Design considerations are crucial when choosing an adhesive to stick wearable medical devices to fragile skin.

Del R. Lawson, 3M’s Medical Solutions Division

Gone are the days where we had to be in the hospital to track and collect data from our bodies. We’re now able to create smaller, smarter, more accessible devices that integrate into our everyday lives. The advantage of adhering a device directly to the skin is it creates an intimate interface between the device and the wearer that enables a sensor to measure a key attribute and transfer data to the device. However, these conveniences mean new considerations for device design engineers, specifically when selecting adhesives intended to stick to fragile skin.

Skin is a major factor in the design and performance of a wearable device, but it often gets overlooked. When it comes to adhering a device to fragile skin, it’s not the same as adhering to static substrates or even non-fragile skin. Although fragile skin makes many people think of the elderly and infants, it can affect everyone. Physiological factors, such as the skin’s location on the body (face and eyelids), play a large role in fragility, in addition to pathological (acne, rosacea, etc.), circumstantial (environmental, mechanical) and latrogenic (medicinal treatment, aesthetic procedure) conditions.

A designer should consider the challenges of fragile skin when selecting an adhesive because it will affect the user and how the device performs. Before choosing an adhesive for fragile skin that will work best, it is critical to consider the intended design of the device.

Design considerations

Because devices are a system made up of smaller parts that need to all work in unison, it’s crucial first to understand the device’s construction, components, application and end-user requirements. Below are five key questions to consider when designing a stick-to-skin device.

• What is the application? Skin adhesives can serve multiple purposes, including protecting a device while holding it onto the skin as a cover tape and bonding a device directly to the skin. Understanding each component’s requirements and how all of them interact with one another is key to figuring out what types of adhesives are ideal for the application.
• How long will the device be worn? Wear time is critical in selecting the best adhesive because its properties, chemistries and strength should match the product’s required wear time. Also consider reapplication of the same device or a replacement device adhering to the skin on the same site repeatedly. When not planned for, either instance can result in skin damage, especially for fragile skin.
• Who will wear it? A device specifically intended for the elderly, or infants, requires fragile skin considerations. Since fragile skin conditions can affect anyone, consider the health and condition of the wearer’s skin. And if the device is for a specific medical condition, think about how the condition may affect the skin.
• Where will it be worn? Consider the intended location on the body on which the device will be worn. Gentle to skin silicone adhesives are advised when adhering to sensitive areas of the body, such as the face, around the eyes and neck areas. Another consideration is the contour of the body where the device will be worn. Adhesives, backings, and device components made with materials that move and give with the body during use will improve performance.
• What is the end user’s activity level? The adhesion requirements for a sedentary application, such as a sleep or snoring device, are inherently low-activity and may not require the same adhesion level as an active user. Environmental influences, including increased movement, sweating and climate conditions, should also be considered.

Medical adhesive options

There are three main categories for stick to skin pressure-sensitive adhesives (PSA) for wearables, and each has its benefits:

1. Acrylic/acrylate: Proven compatibility with skin, variable adhesion profiles, low sensitization, good processability
2. Silicone: Repositionable, gentle removal, very low sensitization
3. Synthetic rubber: Good initial tack, adhesion to low surface energy, good moisture resistance

When it comes to fragile skin, silicone adhesives are known for their gentle adhesion, inert chemistry and pain-free removal. Due to inherently different physical properties that enhance their behavior in application and removal, silicone adhesives are often ideal for fragile skin applications.

Designing a wearable device for fragile skin brings on its own set of challenges. By identifying adhesive requirements and understanding design considerations early on, you will be able to select the suitable adhesive to ensure the device operates properly while keeping the end-user as comfortable as possible. 

Del R. Lawson is R&D Manager in 3M’s Medical Solutions Division. He has over 25 years of experience at 3M in laboratory management, strategic product platform creation, and Lean Six Sigma operations. His experience has involved new technology creation in advanced analytics and sensors, biotechnology solutions, and medical adhesives. To learn more about designing devices for fragile skin, download 3M’s white paper.

The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of MedicalDesignandOutsourcing.com or its employees.