The science of skin behind medical device innovation

(SPEECH) [MUSIC PLAYING] (DESCRIPTION) Text, 3M Medical Materials and Technologies. Making Skin Your Friend. Chapter 1, It's Not Easy Sticking to Skin. A man wearing a blue shirt slides onto the screen. A circle extends from his arm revealing a section of skin. A magnifying glass shows different shapes representing microbes. The skin snaps and the microbes fly off. (SPEECH) Skin does an amazing job of protecting us from microbes and outside contaminants, like a large, watchful guardian. (DESCRIPTION) Text, Medical Device. (SPEECH) But when you're designing stick-to-skin medical devices, skin can be a fierce adversary. (DESCRIPTION) Water droplets drip from the word Skin. (SPEECH) In this video series, we'll help you understand the unique challenges skin poses and help you choose appropriate adhesive materials for your applications, so you can make skin your friend. (DESCRIPTION) Tape adheres itself to the word skin. Text, What are the challenges of skin? The man reappears. He places an adhesive strip onto his upper arm. (SPEECH) Before we can understand how to stick medical devices to skin, we need to understand what skin is and why it's challenging. Obviously, skin is what's on our outside, but what makes it unique is what happens on the inside. (DESCRIPTION) A cross-section of the man's skin appears. The epidermis appears yellow and is the top layer with hair sticking out the top. The papillary layer sits underneath the epidermis and is a thin layer. The third layer and largest layer is the reticular dermis. The bottom layer is the hypodermis. (SPEECH) Skin has a micro-layered structure. From the outside-in, skin consists of the epidermis, the papillary dermis, the reticular dermis, and the hypodermis. The top layer of the epidermis, the stratum corneum, consists of dead skin cells that are regenerated about every 14 days. This constant regeneration of skin is a key challenge in formulating adhesives that can stick to it. (DESCRIPTION) Icons of a clock, drops of water, and a fire appear in circles. (SPEECH) But that's not all. There are other biological factors that can make sticking to skin difficult. (DESCRIPTION) Text, Age. (SPEECH) When designing devices for skin, the age of the wearer is a key factor. (DESCRIPTION) The man wears a name tag that reads Guillermo, age 32. (SPEECH) As you age, skin becomes more fragile, drier, and easier to damage. (DESCRIPTION) The man's hair turns gray and his skin wrinkles. The age of the name tag changes to 62. (SPEECH) That's because with age, the epidermis flattens and thins, making it easier to shear off its cells and damage that skin layer. (DESCRIPTION) Green bubbles rise from the epidermis. (SPEECH) We also lose hyaluronic acid, which gives skin its sponginess, so skin becomes more fragile and brittle. (DESCRIPTION) The man transforms into a baby holding a lollipop. A cross-section of the skin compares the thinner layer of the baby's epidermis to the thicker layer on the adult. (SPEECH) Babies also have fragile skin. In neonates particularly, the epidermis is not fully developed, so the skin layers are much thinner than normal. For patients with sensitive or fragile skin, engineers should consider gentler adhesives. (DESCRIPTION) Text, Moisture. Two layers of the skin open and close like a mouth. (SPEECH) As a living, breathing organ, skin shouldn't be occluded or blocked for long periods of time. (DESCRIPTION) Water droplets rise from the surface of the skin. (SPEECH) Skin needs to expel moisture. (DESCRIPTION) Water moves from the cross-section of the skin into a clear cylinder. The number 15% appears on the front of cylinder. (SPEECH) The stratum corneum contains about 15% water, but as you go deeper into the epidermis and dermal layers, skin is about 70% water. (DESCRIPTION) The number changes to 70% as more water enters the cylinder. (SPEECH) That water is constantly trying to make its way up and out through the top layer of skin. (DESCRIPTION) A medical device strip sits on the surface of the skin. Water pools underneath the device. (SPEECH) A device that occludes the skin can trap water that's trying to escape. This can lead to a problem called maceration. More on that later. Just remember, for skin, breathability in devices and adhesives is good, while trapping moisture is bad. (DESCRIPTION) Text, Hair. Little hairs stick up from the surface of the skin. (SPEECH) You'll notice that there are hair