Let’s stick together: The important role adhesives play in wearables
Tony Kaufman, and Del R Lawson, 3M’s Critical and Chronic Care Solutions Division, outline the role that adhesives play in digital wearable medical devices.
How adhesives may impact the future of wearable medical devices
Many people habitually wear a device to track fitness or daily steps, nightly sleep and what they’re eating. Some people also wear devices to help manage chronic illness, such as diabetes. Consumers and patients alike are now able to take more control of their health by using real-time data collected by wearable devices to help make health-related decisions. They want to proactively manage and improve their health without a device getting in their way. As a result, the wearable medical device market has seen rapid growth in recent years.
The wearable medical device market will further evolve as researchers determine ways to improve current non-pharmaceutical therapies and digital monitoring. Manufacturers will need to put those findings into practice and build products that enable more effective, personalised monitoring to keep pace with market need.
One way device manufacturers are already addressing this growing need is by making devices that easily integrate into everyday life. Devices are getting smaller, lighter and less invasive. How? From adhering a device together to sticking a device to a user’s skin, adhesives are a critical component in a device’s success. They also provide solutions to complex design challenges for manufacturers and help protect the end user from potential harm caused by their device.
The impact of wearable devices
Psychosocial impact
People who use wearable devices to track fitness goals are trying to lose weight, monitor calories burned or get to the next level in their training. In other words, they’re choosing to use a wearable device to aid them in reaching their goals. These users tend to be more open to sporting their devices as a proud testament to what they’re trying to achieve.
For others, wearing a device isn’t necessarily a choice and might be worn for a much more critical reason – they’re trying to manage a chronic illness. These users may not want to draw attention to their condition, meaning the device should be small in size and unobtrusive in design. The use of thin, clear, breathable films may provide the additional benefit of discreteness, while maintaining the wear duration benefits of an adhesive border, or skirt, around the device’s perimeter. Design engineers should consider the appearance of the design when selecting the materials.
Band vs. stick-to-skin applications
There is a distinct difference between devices designed for consumers looking to improve their fitness and devices designed for patients who are working to manage chronic illness. In some cases, these differences result in two different design styles – a wrist band and a stick-to-skin application. Devices as wrist bands may be more visually appealing and fashionable, but they don’t offer the level of accuracy and precision that’s required for critical medical diagnostics and delivery. In illustration, let’s take a look at fastening devices, like a band or wrap. They rely on a tight fit, but how ‘snug’ can and should the device be? If it is too loose, the sensor could slip, slide or rotate, leading to an inaccurate measurement. On the other hand, with stick to skin devices like adhesive patches, the sensor can be stuck where it is needed, minimising potential error associated with adjustable fasteners. They also allow a ‘one-size fits most’ design.
The danger of information fatigue
With so much data at our fingertips, it’s normal to come to a point where you’re not processing it anymore. Users have the power to shut off some points of interaction by turning off a device’s volume or discontinuing alert updates. The challenge facing wearable medical device manufacturers then is coming up with creative ways to keep their devices’ data relevant to prevent users from reaching information fatigue and no longer interacting with the alerts. Keeping the data simple and manageable, along with an adhesive system and wearable design that allows the user to forget it is there, is the best way to keep users engaged.
Now that we’ve discussed the impact of wearable devices, let’s dig into the key areas in which adhesives will help progress them.
How adhesives help advance wearable devices
Device size and weight
Mobile phones aren’t the only electronics getting sleeker. Consumers and patients alike want wearable medical devices that are smaller, lighter and less cumbersome. The design process can be challenging as the devices must maintain accurate sensing capabilities, but also reduce friction to ensure precise data collection. Options with flex electronics and adhesive selection, as well as addressing battery implications and electromagnetic interference may provide potential opportunities for future innovation.
Resilience and durability
Users who enjoy activities such as hiking, rock climbing and swimming should be able to do so without their device getting in the way, figuratively or literally. The prospect of a device touching water and moisture often challenges the design process, and makes design engineers cringe but the level of wear and tear a device can handle is crucial to its success long term and overall marketability. Adhesive solutions that provide durability and extended wear time exist to help devices stay intact and attached longer. For example, using a nonwoven, acrylic-based adhesive with a nonwoven, breathable backing can provide a solution. Adhesive manufacturers, like 3M, will need to continue improving breathable adhesive and backing options in order for devices to increase their durability, resilience and wear time.
It’s important to note that wear time is a key consideration with adhesive selection. It not only impacts how the device is designed and what it can handle, but also the user and how often they will have to change their device. Fourteen days appears to be the longest possible adhesion time because skin regenerates itself within that approximate timeframe. Since skin is continuously shedding, after about two weeks, the top layer of skin is well on its way to completely regenerating itself. Even if the adhesive is still sticking to skin, the skin may no longer be sticking to the user. This specific wear time length allows device manufacturers to work towards creating devices that can function for the same length of time. One way manufacturers measure their adhesives’ functionality and make improvements and refinements is by conducting human wear time studies. Researchers test adhesives in real-life situations to evaluate their performance so that when certain requirements are needed out of an adhesive, design engineers know what they’re getting.
Comfort
Regardless of how long a device is worn or how long an adhesive is stuck to skin, comfort of both the device and adhesive is important. But as the length of wear increases, comfort becomes more critical. As mentioned, users don’t want their device to be a burden. Large, clunky devices get in the way and can be heavy and awkward.
Skin health also contributes to comfort levels. As a living organ, it needs to breathe, expel moisture and move. When something gets in the way of these needs, skin does everything it can to force the foreign object off. A common mistake is choosing an adhesive that sticks to skin but isn’t breathable. Moisture will get trapped underneath, which can cause maceration (whitened layer of skin caused by trapped moisture, essentially drowning the skin). Adhesives can also cause pain upon removal, if they’re too strong for the application. Future adhesive and device iterations will need to incorporate breathability and skin-friendliness into their designs in order to produce a comfortable product.
To enable further growth in the wearable medical device market, adhesives must continue to push the boundaries of what’s expected and what’s thought to be possible.