There’s no one-size-fits-all adhesive for CGM wearable devices, but considering materials and user needs will lead to an optimal solution.
By Henry Milliman, Avery Dennison Performance Tapes
Skin’s anatomical properties present a variety of CGM adhesive challenges. [Image courtesy of Avery Dennison]
And it’s no wonder why so many manufacturers want in on this revolution: According to Mordor Intelligence, the continuous glucose monitoring (CGM) device segment is worth $11 billion globally and is forecast to grow at a CAGR of 10% between 2024 and 2029.
Adhesive selection is a critical element of the device design process
One of the keys to success in this dynamic market is reliability. Providers and patients alike expect durable, effective devices that and allow the wearer to experience daily life without discomfort. Any failure of any element of the device could lead to a device failure.
Nevertheless, engineers may be tempted to de-prioritize the selection of an adhesive. After spending significant time and resources to develop elements such as the processor, transmitter, and power source, they simply specify the most economical or easy-to-access off-the-shelf adhesive solution.
This is a missed opportunity at best, and a pitfall in the design process at worst.
Adhesives have a significant effect on device reliability. Modern medical adhesives are increasingly sophisticated and diverse, building on decades of innovation. Different adhesive chemical formulations can make a device better suited to different applications.
Taking the time to get the adhesive selection right can truly differentiate a device in a competitive marketplace. Device engineers owe it to themselves to treat the adhesive as an investment, and approach adhesive selection as an integrated part of the overall device design process.
Key challenges for CGM device adhesives
Accounting for the human element can be a daunting technical challenge. This is certainly true when selecting an adhesive for a wearable CGM device. Here are some key challenges device engineers should consider:
1. Bonding to various device substrates
Adhesives used in device construction (for bonding parts together and bonding the entire device to the skin adhesive) must be compatible with the types of substrate materials used in the device.
Most CGM devices are made using polyethylene, silicone or polycarbonate. Each of these substrates presents different challenges to an adhesive, and certain adhesives are more effective with certain substrates. Low-surface-energy silicone, for example, can be more difficult to bond to than a high-surface-energy material such as polycarbonate. However, adhesives optimized for various surface energies are readily available.
2. Skin compatibility
A device adhesive must minimize the risk of skin irritation while ensuring sufficient adhesive strength throughout the device’s wear time. There’s much variation in skin quality and adhesive compatibility from person to person, often based on factors such as age, health, and the general condition of their skin.
It’s crucial to balance the adhesive’s strength and its compatibility with skin types, necessitating a careful selection process to align with standards such as ISO 10993 and wearer well-being. An adhesive should work appropriately for the majority of the user group.
3. Wear time
CGM devices are typically worn for at least seven to 14 days. That means a device must withstand up to two weeks of real-world stress, including bodily movement, exposure to moisture, temperature variance, and rubbing against clothing.
A device adhesive should offer a secure bond under such conditions while being breathable, flexible and hypoallergenic to minimize skin irritation or damage. Other factors, including the wearer’s age, skin type and activity level can play an important role in selecting an adhesive.
Wear-time testing is essential for evaluating adhesive performance in terms of wearability, adhesive strength and user comfort. Such testing is optimal when conducted with scientific rigor, but even casual testing — perhaps involving a handful of company volunteers willing to wear a device and record their experiences — can provide useful insights during the development process.
4. Quality of life
One of the great advantages of CGM wearables is that they allow patients to go about their daily lives without being preoccupied with glucose monitoring. It may be a stretch to think of a device as comfortable to wear, but any device engineer should work to create an overall positive experience for the wearer. Achieving this means, among other things, selecting an adhesive that securely attaches the device without excessive pressure or tension, accommodates natural movement, and minimizes discomfort or pain upon removal.
Silicone-based adhesive chemistries, for example, are renowned for their gentle release properties but typically do not have the bonding power of more traditional acrylic-based chemistries. Adhesive selection may involve striking a balance between performance and wearer comfort.
Determining the right adhesive for your needs
While there’s no one-size-fits-all adhesive for CGM wearable devices, there likely is an optimal adhesive based on a device’s materials and target wearer’s needs. Determining that optimal adhesive is the tricky part, but it can pay handsome dividends once a device is in-market.
What we’ve provided in this article is a framework to help you understand the challenges that must be overcome when choosing an adhesive. But thoroughly understanding your options will likely mean working closely with an adhesive manufacturer — preferably one that can provide design support such as samples, prototyping and wear-test guidance.
As stated earlier, adhesive selection should be an integral part of the overall device design process. That may mean additional investment. But considering the effect of adhesive on device reliability, it’s an investment worth making.
Henry Milliman [Photo courtesy of Avery Dennison]
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The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design & Outsourcing or its employees.
