Silicone PSAs offer new advantages to wearable medical devices
Christine Weber and Audrey Wipret, Dow Corning outline how silicone pressure sensitive adhesives are helping to meet the challenges of medical device adherence
With the growth of wireless monitoring and the move to outpatient and home-based care, more patients are wearing medical devices attached to their skin. In addition to traditional prosthetics, heart monitors and ostomy devices, wearable devices include new designs that enable advanced functionality, such as monitoring skin exposure to ultraviolet (UV) rays or relaying information about body movements to guide proper back exercises. The diversity of skin-adhered devices and their growing use outside the acute care setting require new pressure-sensitive adhesives (PSAs) that can deliver flexibility and breathability without skin sensitisation – all factors that promote patient compliance.
New silicone-based PSAs offer important advantages over acrylic adhesives. Not only can acrylic adhesives cause skin irritation in some patients, but they also tend to increase in peel adhesion over time, making removal of the device uncomfortable. Besides solving these problems, silicone-based PSAs can handle heavier loads than silicone soft skin adhesives, up to several grams, over extended periods. This advanced technology will be an important enabler of next-generation wearable device designs.
New wearables call for improved PSAs
The global market for wearable medical devices is forecast to grow to $7.8 billion (£5.4 billion) by 2021. This boom is being driven by several trends:
- Advances in wireless technology such as Bluetooth Low Energy (BLE), which supports long-term usage and increased connectivity
- Consumers’ fascination with self-monitoring fitness bands and smart watches, which carries over into the clinical arena
- A rise in chronic conditions, from diabetes to heart disease to COPD, whose management depends on ongoing monitoring; and
- Efforts to cut healthcare costs by shifting care to outpatient settings, including the home, while maintaining clinical oversight of the patient
These trends are driving the development of new wearable devices that adhere to the patient’s skin and provide a range of functions:
- Monitoring of vital signs, sleep quality and exposure to environmental hazards such as UV light
- Administering drugs such as insulin through convenient and discreet patch pump devices
- Tracking of body posture to prevent or detect falls
- Tracking of patient movement to monitor compliance and avoid bedsores
- Concussion monitoring
- Remote monitoring of patients with cardiac arrhythmias
PSAs for new wearable devices need to provide stable, long-term adhesion performance; flexibility and breathability for enhanced patient comfort; practicality for home use, such as water repellency to allow showering and sports activities; and avoidance or minimisation of skin sensitisation. A range of adhesion levels, from light to very high, are needed to support novel designs and different device weights and functions.
Silicone PSAs are ideally suited for the increased requirements of new wearable medical devices. Silicone technology checks all these important boxes:
- Biocompatibility: Silicones are biocompatible, based on their long history of use in medical devices, including long-term implants. They are non-cytotoxic, non-irritating and non-sensitising to the skin.
- Spreadability: Silicones spread easily to form films over skin and other substrates
- Permeability: Silicones allow the diffusion of oxygen, carbon dioxide and water vapor to improve comfort.
Innovative Silicone PSAs
The Dow Corning MG-2XXX series of PSAs comprises four products that offer device designers and manufacturers a broader choice of properties.
They are available in a range of tack and peel adhesion values, solvent types and solid contents to meet specific application needs and processing parameters. Specifically, MG-2402 and MG-2502 silicone PSAs can be processed using conventional roll coating equipment for solvent-based systems. MG-2410 silicone PSA can be applied using conventional hot melt coating equipment and the MG-2401 silicone PSA is designed to be used in applications where the liquid adhesive is brushed or sprayed onto the device.
They also deliver performance advantages over traditional adhesives. The four PSA product offerings provide strong, consistent adhesion of medical devices to the skin over extended wear periods, withstanding shear force of up to 21kg. They also offer excellent permeability to gas and water vapour, making them well suited for medical applications in which increased aeration is required.
All four grades have successfully passed biocompatibility testing for cytotoxicity, skin irritation and skin sensitisation according to US Food and Drug Administration (FDA) regulations for non-clinical lab studies (21CFR58).
Superior comfort encourages compliance
Silicones have proven their success in the healthcare sector for many years, and are finding new applications in the growing wearable device market. Silicone-based PSAs surpass traditional acrylic-based adhesives by avoiding skin irritation and maintaining a stable level of adhesion, as well as providing many other desirable properties. By optimising comfort, these products can make an important contribution to compliant use of skin-adhered medical devices.