“According to the World Health Organization (WHO), more than 400 million people worldwide have diabetes, and the number of people with diabetes has nearly quadrupled since 1980. Behind these numbers, the real tragedy is that diabetes can lead to serious health complications such as blindness, stroke, lower extremity numbness and amputation, heart attack and even death.

“

By: Steven Dean, Marketing, Signal Processing Business, Wireless and Medical Division, ON semiconductor

According to the World Health Organization (WHO), more than 400 million people worldwide have diabetes, and the number of people with diabetes has nearly quadrupled since 1980. Behind these numbers, the real tragedy is that diabetes can lead to serious health complications such as blindness, stroke, lower extremity numbness and amputation, heart attack and even death.

Measurement and monitoring are key to effective management of both type 1 and type 2 diabetes. Both typical and conventional measurement techniques require the use of a blood glucose meter (BGM). Another technology option the market offers for people with type 1 and type 2 diabetes is the continuous glucose meter (CGMS). The advantages of continuous measurement are many, such as allowing people to learn more about the human body and how blood sugar changes over time with various daily activities such as physical activity, diet and even sleep. As more is learned about the behavior of the human body continuously rather than discretely, corresponding treatments and improvements can be made.

Since these instruments typically measure interstitial fluid subcutaneously, until recently, regular blood calibrations required an old-school finger poke. However, with advances in technology, some CGMs now do not require calibration on whole blood.

The microelectronic properties of continuous glucose monitoring systems are generally the same, with a few key exceptions. Also, these devices are often wearable, so size issues mean that higher levels of integration and efficient power management are required to increase the optimum level of energy efficiency of the semiconductor devices used.

In addition to measurement and monitoring, technologies for insulin delivery are advancing, with closed-loop systems combining continuous monitoring with insulin delivery through a so-called artificial pancreas. This leads to better, more accessible healthcare and a more optimistic long-term outlook for millions of people with diabetes.

measure blood sugar levels

Traditional BGM can be purchased at a pharmacy or any drugstore chain. Use the included lancet device (a very small thin needle) to prick your finger and draw a small drop of blood, which you touch to the test strip inserted into the meter.

When the blood sample chemically reacts with the test strip, some AC or DC excitation voltage or current is usually applied to the blood sample. The result is read by the data converter. After a short wait for the microcontroller to complete its calculations, the final blood sugar level will be displayed on the screen.

Figure 1. Simplified blood glucose meter (BGM) block diagram

More advanced blood glucose meters include Bluetooth low energy connectivity to transmit these discrete blood glucose results to a smartphone, which typically runs a cloud-connected app. Results are stored and can be viewed by family members or caregivers immediately or at a later date to improve treatment outcomes.

continuous blood glucose measurement

Today, system architectures for continuous glucose meters (CGMs) typically integrate analog/digital (A/D) and digital/analog (D/A) and input and output functions into a single piece of silicon, usually a custom application-specific integrated circuit (ASIC). ) Analog Front End (AFE) or Application Specific Standard Product (ASSP). Combining 1 Bluetooth Low Energy (BLE) and Micro Control Unit (MCU) such as RSL10 in a small Wafer Level Chip Scale Package (WLCSP), this helps solve the challenge for users to make long-term wear The device becomes as unobtrusive and functional as possible.

Besides the circuit, another major factor affecting size is the required battery. For example, in hand-held BGMs, one or two AA, AAA or AAAA batteries are typically used. These are too heavy and too large for a CGM, so the size and chemistry of the battery often dictates the coin cell form factor. To be practical, system power must be carefully managed. Peak and total current must be minimized because the maximum current drawn from a coin cell battery is much lower than what an AA battery can provide. Another consideration is the discharge curve. For example, if silver oxide chemistries are used, they typically produce a maximum of 1.55V, with a lifetime down to 1.2V. If a manganese dioxide chemistry is used, the rated voltage is 1.5V and the service life is reduced to 1.0V.

Insulin Delivery: Syringe

Insulin has traditionally been self-injected when needed using clinical-grade syringes and needles, much like receiving injections in a doctor’s office. There are many types of insulin that are already on the market. Rapid, short, medium, and long-acting types of insulin can be injected individually or mixed as needed.

More recently, alternatives to subcutaneous injections have entered the market. An alternative is a jet injector, which delivers insulin in a trickle and into the skin. The other is a syringe pen, which dispenses insulin more automatically through an ultra-fine needle. Convenience and comfort are greatly improved while reducing injection fear.

Figure 2. Smart Syringe Pen Diagram

These alternative devices are actually more electro-mechanical and “smart”, just like traditional blood glucose meters. The pen is designed with a microcontroller and a Bluetooth low energy radio to capture and report discrete injection times, injection volumes, and more.

