Materials Matter When Manufacturing Components in Stick-to-Skin Wearable Medical Devices

Drawing of layers and materials used in a stick-to-skin wearable medical device

MBK Tape Solutions, a Boyd company, help product engineers design and manufacture the various component layers in stick-to-skin medical devices and wearable biosensors. Skin-friendly devices are used for a variety of applications, such as diagnostics, bio-fluidics, monitoring blood pressure, heart rate, and glucose levels, and treating health issues using electrical stimulation or transdermal drug delivery. Depending on the application, the medical device construction contains several layers of adhesives and materials, each serving a different function.

Multi-Layer Construction in a Skin Friendly Wearable Device

In the past two decades, there have been many scientific advances in stick-to-skin adhesives, making them gentler on the skin, easier to remove, and extending wear time. With the rise of wearable technology, devices have become smaller, lighter, and more complex. For example, transdermal patches deliver compounded drugs or ingredients in the adhesive that can be separated with a membrane or laminate material. Medical wearable devices typically consist of multiple layers of materials such as a monitoring device that requires electrical components and batteries to enable Bluetooth technology. There is no one adhesive solution that fits all wearable devices.

Multi-Layers in a Stick-to-Skin Device

Each layer in a wearable device has different application requirements. A skin-friendly medical device typically consists of the following layers and materials:

  • Cover/Overlay Layer: a protective film that is breathable, waterproof, and/or printable.
  • Device:
    • A custom-molded plastic enclosure that can house electrical components, PC board, batteries, conductive inks, biosensors, and other components.
    • A cushioning foam to protect, seal, or insulate the components.
    • Conductive or thermal interface materials such as metal foils or coils keep components from overheating.
  • Tie Layer: a transfer adhesive or differential double-coated adhesive that bonds the device components together.
  • Skin Contact Layer: biocompatible medical-grade adhesives and backings require the right balance of adhesion, breathability, conformability, removability, and comfort on the skin.
  • Delivery Liner: a customized silicone or fluoropolymer release liner to help make the product easy to use by the practitioner and end-user with features like pull tabs, oversized perimeter skirts, or split/folded liner to aid in removal.

Adhesives & Materials in a Skin Worn Wearables

Medical grade pressure-sensitive adhesive tapes consist of an adhesive coated on one or both sides of a material, also known as a substrate. Depending on the chemistry and the tape construction, adhesive-backed materials are used for bonding, sealing, insulating, protecting, electrically conducting, and thermal management. Knowing which adhesive and substrate work best for the applications can be challenging.

Adhesive Tape Applications in Wearable Device Layers

  • Bonding Adhesives: Bonding adhesives are used during construction to hold component parts together (called the tie-layer) and biocompatible adhesives are used to hold the device to the skin.
  • Moisture Management Adhesives: Whether moisture comes in the form of sweat, oils other bodily fluids or environmental factors like water contact, adhesives can either absorb the fluid to prevent skin irritation or allow moisture to evaporate (moisture-vapor transmission). An experienced converter partner not only knows which material to use for moisture management but can also help design a component to move fluids or deliver active ingredients through the skin.
  • Sealing & Insulating Materials: Devices sensors, batteries, or other electrically conductive components are typically housed in airtight molded plastic enclosures but may need sealing to keep out moisture and contaminants and insulating to prevent vibration damage to the components.
  • Thermal Management Tapes & Materials: Keeps the components from overheating utilizing advanced cooling technologies.
  • Protective Films: Protect the device from external and environmental factors such as sweat, UV light, water and moisture, and even dynamic movement.

Medical Grade Adhesives & Materials in Skin Friendly Wearables

In skin-worn wearables, biocompatible medical-grade adhesives include acrylic, rubber, silicone or the newest technologies, hydrocolloids, hydrogels, and silicone gels. Rubber adhesives are sturdy and tolerate moisture. Acrylate adhesives are hypoallergenic and low-sensitizing and silicone adhesives can be super gentle. Typical backing materials include films, non-woven fabrics, foams, and conductive metal foils.

