Less space, more power: The challenges of ultra-thin batteries
Ilika Technologies is trying to tackle medtech’s power – and space – problems with its Stereax M50 ultra-thin batteries. Editor Dave Gray caught up with Denis Pasero, product commercialisation manager at the group, to discuss the challenges in this important field.
The medtech space is one of the most challenging environments for battery technologies. Batteries need to be small enough to be unobtrusive, enabling implantable devices to be charged in a way that does not restrict a patient. The batteries need to have as long a life-span as possible, avoiding the risks of repeated surgical intervention. They also need to be biocompatible so that they do not pose a risk of leakage.
Each device application may require different sizes and form factors, which Ilika says can now be accommodated with the customisable battery sizes and shapes enabled by its latest launch, the Stereax M50.
Innovation in applications that require injection into the blood stream, monitoring heart rhythm or attachment onto the peripheral nervous system for neurostimulation can be enabled with this technology. These batteries enable self-sustaining power sources that do not need to be changed regularly or use inconvenient cabling.
I asked Pasero where people sometimes go wrong when factoring in power supplies for increasingly small medical devices:
“Whether in medtech or any other IoT fields, people never really think about the battery first. They quite often design the device first, and then go looking for a battery for it. People don’t always think of the battery as a core function of the device.
“The two questions they need to be asking are: how much power is required, and how much volume is available?
“We find that we sometimes have to discuss with people about adapting the use case to the energy available in the battery. How often is the device going to be re-charged, and how, for example?”
Stereax M50 is Ilika’s smallest solid-state battery yet, and there are a range of medtech areas where advances can be made. In the case of medical applications, Ilika points out, it is not the case that ‘one size fits all’.
Pasero continued: “Customers talk to us very early on in the process. Some will say ‘we need this particular battery, with all the specs’. Still others will go the other way, and say ‘this is the power demand, can you design the battery for us?’
“In this second case, we’d revisit the design together and look at ways to optimise the efficiency of the design.”
Making the right battery choice is also increasing in importance due to the rise in remote monitoring devices. Devices which require maintenance at the hands of the patient (as opposed to the healthcare provider) need to factor in usability as well as patient adherence concerns. For example, the battery itself needs to be quick and simple to re-charge (if it is re-chargeable).
“I believe that product designers have patient adherence very much in mind. There might be for example a case where the user has to charge a wireless pacemaker, by placing it on a charging cushion. However, the patient could forget. So the designer has to ‘over-design’ critical devices like this. They may have to put two batteries in the same device. One is in use, and the other is a backup,” said Pasero.
The Stereax M50 is designed to be “totally flexible in terms of size as well as shape”, according to the company.
Second generation medtech devices could be made much smaller, helped by smaller, denser batteries which can be recharged wirelessly and could even benefit from energy harvesting through small movements and temperature changes within the body.
Pasero explains this: “Some people are trying to build in energy harvesters to power the devices using energy from inside the body. For example, the beating of the heart, or the movements of the lung, or the small temperature changes in the skin can be used to harvest energy for batteries.
“This sort of technology is part of our ecosystem, and we want to work hand-in-hand with people working on these projects.”
He says the firm is keen to network experts in the energy harvesting field: “We know of some, but there will be others we don’t know”.
The miniaturisation of solid-state batteries from Ilika means that devices which have previously been placed outside of the body, or just outside of the organ, can now be reduced in size and sited within the organ itself with no cumbersome wires required.
Stereax also features biocompatibility, so it’s suited to certain types of devices such as glucose and blood pressure monitors. The batteries can be recharged using inductive charging probes, reducing external wiring and the risk of the battery running out of charge.
Applications for ultra-thin batteries
Blood pressure monitors
Early warning pressure sensors are sited within the lungs to monitor blood pressure in the arteries, sending data which would give early warning signals to avert a cardiac arrest or heart failure. Rising pressure in the arteries can happen several months ahead of crisis point, with an alert sent to a doctor or to a self-monitoring patient meaning that corrective action can be taken and a serious condition isn’t left to deteriorate.
Cardiac devices and pacemakers
Currently cardiac monitoring devices are relatively bulky and so need to be located outside the heart with leads passed through holes created to feed the wires into the heart. When a battery needs changing, further surgery is required for the device to be removed and, as the same holes cannot be reused, new openings need to be formed for the replacement device and leads to be fitted. With the miniaturisation of biocompatible battery technology, next generation devices are much smaller in size and so can be fitted directly onto the heart. Additionally, long battery life, with wireless recharging also possible, making intervention much less frequent.
Neurostimulators
Incredible improvements to a patient’s health can be achieved with a neurostimulator, including significantly reducing the muscle tremors associated with Parkinson’s disease, treating anxiety, alleviating depression, reducing the pain of rheumatoid arthritis, rebalancing OCD, and easing many more life-affecting conditions. The neurostimulator sends impulses to the vagus nerve, which in turn can regulate a wide range of conditions. Currently devices are relatively bulky and in two parts with one part fitted to the base of the spine and one part fitted to the back of the head. Advances in technology mean that devices will be much smaller in size, attached directly to the vagus nerve and with integrated sensors capable of communicating with doctors so that data can be analysed to monitor and improve treatment.
Smart contact lenses
An alternative to thumb pricking or patches to monitor glucose levels would be a welcome change for many diabetes patients. The medtech industry is working towards battery powered sensor technology so minuscule that it sits inside your contact lens, making self-monitoring of glucose levels totally unobtrusive.
Smart dental braces
Smart dental braces have minute built in sensors collecting data which can track the movement of the teeth over time, but can also monitor how much the brace has been worn and whether the patient has in fact kept to their prescribed amount of wear.