The development of medical wearables requires an elaborate design that both fulfills regulatory requirements and takes user comfort into account. (Credit: romaset/AdobeStock)

Not only the use, but also the wearing time of medical wearables continues to increase in modern healthcare. However, to ensure that wearable products do not cause skin irritation, product designers must consider the moisture vapor transmission rate (MVTR) during development. It plays an important role in skin compatibility and wearing comfort — and can be decisively influenced by the right joining technology.

The MVTR shows how much moisture vapor passes through a material per day. A high MVTR value indicates that the skin can breathe better, and the risk of skin irritation is reduced. However, medical wearables such as continuous glucose monitor (CGM) systems that are worn directly on the skin can restrict the skin’s ability to breathe.

This becomes particularly problematic when stronger skin adhesive formulations or higher adhesive coating weights are used in the products. These prevent moisture from escaping, which increases the likelihood of skin irritation. To avoid irritation to the skin due to prolonged wearing times of medical wearables, it is essential that the MVTR is already considered in the early phase of product development.

Challenges in the Design of Medical Wearables

The development of medical wearables requires an elaborate design that both fulfills regulatory requirements — such as those of the FDA — and takes user comfort into account. Manufacturers have to keep various factors in mind:

  • Adhesion: The device must be securely attached to the adhesive patch without restricting the skin’s breathability too much.
  • Flexibility: Materials should adapt to the contours of the body to ensure comfort.
  • Durability: The connection between the sensor and the skin must be reliable and resistant to perspiration, movement, and long periods of wear.

Critical Factors for the MVTR

To attach medical wearables to the skin, a skin adhesive with a nonwoven backing is often used, creating a skin adhesive patch. The sensor or device is attached directly to this adhesive patch. Even if the adhesive plaster has a good MVTR, the breathability of the skin is restricted or blocked by the device alone.

Additional barriers can result from using unsuitable joining technologies to connect the sensor or the device to the nonwoven material on the back of the skin patch. So far, this has usually been done by heat sealing or the use of adhesives.

However, conventional adhesives or heat-based bonding methods often reach their limits. The chemicals contained in adhesives can cause allergic reactions and act as an additional barrier to the breathability of the skin. Although the use of additional sensor mounting tape or reactive adhesives ensures a reliable hold, they form an additional barrier and therefore pose a further risk of skin irritation.

Thermal joining processes, on the other hand, can have a negative effect on the soft material properties of the nonwoven patches, impairing their flexibility and comfort. In addition, joining processes with excessive thermal loads can create microchannels that weaken the connection and therefore do not guarantee a reliable hold on the wearer’s skin.

Ultrasonic Welding as an Alternative Solution

Ultrasonic welding is an innovative alternative to conventional bonding processes. This technology uses high-frequency mechanical vibration to weld materials together at specific points. The heat generated remains limited to the predefined joining points, which protects the surrounding areas of the application.

This process offers several advantages. As no chemical joining materials are required, allergic reactions are avoided. In addition, the soft material structure is retained, as a very short and reduced thermal load only occurs strategically in the desired weld zone. The bonding strength of the connection is very high, which ensures a long shelf life of the wearables. Moreover, it allows for the design of ventilation gaps and drainage channels, improving airflow and reducing the risk of moisture buildup.

Long-Term Benefits for Manufacturers

Ultrasonic welding is also beneficial from an ecological point of view, as material consumption is reduced, and the recyclability of the products is maintained. Another plus is the increase in efficiency in manufacturing, as it eliminates the need for curing the adhesives. The ultrasonic welding process only takes a fraction of a second.

In addition, there are no costs for purchasing, storing, transporting, and declaring the adhesives, which can significantly reduce the operational costs of manufacturing.

A Glimpse into the Future

The trend toward medical wearables will continue to grow in the coming years. At the same time, the requirements for skin compatibility, wearing comfort, and sustainability are increasing. Ultrasonic welding offers a reliable alternative to conventional bonding techniques to meet these increasing requirements. The joining process increases wearer comfort, minimizes skin irritation, and improves the environmental balance of the products.

At the same time, manufacturers benefit not only from higher product quality, but also from an environmentally friendly and more efficient manufacturing process, which can provide further competitive advantages.

This article was written by Michael Boemer, Head of Global Business Development – Plastics, Herrmann Ultrasonics, Karlsbad, Germany. For more information, e-mail This email address is being protected from spambots. You need JavaScript enabled to view it. or visit here  .

Read more about designing wearables in this white paper.

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Key Considerations for Designing Medical Wearables

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Manufacturing & Prototyping Medical Wearables

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    Medical Design Briefs Magazine

    This article first appeared in the May, 2025 issue of Medical Design Briefs Magazine (Vol. 15 No. 5).

    Read more articles from this issue here.

    Read more articles from the archives here.

    Overview

    The document discusses key considerations in designing medical wearables, emphasizing the importance of Moisture Vapor Transmission Rate (MVTR) and effective bonding methods to enhance patient comfort and device performance. MVTR measures how moisture vapor passes through materials, with higher values indicating better breathability. This is crucial for medical wearables, as they can create a skin barrier that traps moisture, leading to skin irritation and conditions like contact dermatitis, especially during prolonged wear times (e.g., infusion sets worn for 3-7 days and continuous glucose monitors for up to 14 days).

    To mitigate these issues, manufacturers must prioritize skin compatibility by maintaining high MVTR levels during product development. The document highlights the challenges of securely attaching sensors or devices to skin adhesive patches without compromising comfort and breathability. A common approach involves using a non-woven backing with a skin adhesive, but this can create an undesired barrier that traps moisture and heat.

    The document also addresses the challenges associated with using heat sources for bonding. High temperatures can compromise the flexibility of non-woven materials, leading to a stiff surface that reduces comfort. This is particularly relevant in industries like hygiene and textiles, where maintaining material properties is essential.

    An innovative solution presented is ultrasonic welding, which eliminates the need for additional adhesives in the bonding process. This method not only enhances the durability and comfort of medical devices but also supports sustainability by reducing material costs and environmental impact. By minimizing the use of adhesives, manufacturers can improve process efficiency and contribute positively to sustainability goals, allowing products to be recycled more effectively.

    In conclusion, the document underscores the need for a comprehensive approach to designing medical wearables that balances patient needs with technical demands. By focusing on high MVTR, effective bonding methods, and sustainable practices, manufacturers can create wearables that promote health outcomes while ensuring user comfort. The future of medical wearables lies in innovative, eco-friendly design solutions that prioritize both functionality and sustainability.