The growth of the medical device market is fueled by population demographics (the aging boomer population), product innovation, and increased market potential within and outside of the United States. The United States medical and surgical device market is estimated at $94.9 billion in 2010. The United States spent 17% of its GDP on healthcare in 2008, with growth expected to 20% by 2017. There are roughly 8,000 medical device firms in the U.S., with about 20% of the manufacturing outsourced. Two areas experiencing growth are surgical drapes and ostomy device components.
Surgical drapes are used during operations to reduce infection and facilitate the handling of skin around an incision. Typically, these drapes are manufactured using adhesive-coated, plastic film. The drapes come in various sizes and shapes and contain an opening for the surgical procedure. They can be single- or double-coated. Surgical drapes are often designed to enhance skin friendliness on one side. However, they may also be required to adhere strongly on a second side to a different substrate, such as another drape or different surgical device. Ostomy and continence device components require a pouch assembly with double-coated tape that bonds to plastic film to provide the necessary moisture barrier properties.
Materials and Adhesives Options
A range of materials can be used in the manufacture of ostomy or drape medical devices, with a trend in the industry toward the increased use of polyolefins. Materials can include polystyrene, polycarbonate, acrylics, silicone rubber, polyethylene, polypropylene, and synthetic rubbers. Each material has its own challenges and must be carefully matched with the appropriate adhesive. For example, nonstick low surface energy (LSE) plastics such as polyethylene and polypropylene require the use of new adhesives specifically designed to form strong bonds with these materials. LSE plastics challenge the ability of adhesives to effectively wet the surface of the plastic. New adhesives delivered via liquids or thin film pressure-sensitive adhesive (PSA) systems produce strong bonds with LSE plastics.
The primary types of adhesives used in such applications include acrylics, epoxies, silicones, styrene block copolymers, and PSAs. Fast curing acrylics are available in one-part anaerobic adhesives that cure in the absence of oxygen, one-part light-cure adhesives that set up in seconds, and two-part formulations with improved viscosity and handling characteristics. Cyanoacrylates are also popular. They include one-part formulations that cure within seconds and are suited to join LSE and other difficult-to-bond materials.
Epoxies are also extensively used, especially with film adhesives that can be die-cut to intricate custom shapes. Thin-film bonding systems are a good choice when the bond line geometry presents a gap that must be filled. Silicones provide strong biocompatibility and very high flexibility.
PSAs consist of adhesive transfer tapes (adhesives on a roll or sheet) and double coated tapes with a carrier added for stability. These lend themselves to laminating operations and have immediate quick stick characteristics. PSAs can be supplied as die-cut parts with uniform coating thickness adjusted to the application. They don’t require activation by water, solvent, or heat to bond with a substrate. Light to moderate pressure is all that’s necessary. PSAs are available as coated films, foams, and fabrics.
PSA tapes are generally available as follows:
- Transfer tapes—a layer of PSA is coated onto a protective release liner without additional support or backing.
- Single-coated tapes—come on a carrier of film, foam, or woven material, which is coated on one side with a PSA and protected by a release liner.
- Double-coated tapes—carrier such as polyester or film, coated on both sides with a PSA, protected by one or two release liners.
Engineers occasionally make the mistake of treating adhesive as an afterthought in their design. Selecting the right material is only half the story – not considering adhesives at the start of the design process can severely constrain the engineer’s bonding options, depending on the material. Adhesive selection is an important decision for both the design engineer and the manufacturing engineer, who is responsible for the efficient manufacturing of the device to specification and within overall cost parameters. Both engineers look to converters for expertise in identifying the distinct advantages and disadvantages of different materials and adhesives.
Adhesive properties that are important in the selection process are as follows:
- The ability to withstand sterilization.
- Hypoallergenic properties.
- Repeatable skin contact.
- Conformability to adhere to nonregular shapes and surfaces.
- Fluid resistance.
- Elongation properties.
Steridrapes are used in a range of surgical procedures including orthopaedic, cardiovascular, obstetrics, urologic, opthalmic, and neurologic.
Surgical drapes consist of flexible plastic film, which is adhesive-coated or uses pressure-sensitive adhesive coated tape. Drapes are applied to the area of an operation prior to making an incision. The drapes are typically three layers, consisting of a polyurethane film laminated to a releasable layer and a strengthening layer of thicker plastic material, such as polyethylene. Drapes are often designed to soak up spills and splatters while not allowing fluid strike-through.
