For our latest Ask an Expert blog, we invited people to submit any questions they had about Medical Wearables. We received questions spanning a breadth of topics, so we had one of our wearable device experts, Steve Baker, answer them.

What components typically make up a medical wearable?

The components in a medical wearable depend on the type, but transmitting wearables with on-board electronics usually include a cover film, thermoformed foam cover, printed flex electrode, printed circuit board assembly (or a printed assembly circuit with a battery), a stick-to-skin adhesive, conductive hydrogels, and a delivery/release liner. For wearables without on-board electronics, they can use a snap connector (or printed flexible electrode with connector), adhesive layer, stick-to-skin foam layer, conductive hydrogels, and a delivery/release liner.

We recently made a video that explains these different medical wearable components in detail.

What are some challenges unique to medical wearable design?

The biggest challenge to medical wearable design is usually deciding how long the adhesive needs to stick to the patient’s skin. What we see from the industry right now is typically seven to twelve days, but there are a few adhesives out there that can be worn for up to twenty. The release factor then becomes a concern; does it irritate the skin based on the aggressiveness of the adhesive? We’re always working with adhesive manufacturers to source new, highly engineered options that enable longer adhesion and more patient comfort.

The other unique wearable challenge is the flexibility and breathability of all the materials in the stack-up. Does the device flex well? Is it comfortable for the patient? Factoring in both challenges into cost structure is always important.

What is something people tend to overlook when designing medical wearables?

Simplicity. It’s counterintuitive, but wearable designers can overestimate their needs with adhesives and layers. Thinking that you need extremely tight tolerances, additional spacers, or the longest-lasting stick-to-skin adhesive sounds great, but it can increase cost and isn’t always necessary. Boyd relies on our years of knowledge and history creating wearable devices to say, that layer isn’t really necessary, this spacer will give you enough of a gap for the hydrogel this adhesive is less expensive and will hold up to the outdoor environment. And if there is a unique use case for a wearable that requires highly engineered materials, we can help work those in, too.

How do you decide on a stick-to-skin adhesive?

Adhesion is the critical factor, which comes down to how long it needs to be worn and the wear conditions. If you go too aggressive with the adhesive, it may cause skin irritation. If you don’t go with an aggressive enough adhesive, it may not stick based on the wear condition. We work with most medical adhesive manufacturers and compounders to meet different requirements. It’s best to reach out to Boyd’s team with your specific project requirements so we can suggest the right adhesive.

What is the tightest tolerance you can achieve on a wearable?

We frequently work with medical wearables that require extremely tight tolerances. It ranges a lot depending on the component, material, complexity, and geometry, but it can get down to +/- 0.05mm for complex, multilayered parts. We’re always happy to look at specific designs and suggest suitable fabrication methods for tolerance requirements.

How can you make wearables more durable?

It’s often moisture ingress that shortens life and decreases performance of a wearable, so the biggest factor is ensuring that you have the right adhesives that seal properly. Adhesives that not only stick to skin, but also between the different layers of the device. This all depends on the use of the wearable and the materials used in the different layers in the stack-up.

What is one of the most exciting medical wearable applications that you have worked on?

We recently worked on a continuous glucose monitor that had unique challenges. It required a very small footprint and included electronics for constant monitoring, so it had to be comfortable and long-lasting, even with all the design parameters involved. It’s always exciting to use our expertise to push the envelope on a solution like this.

That said, I don’t want to downplay simpler wearables, like ECG or EKG sensors. They’re high-volume and cost sensitive, but still have multiple layers and interesting design aspects. It’s also exciting to bring a high-volume, competitive, disposable device to the marketplace.

What do you think is the future of medical wearables?

Wearables are already a multi-billion-dollar market, and it’s growing rapidly. Improvements in battery life technology, stretchable conductive inks, and enhancements to near-field communication (NFC) and Bluetooth are coming. It’ll make the wearable industry much stronger, offering continuous remote patient monitoring outside of doctor’s’ offices and hospitals. It’ll be fully remote, and that’ll really change the medical wearable industry.

We’d like to thank everyone who submitted questions! To learn more about our Medical Wearable capabilities or inquire about your specific requirements, visit our Medical Wearables page or schedule a consultation with our experts.

Streamlining Medical Wearable Device Design for Performance & Total Cost Optimization – Part 1

We sat down with one of our Field Application Engineers to discuss how to optimize and streamline Medical Wearable Device design. Boyd is an expert in streamlining innovative design, manufacturing, and assembly of medical wearables to help product designers and medical device companies design for excellence (DFx). We help designers consider patient comfort & safety, manufacturing efficiency, product lifecycle, and total cost while navigating complex regulatory processes, providing global agility, assuring business continuity, and accelerating time to market.

Here are common questions we get as we work through Medical Wearable Device design projects with leading medical device design and manufacturing clients:

What are the best and safest ways to attach Medical Wearable Devices to the skin?

There are two important factors to consider regarding the attachment of the medical wearable: The attachment of the device itself to the skin and the style of conductive electrode used. All devices that attach to the skin must be highly tested and regulated to assure patient comfort and safety. Wearable devices must reliably attach to the patient for intended wear times without irritation while still being removable without damaging patient skin.

Wearable Device Adhesive Considerations

Selecting the right medical grade adhesive for wearable devices are selected based on:

• Required adhesion level (for example higher adhesion is necessary for longer wear times),
• Breathability: water against the skin needs to escape to help promote better wear time
• Ease of Removability,
• Wearer Comfort Level,
• Repositionability or Re-application (if required), and
• other application considerations.

Medical Wearable Design and Use Conditions

The shape and type of the skin contact layer may also be influenced by whether the wearable device needs to protect hydrogel electrodes or sensitive electrical components sandwiched within the patch from outside water ingress. In some unique applications when wear time is short, water ingress is not a factor, and repositionability of the wearable is desired, the adhesive skin contact layer can be foregone and rely on hydrogel components to provide the desired level of adhesion. We collaborate with many global raw material suppliers that are the world’s leading innovators in skin contact comfort and performance to help recommend materials to customers based on these factors to improve product comfort, care, and safety.

Medical Wearable Device Electrode Components

As for the electrode component, one traditional type of material used is open cell, medical grade foam pad saturated with a conductive gel as the electrically conducting medium. This style electrode can be more difficult to handle as a raw material and can impact manufacturing efficiency and cost. We have been steering customers towards hydrogel-based electrodes. Hydrogels present some cutting challenges, but our proprietary converting methods can offer a better option: they’re available in roll form and solid means a component easier to cut, handle, and place with greater quality control. There are several different global hydrogel raw material manufacturers available that offer responsive support and supply chain stability, enabling us to secure dual sources that can be compliant with regulatory and certification controls. Many material formulations to choose from, means we can typically find the right hydrogel to fit the specific electrical and application requirements.

We’ll continue our interview with our Medical Wearable Device FAE in an upcoming post!

Biocompatibility:

Power Management:

Flexibility and Stretchability:

Sealing: