Originally Published MPMNSeptember 2004

PRODUCT UPDATE

Creating Stronger Bonds

Adhesives fulfill a variety of needs in manufacturing medical devices

MelodyLee

Adhesives in the medical device industry continue to expand their capabilities and their range of use. They challenge existing bonding methods in medicine and in device assembly. Dispensing systems are also evolving to handle medical device needs. This article explores some of the advancements in adhesives used on devices and in assembly processes, and discusses trends in dispensing systems. 

Films and Coatings Provide Added Support

In June, industry research company The Freedonia Group (Cleveland) reported its predictions regarding demand for medical adhesives and sealants. The report says that, in the United States, the market will grow 7.5% per year through 2007. According to the study, the $1.3 billion market is driven by the use ofadhesives with sutures and staples rather than bandages. The main cause for the growth points to the aging U.S. population. 

Coatings or layers of adhesives are often used on patient-contact devices such as sensors. According to Melinda Hopp, director of marketing for Adhesives Research Inc. (Glen Rock, PA), trends in this area include tight tolerances, optical properties, and biocompatibility. She cites how sensors are becoming quantitative in measurement outcomes. This means that materials used on the sensors, like the adhesives, need to have very specific tolerances. 

There is also a "demand for multifunctional adhesives that do more than adhere to or bond substrates together," Hopp says. An example of this is the company's ARflow products. The line includes coatings, pressure-sensitive adhesives, and heat-sealable tapes. The adhesives are active in bonding components and wicking biological fluids in in vitro diagnostic devices. Dual-coated tapes can have a hydrophilic coating on one side and a pressure-sensitive or heat-sealable coating on the other.

"The demand for these technologies is driven by the products' hydrophilic properties," says Hopp. "[This includes] the ability to reduce the surface tension of fluids. The adhesive coating provides several key benefits, including reduced analysis time andmore-efficient transport of fluids with smaller sample volumes."
 
For films and tapes that are applied directly to skin, Scapa Medical (Windsor, CT) offers a high-molecular-weight, rubber-based product. The MG-series adhesive is applied to sensors and bandages that are placed on patients' skin. Made of a gelatinous thermoplastic material, the product acts like a solid adhesive and will not dry out. It can be used on a number of substrates including polyurethane films, nonwoven fabrics, and polyethylene and polyurethane foams. 

Adhesives Bond Surfaces Together

In addition to direct skin placement, adhesives can bond one surface to another in medical device assembly. "For devices made of plastics, welding and soldering are not options," says Walter Brenner, R&D manager for Master Bond Inc. (Hackensack, NJ). "Using adhesives also means that [the process is] nontoxic. You don't have traces of metal parts or contaminants that can enter the bloodstream and cause damage."

For a product that resists exposure to repeated sterilization, Master Bond Inc. produces a heat-cured epoxy adhesive. The two-part EP45HTMed can withstand long-term exposure to temperatures ranging from -80° to 500°F. Suitable for use in the assembly of reusable devices, the product adheres to metals, glass, ceramics, wood, plastics, and vulcanized rubber.

An epoxy offered by Devcon (Danvers, MA) avoids chemical hazards that may occur in welding or soldering processes. The company's electrically conductive adhesive can bond electrical components that could be damaged by a hot solder. The Syon Tru-Bond 206A epoxy mixes and pours easily, fills voids, and cures with minimal air entrapment. The material can be used in service temperatures from -65° to 200°F. 

Automation--The Future of Dispensing Systems?

According to Stephen Buchanan, president of Adhesive Packaging Specialties Inc. (Peabody, MA), the adhesive packaging segment of the medical market has gone from steady to strong in the past three years. That's good news for suppliers of adhesive packaging and dispensing systems that are continually improving their capabilities. 

"The move that we see [in adhesive dispensing] is toward automation but with more application-specific equipment," says Jere Donohue, CEO of Integrated Dispensing Solutions (Agoura Hills, CA). "Any of our dispensers can also be mounted on a robot. It just becomes more economical as the price of robots keeps falling."

The company offers a number of systems, including air-free syringes, tube dispensers, pens, and multishot applicators. A full-featured digital shot meter provides up to six different time settings, easily recalled for sequential operation. Two valves may also be controlled with the unit, delivering same-size shots. The machine processes up to 900 units per minute. 

Another type of dispensing system is a syringe offered by Adhesive Packaging Specialties. Housing two-part reactive adhesives, sealants, or resins, the system mixes and dispenses a small amount at a time. The dual-style product provides on-demand mixingand dispensing in a controlled process. Premixed and frozen resin systems are ready for use oncethey are thawed. 

When using premixed syringes, "you get the same result each time," says Donna Bardell, sales manager for Adhesive Packaging Specialties. "If you mix it yourself, the ratio will be off every time. We precisely measure an entire batch and put it into the syringe all ready for use. The fumes are kept contained, the mixing is precise, and no guessing is involved. The waste is alsominimal."

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