Swab applications and market trends
These small consumables make an impact in big markets
By Robert McIlvaine and Betty Tessien, The McIlvaine Company
There are three broad categories of wiping products: woven flat wipers, non-woven flat wipers, and swabs. The main advantage of swabs is the variety of shapes and materials in which they are available. This makes them ideal for cleaning in very small, very precise areas.
Swabs are used in applications including cleanrooms, electronics, scientific, forensic DNA collection, medical/dental, equipment manufacturing, pharmaceutical, and food testing.
Types of swabs
Swabs can be application matched and modified by the manufacturers to meet specific user needs. Parts can be either natural or synthetic. Variables include handle length and material; tip size, shape, and material; and solvent retention, absorbency, and adsorption capabilities. Foam, polyester, and cotton are some of the head material choices. The heads can be bonded thermally, folded, or melt welded. Some new heads have spirals that may grab more debris.
Polyester swabs have low nonvolatile residue qualities (NVR), low particle shedding, and are chemically resistant. A swab with a head of laundered polyester knit fabric provides low levels of releasable particles, high recovery, and low background when total organic carbon (TOC) measurements are employed as the analytical technique.
Handles can be polypropylene, nylon, glass-filled nylon, glass-filled polypropylene, wood, or styrene. Swabs vary in handle length (from 7 to 25 cm) and in head shape and size (from 4 to more than 16 mm). The handle can also be notched for easy breaking.
Solvent-safe swabs are designed for electronics manufacturing and repair. Different absorbencies are available. Packaging options are available, including ESD-safe options and cleanroom-compatible swabs. Pharmaceutical manufacturers and those using cGMPs need products that maintain sterility. Some swabs are made without the use of adhesives or binders. Puritan Medical Products Co. actually holds the patent on fluid-filled swabs, which contain a solution in a non-glass ampoule that is broken to release a solvent, often alcohol, into the swab. These are especially useful in field service to avoid cross-contamination or spilling of a solvent. Solvent contamination is always a concern.
Cleaning, validation, and standards
Swabs reach areas, crevices, and gaps that can’t be reached or cleaned with conventional methods. Once the swab picks up residue, it must be retained. Swab sampling can be considered the most widely used cleaning validation sampling technique. It is a crucial step in cleaning validation assessment. The physical characteristic of the swab and the substrate surface, as well as the physical swabbing motion, all contribute to the physical validation process. The chemical process is controlled by the dissolution of the analyte from the surface of the substrate into the wetted swab and then by the extraction of the analyte from the swab into the recovery solution. The swabbing motion needs to be standardized to assure that recoveries validated during analytical studies are replicable by those performing the swabbing. The procedure should be documented in a standard operating procedure.
There is a specific method to wet the swab head and prevent excess liquid from spreading the residue to be picked up onto the surrounding surface. Errors in technique lead to inconsistent results. The swab should be damp but not saturated. Pre-cleaned vials and swabs are available that provide TOC background levels of less than 10 ppb for solutions and less than 50 ppb for swabs.
The pharmaceutical industry uses swabs for validation as well as cleaning. Technicians swab an area as small as 1 inch by 1 inch for surface validation. These swabs often have handles that break so the swab can be place in a container with media to extract the particles from the swab.
WG-CC025: Evaluation of Swabs Used in Cleanrooms is a recommended practice published by IEST. It describes methods for testing swabs used in the cleanroom and other controlled environments for characteristics related to both cleanliness and function.
Swab prices range from less than $0.10 to more than $0.30 each. Often swab choice depends on the size of the particle that is of concern and whether it will create loss of yield. After swab features such as bioburden levels, absorbency, adsorption, particle counts, and pre-saturation, competition often comes down to pricing. Foam swabs can be more economical, and many still contain no adhesives.
Manufacturers are often located where labor is cheap, such as in Asia or China, or in a place where the white birch wood for handles is readily available. Some of the largest U.S. manufacturers are located in Maine, Colorado, and Wisconsin.
Chris Collopy, sales manager of industrial products at Puritan Medical Products in Maine, says that the company has been manufacturing since 1919. It has introduced 17 new styles for use in the critical environment, including a micro-fiber product that offers wipe/dry characteristics especially important to the optics arena. The company offers a folded and twisted swab with no seams or edges that doesn’t generate particles. It has also recently produced a sonically welded swab specifically requested by and manufactured for the aerospace industry (see Fig. 2).
