Tribo-Charging, Who Really Discovered Electricity?
The relationship between static electricity and particle attraction has been long known. The Ancient Greeks when polishing their jade and precious stones noticed that straw, chafe and other particles were attracted to the exact things they were trying to clean, the family jewels. This phenomena became known as “Tribo-charging“. Simply stated it was the contact and friction that generated an electrostatic field around the parts that attracted the debris.
The Plastic Attraction
In the Life Sciences Industry of today most companies use plastics in their process. Whether it is to replace body parts, catheters, injection systems, pumps, blood separators or their packing, plastics are here to stay. Not only are they here to stay, but plastic is being used in this process at an increasing rate. Most of these engineered plastics are for a specific need but the premise is the same, they generate huge amounts of static that causes Foreign Matter (FM) to be attracted to the products and the process.
Medical Device Manufacturers most often individually package each medical device and they are subjected to 100% inspection. When the inspector sees a speck of debris (FM), which could be in the form of plastic bits, fuzz balls from clothing, or even human hair, the package is then ripped open and put aside for repackaging. These units are tracked in what is generally called “the tear down rate”. In almost every case, the root cause was the forces of static electricity pulling unwanted particles onto the product and the packaging materials. In addition to the packaging level there are various stages in the assembly process where FM causes rejects. Some of those stages include Injection Molding, Coating, Ultrasonic Welding, Bonding/Gluing, Forming, and handling during the assembly processes. These are also key functions that need to be addressed. The common denominator being that contact and separation (tribo-charging) occurs, static is generated and FM comes into play to contaminate products that could end up inside the human body or blood stream. The FM could also potentially block injection or fluid systems clogging pathways designed to deliver medicine.
Gains are Being Made, Reducing FM
The front line of defense is a properly maintained clean room, but that doesn’t address process problems at the local level, aka the workstation or cell. How does static control reduce particles via ionization in the fight to reduce FM? Static Clean did a job last year for a major medical device company that was experiencing a very high tear down rate. They approached us to come up with a system where they could pass their products thru a blow-off, ionized, vacuum table. The results of this first system allowed them to run 50,000 parts without a single tear-down.
While not all medical device manufacturers have identical assembly lines, let’s take a look at the types of static controls are that implemented for specific reasons or points in the process.
Room Ionization: In this installation, ionizers are mounted in the ceilings and the preferred method is to locate the ionizer right under the Fan Filter Unit. (FFU) to take advantage of the clean air being delivered into the room.
Local Ionization: is another method of static control. These ionizers could be in the form of an ionizing air gun or nozzle, static bars, specific ionizing fans at the work bench or a two or three fan overhead ionizing air blower when bench space is at a premium.
The Increasingly popular approach has been to use source capturing methods in conjunction with ionizing air tools. Recent gains have been made in the development of customized medical cleaning workstations that meet clean room protocol and are tailor engineered to a specific product or package.