follicles throughout the skin. (DESCRIPTION) A razor shaves off the hairs. (SPEECH) Even though hair is usually removed before wearing a medical device, hair continues to grow under the device, pushing up and against the adhesive. (DESCRIPTION) Red spots pop up around the hair on the surface of the skin. (SPEECH) Hair follicles also contain microbes, which can potentially lead to folliculitis, which is an inflammation of hair follicles that accompanies infection. (DESCRIPTION) The man lifts weights. (SPEECH) In addition to skin challenges, device designers will also want to consider the activity level of the user. Will they be active or sedentary? (DESCRIPTION) Then, the man sits on a couch watching TV. (SPEECH) Where on the body will the device be worn? (DESCRIPTION) Circles pop up on different areas of the man's body. (SPEECH) How long will it be worn? (DESCRIPTION) Text, Metal, plastic, or silicone rubber. (SPEECH) What materials will it need to be compatible with? What's the manufacturing process? Is sterilization required? It's a lot to think about. What's a device engineer to do? (DESCRIPTION) Chapter 2. (SPEECH) We suggest joining us for our next chapter, "Befriending Skin with the Right Adhesive." [MUSIC PLAYING] (DESCRIPTION) Text, 3M. Science Applied to Life.

(SPEECH) [MUSIC PLAYING] (DESCRIPTION) Text, 3M Medical Materials and Technologies. Making Skin Your Friend, Part 2. Chapter 2, Befriending Skin with the Right Adhesive. A cartoon of a man in a 3M lab coat pointing at a chart in the style of the Periodic Table. One square, labeled A-D, Adhesives, pops out and enlarges. (SPEECH) At 3M, adhesives are one of our 46 core technology platforms. We've been studying skin and skin adhesives for over 55 years. (DESCRIPTION) A new illustration replaces the chart. It is a cross-section of Skin, showing hairs and follicles through the layers of skin. Text on the poster, since 1962. The skin grows cartoon arms that grab a heart shaped inset of the upper skin layers breathing and then drops the heart when it fractures. (SPEECH) During that time, our experts have learned a lot about what skin likes and what it doesn't. (DESCRIPTION) A cartoon of a piece of notebook paper populates with rolls of adhesive, question marks, and the text, Dear Expert, we need your help! (SPEECH) We've invited one of our skin experts here today to help guide you through the process of choosing a skin-friendly adhesive. (DESCRIPTION) The notebook paper folds into a paper airplane and flies to a cartoon woman who catches it. (SPEECH) Hi. I'm Diana Eitzman, Director of Agile Commercialization, 3M Critical and Chronic Care Solutions Division. But enough with the small talk. Let's get into the good stuff-- adhesives. If you're adhering a wearable device to skin, chances are you'll need a Pressure Sensitive Adhesive, or PSA, which can be used in medical applications. (DESCRIPTION) Several cartoons play as she talks. A man attaches a device to his arm. The device levitates from the skin to reveal a layer underneath labeled PSA. A bucket of adhesive is poured onto the tape in between two spools. One of the spools pops into a roll that sits alongside other rolls of adhesive, in brown, blue, and white. (SPEECH) PSAs are coated on a variety of backings to form medical adhesive tapes. These tapes should be developed using design controls as part of a quality management system, such as ISO 13485. (DESCRIPTION) The rolls drop onto an assembly line in front of a worker in sterile lab dress. Clipboards hold a supply chain audit and test results for biocompatibility. (SPEECH) They should also be manufactured in a clean facility that has dedicated, validated equipment, supply chain traceability, and is regularly audited for compliance. (DESCRIPTION) A hand taps on a phone app for biocompatibility testing. (SPEECH) Biocompatibility is also an important consideration, since it will be worn on skin. 3M can supply biocompatibility summaries for its adhesives. But device manufacturers need to test to ensure their final device is biocompatible. (DESCRIPTION) Cartoon examples pop up. The rubber latex is brown, the acrylate is white, and silicone is blue. (SPEECH) There are several types of adhesives. The most common are natural rubber latex and synthetic rubber, acrylate adhesives, and silicone Adhesives. (DESCRIPTION) An Adhesive Dictionary slides into view, and the properties are listed with video showing a rubber latex adhesive on a grey plate