Where 3D Printing Makes Sense for Micro Medical Devices
Potomac Photonics, a contract manufacturer located in Baltimore, Maryland, is familiar with the common challenges of 3D printing, like build orientation, resolution and surface finish. But in Potomac’s case, these challenges are magnified—literally. The company is known for its microfabrication work, and has the ability to machine, laser cut and 3D print parts on a very small scale. Micromachining expertise combined with a dual-material SLA 3D printer enables the company to create a number of medical devices and device components, both in prototype and for end use.
Founded in 1982, Potomac Photonics is located at “Bwtech@UMBC” Research and Technology Park, the university research park for the University of Maryland, Baltimore County. The company has conducted collaborative projects with commercial and government agencies in medical device manufacturing, biotech and electronics fabrication. Using technologies ranging from laser micromachining to hot embossing, the company can micromachine materials including polymers, metals, ceramics and glass. The parts the company produces frequently demand features down to 1 micron, and in some cases even smaller, says Mike Adelstein, president and CEO.
For its additive manufacturing work, Potomac relies on a 3D Systems Projet 3500 3D printer capable of layer thickness down to 16 microns (smaller features are achieved by micromachining printed parts. The SLA printer uses a two-material process that can print wax supports and voids alongside the polymer for the part. Once the build is complete, support removal is fast and easy. The wax is melted away in an oven, leaving behind a surface finish that is good enough for functional prototyping and even some end-use applications. Two example applications for the medical industry are pictured in the slideshow above.
The first photo (Figure 1) shows a pair of components developed with Memorial Sloan Kettering Cancer Center that compose a microfluidic mold. The mold in turn is used to make a polydimethylsiloxane (PDMS) microchamber for growing cancer cells in a controlled environment. These microchambers are commonly used in biology and biomedical applications, but developing and producing them using traditional moldmaking can create a costly bottleneck. By 3D printing these acrylic prototypes, Potomac was able to save cost and reduce lead time for the cancer center.
Figure 2 shows a set of components for an ear implant used to treat otosclerosis disease. Otosclerosis is an abnormal hardening of the stapes bone inside the middle ear. Commonly called the stirrup bone, the stapes is responsible for moving the inner ear fluids to enable the sensory process of hearing. If the bone becomes fixed, its ability to generate these vibrations is limited, resulting in hearing loss.
The parts pictured were created for a stapes prosthesis developed by the Institute of Micromechanics and Photonics at Warsaw Technical University in Poland. Though these are prototypes, they were used to verify that the device geometry would allow it to be implanted into a temporal bone. Prior to turning to Potomac, the institute had tried another 3D printing process that did not achieve the small, precise geometries and tight tolerance necessary for this verification. Given the quality that Potomac has been able to achieve in these small prototypes, it may be economically viable to 3D print short production runs of this prosthetic.
In both cases, the parts are shown following the removal of the wax, but without any additional postprocessing. Achieving these results is part equipment, part trial and error, and part know-how. The resolution of the printer contributes, but factors such as laser power and orientation also play a role. The shop has learned through experience what the best orientation for a given part is likely to be, but also performs testing when needed. The Projet's 11.75 × 7.3-inch (298 × 185-mm) build platform enables Potomac to print the same component in multiple orientations in a single build, so as to quickly determine the optimal orientation.
Even with past experience and up-front work, though, “Sometimes we reach the limits of what 3D printing can do,” says Adelstein. In these cases, the shop turns to a combination of its micromachining technologies. It might 3D print the part as near-net-shape as possible, then use the laser to machine the smallest features, for example. Or the company might switch from 3D printing small batches of a part to machining or molding it if production takes off. “It could be good for one stage of the project, but it’s not always good for the whole project,” he says.
In all cases, Potomac seeks to choose the technology that will best serve the needs of its customers. The 3D printer is used where it can save time and cost while meeting required tolerances. As the technology develops and new materials are introduced, Adelstein sees its usage for production growing.
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