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Medical devices, implantables in particular, need components that are the best of the best. Companies that are well established in other industries are now adding their expertise to create innovative medical devices.

Cambridge Consultants Inc. is a product development and design company with three main divisions, one of which is one of the world’s biggest independent wireless divisions. 

Dr. Arun Venkatasubramanian, senior consultant with the company, said that communication and  power transfer are the main challenges in critical wireless medical devices. “Many of our customers have a core skill in medical device development,” he said, “but what is new to them, is the radio design aspect of it; how to get electromagnetic energy from inside of the body to the outside and vice versa. That is our expertise.”

Taking a close look at these devices reveals that the biggest part of all implants is the battery, so reducing its size is a key issue. Another issue is keeping data safe. Until now, all device companies using radios have worked with the FCC, which has allocated a certain part of the spectrum for them to use. FCC-allocated space is from 402 to 405 MHz and is called the Medical Implant Communication System (MICS) band. Also, the radio chip currently used in all implantable devices is made by one of two companies, Texas Instruments or Microsemi. Medical designers have very few choices. Many are looking at moving to Bluetooth, because it opens up many more radio chip manufacturers to choose from. This brings down cost and also alleviates the need for custom external hardware to communicate with the implant device, and enables the implant device to talk to an application on a phone or tablet owned by the patient or the caregiver.

“While Bluetooth no longer needs a proprietary external device, the biggest challenge is how safe the data is,” said Venkatasubramanian. “This is something the FDA is looking at.”

Because Cambridge Consultants works directly with its clients, all technology is highly proprietary. However, Venkatasubramanian said that there is one public knowledge partnership that he can use as an example of what they provide.

EBR Systems has developed a leadless, “grain-size” pacemaker implant that is externally powered called Wireless Cardiac Stimulation System (WiCS). This pacemaker fits into the part of the heart where leads could not be used.

“We used ultrasonic energy for that application,” explained Venkatasubramanian. “This device is used along with a normal pacemaker. It allows for biventricular pacing where a traditional pacemaker paces the right ventricle and EBR WICS electrode paces the left ventricle. This prevents complex surgery and allows for pacing of heart muscles that are typically hard to reach with standard pacemaker leads.”

The biggest challenge in communicating with implantable devices is range of communication. The body itself is like a sponge. It absorbs radio energy. The higher the frequency of the radio signal the more the body will absorb the energy. The challenge is getting a signal out of the body, and then three meters farther. Another challenge is that no one size fits all.

“It would be ideal if a single solution could work the same for every patient, but every patient has a different body morphology and it will change over the life of the implant; patients will gain or lose weight, other muscular changes may happen. So all of these scenarios will affect the implant signal. Signals need to not only be strong, but adaptable,” said Venkatasubramanian.          

Cambridge Consultants does detailed testing in its laboratories with “body phantoms” that mimic different body tissue types so simulations can be done for all different parts of the body where implants are typically inserted; ocular, cochlear, heart, muscle, skin, blood, and bone. Using these phantoms, the firm can design a solution that fits not only current, but future worst-case body scenarios.        

Making the antenna tunable to body type is one of the things Venkatasubramanian  has been working on. Most antennas are either pieces of wire or solid printed metal. He is working on an antenna made from a gallium alloy that is liquid at room temperature.

 “The antenna can be made of fluid channels on a soft material. The alloy can be moved in the channels to change the shape of the antenna based on closed-loop control of the strength of the wireless signal,” he said. “For example, if the patient has lost 30 pounds, then the signal doesn’t have to go through layers of fat. The geometry of my antenna can adjust for that. A liquid metal antenna can do that. This is just one of the types of innovations we are pursuing internally, but it still has a long way to go before it will be in an actual Class III FDA approved medical device.”

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