With the advent of wearable technology, devices such as smart watches, sleep trackers and heartrate sensors have become a part of our life. In addition to fitness and wellbeing, these wearable electronics find many applications in medicine and healthcare, and they have tremendously helped in improving the quality of life for many people globally. Adhesives are integral to wearable technology and we can find them in almost every device on the market including medical patches, smart watches, activity trackers, emergency call buttons, virtual reality (VR) devices, health monitoring devices and more. Because of the critical nature of assembly adhesives and sealants in these devices, research and development has grown significantly in this area in the recent past to ensure that products not only perform well over their lifespan but that they also don’t negatively interact with the body wearing the device. This post focuses on the uses of adhesives and sealants in wearable devices, their significance in the medical and healthcare industries, and what kind of materials are used to make them to ensure safe user interaction.

smartwatch-components
The use of adhesives in consumer electronics – wearable technology.

Use of Adhesives and Sealants in Wearable Devices

Adhesives and sealants are used in wearable devices in many ways – on printed circuit boards to fix components, for environmental protection and waterproofing, in assembly of sensors componentry, for thermal and electrical conductivity and/or insulation and even fixturing onto human skin.

  • Adhesives Used in Wearable Device Assembly:The PCB assemblies for wearable devices have many small, intricate components. These components are fixed using adhesives and protected from the environment with coatings.  Board level adhesives tend to fall into epoxy, silicone, acrylate or urethane chemistries and are formulated based on the requirements of the specific application. Some of the board level applications could include micro-electro-mechanical systems (MEMS), electromagnetic interference (EMI) shielding, die and chip attachment and flexible printed circuit (FPC) reinforcement.  Usually these adhesives can offer some or all the following benefits:
    • Heat dissipation
    • Stress absorption/reduction
    • Vibration, shock and impact resistance
    • Electrical insulation
    • Chemical resistance
    • Structural adhesion

Assembling and sealing the enclosures within wearables and the device itself is also generally accomplished with adhesives and sealants. Cover glass bonding and enclosure/lid attachment is generally accomplished with structural adhesives that form strong, structural bonds between substrates while also providing excellent chemical resistance, superior shock and impact resistance and often these adhesives and sealants are developed to be reworkable for ease of repair should components break from wear and tear in the device.

Adhesives used in the assembly of wearable devices generally can be manually or automatically dispensed and curing can be accomplished via moisture, UV light, thermal exposure, mixing of two components or any combination of the above.  Many adhesives developed for these applications have superior adhesion to common substrates such as FR4, FPC, metals, glass, ceramics and plastics. 

  • Adhesives Used for Fitting on Human Skin: These adhesives come in intimate contact with skin and are formulated and tested to be extremely safe for human use. They are formulated to be moisture, sebum, saliva and sweat resistant, so that these fluids do not come in the way of health monitoring such as pulse rate and activity level calculation. It is very common that these adhesives are latex free as some people may be allergic to it. Rubber-based adhesives tend to be used if the device is meant to be worn for a short period of time. Acrylic-based adhesives are generally meant for longer-term use as they tend to have higher adhesion and environmental resistance properties. These adhesives are generally formulated to be dispersed onto a film backing creating a tape which in turn is used to adhere to the body.

Benefits of Adhesives in Wearable Devices

The medical industry today heavily relies on electronics and technology for improved, quick, and non-invasive healthcare. This calls for the use of safe, biocompatible adhesives to fit these devices on human skin for various purposes such as continuous monitoring of certain physical parameters, generation of medication alerts, and disease prevention. Thus, the demand for wearable adhesives has surged over the last few years and they have special importance in the medical and fitness industry. These adhesives have transformed the devices in the said industry in the following ways:

  • Adhesives are being formulated to be safe and biocompatible for use on a human body.
  • They are crucial to the effectiveness and accuracy of the device to give the right output – especially in sensor assembly.
  • Adhesives used in attachment of medical devices are thin and breathable and can easily hide behind clothes.
  • Replacement of mechanical fasteners helps devices become more lightweight and slimmer.
  • Replacement of welding removes possibility of damaging sensitive componentry.
  • Replacement of solvents allows for more environmentally friendly assembly methods.

Applications of Adhesives in the Medical and Fitness Industry

Adhesives are widely used in the following applications of medical and fitness industry:

  • Heart monitoring devices
  • Temperature monitoring patches
  • Glucose monitoring devices
  • Transcutaneous electrical nerve stimulation (TENS) electrode for muscular pain relief
  • Arm bands
  • Special shoes that help prevent injury
  • Smart watches
  • Fitness trackers

For over 30 years, Chemence® has formulated and manufactured adhesives and sealants for industrial use, electronics assembly and consumer use.  Chemence® Medical also develops and manufactures Class 2 and Class 3 adhesive-based medical devices in its ISO13485 accredited facility in Georgia. Chemence’s line of KRYLEX® adhesives and sealants have been developed leveraging our years of experience in electronics and medical adhesives.  If you are a manufacturer of wearable devices and you require assistance in designing and manufacturing of your device, Chemence® is here to help.