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Is This the Future of Wireless Power in Medtech?

WiTricity's wireless power technology has already sparked some interest in medtech circles. Discover some of the next steps for WiTricity.

Chris Newmarker

WiTricity resonant power transfer
(Infograph courtesy of WiTricity

Eight years after it was founded with MIT-based technology, WiTricity appears ready for the bigtime with its wireless resonant energy transfer system, which is based on finely tuned oscillating magnetic fields between coils at a distance.

WiTricity (Watertown, MA) has an agreement with Intel to power computing devices over a distance without a cord. And Toyota has licensed the technology to use it in wireless power stations for electric cars.

In medtech, WiTricity has created a system for Thoratec that can transfer 10 watts of power into a human body to power an LVAD--a system that in the future should hopefully do away with the need for LVAD patients to have a wire running through their skin, says Colin McCarthy, sales engineer for medical and industrial at WiTricity.

"So even with high-powered devices, you could send it right through the skin," McCarthy says. (See McCarty discuss wireless power technology at MEDevice San Diego, September 1-2.)

Expect WiTricity technology to show up in more medical devices, both inside and outside the body, McCarthy says. "We're really targeting portable medical devices and all kinds of different hospital applications."

McCarthy recently answered some questions from Qmed/MPMN about WiTricity and the future of its technology in medtech:

Qmed/MPMN: What is the major advantage of WiTricity's technology?

McCarthy: "One of the nice things about resonant wireless power transfer systems is that ... it can be very easy to charge something, to have someone sit in a chair or just not have to worry about charging a device, And because of that, it's a little easier to say we'll have people with implants charge more frequently. It's not as much effort to do that. You can start to think of situations where you might decrease the weight and size of the battery in the device because its so easy to recharge it quickly.

"Because you have wireless power available to you, you can start to do more interesting things with implants. You can have them firing more often or using much more energy. Your kind of limited by how small these implants can be, and that limits your battery size. You have to figure out, 'How do we make this a low power device?' If you can easily charge it, it adds a lot more functionality to something like an implant."

Qmed/MPMN: What makes your wireless resonant energy transfer system different from, say, traditional conductive power, in which you take two coils and line them up in close proximity?

McCarthy: "There are neurostimulators as well as some other devices on the market that use that technology, as well as other devices. The issue with that is that the efficiency tends to be quite low. Because of that low efficiency, you're limited with how much power you transfer. If you transfer too much power at low efficiency, you'll heat the device up. ... Our technology allows you to improve that efficiency quite a bit.. ... You need very high efficiency systems in these complex environments and complex applications."

Qmed/MPMN: How small can WiTricity make a charging system?

McCarthy: "The coils can be quite small. With many of these devices, we'll actually design a custom resonator. ...  We can make resonators on flexible PCBs, circuit boards. It doesn't have to be a wound wire coil. It could be on a flex PCB. It could be thin and very light. You can bend it into the shape and size of the device you want it in. ... You can get it down to less than a millimeter. We've demonstrated prototype hearing aid coils small enough that it could fit into a battery component of a hearing aid, where you're limited to 8 mm diameters. We can fit it into the existing assembly."

Qmed/MPMN: So it could even be fit into a pacemaker can?

McCarthy: "We would put it into the header of the pacemaker. We can set power through most materials--essentially anything that is nonconductive or nonmetallic we can send power through. A titanium can is not preferable, although there are some scenarios in which it's possible. What we'd prefer to put it in the header of the device, where we can set the coil in the header and seal it with epoxy."

Qmed/MPMN: How much power could you transfer into a human body?

McCarthy: "A lot of it comes down to the shape and size of coils and how dense everything is. What we do is we use some pretty sophisticated model tools to look at the interaction of these systems inside humans. That's how we make sure they're safe and pass FCC and international regulations on field exposures and heating. It's very much a case by case basis. But all of our systems are designed to work around humans and have humans in the presence. The LVAD example is a good example where we sent a pretty substantial amount of power into the body."

Qmed/MPMN: Are there any heating issues you have to look out for with inductive resonance?

McCarthy:  "It's a design consideration. It's something that you would make sure you're aware of and design into your system. It's an effective of efficiency. Because resonance is more efficient, you can get more distance before you run into that heating issue. You'll see the heating if the efficiency drops low. Any power that isn't transferred has to show up somewhere. Most of it, we can design our system where it shows up in the source. But ultimately, it's something you have to keep in mind. That's why low efficiency traditional inductive systems run into trouble is because of that heating."

Qmed/MPMN: With so many things potentially being transmitted in medical settings, how do you get around that with WiTricity charging?

McCarthy: "Let's say you have a medical cart or other piece of equipment. You could ... push it up against the wall as a charging point. You could transfer a few hundred watts of power. The effects of that system will only be between that cart and the wall. It won't affect Wi-Fi or any other wireless power systems in the area. It could be foreseeable that there is some standard for wireless power. In the consumer space, in the automotive space, WiTricity is involved in standard-based solutions. On any cell phones or manufacturer's charging network that standard is called the A4WP, the Alliance for Wireless Power. It's actually called Rezence. And then there's a standard similar to that for automotive charging, so that all the different brands of electric vehicles will be able to be charged at your local shopping center or at work. ... For now, we see the system being it's own little ecosystem."

Qmed/MPMN: What makes your technology better than your competitors?

McCarthy: "WiTricity has been around for a number of years. We have a large engineering staff just dedicated to creating wireless power solutions. We're kind of considered the industry leaders ... and hold the foundational patents for wireless power transfer over the distance using magnetic resonance. Our systems will show more efficiencies than other systems. ... It's also little different from other technologies such as RF harvesting, which will have low efficiency and low power."

(See McCarty discuss wireless power technology at MEDevice San Diego, September 1-2.)

Qmed/MPMN: How soon will we see the technology out there?

McCarthy: "Over the course of the next few months, you'll see it everywhere. It's like every new technology. It takes time to get it into the market and create the infrastructure. ... We've been working very hard to get these systems going in consumer electronics. ... What this has involved is creating the standards and laying the groundwork to have a large-scale deployment of wireless power. ... We've made some pretty exciting announcements with companies like Intel and Foxconn and some really big names in the consumer electronics space that are excited about the technology."

Chris Newmarker is senior editor of Qmed and MPMN. Follow him on Twitter at @newmarker.

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