclosure interior is then evacuated to a relatively low sub-atmospheric pressure.  After reaching a preset low pressure, a gaseous sterilant is continuously admitted to the enclosure for a preset time to precondition the enclosure's interior and the medical devices.  This preconditioning phase is typically repeated a few times, each time establishing different preset pressures, thereby purging any residual trapped air.

By virtue of the perforated electrode surrounding the sterilization zone, only neutral active particles are allowed to traverse the perforated matrix, while the electrically charged species are isolated and retained in the annular region exclusively. The inner perforated electrode may thus be viewed as a so called Faraday Cage.

The active neutral particles pass through the gas permeable walls of the pouches and interact with the surfaces of the contaminated medical instruments within, thereby denaturing any proteinaceous molecules of any microorganisms residing on such surfaces and achieving large kill rates of only one survivor in a million.

The sterilization enclosure is evacuated to a preset low pressure. When the preset pressure is reached, the vacuum pump is isolated from the enclosure, and the enclosure is thenbrought up to atmospheric pressure by allowing ambient air to enter the enclosure via a bacteria-retentive filter. 

Once atmospheric pressure is established within the enclosure, its door can be opened and the (now sterile) packaged medical devices and materials can be withdrawn.

The diagram below shows the plasma sterilizer integrated within a commercial system.

A programmable logic controller (PLC) controls theRF power source and valves for gas and fluid control. Liquid sterilant precursor is vaporized by a heater associated with the sterilant source.

These vapors are cycled appropriately by the controller, and are supplied to both the annular region and the interior of the perforated electrode.

In the very early 2000s, Dr. Jacob transferred his invention's patent rights to Advanced Sterilization Products (ASP), a division of Ethicon USA, a Johnson & Johnson company, for commercialization. The resultant 'STERRAD' product line, achieving sterilization by means of a Hydrogen Peroxide low pressure, low temperature plasma has been marketed globally to the healthcare industry ever since.

the interior of the STERRAD NX plasma sterilization chamber shows a clear and obvious resemblance to the sterilization chamber drawing in Jacob's patent.

the interior of the STERRAD NX plasma sterilization chamber shows a clear and obvious resemblance to the sterilization chamber drawing in Jacob's patent.

Features of the Sterrad NX

  • Designed with Next Generation technology--the most advanced low temperature PLASMA sterilizer.
  • Process flexibility:  Standard Cycle (47 min.); Duo Cycle (60 min.); Flex Cycle (42 min.); Express Cycle (24 min.).
  • Enhanced process quality control, including large touch-screen display; sterilant concentration/quantity monitoring; instantaneous error detection for chamber overload and presence of absorbent material; network connectivity for remote cycle observation.
  • Capable of sterilizing the narrowest-bore (>0.7 mm) and longest (up to 850 mm) endoscopic equipment in the shortest cycle time.
  • Gas plasma technology safely minimizes surface vapor residuals on medical devices and materials.

In Summary...

Dr. Jacob's invention of a novel, safe and rapid means for sterilizing contaminated medical devices and materials incorporated numerous and compelling improvements to the prior art of plasma sterilization.

  • Substantial process automation
  • Process flexibility
  • Non-toxic
  • Residuals (after sterilization) removed simultaneously during sterilization
  • No flammability hazard
  • No air pollution risk
  • No restricted access
  • No prior need to dry medical devices and materials at end of  sterilization  
  • High process efficiency and short turnaround times
  • Extreme ease of operation and minimal maintenance requirements
  • No special first-aid equipment needed
  • Process pressure regime very low
  • No relative humidity effects on process performance
  • Safe reprocessing after system malfunction
  • No aeration and frequent air-changes required
  • Excellent long-term reliability of exposed optical devices
  • Non-critical system unloading procedures
  • Non-hazardous storage and no critical disposal procedures

As we have seen, these benefits motivated the development and marketing of a product line of plasma sterilization systems widely sold to the global healthcare industry to the present day.

The following series of videos are segments of an interview with the inventor, Dr. Adir Jacob, conducted by Trustee and Collections Manager Dan Eyring, and help illuminate the invention process, and the science behind the technology of this extraordinary low temperature, low pressure, gas plasma sterilizing unit.

Dr. Adir Jacob, inventor of a revolutionary low temperature plasma sterilizing technology that is now a global medical and dental standard for the sterilization of medical instruments, explains here that he was inspired to donate his sterilizing unit prototype to the Charles River Museum of Industry and Innovation by his young grandson, Sam Jacob.
Dr. Adir Jacob discusses his educational and professional background and progression and process of inventing his revolutionary low temperature plasma medical device sterilization technology and prototype.
Dr. Adir Jacob explains plasma. Harnessing low temperature plasma was the key to his revolutionary invention of the medical device sterilization technology that is now the global standard in hospitals, medical, and dental offices.
Dr. Adir Jacob explains his scientific and technological breakthrough that led to his low temperature plasma sterilization method becoming the global standard for medical and dental instrument sterilization.

Johnson & Johnson's Sterrad Marketing Video