Low-Power Tech Transforms Medical Wearables

September 24, 2024

Blog

Globally, we are, on average, living longer – improved access to better healthcare means that global life expectancy has increased by more than six years between 2000 and 2019, to 73.4 years. According to the World Health Organization (WHO), the proportion of the world's population aged over 60 years will nearly double between 2015 and 2050, from 12 percent to 22 percent.

With more people living longer, we need effective and affordable healthcare services. One big area where technology can help is medical wearables, where advances in ultra-low-power operation are driving rapid growth. Power-efficient operation is revolutionizing medical wearables, enabling compact devices that can run for long periods between battery charges or replacements.

In healthcare, the key requirements for wearables are the ability to provide accurate, high-quality data with continuous monitoring to provide real-time, actionable insights into an individual’s health status. Wearable devices must be small, light, and easy to use, and sufficiently secure to protect sensitive data from unauthorized access.

In this article, we’ll explore how ultra-low power technology can be used to create cutting-edge medical wearables, using diabetes monitoring as an example. We’ll look at solutions which integrate Bluetooth Low Energy (Bluetooth LE) technology and continuous glucose monitoring (CGM) capabilities.

Continuous Monitoring for Diabetes 

There are various chronic diseases and conditions where patients can benefit from wearables, but one of the most common is diabetes. In the USA alone, 38 million people live with diabetes, and prediabetes impacts an additional 98 million Americans.

Diabetes can lead to serious health complications, and effective monitoring is essential to manage it safely. Traditionally, this has required a blood glucose meter (BGM) to measure glucose levels, which uses a fingerstick to draw a blood sample and measure glucose levels at a single moment in time.

More recently, people with diabetes are relying on continuous glucose monitors, which are more convenient and provide immediate feedback with insights from data collected constantly rather than at intermittent intervals. With continuous measurement, we can learn more about how a person’s blood glucose levels change over the course of their day, and how it responds to their diet and activity levels.

CGM has become increasingly reliable. It has demonstrated how it can help to reduce A1C (blood sugar) levels and hypoglycemia and improve the time a person spends in their target glucose range.

A continuous glucose monitor typically measures the glucose levels in a person’s interstitial fluid, which is the fluid between blood vessels and cells, using an electrochemical sensor. In this kind of sensor, particles of the substance under test encounter a “working electrode” (WE), and an electrochemical reaction takes place. The loss or gain of electrons in this reaction leads to a flow of current, which can be measured.

As it is worn continuously on a person’s body, a CGM needs to be as compact and lightweight as possible. To achieve this, it is often powered by a coin-cell battery. The CGM also needs to have a charging interval that is as long as possible. This means that the device’s semiconductor components need to be small in size with low power consumption.

To meet these requirements, a CGM commonly includes an analog front-end (AFE) component, which integrates the required A/D and D/A and input/output functions. Alongside the AFE, the CGM also includes a microcontroller (MCU) with wireless capabilities, such as Bluetooth Low Energy (Bluetooth LE) technology, that can communicate with the user’s smartphone, or with a dedicated external controller, as shown in this interactive block diagram.

Compact, Low-power CGM Solution

Let’s look at an example of a solution developed for CGM, based around the CEM102 electrochemical sensor AFE and its RSL15 wireless microcontroller featuring Bluetooth 5.2 .

The CEM102 is an AFE that enables electrochemical sensing with excellent accuracy at very low currents. This is important to precisely measure the much smaller currents that are generated by recent generations of physically compact sensors.

As well as medical wearables such as CGM, the CEM102’s small form factor and low power consumption make it ideal for applications where very low current measurement is required, such as gas detection, food processing and agricultural monitoring.

The CEM102 is designed to be used with onsemi’s RSL15 wireless MCU, a Bluetooth LE MCU, bringing several additional system-level benefits such as operating at optimized system power consumption and supply voltage.

The system can operate over a 1.3 to 3.6 V supply voltage range, typically using a single 1.5 V silver oxide battery or a 3 V coin cell. The CEM102 consumes 50 nA in disabled mode, 2 µA in sensor-biased mode and 3.5 µA in active measurement mode with the 18-bit ADC continuously converting. This enables it to deliver 14 days of operation with only a 3 mAh battery, or several years’ operation if larger-size batteries are preferred.

The RSL15 is an ultra−low-power MCU, based around an Arm Cortex−M33 processor, and supporting Bluetooth 5.2. It includes built-in power management, flexible GPIO and clocking scheme and an extensive set of peripherals to maximize design flexibility for high-performance and ultra-low-power applications. The RSL15 includes 80 KB RAM and is available in 284 KB or 512 KB Flash options.

To speed up system and firmware development, onsemi offers a CEM102 evaluation and development board (EVB). In addition to the CEM102, this includes the RSL15. A sample code to set up and perform measurements is available for both devices, which is complemented with apps for iOS and Android phones and tablets.

Conclusion: Wearables Transforming Healthcare

Used together, the CEM102 and RSL15 enable an electrochemical sensor to accurately measure current while operating with very low system power consumption and wide supply voltage range. This enables a glucose level figure to be derived by a CGM, which then sends its data via Bluetooth LE technology to a cloud-connected system for analysis, storage, and action.

The hardware and software integration of these two components, along with their compact size and power efficiency, enables a CGM monitor to be small and unobtrusive. Its ultra-low-power consumption enables an extended operating time between charging or replacing batteries – up to several years in practice.

In summary, the CEM102/RSL15 solution addresses the key requirements in healthcare wearables we identified earlier:

• Continuous monitoring: extremely low system current of 3.5 µA with sensor converting enables frequent samplings
• Data quality and accuracy: high accuracy sensing of CEM102 with 18-bit ADC
• Convenience (small and light): small form factor and industry’s lowest power consumption enable miniaturization and long operation time
• Privacy and security: RSL15 integrated hardware-accelerated cryptographic service protects captured patient data

We have looked at glucose monitoring as one example application, but there are countless other uses for compact, low-power components in medical wearables – including monitoring factors such as heart rate, motion, temperature, skin impedance and providing regular drug delivery for insulin and other medications. The continuous availability of data, and the capability to respond in real-time, means that new applications are being developed for wearables, using continuous and closed-loop feedback to go beyond our current systems. For example, CGM and insulin delivery can work together to provide an “artificial pancreas.”

 

 

By providing convenient and reliable functions, today’s generation of wearables has the potential to transform healthcare for millions of people around the world. As power efficiency improves and semiconductor devices become smaller and more fully featured, the opportunities for positive change are substantial.