Insulin Delivery: Pump

Insulin pumps provide precise control of insulin delivery in people with type 1 and some type 2 diabetes, but the more common application is for people with type 1 diabetes. These pumps are a key part of the protocol and ultimately function in a “closed loop” system, an artificial pancreas. Continuously measuring blood sugar, a system that uses an insulin pump to receive this data, coupled with appropriate delivery controls and algorithms, creates an artificial pancreas, the holy grail of diabetes management.

Using CGM instead of multiple finger pricks is a better measure that utilizes continuous data rather than a few discrete data points. Again, being able to eliminate low and high blood sugar throughout the day is an improvement. The so-called artificial pancreas means that patients no longer have to worry about nighttime low blood sugar, low blood sugar levels during sleep, or the frequency of measurements and injections. This can greatly improve their health, quality of life, and possibly lifespan.

Figure 3. Simplified Insulin Pump System Diagram

As you can imagine, the use of automated insulin delivery requires the safety, reliability and accuracy of the system, so the choice of technology, system and component suppliers is critical for device manufacturers.

Building an artificial pancreas

Figure 4. Diagram of the artificial pancreas

Although artificial pancreases are both worn on the body or attached to the user’s belt, their physical designs vary widely, the architecture shown depicts the most common approach utilizing a highly integrated custom ASIC with all analog front ends (AFEs) module, power management, MCU or control module, and an integrated Bluetooth low energy radio to aid communication. All systems include some type of insulin reservoir, a pump or actuator system that provides the appropriate drive mechanism, a catheter or cannula system that delivers insulin through a hypodermic needle, and various types of sensors (motion, pressure, temperature, blood sugar, etc.) ). The main difference between discrete or uncoupled measurement systems is continuous and closed-loop feedback.

In addition to blood glucose sensors, several sensors such as low-gravity accelerometers and temperature sensors for body-worn devices can be used to monitor activity levels to improve dosing algorithms. These sensors continuously provide information about body movement and the external environment, while also providing continuous information about blood sugar levels. Artificial intelligence (AI) can be used to estimate short- and mid-term insulin therapy needed.

Most systems use Bluetooth Low Energy to communicate with smartphones connected to the cloud. However, some people use headless, carry-on pods to communicate with a separate control system or system sometimes called a “personal device manager” (PDM). In these cases, PDM is used for user interaction and can be used as an open-loop (not closed-loop) control system. PDM is also a function that provides cloud connectivity, usually via Wi-Fi or LTE.

With cloud connectivity, caregivers can be notified and connected. In addition, through cloud computing, more functions can be obtained from big data analysis and population management.

In some cases, in addition to IC integration, even passive components are integrated with highly integrated semiconductor ASICs in advanced 3D hybrid modules. This is the true expression of size, weight and performance advantages.

Bluetooth Low Energy Radio Selection

Going back to the need for coin cell battery operation and low-power operation, devices such as ON Semiconductor’s RSL10 Bluetooth® 5 certified radio system-on-chip (SoC) provide the appropriate option for communicating with artificial pancreas solutions . The RSL10 is validated by the Embedded Microprocessor Benchmark Consortium (EEMBC) to provide the industry’s lowest power consumption and has recently been certified for implant/life-critical medical applications. It is especially suitable for ultra-low power battery powered devices. It uses an Arm® Cortex®-M3 processor and ON Semiconductor’s LPDSP32 digital signal processor to provide the robustness required to support complex designs. Onboard 384KB flash memory and 160KB RAM provide users with flexible programming options. RSL10 also provides opportunities for the Bluetooth low energy protocol stack and the ability to develop firmware over-the-air (FOTA) applications.

Figure 5. RSL10 system block diagram

A lesser-known benefit of the RSL10 is that ON Semiconductor’s Bluetooth low energy intellectual property (IP) can be reused for ultra-low power custom ASICs to meet needs covering a wide range of sensors and sensor interfaces. Since unique digital-to-analog (D/A) and analog-to-digital (A/D) conversions are common in measurement systems and insulin delivery systems, customization is almost always required. For example, in an insulin delivery system, only Bluetooth low energy transmission may be required, reducing baseband RF and controller costs. Many applications are bulky or potentially disposable, so it is key to be as energy efficient as possible based on silicon to save cost and size.

Diabetes classification

There are two main categories of diabetes: type 1 diabetes and type 2 diabetes. Type 1 diabetes is caused by the inability of the human immune system to produce enough insulin in the pancreas and can be inherited from parents. Patients with insufficient insulin production often require insulin injections to survive. Type 2 diabetes is caused by other factors, such as obesity, low activity/exercise levels, and high cholesterol and blood pressure. Type 2 diabetes is caused by the body’s inability to properly use the naturally produced insulin.