TPU films offer a combination of flexibility, stretchability, biocompatibility and manufacturability for next-generation printed electronics.
By Timothy Frisch and Justin Spitzer, Covestro
As the demand for more sophisticated, comfortable, and reliable wearable medical devices grows, TPU films will continue to shape the future of remote patient monitoring and personalized healthcare. [Photo courtesy of Covestro]
Innovations in medical wearable solutions are revolutionizing healthcare delivery, portability, user comfort and patient outcomes. Materials like thermoplastic polyurethane (TPU) films are enabling devices that are both more durable and more comfortable for long-term wear, improving patient acceptance and compliance.
TPU films offer a wide range of benefits that make them an excellent choice for medical and wearable technology. They have multiple uses in medical wearables, from adhesive mountings to top cover layers to electronic substrates. Outer TPU layers provide a soft hand feel and can be color customized, while inner layers provide electronic functionality and user comfort contributing to the overall user experience of products made with these materials.
TPU films are flexible, stretchable and conformable
TPU films are known for their exceptional mechanical properties. Their flexibility, stretchability, and conformability enable devices to dynamically move and conform to complex body shapes, ensuring comfort and effective adhesion over extended periods. TPU’s inherent resistance to tearing, puncturing, and abrasion contributes to wearable durability and longevity. Their high abrasion and wear resistance ensures they can withstand physical stress and mechanical wear in applications like clothing and hospital bedding.
Compliant over a wide range of temperatures, TPU films exhibit good low-temperature flexibility and impact strength. Some varieties remain flexible even at sub-freezing temperatures, allowing for a broad range of indoor and outdoor uses.
The films’ stretchable nature, paired with a stretchable conductive ink, enables the creation of conductive circuit layers that can flex and stretch without compromising functionality.
Biocompatibility and engineered adaptability (Multifunctional performance)
Another key feature of TPU films in medical applications is their ability to be formulated free of solvents and/or plasticizers , making them safe for prolonged skin contact.
This biocompatibility is complemented by their breathability, which allows for air and moisture exchange to prevent skin irritation. The films can be engineered to provide an excellent balance of blocking liquids while remaining highly permeable to water vapor in applications like wound coverings.
Antifungal or antimicrobial formulations can provide a key advantage in minimizing bacterial and viral transfer and growth in medical settings. TPU can also handle sterilization methods such as ethylene oxide (EtO), gamma radiation and electron beam (e-beam) radiation.
Electrical properties of TPU
Electrocardiogram (ECG) sensor patches made with thermoplastic polyurethane (TPU) film [Photo courtesy of Covestro]
TPU films exhibit key electrical properties that make them optimal electronic substrates. TPU films can be produced to exhibit optimal surface topographies for printed circuits, and their inherent insulating properties make them an ideal material in protecting wearers from shock, electrostatic discharge and other electrical intrusions or leaks. The stable dielectric constant is important when using TPU films in applications that may include electrodes, antennas or capacitive circuits. These properties collectively make TPU films a reliable choice for electronics, enabling the creation of flexible and stretchable circuit assemblies.
Environmentally robust
Wearable technologies are often subjected to varied and uncontrolled environments, and key properties of TPU films are well-suited for environmental protection. Aliphatic TPU chemistries exhibit excellent resistance to ultraviolet (UV) radiation, preventing degradation and maintaining structural integrity when exposed to sunlight.
TPU films can withstand a wide range of temperatures, maintaining flexibility and strength even in extreme cold or heat, making them ideal for outdoor user applications where temperature fluctuations are common.
Polyether-based TPU films in particular demonstrate strong resistance to hydrolysis when exposed to sweat, body fluids, humidity, moisture and even submersion, making them an excellent choice for protecting electronics in showers and bathing. Additionally, TPU films are resistant to many chemicals, including oils, greases, cleaning fluids and solvents, helping them maintain performance and durability in challenging environments.
Manufacturing
From a manufacturing perspective, TPU films can be seamlessly integrated into existing high-volume printed electronics manufacturing processes, making them a practical choice for large-scale production. New TPU film offerings, some with a stabilizing carrier, are designed for high printing quality, excellent processability, and handling. These properties facilitate easier printing, curing, and converting processes for printed electronics.
TPU films can be further shaped by thermo-forming. And finally, TPU films can be bonded using thermal, radio frequency (RF) or ultrasonic methods to additional layers of TPU or other substrates without additional adhesives, offering unique solutions for sealing, assembly, reduced overall layer count and increased flexibility.
Conclusion
TPU films represent a valuable enhancement for wearable medical devices. Their unique combination of flexibility, stretchability, biocompatibility and manufacturability makes them an optimal choice for the next generation of printed electronics in healthcare.
Timothy Frisch [Photo courtesy of Covestro]
As the demand for more sophisticated, comfortable, and reliable wearable medical devices grows, TPU films will continue to shape the future of remote patient monitoring and personalized healthcare.
Timothy Frisch is the innovation manager for specialty films at Covestro. He has worked for over 10 years in product development, application development, and manufacturing of polycarbonate and thermoplastic polyurethane resin and film products.
Justin Spitzer [Photo courtesy of Covestro]
Justin Spitzer has over 25 years of experience in flexible printed electronics focusing on application development, market strategy, and product development. He has successfully managed business development, sales teams, and strategic initiatives across various technology sectors in the Americas region and globally.
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The opinions expressed in this blog post are the author’s only and do not necessarily reflect those of Medical Design & Outsourcing or its employees.
