Mastering the Challenges of Continuous Glucose Monitor Design

The popularity of wearable healthcare products is expanding. Some 30% of U.S. adults are already using a wearable medical device, according to the National Institutes of Health, and the market is expected to grow from $59 billion in 2020 to $156 billion by 2024.

These new medical technology or “medtech” offerings can significantly improve quality of life for patients by monitoring health outside the confines of a clinical setting. One of the most impactful and best-selling wearables is the continuous glucose monitor (CGM). It is also a prime example of the intensive product development required to bring a new wearable idea to market.

Below is a quick glimpse inside a CGM to see how current miniaturization and ruggedized component challenges can be addressed with design for manufacturability (DFM) techniques to make a successful commercial product.

A Convenient, Proactive Solution

Designed to aid patients with type 1 and type 2 diabetes, CGMs reduce the need for uncomfortable periodic finger pricks to measure blood glucose levels. Instead, a sensor resting just below the skin checks glucose every 10 seconds, sending readings to a patient device every 5 minutes.

With continuous monitoring, patients can be alerted to take action when results reach dangerous levels — an important benefit for a disease that doubles the risk of serious conditions like heart disease and stroke. Regular feedback also encourages patients to pay closer attention to diet and lifestyle choices affecting their health. One study found that patients using a CGM reduced their daily caloric intake, increased exercise and reduced body mass.

A CGM consists of a sensor about the size of a quarter, an adhesive holding it in place on the abdomen or upper arm, and a user-operated applicator.

For patients, the device is simple and straightforward because it needs to be user-friendly for a broad audience. For designers and engineers, it’s a different story.

Design Challenges

CGM design is constrained by many factors. To be wearable, the device must be small and lightweight. This means that electronics — including microprocessors, batteries and antennas — must be powerful while fitting into an extremely compact space. Because patients are expected to wear CGMs for up to 2 weeks at a time, a highly reliable power source or user-friendly method of recharging is also required.

A device worn continuously for this length of time will be exposed to the patient’s sweat, external moisture and debris — and, potentially, accidental bumps and drops. To ensure tight seals and dependable operation, the housing typically requires precision injection molding for both rigid and flexible materials.

The outer surface also needs to be comfortable for users, yet made of biocompatible materials to avoid irritation or toxicity. Receivers must be easy for non-technical users of all ages and abilities to operate. Data must be compatible with the corresponding medical software system used, and data transfers and storage must follow strict medical privacy and security regulations.

Manufacturing and Assembly

Solving for just these design challenges would be a daunting task, but today’s wearables involve even further complexities. Devices in this competitive market must also be developed for smooth manufacture and assembly. Automated production techniques required for speed and efficiency often impose yet another set of considerations.

To anticipate and address challenges in an agile way, engineers should follow DFM best practices. This involves a close reevaluation at every stage of production — optimizing for safety, cost and efficiency during key stages of manufacturing and assembly. Case in point: Some parts of a CGM, such as the printed circuit board (PCB) assembly, require specialty manufacturing approaches with several rounds of visual, software and x-ray checks.

For structural and mechanical components, simplicity should be a guiding principle. Custom machining can be kept to a minimum and supply problems reduced by employing commercial, off-the-shelf parts. The number of components can also be reduced or combined for easier assembly. For example, fasteners can dominate 20% to 50% of assembly time, but can often be incorporated into structural parts — eliminating the need for screws, bolts and other small accessories.

In terms of injection molding tooling, uneven surfaces should be minimized and forms should be evaluated for thermal management. Dense parts take longer to cool, increasing manufacturing costs and creating the risk of sinking and/or structural weak spots.

Co-optimization Brings Best Results

Clearly, creating an effective CGM requires expertise across many disciplines.

Engineering teams must source parts ranging from microelectronics to metals and plastics; meet highly specialized technical and compliance requirements; and ensure compatibility, usability and compliance. At the same time, teams must adjust for manufacturing processes that will be conducted by providers and vendors who may be scattered across the globe.

Creating a coherent design under these circumstances is difficult at best. No single team or vendor has competencies across all these domains, and optimizing for one process could exacerbate difficulties for others. This could cause delays, mistakes and cost overruns.

The best solution is to foster collaboration across these different teams from design inception through final product assembly. Known as co-optimization, this methodology allows all designers, suppliers, vendors and manufacturers to communicate their expertise as the work proceeds. Everyone gains a system-level view to improve discrete capabilities without making sacrifices in critical areas such as power, space or cost.

Working with a contract development and manufacturing organization (CDMO) can give product teams access to the wide network of experts they need within a single, integrated organizational framework that fosters cohesive communication, consistent co-optimization and coordinated DFM. CDMOs often provide one-stop access to design engineers, tool makers, software developers, regulatory specialists, supply chain resources and more.

Taking this approach recently helped one CGM design team solve a number of vexing problems. Collaborating with Phillips-Medisize, the team worked with several specialized disciplines to create a sealed encasement combining soft- and hard-molded plastics to seal out moisture and debris. They were also introduced to miniaturization experts at Molex, who helped fit high-functioning electronics into a device space the size of a single cubic inch. This approach enabled the innovative design of a specially printed antenna that wraps around the circuit board and delivers a robust signal, without increasing power demands.

In an endeavor as complex as CGM design, successful innovation requires collaboration among experts in many fields. With over 6 decades of experience working with medical device companies and across highly regulated industries, Phillips-Medisize offers integrated, one-stop access to a vast network of design and manufacturing specialists who can help today’s leading organizations create high-performance innovations with optimal efficiency. As a Molex company, Phillips-Medisize also provides ready access to the latest sensor, electronics, connectivity and global supply chain solutions. To learn more about CGM and co-optimization, check out our latest whitepaper: Managing the Complexity of Medical Device Development.