Wear time for patient monitoring and wearables continue to dominate the conversation of innovation in the space. OEMs are coming to suppliers to help lengthen the wear time of their devices through adhesive design and choice of web material, as well as having conversations about conformability and deformation resistance for flexible components.
“By far the biggest request we see is long term wear,” Steve Schroff, business development chemist at Mactac, told MD+DI. “OEMs are constantly seeking longer wear times for devices. Other requests we see are conformability and comfort related.”
Adhesive Longevity and Conformability Innovation
3M is one company pushing boundaries in adhesive innovation for health monitors, sensors, and long-term medical wearables. In February, the company launched its new adhesive offering with a wear time up to 28 days. The 3M Medical Tape, 4578 consists of a white spunlace polyester nonwoven backing coated with a pressure sensitive acrylic adhesive used for longer wear applications. The 28-day wear time is double what was available prior to 2022, according to 3M, when the standard wear time for extended medical adhesives was up to 14 days.
4578’s liner free stability also means that it can be stored for up to one year, “giving device makers more flexibility in the design process,” according to the company.
Among new adhesives wear times, a push to create devices with the ability to withstand stretching, deformation, and conformation has resulted in products like Toray Industries Reactis stretchable film. The film, which has a plastic wiring circuit printed on it, can be subjected to repetitive deformation such as “linear pulling and twisting, and can easily accommodate expansions, contractions, and torsional deformations of circuits and 3D curved surfaces,” according to the company. It can recover its shape up to 97% between -4°F and 176°F while also maintaining heat resistance even after treatment at 392°F.
The device has characteristics the company said are ideal for smart wear, medical monitoring hear, biometric exercise device, and robotic systems, and is made with a proprietary polymer structure design and film forming technique which combines cross-linked and stretchable components.
“[Innovations] continue to push the length of wear of devices through both adhesive design but also through the choice of web materials used,” Schroff said.
Loomia is one company betting on flexible circuitry that can be used for these devices. Its Loomia Electronic Layer (LEL) is an e-textile circuit that is scalable with multi-axis flex. It consists of five main components: the soft layer, the interconnect, integrated components, adapter cable, and power source that do not break from stress. Additionally, the LEL is “more drapable than flex PCBs, wires on mesh, or most other flexible electronic options. We have a similar flexibility to printed ink on TPU. However, because our technology is not printed, it allows us to design low-resistance conductors that do not easily change resistance when stretched,” according to the company.
From a manufacturing standpoint, the technology can cost a little as $0.05 per square inch and is scalable up to 20,000 units a week in an ISO 9001 and ISO 13485-certified facility. The circuitry can also be patterned to be 4.15 to 340 times lighter than a hard wire equivalent for power and data buses.
As for the next leap in patient monitoring comfortability, easier adhesive removal comes to mind for Schroff.
If not careful, frequent removal of pressure sensitive adhesives can result in medical adhesive-related skin injury (MARSI) like persistent erythema, skin stripping, blisters, or bleeding. This becomes a larger concern for patients with fragile or delicate skin like older adults, and those on specific medications like corticosteroids. Currently, there are two common methods for removal: low and slow or distortion, which requires a device that can be stretched in a way to pull it from the skin.
While there are many “hacks” for helping to remove devices adhered to the skin painlessly, like alcohol-based adhesive removers, they are imperfect solutions. Schroff told MD+DI that he thinks the next innovation will be an adhesive that can be activated for application and then deactivated for removal.
“I see the next innovation being an adhesive that can be activated/deactivated for easier removal from the skin,” he said.