U.S. Health Secretary Robert F. Kennedy Jr. says wearables can help Americans learn the impact of diet on their health, including "what food is doing to their glucose levels". When most people think of wearables, they think of smartwatches. However, smartwatches cannot directly measure glucose levels, so what devices can be used and how can the manufacturers integrate the optimum battery to keep these devices practical to use whilst reliably transmitting the data?
What devices can be used?
Traditionally, monitoring glucose levels was achieved by pricking the finger with a needle, putting a drop of blood on a test strip, then inserting it into a glucose meter (glucometer). However, this relies on the person remembering to take the readings and having to transport needles, test strips, and glucose meters with them whenever they travel.
Since 2004, a far more convenient and near real-time way of monitoring glucose levels has been used. Known as continuous glucose monitors (CGMs), these small sensors are inserted under the skin and a sticky patch helps them to remain in place. Each time the sensor collects the glucose level, the data is transmitted to a receiver and displayed via software on a smartphone or a separate handheld device. Having a separate device is useful for situations where phones are not allowed, such as in military bases, government buildings, classrooms, and airplanes.
When designing continuous glucose monitors, manufacturers have many decisions to make, such as selecting the best software, sensor, and sticky patch. With so much to think about, one component is often overlooked - the battery. Yet, selecting the right battery can make a huge difference in terms of the practicality of the device for the wearer and how reliably the data is transmitted.
Making the devices practical to use
Because a CGM sensor is inserted into the body, it can only last for around 7 to 14 days (device dependent) before it must be disposed of. Therefore, they are usually sold with a non-rechargeable battery embedded because these have a higher energy density than rechargeable counterparts (meaning they can store more energy for their size), allowing the patches to be manufactured in the smallest possible size whilst maintaining a high level of performance. The smaller the CGM, the less it will protrude and the lower the risk of it getting caught on clothing when the wearer gets dressed.
However, there are different types of non-rechargeable battery and some have far greater energy density than others. For example, Ultralife manufacture Thin Cells® that have an energy density of around 500Wh/l and 400Wh/Kg compared to just 300Wh/l and 260Wh/Kg for the best lithium coin cells. Thin Cells® can also be made in custom sizes to fit the available space inside the CGM.
Reliably transmitting the data
Every few minutes, when the device is transmitting the glucose level to the receiver, high bursts of energy are needed to power RF transmitters. The use of low resistance current collectors allows Ultralife Thin Cells® to outperform coin cells in these applications.
Diabetes levels are rising in many countries across the globe, including the United States, China, India, and Pakistan. Although there is no clinical evidence that monitoring glucose levels alone prevents diabetes, it can help to identify prediabetes or glucose spikes. Reliable power helps continuous glucose monitors (CGMs) to collect and transmit glucose levels more efficiently and effectively.
