Parylene and Wearable Devices

Wearables are no longer an emerging technology — they are here. Whether a wearable is a medical device like an insulin pump, a smart watch or even a finely woven piece of smart fabric, they all have one basic fact in common. All of them contain technologies that need protection from the outside world, and in nearly every scenario, Parylene stands out as the optimal choice for protection.

Parylene is the most unique of all conformal coating compounds. While others are applied as a liquid, Parylene deposits as a vapor. Most coatings need to be applied in thicknesses measured in mils, while Parylene is effective at thicknesses measured in microns. Finally, many conformal coatings are especially good at one or two things while Parylene is great at just about everything.

The Wearable Challenge

The life of a wearable device is harder than it might seem. After all, it goes everywhere that its wearer goes. At first glance, these conditions might not seem that extreme. After all, the places that people go usually do not harm or kill them. However, from the perspective of a device, consider the many challenges that it faces:

• A wearable device could be exposed to summer in Phoenix (115°F) and winter in Minneapolis (-25°F), giving it a 140°F range.
• Wearables need to be small and light enough to be comfortably worn. Generally, they also need smooth surfaces for comfort, especially where they are to touch the skin.
• A user working outdoors may inadvertently subject their device to eight to 12 hours of direct sunlight and UV rays.
• Wearable devices get exposed to corrosive spray when they are taken to the beach or on a boat.
• Household cleaning chemicals — that are likely to end up landing on a wearable device — contain harsh compounds and powerful solvents.
• Between office equipment, wireless personal devices and high-tension power lines, wearable devices are constantly bombarded with RF and EMF signals of varying strength.
• Wearable devices are in a constant state of vibration and motion and are at risk of abrasions and impacts at any time.
• The human body itself exudes gases, liquids and maintains a constant temperature that is almost 30°F above room temperature.

The Parylene Solution

Parylene presents a comprehensive solution to the myriad challenges faced by wearable devices. Here’s a breakdown of the benefits that Parylene offers:

• Parylene withstands temperatures as high as 350°C with no degradation and can go as low as -270°C. At body temperature, it can last forever.
• Because its coating is so thin, Parylene adds almost no perceptible weight or size increase to the item that it coats. Its exceptional biocompatibility and dry film lubricating capability ensure comfort and non-irritation against the skin, and even inside the body.
• Parylene exhibits exceptional resistance to water, corrosive substances, chemicals, and solvents, making it an excellent coating for diverse real-world applications.
• Of all coatings, Parylene is one of the most effective dielectrics in a thin coat, blocking EMF and RF interference.
• While it does not offer the cushioning properties of a thick coat of silicone, Parylene is tough and able to withstand impact and abrasion.
• Parylene provides a truly conformal coating that effectively blocks gases from permeating the coated item.

Parylene and Two Wearable Challenges

Wearables present two distinct challenges, both of which Parylene adeptly addresses. Firstly, many wearables feature sensors that relay information about their activities or monitor the wearer’s actions. Microelectromechanical (MEMS) sensors, in particular, are delicate components that necessitate safeguarding without impeding their functionality. Parylene’s exceptional capability to uniformly coat even the tiniest and most intricate devices positions it as the optimal choice for shielding wearable MEMS.

The dielectric attributes of Parylene are typically advantageous, yet they may hinder the functionality of a wearable device designed to capture data from its surroundings or the user. Fortunately, prior to coating, these devices can be masked. The masking process prevents Parylene from adhering to the sensors, ensuring their proper operation while still benefiting from the conformal coating elsewhere on the device.