Sticking to Skin: How to Overcome Human Factors

Critical & Chronic Care Solutions Division, 3M St. Paul, MN

The qualities that make skin an incredible organism are the same ones that make it a challenge to stick to. Engineers may know all too well the headaches that can come with selecting adhesives for their stick-to-skin medical device projects. But it’s not all irritations, rashes, and pulled hair.

Understanding the challenges of each project not only prevents some of those side effects, but also instead maximizes comfort for users and produces better end results. Whether it’s for a wearable device or an advanced dressing, here are four challenges engineers must consider when developing their next project.

Length of Wear Time

One of the first items engineers must determine is how long the device will be in contact with skin. Since skin essentially renews itself every two weeks, an adhesive that has to stay on for that amount of time will use a different combination of material and backing than one that must only be secured for hours. 3M conducted 8-day and 21-day trials on human volunteers to help medical device manufactures determine the best adhesives for their specific projects. These studies also help to further educate device manufacturers on how to evaluate wear time and the importance of examining skin health. Both studies produced key take-aways for engineers such as questions that must be asked when considering longer- or shorter-term wear, including but not limited to:

• Who is the intended end user?
• Will the adhesive secure a device? If so, how long will that need to be on?
• Where on the body will the device be secured?

Knowing answers to pertinent questions will better steer the project in the correct direction at the start of the process.

The Right Adhesive for the Right Application

Proper adhesive selection can dictate a project’s success. After all, not every adhesive is meant for all substrates or applications. Choosing the right one will help the design and development process flow more smoothly, and, hopefully, prevent redoing clinical trials and studies later on. Plus, the proper combination means avoiding other consequences like irritated skin, difficult removal, and a device falling off prematurely.

Here’s a quick overview of the most commonly used substrates for medical devices:

• Polyethylene: Soft to the touch, comfortable, easy to work with, and reasonably priced.
• Polyurethane: Great flexibility, soft, can withstand sterilization processes, ideal for wound dressings and other medical needs.
• Polyester: Easy to adhere to, moldable, clear, hard, protective, and inflexible.
• Silicon: Popular for medical devices, difficult to stick to.
• PVC: Flexible, resistant, clear, hard to dispose of, and can negatively interact with tapes due to plasticizer migration.

Choose the Proper Backing

Selecting the right backing for each adhesive is like picking the proper outfit based on the weather. Make the wrong choice, like wearing a winter coat during a Houston summer, and you will be uncomfortable. Human skin feels the same way about how adhesives and backings are paired. When skin feels suffocated, it may eventually react to whatever is causing the discomfort, so be sure to incorporate breathability into the adhesive and backing combination.

There are other factors to consider as well, particularly when the adhesive is used to adhere an occlusive device for multiple days or weeks. It’s key to understand how the device pairs with the adhesive and backing, and to optimize the entire construction to avoid migration of skin irritants. Three other aspects to incorporate into design are moisture management, flexible backing, and backing that extends beyond the device’s edge. While the device may be occlusive, incorporating these design considerations can help the skin continue to move, flex, and breathe around the device.

Diversity of Factors Affecting Adhesion and Wear Time

Both adhesion and wear time are greatly impacted by the convergence of human and design factors. Human elements, like the amount of oil on the person’s skin, hair growth, and application site, can be difficult to manipulate. Still others are harder or impossible to control, like culture, health, age, and environment. Understanding the differences between wear time and adhesive capabilities on an elderly person’s skin as opposed to a baby’s might not be top of mind for most engineers, but knowing these nuances will play a critical role in the end use success.

Design-wise, the bottom line is to only ask the adhesive to do what’s required of it. While this may seem like obvious advice, there can be a tendency to overdesign and use an unnecessarily strong tape.

Keeping tabs on these four challenges at the start of a project will benefit the product development process, and in turn, the manufacturers, engineers, and end users involved. Not only will the process be more efficient and less costly, but the end products will do their jobs better. Those who neglect addressing these issues may go down the wrong path from the get-go, potentially squandering precious resources, causing delays, and raising budgets.

Negative outcomes can be avoided when engineers and customers work together to mutually understand the nuances and offerings of medical tapes, and how each can affect a particular medical project. Some companies, like 3M, offer engineers support during the entire design and development process by providing a critical lens on projects and offering advice on design and adhesive options. A greater level of success comes with understanding of these stick-to-skin challenges.

This article was written by Diana Eitzman, PhD, Director of Agile Commercialization for 3M’s Critical & Chronic Care Solutions Division, and Kris Godbey, Senior Applications Development Engineer at 3M, St. Paul, MN. For more information, Click Here .

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