VictorRen@zs-crown.com / export@zs-crown.com +86-13802693067

Key to Wearable Device Bonding: How Does Pressure-Sensitive Adhesive Functional Film Achieve Softness and Breathability for Skin-Contact Scenarios?

2025-12-08

Imagine waking up, slipping on your smartwatch or fitness tracker, going for a run in the rain, taking a shower, sleeping with it, and seven days later, it’s still sitting comfortably on your wrist, no red marks, no itchy skin, no peeling corners. It feels almost like a second skin.

This might seem like a break from the norm, but it's possible due to a super-thin sticky film that you can't see. This film, known as a pressure-sensitive adhesive functional film, is so tiny that a strand of hair is bigger than it, and it does five important jobs in device bonding.

It feels soft that you almost don't have an idea that you have anything on your wrist
It lets the skin breathe
It doesn't hurt the skin even after being worn for weeks
It sticks very effortlessly even while swimming, taking a shower, or sweating
It stretches each time there is movement around your wrist

Now that we know the functionalities of this film, let's find out how they happen.

Softness (Gentle on the Skin)

A regular sticker feels hard and like plastic when touched. So, if it sat on the skin for a couple of days, it feels terrible, but the pressure-sensitive adhesive film is absolutely different, and this is because it is made from silicone gel. If you have ever poked a soft earbud tip, you probably have an idea what this feels like.

Although several pressure-sensitive adhesive films are made from silicone gel, others use a certain type of acrylic that almost becomes jelly-like after making contact with the skin. When looking to measure softness, engineers use a parameter called “Shore hardness". While regular plastic stickers have a shore hardness of 80-99, PSA films can go as low as 10. That's so soft that a gummy bear even feels harder.

Due to how soft it is, when your wrist moves, the film moves along instead of putting up any resistance.

Breathability (The Tiny Invisible Holes)

The skin is living. You know this already. It sweats and thrives on air. Due to this, it starts looking soggy and white when covered with a regular tape for a couple of days, and this clearly doesn't feel good.

Key to Wearable Device Bonding: How Does Pressure-Sensitive Adhesive Functional Film Achieve Softness and Breathability for Skin-Contact Scenarios? 1

Back in the day, tapes were made breathable by using fabric. Interestingly, fabrics are not good enough for smartwatches. They are not waterproof and are also too thick. To deal with this, scientists created micro-holes. These holes are so tiny that you can only see them properly when you use a microscope. Nonetheless, if you hold a film close to light, you could notice some of these holes.

This is where it gets interesting. When you sweat, it leaves your skin in the form of vapour. Now, if you have just any material on your skin, the sweat would be unable to make it beyond the skin's surface. However, the presence of tiny holes on PsA films gives room for sweat to get off the skin easily. Ultimately, keeping the skin comfortable.

These micro holes come in various shapes. Sometimes, they are wider on the side of the skin and narrower on the other side. This ensures the easy release of sweat and also makes it difficult for water to get in while having a shower.

Skin Friendliness (No Itch, No Rash)

It is commonplace for folks to develop itchy, red skin when they wear cheap watch straps. There are various reasons for this. First, sweat gets trapped. Also, several glues are made from harsh chemicals.

Unlike the average glue, PSA glue films are made from medical-grade ingredients. They are either made from gentle acrylics or silicone gel. The reason for this is that people with extremely sensitive skin can comfortably wear products made from silicone gel. Also, gentle acrylics go through a process that ensures they are stripped of any chemicals responsible for allergies.

That's not all. This film can soak up a bit of sweat before releasing it. This helps avoid the buildup of anything nasty on the skin.

Staying Stuck Even When Life Gets Wet and Wild

The best trackers can comfortably deal with a jump into a pool, a long shower, and a rainy run. All these are great. Nonetheless, you might be uncomfortable if your tracker has no breathing room. Well, dealing with moisture effectively and breathing at the same time might seem like asking for too much, but it's possible.

The firm's top layer is waterproof. It is sometimes made from TPU or PU, a super-thin plastic that is used in making phone screen protectors. So, it's easy for showers and raindrops to bounce off. Also, as mentioned earlier, micro-holes allow vapour out but leave no room for liquid to come in. It's basically a one-way street.

Some firms even take things to extreme levels and get rated IPX8 or IPX7. The implication is you can go for a swim without being worried.

Moving with you like a Best Friend

Your wrist stretches, bends, and twists frequently because it isn't flat. Regular stiff tape films begin to lift at the edges when these happen, but PSA glue films are different. They are almost like leggings and can stretch by 800% without breaking. Also, it never gets loose, as it snaps back after a stretch.

Conclusion

Some years ago, stickers had to make your skin feel uncomfortable, but those days are long gone. Right now, health patches, fitness trackers, and smartwatches can remain on the skin for a very long time without creating the slightest form of discomfort.

Are you a wearable device manufacturer looking for the right adhesive bonding for your products? Consider working with Crown Adhesive Tape. Contact us for a custom solution to your manufacturing needs or check our list of adhesive materials.

Household Appliances Fixation: How Modern Pressure-Sensitive Adhesive Tapes Achieve Permanent Bonding under Extreme Conditions

New Energy Vehicle Battery Pack Fixation: How Does Pressure-Sensitive Adhesive Tape Achieve Shockproof and Flame-Retardant Properties to Ensure Battery Safety?