The main challenge for the design engineer is sticking materials to the skin, a dynamic organ that is constantly in flux. Skin-friendly adhesives must comply with biocompatible ISO 10993 testing, in terms of cytotoxicity, sensitization, and irritation, ensuring they are compatible with short- or long-term exposure to skin.

Adhesives for stick-to-skin applications typically must provide a balance of adhesion and ease of removal; breathability and moisture resistance; resistance to friction and conformability. It is also important to consider the device’s weight, surface texture, and placement on the body.

Knowing more about the intended application and the user will help determine the adhesives and materials to use. Whether wearing the device for short-term (30 minutes to 5 days) or long-term (up to 21 days) may be a determining factor in selecting materials. It is also important to choose a material based on the end-users age (neonatal, midlife, geriatric) and activity level. Because of the direct impact on the user’s comfort, health safety, and product performance, the designer must choose the medical adhesives and materials wisely. 

Material Compatibility  

Getting all these materials to work in harmony throughout the medical device is critical, especially when it comes to the moisture management and product performance. If an adhesive used in the skin contact layer is breathable but the construction layer does not allow moisture-vapor transmission, the product may not perform as intended. Additionally, certain polymers from one layer can interact with adhesives in another layer after assembly, potentially causing failure.

Thus, it is imperative to use the correct combination of medical-grade adhesive and substrates throughout the entire design of the medical device. An experienced converting partner can recommend the best material combination to ensure consistent product performance.

Material Sourcing 

MBK has close working relationships with medical tape manufacturers and suppliers around the world including, but not limited to, 3M, Avery Dennison, Adhesives Research, Berry, DermaMed, Mactac, and Polymer Science. Leveraging these relationships, we can streamline material sampling, prototyping, and testing. As a 3M Preferred Converter, the MBK sales team stays abreast of the newest products and technological advances.  Working with coating partners, we can customize the adhesive and liner combination to meet our customer’s exact requirements.  MBK’s in-depth knowledge of material properties and compatibility assures optimum material performance for even the most complex multi-layer products.  Check out the MBK online Catalog of Medical Adhesives and Materials to learn more.

Material Scalability  

Not only is it important to select materials based on functionality and compatibility, but also on availability. After experiencing supply chain shortages throughout the world this past year, it is crucial having access to materials in a timely manner and secure a converting partner capable of converting materials to scale.

Partner with Boyd throughout the Wearable Device Project Lifecycle

MBK Tape Solution, a Boyd company, is a converter, fabricator, and component manufacturer that can help throughout the entire wearable device project lifecycle. We have the expertise, experience, state-of-the-art equipment, and resources to design and manufacture wearable devices, from start-up to large-scale manufacturing. With Boyd’s R&D and manufacturing facilities on three continents, we are regionally flexible, allowing us to manage redundant processes and deliver products in a cost-effective, timely manner.

At the MBK converting facility in Southern California, our application engineers will help select and source the right materials and design for manufacturing, ensuring that each component is designed for optimum performance and cost. Our converting capabilities include prototyping, precision die-cutting, multi-layer laminating, slitting, and printing in a controlled cleanroom environment, under ISO 13485 certified quality management systems. We provide custom die-cut parts, island placement, registration, and release liners using extended liners, finger lift tabs, and perforated, split, or butterfly folds.

Since joining the Boyd company, MBK’s capabilities have expanded tenfold. Boyd has a long history of developing, designing, testing, and fabricating thermal management solutions. Utilizing global material supply partners and innovative engineering, Boyd customizes molded decorative plastic components, molded silicone components, rubber seals, and gaskets. Boyd also offers printed flexible traces, graphic overlays, and membrane switches. The MBK project manager will coordinate with the Boyd team to assist with component manufacturing and assembly, kitting, sterilization, and the delivery of your FDA-compliant finished wearable product. To learn more about Boyd’s medical offerings, check out the Boyd website.

MBK Tape Solutions has over 50 years of experience and expertise in helping customers find the ideal adhesive solution for their medical devices and Boyd has the resources and capabilities to assist in the full product life cycle. Call MBK today at 818-998-1477 to help in the early-stage design and produce all the components in your skin-friendly wearable device.

Animated video explaining the different layers in a wearable medical device

Click to watch this short animated video on the various components and layers in a wearable device.

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