Report from IMAPS: Biomedical devices present unique challenges, opportunities

by Meredith Courtemanche, contributing editor, Advanced Packaging

The tech-friendly atmosphere of San Jose, surrounded by silicon wafers inside and outside the IMAPS show, generated the ideal mood to study harsh-environment medical electronics at IMAPS 2007, the International Microelectronics And Packaging Society’s 40th annual international symposium on microelectronics. The Body Worlds exhibit at The Tech Innovation Museum, where real cadavers are preserved to expose the makeup of the human body, provided a fitting backdrop to a half-day session titled “Biomedical Materials, Devices, and Packaging,” with discussions about the challenges and potential breakthroughs in medical engineering.

As evidenced by the failure of complete synthetic hearts inside the body, perfect mechanical and electronic performance means nothing in a medical device if the body rejects the implanted system. Z. Joan Delalic of Temple U. began the session with the mantra of “the body is one of the worst environments for electronics,” with a host of conditions working against medical devices: acidity, electromagnetic interference (EMI), fluctuating pressure, vibration, humidity, etc. The dangers range from electrical failure to corrosion, resulting in everything from restricted mobility to toxicity and infection. Hemorrhaging is a constant worry with implanted medical electronics, she noted.

The list of considerations for engineering a medical device, particularly one that goes inside a human body, is long. Implanted devices need to communicate with external instruments, either with connecting leads or wireless transmission. Biomedical device frequencies are regulated by the FCC, but the risk of signal interference is still a factor. Interaction with other machinery (hospitals and EMT vehicles are rife with electronic devices operating and transmitting), passive/active interaction with the user, thermal management, and other issues typically encountered with electronic devices are magnified in the medical sector. Recalls can be costly, if not devastating. Plus the standard concerns of high-reliability electronics apply: acceptable solder joints, functioning IC components, long in-field life, etc.

Delalic noted that while most other electronics production moves abroad, biomedical electronics production is a sector of packaging services that remains in the US, due to intensive R&D, Food and Drug Administration (FDA) regulations, and lengthy test periods.

More research is needed into new sensors, particularly those comprised of bio-neutral or inert materials, which gather accurate readings and lower human risk. Because sensor components are “the building blocks of medical equipment,” the industry is pushing for more accurate and wider-scope sensors that cause less irritation to the patient. These could lead to everything from killing cancer cells to regulating organs like the kidneys and bladder. Materials science is key to future generations of sensing modules, from the gates of an individual sensing circuit to a complex miniaturized system like a cardiac-assist device. Drug-delivery devices also factor into this area.

The ideal medical electronic device should be 100% biocompatible, small and noninvasive, safe, effective, and reliable. While the reality of such a device is still in the future, nanomaterials are enabling more biocompatible assemblies. Nanometer-thin carbon-based coatings provide a hermetic barrier between living tissue and functioning electronics. Conformal coatings will figure into this equation, allowing devices like sensor arrays to be insulated and smaller. Advanced medical devices will use carbon nanotubes as a moldable interface, connecting electronic sensors, transmitters, and signal conditioning modules to human tissue. Today, the majority of implantable medical electronics are coated with engineered polymers that can be extremely costly and difficult to manufacture, Delalic acknowledged, though the advantages of increased biocompatibility offset costs, she added.

Device design and packaging in the biomedical sector is a unique field from most electronics segments, even other harsh-environment areas. “Packaging is less about interconnection and encapsulation, and more about protecting the body and the device from each other,” explained Delalic. But the aim of packaging a component remains the same — to ensure that the device functions as accurately and effectively as possible, for as long as possible, without detrimental effects. With everything from sensors to nanoscale electromechanical systems to lab-on-chip to organ-assisting devices appearing in the medical sector, improvements in packaging, encapsulation, system design, and materials engineering are at a premium. M.C.


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