According to Collopy, the flexible paddle tip is made of laundered micro-fiber. The NVR swab results show 0.003 mg/swab. The absorbent micro-fiber is excellent for lenses and optics, leaves no lint or residues, and both the PP handle and tip are chemical resistant, he notes.
Powell Products, a manufacturer of swabs and transfer devices that was founded in 1959, has more than 110 employees and manufactures 160 million swabs per year in its Colorado Springs, CO, facility and another 20 million in Mexico.
The worldwide cleanroom wipers and swab market totals more than $600 million. These are annual sales calibrated by the end purchasers’ payments. The cleanroom swab market is presently estimated at $70 million worldwide with a growth rate of eight percent projected over the next five years.
The 10 leading purchasers of swabs by country are:
- United States
- South Korea
- United Kingdom
The swab market in China will grow faster than in any of the other top 10 countries. Thus over the next decade, China will move near the top of the purchasing countries.
The semiconductor industry will continue to be the main purchaser, but the flat-panel display and other segments will grow faster.
Manufacture will be increasingly global with a few suppliers dominating the worldwide market. Low cost regions will be selected for future manufacturing facilities. Distribution will be broad with many international distributors providing the products in various regions.
Michael Balestri, category manager at VWR, notes the swab market has been driven lately by TV shows such as “CSI (Crime Scene Investigation).” The shows have actors using new, state-of-the-art swabs; real swab users then ask for similar products. This has increased the trend for swabs with containment caps on the ends (refer to Fig. 1 for an example) and for individually wrapped swabs. According to Linda Grassia, marketing manager of Qosina, a new swab Qosina offers has a polypropylene vented cap that slides down a wood shaft to allow sampling, then slides back to cover the swab head with a snap-on cap.
A noted market trend is the individually sterile wrapped swab. These are often used in medical applications. ETO sterilization is frequently used for these swabs. Other cleaning devices and materials that used to be hand-held, such as surgical scrubs and solutions, are being put on the end of a swab to avoid cross-contamination, even if a glove is used.
The electronics industry holds a large share of the swab market. This segment is less likely to shop around but sticks to a tried and true swab, according to one vendor. In the flat-panel and circuit board industries, swabs are used to clean space not accessible by other cleaning methods, inside orifices or tubes. In semiconductor manufacturing, swabs are needed to clean O-ring chambers before the device is sealed. However, static is a huge issue in the electronics industry, such as in hard disk drive manufacturing. Even a minute amount of static can render a product useless. Often a swab is dipped in an alcohol solvent that is placed on a static discharge mat and the user wears static discharge wrist straps. Handles on the swabs are also often made to dissipate static. Some of the newest swabs contain carbon black or inherently static dissipative-polymers for this purpose. “It is important that the swab handle allows a path to ground as well as being low in tribo-charging properties. The use of carbon powder allows for fast static dissipation while the inherently static-dissipative handles allow for a controlled path to ground and low particulate and contamination potential,” says Kurt Edwards, sales and marketing manager for Lubrizol Conductive Polymers (formerly Stat-Rite). The company’s Stat-Rite® IDP alloys are currently being used by several ESD/cleanroom swab manufacturers for swab handles.
Another development is a split head swab. This is especially useful in cleaning both sides of a tube or cable. Other application-specific swab head shapes and sizes are being manufactured. High-Tech Conversions offers a large 16-inch swab with a very large head called a “lollipop” swab.
Another growing market is swabs used in the cosmetic industry, not only for production but also for applications at home. Because of the ability to change the shape of the tip for various applications, they are more desired than the older brushes. They are cheaper and can be replaced often for better hygiene.
Micro-fiber is a non-woven, ultra-fine, durable synthetic fiber, which can be made from polyester, acrylic, nylon, rayon or a blend of these materials. Micro-fiber offers a huge surface area. It has been shown to clean with no solvents or detergents, has no organic shedding, and is durable. It holds a tremendous amount of liquid by high adsorption. Swabs and wipers are now being made of this material.
Robert McIlvaine is president and founder of The McIlvaine Company in Northfield, IL. The company first published Cleanrooms: World Markets in 1984 and has since continued to publish market and technical information for the cleanroom industry. He can be contacted at firstname.lastname@example.org.
Betty Tessien is the cleanroom publications editor for The McIlvaine Company. She can be contacted at email@example.com.
The following individuals provided industry and product information: Michael Balestri, VWR; Chris Collopy, Puritan Medical Products; Kurt Edwards, Stat-Rite; Charles Garber, SPI Supplies; Linda Grassia, Qosina; and Claudio Orefice, High-Tech Conversions.