Small but mighty: Challenges of powering small implants and devices
After participating in a panel session discussing the exciting developments in neuromodulation therapies, Denis Pasero, product commercialisation manager, from Ilika sat down with Ian Bolland to discuss the design challenges for battery manufacturers when it comes to small, implantable devices.
Ilika believes that one of the main challenges of powering miniature implants in the sector is to make sure they’re properly powered while not compromising on design and power potential. Then there’s the issue of the end user, are they going to be prepared to recharge the batteries?
Pasero explains: “You can’t expect any technology to have the same power when the battery is a few millimetres long, it needs a conversation with the patient. Is the patient going to be happy with charging the device by themselves? Perhaps every day? That’s not a given. People will be worried that they’ll miss a day. What’s going to happen to that implant? That’s a risk the designers are taking with good signs that this could be accepted at some point because what you have then is a much smaller device, a less risky operation, a device that you won’t even notice.”
Ilika is an expert in the manufacture of solid state batteries working with its customers to develop Stereax micro batteries for next-generation implantable devices. The company is presently fitting out a new facility which will enable it to produce these batteries at scale which will make them the first volume manufacturer of solid state micro batteries for medtech in the UK and possibly Europe. They’ve been working on adapting to smaller implants and batteries for a number of years. Pasero described some of the ideas that medical device developers have for implants as “almost science fiction” with some suggesting new devices and implants could be as small two millimetres wide, be placed in the heart, the lungs or inserted through a catheter. The use of solid state batteries compared to the more conventional lithium ion batteries can have its benefits.
“There are miniaturised cylindrical batteries - take the AAA battery - and the big medical battery giants are now designing miniature batteries that could fit onto your finger. The problem is they’re made out of conventional, usually lithium ion, chemistry so they have liquid inside. You need to ensure the liquid does not go inside the body, so it’s encased in a metallic can, like an AAA battery but smaller. The problem with that is the volume, as you reduce it down at some point you’ve got only can with no battery left inside.
“They are limited to a level of miniaturisation unlike solid state which don’t contain liquids. They are just bare dies like an integrated component, like an IC chip without the packaging and it’s just a piece of ceramic, so you can make them very small – smaller than those cans. The challenge with miniaturisation is energy density. As the battery becomes smaller, you’d expect it to have less and less energy. At Ilika, as we miniaturise, we ensure we make the batteries very energy dense using patterning and energy dense chemistry.”
Neuromodulation, Pasero explains, has been around for decades, but the miniaturisation of such devices has allowed them to become increasingly closer to the brain, the spine and in general the organ to be treated. After his panel session with industry leaders from Teliatry and NXTStim, Pasero said that the experts know how to reduce pain levels within people, they just need the physical devices to allow them to execute it.
He believes that this kind of miniaturisation began some years ago with the smart contact lens.
“The very first one was created for diabetics, giving them real time sugar levels in the body by measuring glucose in the eye. This didn’t initially work very well and many thought smart contact lenses were never going to catch on.
“However there’s now dozens of companies working with them and not just for health conditions. From sensors that measure sugar levels, to those that measure pressure in your eye. Glaucoma is a condition that results from an optimised pressure inside the eye and with a little bit of electronics on the contact lens, it could read the pressure and even correct it. There’s also the smart contact lenses that get publicised more - the AR and VR ones, where the lens comes with a display.
“The contact lens that can communicate with a device, like your phone. These are gaining a lot of investment. Some companies are getting hundreds of millions of dollars of investment for ideas like that. The market is huge, but what battery is going to be put on a contact lens? It’s got to be extremely small.”
It's not just the contact lens. When explaining about the relatively easy accessibility of ultra-low power electronics, he spoke about the exciting advancements that have been made in this area.
“The idea of next generation implantable devices is to make them smaller and more efficient. For example, when you have a pacemaker or neuromodulation device, it’s quite large and it goes in your chest or in your back. When there is a large area you’ll have connectors inside the body, electrode not wires, going to the place where the operation needs to be. It could be your brain, right? Your heart? Or it could be on your spine, but the device itself can’t be next to it currently, because it’s too big.
“So the idea is that you only make one device, if the device is small enough then it can be in your brain or at the back of it, it can be in your lungs, it can be on your spine. Then it becomes more efficient because it’s right next to the organ. It’s amazing. People even want to put something inside their heart; replace the idea of an external pacemaker with an internal pacemaker. That’s sci-fi but it exists.”