Key Considerations for Achieving Optimal Stick-to-Skin Adhesion for Wearable Devices

by | Jan 8, 2024

Wearable medical devices and sensors continue to revolutionize healthcare, offering real-time monitoring and data collection. However, achieving optimal adhesion to the skin presents challenges that demand innovative solutions. Whether it is a fitness tracker, glucose monitor, or a more complex medical device, ensuring that the device adheres securely without causing discomfort or skin irritation is critical. In this blog post, we explore the key challenges faced by wearable device engineers when it comes to sticking to skin.

  1. Skin Variability: Navigating the Diversity

Individuals have diverse skin types influenced by factors like age, ethnicity, skin oils, moisture levels, and hair density. For instance, a neonate will typically have thinner, delicate skin that tends to dry out more quickly whereas a teenager typically has more oily skin, especially around the nose, chin, and forehead. These properties of the skin make it a challenge to find one adhesive that will work the same on every skin type. To address this challenge, adhesive manufacturers must design adhesives that cater to a wide range of skin conditions. Extensive skin compatibility tests help identify potential issues, allowing for tailored solutions.

  1. Skin Irritation: Prioritizing Comfort

Prolonged contact with certain adhesives can lead to skin irritation, especially for users with skin sensitivities. An example would be individuals who have a sensitivity to latex. The solution lies in utilizing medical-grade, pressure-sensitive acrylic adhesives that prioritize skin-friendliness. Today, most skin adhesives consist of synthetic polymers and are latex-free. It is also important to identify an adhesive that has been evaluated by ISO-10993 standards which will determine the irritation potential of the adhesive.

  1. Moisture and Sweat: Defying Hydration Hurdles

Skin moisture and sweat can compromise adhesive performance, leading to detachment or reduced effectiveness. Designing a medical tape that resists or repels moisture is key, ensuring a secure bond even in humid conditions. Selecting the right adhesive chemistry and breathable backing materials such as woven and non-woven fabrics or polyurethane films prove instrumental in managing moisture (increasing MVTR) and preventing skin maceration.

  1. Environmental Factors: Adhesion Under All Conditions

Environmental conditions, such as changes in humidity, temperature, and shower exposure, can impact adhesive performance. Manufacturers must account for these variables during the design phase, ensuring adhesives maintain their integrity under various wear conditions through rigorous lab testing and wear studies.

  1. Ease of Application: Simplifying the Process

Applying wearable devices correctly can be challenging, especially for individuals unfamiliar with the process. The incorporation of features like pull tabs, split liner, or oversized liner at the converter level will help facilitate easier removal of the release liner, simplifying the application for the end user. Also, providing an IFU (instructions for use) printed on the device or provided in the packaging will further enhance the user experience.

  1. Secure Adhesion vs. Comfort: Finding the Right Balance

Balancing the need for secure adhesion with user comfort is crucial. The solution lies in understanding the patient skin type, size and weight of the device, exposure conditions, and the intended wear time. Adhesive manufacturers offer tape solutions designed for applications with required wear times ranging from minutes to days or weeks. Adhesive and backing material selection plays a key role, and iterative testing is essential to find the optimal combination.

  1. Device Placement: Adhering to location

Wearable devices require specific placement on the body for optimal functionality. Understanding the intended use and designing the adhesive accordingly is paramount. For example, a device designed to be worn on the back of the arm will experience different stress compared to a device that is to be worn on the abdomen due to the curvature of the body and the stretchiness of the skin. Further, the activity level of the patient may place additional strain on the adhesive through friction or bumping the device. A solution developed around the device’s end-use requirements and location on the body enhances both adhesion and user experience.

  1. Removal without Residue: A Clean Break

Ensuring devices can be removed easily without leaving residue or causing skin trauma is vital. Otherwise, any adhesive residue left on the skin could result in a negative experience for the end user. The adhesive developer must ensure the adhesive provides a secure attachment to the skin throughout the required wear time while also minimizing any residual effects on the skin.

  1. Durability and Long-Term Wear: Endurance Matters

As wearable devices continue to advance through sensor technology and longer-lasting batteries, devices are expected to be worn for longer periods, requiring adhesives to maintain their performance over time, even beyond 14 to 21 days. Further, users expect to be able to continue their daily routines including exercise, yard work, and showering. Rigorous testing for durability and long-term wear, including assessments for adhesive strength and effectiveness over extended periods, is essential.

  1. User Education: Empowering Users

Users may not be familiar with proper application and removal procedures. Providing clear and concise instructions, including video demonstrations and educational materials, ensures correct usage and minimizes user-related challenges. Instructions might include methods for prepping the skin to achieve optimal adhesion, proper handling of the exposed adhesive to avoid contamination, applying the proper pressure to secure the device and instructions for removal to minimize trauma.

  1. Device and adhesive patch design: Taking shape

Wear performance depends on the device and patch design. The size and shape of the device will determine how well the device conforms to various parts of the body. The height profile and weight of the device will also be a factor. The taller the device the more likely the device will be snagged on clothing or bumped on the corner of a wall. Finally, the footprint of the adhesive patch which holds the device to the skin will influence performance. A patch whose footprint extends beyond the perimeter of the sensor housing will have a greater surface area of adhesive for securing the device to the body and allowing for better conformability.

  1. Prepping the skin – Overcoming the weak links

As mentioned earlier, oily skin which is common around the nose and forehead can have a cumulative impact on adhesive and play a role in a device falling off prematurely. Similarly, dead skin cells can also be detrimental to long-term adhesion. Our skin cells are constantly regenerating, and the dead skin cells contained at the outermost layer (Stratum corneum) are constantly flaking off. Over time, these dead skin cells become the weak link for the device to remain adhered to the skin. There are ways to help improve adhesion to the skin. The first place to start is to make sure the skin is clean and dry. Washing the skin with soap and water will remove any contaminants, oils, and lotions which could negatively impact adhesion. Alcohol wipes are another convenient option. If you are still having trouble keeping the device attached, a skin prep or adhesive primer may be another solution.

In overcoming these challenges, a collaborative effort between the adhesive manufacturer, researchers, converters, and healthcare professionals is essential. Continued advancements in adhesive technology, coupled with a deep understanding of skin dynamics, contribute to improving the overall success of wearable medical devices and sensors. Embracing these solutions ensures that these transformative devices deliver accurate data while prioritizing user comfort and experience.

How can we help you with your next wearable project? For further inquiries, technical specifications, and sample requests, please contact us.

DermaMed Coatings is an ISO 9001:2015 and ISO 13485-certified company offering standard and custom adhesive products to meet the specific end-use requirements for your medical device.