Adhesives: Enabling the Future of Wearable Medical Devices
The wearable medical device market has experienced tremendous growth in recent years. Consumers and patients alike want to have more control of their health by utilizing the data collected in real-time by wearable devices. For some, these devices are used to track steps, calories, and amount of sleep to reach their health or fitness goals. For others, the devices are used to monitor and manage a chronic illness, like diabetes.
Market growth isn’t stopping, and future iterations of wearable medical devices will need to evolve to keep pace with demand as researchers discover new ways to advance current non-pharmaceutical therapies and digital monitoring capabilities. Manufacturers, in turn, will need to exercise those findings by building next-generation devices that enable effective and personalized monitoring.
Device manufacturers are already taking steps in that direction by creating devices that easily integrate into everyday life. They’re getting smaller, lighter, and less invasive. This is in part made possible by a seldom recognized technology: adhesives. Whether they’re adhering device components together or sticking a device to skin, adhesives are uniquely bonded to a device’s success. In order to fully understand how adhesives can continue to enable future wearable device innovation, let’s take a look at how they impact devices through a few different lenses.
The future of medical devices will lean heavily on the future innovations of medical adhesives. (Credit: Hero Images/Getty)
Psychosocial Impact
Someone’s appearance, like the clothing or accessories they choose to wear, are often an expression to the world about how they’d like to be seen. The same sentiment applies to wearable devices. If a wearer is choosing to sport a device to track their health or fitness goals, they may be more open to wearing a brightly-colored device as a proud testament of what they’re working to achieve.
This isn’t always the case, however; as mentioned previously, some people are wearing a device not necessarily out of choice (e.g., to manage a chronic illness), and they may not want to draw attention to it. When designing for these applications, keep in mind that the device should be small in size and unobtrusive in design. Using thin, clear, and breathable films can offer a level of discreteness without sacrificing the wear duration benefits of an adhesive border, also known as a skirt, around the device’s perimeter.
Band vs. Stick-to-Skin Applications
The differences between devices intended for patients working to manage a chronic illness and those designed for consumers looking to improve their fitness often result in two different design styles: a stick-to-skin application and a wristband. Wristband devices might be trendy, but often don’t provide the level of accuracy and precision required for critical medical diagnostics and delivery.
Some may rely on a tight fit, but with consumers applying their own device, there’s no guaranteed consistency regarding how tight or loose the device might be. If the device is too loose, the sensor could slide, slip, or rotate, impacting measurement accuracy. Stick-to-skin applications, on the other hand, can be stuck where the sensor is needed, minimizing potential application error associated with band applications, and allowing for a “one-size-fits-most” design.
Information Fatigue
Consumers are inundated with data—so much so that they can reach a point of information fatigue and no longer want to interact with the data. They’re able to turn down a device’s volume or discontinue alerts all together. As a result, it can be hard for device manufacturers to be heard through the noise. The challenge is to find creative ways to keep the data relevant. Keeping the data simple and manageable, along with an adhesive system and wearable design that allows users to forget it’s there, is the best way to keep users engaged.
Now let’s look at key areas adhesives will help progress wearable devices.
One design factor that can impact wearables is location durability. Devices are prone to catching on clothing and collisions with doors and obstructions—common causes of device failure or removal. Adhesive wear time is also a crucial consideration when designing a wearable device, impacting overall resilience and durability, as well as users themselves (e.g., how often they’ll need to change their device).
Device Size, Weight, and Location
As mobile phones, computers, and TVs get sleeker, so too must wearable medical devices. Both consumers and patients want wearable devices to be smaller, lighter and less cumbersome to use for seamless integration into their everyday lives. The design process can get challenging when devices must maintain accurate sensing capabilities, but also reduce friction to ensure precise data collection. Adhesives can help to keep friction to a minimum by being breathable and maintaining a low profile. In addition, options with flex electronics, as well as addressing battery implications and electromagnetic interference, provide opportunities for advancement.
Device location is also critical. The upper arm can be a good location for “hiding” the presence of the device, but it’s a body part prone to catching on clothing and colliding with doors and obstructions—common causes of device failure or removal. If the upper arm ends up being the chosen location for the device, special consideration should be given to the design of the device edges and profile to minimize catching on clothing and collisions. An adhesive skirt can also improve the overall survival rate of devices in all locations.
Resilience and Durability
The prospect of a device coming into contact with water or moisture also challenges the design process. But users of these devices want to continue their active lifestyles—including activities like rock climbing, swimming, and hiking—without their device getting in the way. Consequently, the level of wear and tear a device can handle is crucial to its overall success and marketability. Adhesive solutions, like using a nonwoven, acrylic-based adhesive with a nonwoven, breathable backing, can help a device stay intact and adhered longer.
Adhesive wear time is a crucial consideration when designing a wearable device, impacting overall resilience and durability, as well as how often the user will need to change their device. While everyone’s skin is different, it’s constantly shedding and can regenerate itself in approximately two weeks. After that time, there’s a chance that the adhesive may still be sticking to the skin, but the cells on the top layer of skin will be beginning to shed. It’s important to keep this in mind when designing a device. One way manufacturers measure adhesive functionality (including wear time) to make improvements and refinements is by conducting human wear time studies.
Adhesives are tested in “real-life” situations to evaluate performance, so when certain characteristics are needed out of an adhesive, design engineers know what they’re getting. Adhesive manufacturers will need to continue developing and improving adhesive options ideal for durability, resilience, and extended wear times.
Comfort
Regardless of a device’s or adhesive’s wear time, comfort is crucial and increasingly important as the industry heads toward longer wear times. As previously mentioned, devices can’t be a burden to users. Whenever possible, design engineers should avoid producing a large device that could be heavy and awkward for the user.
Skin health also impacts comfort. It’s a living, breathing organ that needs to expel moisture and move. If a foreign object gets in the way of those needs, skin will do everything it can to force the object off. When it comes to adhesives, a common misstep is selecting an adhesive that’s able to stick to skin but lacks breathability. Moisture will get trapped underneath, potentially leading to maceration, a medical-adhesive related skin injury (MARSI) that essentially drowns the skin and exhibits as a whitened layer.
Other types of MARSI commonly caused by choosing an adhesive that’s inappropriate for the application include skin irritations like folliculitis (small rash-like bumps on the skin’s surface that are a result of irritation of hair follicles); tension injuries and blisters (typically caused by adhesives that are stretched when applied and create excess tension on the skin as the tape relaxes); and skin tears or skin stripping (when the stratum corneum and the epidermis, the first two layers of the skin, pull apart from another during adhesive removal).
Future iterations of adhesives and devices will need to incorporate breathability and skin-friendliness into designs in order to produce a more comfortable product.
Adhesives must continue to push the boundaries of what’s expected and thought to be possible to keep momentum in the wearable medical device market and to provide the best possible user experience. For more guidance on selecting the right adhesive for your next medical device project, check out 3M’s product selector tool.