with orange adhesive between. (SPEECH) To compare them, we should define the relevant performance parameters. When evaluating adhesives, we look at tack, which is how rapidly the PSA bonds with the substrate. Think of it as how quickly it sticks. Adhesion to steel, this describes the resistance of the adhesive to a 90 degree peel or 180 degree peel from the steel surface, shear strength, which describes how resistant the adhesive is to forces working parallel to the adherent surface. (DESCRIPTION) A set of scales with two rolls of rubber latex adhesive in one pan and a roll each of the silicone and acrylate in the other. (SPEECH) Rubber, acrylate, and silicone adhesives have their advantages and disadvantages. Natural rubber can be a sensitized and an allergen, so it's rarely used anymore. It's been replaced by synthetic rubber. Synthetic rubber has a high initial tack, meaning it sticks quickly. (DESCRIPTION) A cartoon piece of rubber adhesive several inches long falls to a surface and cannot be lifted. (SPEECH) Whoa. See what I mean? It's also strong, but it's not breathable. And it can leave adhesive residue when peeled off. (DESCRIPTION) A calendar flips to 14 days. (SPEECH) It's not recommended for long wear time applications, repeated application of adhesive to the same part of the body, or for sensitive body parts like eyelids. (DESCRIPTION) A cartoon horse lifts a weight, replaced by a white roll. A piece of acrylate appears over a screen with sliders labeled Customization. The tape shifts between shades of green as the sliders move. (SPEECH) That brings us to the workhorse of wearable adhesives-- the acrylate family. Acrylates are nice because they lend themselves to a lot of customization. (DESCRIPTION) An arrow moves along a line below three conditions, moisture, heat, and pressure. (SPEECH) You can change the processing conditions, the additives, use different polymers and monomers, or change how you cure them. And that can help you finely tune, tack, and adhesion. (DESCRIPTION) Arrows representing air flow through the skin surrounding the acrylate adhesive as well as the tape itself. (SPEECH) They're also breathable. So overall, they're a better choice than synthetic rubber adhesives for wearable medical device applications. Silicone PSAs are very gentle adhesives with low peel adhesion, so they typically result in less skin trauma when removed. They're a great choice for babies and elderly patients who have fragile skin. (DESCRIPTION) A medical device adheres to the arm of an elderly man holding a baby. The inset of skin shrinks when age is mentioned. (SPEECH) They're also an excellent choice for repeat applications to the same area of skin or when you'll need to reposition the medical device. But they're used mostly for short-term applications. (DESCRIPTION) The chart shows peel force on the y axis and time on the x axis. (SPEECH) If you look at this chart, you'll see the change in peel adhesion to skin over time for the three adhesives. Synthetic rubber has high initial adhesion, but that drops over time in part due to its low breathability. Acrylates demonstrate adhesion that increases over time because, as they warm against the body, they flow into the nooks and crannies on the top layer of skin and increase the surface area they bond with. This is good for bonding, but it may pull on skin and hair when it's removed and could cause pain and irritation. Silicone shows very small changes in peel adhesion over time. But typically, these adhesives are not the best choice for long-term applications. However, silicone absorbs the stress within the adhesive better, so it is less likely to remove skin than acrylate or synthetic rubber. Now that you know the types of adhesives that are available and how they work-- (DESCRIPTION) A roll of rubber adhesive sticks to her jacket and then her hand. (SPEECH) these are really sticky. (DESCRIPTION) The screen moves to the man in the lab coat, whose eyes widen as several rolls and pieces of tape appear in the periphery. (SPEECH) I'm having some trouble here. [MUMBLING] (DESCRIPTION) When the screen returns to her, she is bound by tape. The man removes the piece covering her mouth. (SPEECH) Now, where was I? Oh, yes. It's important to understand the skin effects associated with these adhesives. Stay tuned for our next chapter, Just Say No to MARSI. [MUSIC PLAYING] (DESCRIPTION) Logo, 3M. 3M dot com slash med tech. Copyright 3M, 2018. All Rights Reserved.