The trend toward shrinking technology has some high-level implications for the design and development of regulated medical devices.
Bill Betten, Betten Systems Solutions
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As in consumer products, shrinking the electronics gives medtech manufacturers the ability to pack new or improved features into a smaller volume. Capabilities and product performance will likely always remain a driver for integration, whether it be on a printed circuit board or an application-specific integrated circuit (ASIC).
Balancing costs with volume
The cost of integrating is lower as well, driven typically by the ability to make many circuits in one batch process. However, the up-front non-recurring engineering costs for developing an integrated circuit are quite high compared to PC boards with discrete components. While there are strategies for mitigating the up-front costs, design costs can reach $1 million and a mask set can cost in the $500,000 to $1 million range, depending upon the process node selected. These costs can be easily amortized if spread over the millions of components for consumer devices but prove a challenge for the relatively low volumes of most medical devices unless the item is single-use.
Other considerations
Developing a custom chip in medical devices is most often driven by other attributes (size, power, performance, etc.) with cost less likely to be the driver. Size can be a critical concern, particularly for a wearable or implantable device in which space is at a premium.
Shrinking the electronics typically also lowers power consumption. However, it also makes the ultimate packaging smaller, which may result in a thermal management issue. Medical devices must be able to dissipate the heat generated by electronics, making materials selection and cooling a critical concern, particularly for an implantable device. While materials selection is always driven by biocompatibility issues if in contact with the body, the need to address thermal management affects the packaging design as well.
Integration does improve reliability. Integrated circuits, interfaces and connections are common points of failure in discrete circuits, but they can be reduced to a metal layer deposited via a batch process, with corresponding higher reliability. However, as technology nodes continue to shrink, the defects inherent in the underlying silicon material can result in both short- and long-term failures. Because medical devices put a premium on reliability and longevity, these factors can be important.
The MEMS factor
While much of this discussion has focused on the more traditional integrated circuit, another family of small devices, microelectromechanical systems (MEMS), is playing an increasing role in medical devices. MEMS can be defined as miniaturized mechanical and electro-mechanical elements (i.e. devices and structures) that are made using the techniques of microfabrication.
MEMS devices can vary from relatively simple structures having no moving elements to extremely complex electromechanical systems with multiple moving elements. While the functional elements of MEMS are miniaturized structures, sensors, actuators, and microelectronics, the most common elements today are the microsensors and microactuators. In medical devices, the promise of compact or unique sensors may be realized through the integration of MEMS structures with traditional integrated circuits.
Facing the challenges
While advantages such as size, power, features, performance, and perhaps manufacturing cost exist, so do challenges for medical device integration. Sterilization of devices, particularly with gamma radiation, can be an issue. Design and testing of integrated circuits reside in the arena of specialists, because cuts, jumpers and probing do not work at the nanometer scale, making device verification and trouble-shooting problematic. Developing a test process for an integrated circuit might easily cost as much as the initial design of the circuit because of the need for wafer, device, and package part testing.
Finally, even with all of the technological advances of the last few decades, certain things just don’t scale. Chief among these are energy sources. While battery chemistries have certainly improved (as have design techniques for energy usage), energy densities are such that the primary solution in products ranging from cell phones to laptops to pacemakers is to increase battery size for more power for the given application. In fact, pacemakers are typically explanted and replaced after 10 years to ensure continued operation. In addition, the antennas required for communication follow the laws of physics, needing to be of a certain size in order to transmit and receive information at their specific frequencies.
‘Technology of the small’
Technology has affected all aspects of our lives and the evolution of the “technology of the small” will certainly continue into the medical device arena, making possible new diagnostic, monitoring, and treatment capabilities, subject to the considerations noted above. Even if we don’t fulfill the vision of sending a team into the body of a comatose patient using a miniaturized submarine to remove a blood clot in the brain (as in Isaac Asimov’s 1966 classic, Fantastic Voyage), it is indeed possible that a remote-controlled miniature “drone” may one day indeed do that or even destroy cancer cells. Stay tuned as science fiction becomes reality.
Bill Betten is the president of Betten Systems Solutions, a product development realization consulting organization. He most recently served as director of business solutions for Devicix/Nortech Systems, a contract design and manufacturing firm. He was also VP of business solutions at Logic PD, medical technology director at TechInsights, VP of engineering at Nonin Medical, and has worked in a variety of technology and product development roles at various high-tech firms.
The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of MedicalDesignandOutsourcing.com or its employees.