Single- and double-coated film tapes, as well as transfer adhesives can be used with surgical drapes. The tapes adhere well to skin but can be removed gently and completely. Double-coated tapes can feature a gentle adhesive on one side and an industrial strength adhesive on the other. Adhesives can also provide antimicrobial activity that won’t be washed away. Adhesives can be formulated to help reduce the risk of wound contamination.
A converter can help a medical device OEM to investigate characteristics that can be tailored, such as tensile strength, skin contact, conformability, and breathability.
If there is a need to adhere another surgical device component to the drape, it might be necessary to design a precision die-cut part that could create an airtight seal. The die-cut part might use double-coated tape for secure adherence with a liner for easy handling. It could also provide the necessary barrier properties to resist fluid escape or penetration.
Ostomy Medical Devices
Applications in ostomy and continence devices focus on securability to adhere firmly to skin and prevent the possibility of any leakage. There are many adhesive options for securing ostomy bags and similar medical device pouches, including nonwoven tapes, film double-coated tapes, foam tapes, and hydrocolloid adhesives. Each adhesive has particular characteristics that make it suitable for different applications.
Nonwovens are a good choice for extended wear ostomy devices because they are highly conformable and breathable. They are elastic and provide excellent adhesion. Nonwovens are used with surgical drapes, pads, dressings, and filtration materials.
Film double-coated tapes offer secure adhesion and are easy to clean. They provide a translucent barrier film. Materials such as polyethylene, polyethylene terephthalate, polypropylene, polyvinyl chloride, and polyurethane can be used. Applications include thin film dressings, surgical drapes, or tape strips. Film tapes can also be used to attach electrodes.
have a soft feel for cushioning as well as insulating characteristics. They deliver a waterproof, antibacterial barrier and an easily cleaned surface. They are often used in applications where support films or papers are not desirable. Medical foam tapes are typically nonsensitizing and nonirritating with good initial adhesion that will last for extended wear—perhaps as long as one week. These tapes can be used as backings or protective coverings in passive and active transdermal applications. Transdermal patches are used to deliver a time-release dose of medication through the pores of the skin. The most common transdermal patch is the nicotine patch.
Hydrocolloid adhesives are the most skin-friendly adhesive option and resist body fluids. They represent a special type of pressure-sensitive adhesive with both fast-adhering characteristics as well as fluid absorbency. They are often used in ostomy applications and wound dressings. These adhesives are available in different formulations for different applications depending on the need for skin-friendly and absorbent properties. They can also be formulated for extended wear. Devices using hydrocolloids can be created to provide moisture vapor transmission, good skin adhesion, and protection from bacterial infection.
Converting, Materials, and Adhesive Expertise
It is important to work with an experienced adhesive converter in the medical device industry, especially with surgical drape
and ostomy applications. Converters deliver die-cut capabilities, as well as advice in selecting the most appropriate materials. They should be relied on to identify the best adhesive for the application.
Flexible materials converters often choose from servo-driven rotary die-cutting, CNC die-cutting, laser die-cutting, and water jet die-cutting to meet the complexity and specifications of sophisticated medical components. For example, servo driven rotary die-cutting delivers high repeatability and tight tolerances ranging from 0.015 to +/-0.005 in. at speeds up to 500 fpm. It is often the best choice for complex, multilayer die-cutting and lamination.
For complex foam tape die-cut components, water jet die cutting delivers clean-cut edges with the foam material. Laser die cutting, kiss cutting, slitting, and laminating, can also be used in converting for medical applications.
Working with a Convertor
With access to a range of materials, an experienced converter can custom convert diagnostic test strips and carrier frames, composite wound-care dressings, die-cut medical foam tape, and woven and nonwoven biocompatible pressure-sensitive adhesive tapes in addition to surgical drapes and ostomy components. A converter can also provide extensive label printing capabilities for tamper-evident and custom pressure-sensitive labeling of medical devices.
Converters should also suggest the appropriate adhesive alternatives for a specific application, such as single- or double-coated tapes, the best liner for the application, whether a foam tape is suited for the application, and what might be available in hydrocolloid tape formulations.
A converter is meant to provide expertise in relationships with materials and adhesives suppliers, and should be contacted at the design stage for medical devices.
The design and manufacture of surgical drapes and ostomy appliances involves expertise in materials and adhesives. By working with an experienced converter in the early stages of design, engineers can create steridrapes and ostomy applications that are specially formulated and constructed to meet specific medical requirements. The availability of new adhesives, including the latest hydrocolloid adhesives, allows engineers to investigate new designs where materials and adhesives are used without bonding challenges.
Jeremy Cooler is a technical specialist for Fabrico (Kennesaw, GA) in the bonding, joining, and sealing business unit.