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Jetting Toward More Precise Fluid Dispensing

The medical device industry may have been stuck on pretty simple ways of applying adhesives. But innovation is finally on the way--with product miniaturization needs and regulatory scrutiny forcing medtech companies to become increasingly sophisticated.

Granted, half of medical device makers are still using manual dispensing technology for adhesives, according to a recent poll. Traditional contact-based manual dispensing is a process most kindergarteners using Elmer's glue would recognize. A person holding a container with adhesive lowers it until it makes contact with the desired surface, adhesive is dispensed, and the container is lifted. The target object is placed onto the adhesive, and then the process is repeated until the job is done.

The trend, however, is moving away from manual dispensing towards automated dispensing systems that can boost throughput and precision.

One technology that is helping the drive that trend is jetting, or noncontact dispensing in conjunction with automation technology in assembly. In noncontact dispensing, a small volume of adhesive is shot towards a component while the dispensing valve hovers above the target. "There are significant advantages to this method," says Amit Arora, global market development manager at Nordson EFD (East Providence, RI). "It is more precise. The volume of dispense is much smaller than with contact dispensing valves. And it can be used to dispense fluids into places that would be hard to reach otherwise."

Jet dispensing processes that use piezoelectric technology have the ability to deposit drops of adhesive at a distance from the substrate. For most applications, the valve is an inch or less from the substrate, depending on the variables involved.

Another disadvantage with contact dispensing is that the valve must move downward to come into contact with the substrate as surface tension is required to pull fluid from the reservoir above. In contact dispensing, the valve initially moves horizontally over the target object, moves down to touch the object, and dispenses adhesive. Then the whole process repeats.

Because noncontact dispensing does not require vertical movement of the dispensing valve, it is typically much quicker than contact dispensing. Nordson EFD recounts one case where a company transitioned to noncontact dispensing and increased throughput by 50% while boosting process control. Another advantage of eliminating vertical valve movement is that it is easier to accommodate a variety of products on the same assembly line. Jet valves can help bolster speed, too, as they are capable of operating at speeds as high as 500 Hz.

One example of where this technology is being widely used is in needle to hub assembly. To glue the needle component, the cannula, onto the plastic hub within the syringe, a significant number of companies are using noncontact dispensing because of the aforementioned advantages--and another one: durability.

Demand for hypodermic needles is growing globally given an aging population. Tens of billions of needles are manufactured annually, Arora says. "Companies are continuously churning out needles left and right."

Depending on the fluid and the dispense parameters, noncontact dispensing valves can last upwards of 500 million cycles before they need maintenance or replacement. For contact dispensing systems maintenance or replacement might be necessary at roughly 50-60 million cycles, again depending on the fluid and dispense parameters.

Refresh your medical device industry knowledge at MD&M Chicago, October 15-16, 2014, and MD&M Minneapolis, October 29-30, 2014.

Brian Buntz is the editor-in-chief of MPMN and Qmed. Follow him on Twitter at @brian_buntz.

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