The able assistance of two materials suppliers allowed a device manufacturer to shave off nearly 16 weeks from the art-to-part development process of a wireless vital signs monitor. The ViSi Mobile system, which performs continuous vital signs monitoring, is currently being developed by DD Studio (Carlsbad, CA, USA) under the aegis of manufacturer Sotera Wireless Inc. (Carlsbad, CA, USA). The device had to meet a set of performance requirements that reportedly were unprecedented in a medical wireless instrument. Thermoplastic elastomer and copolyester-based materials from, respectively, PolyOne Specialty Engineered Materials and Eastman played a critical role in achieving this milestone. PolyOne made the announcement at last week’s MD&M East show in New York City.
The ViSi Mobile system consists of a device worn continuously on the patient’s wrist, a monitor for clinicians and an eight-port charging station. Performance requirements are demanding: they include a small form factor and light weight for wearing comfort; IPX7 submersion rating; resistance to damage from bumps, falls and other impacts; fire safety; and chemical resistance to hospital cleaners. One of the most challenging aspects involved meeting the IPX7 rating to protect internal electronics from water and other fluids commonly found in a hospital environment.
The IPX7 standard requires the product to remain underwater for 60 minutes at a depth of one meter with no water ingress. DD Studio chose the Versaflex TPE from PolyOne for its ability to provide a watertight seal in several areas of the device housing, including a speaker port and microphone. Testing showed that the design and material combination enabled ViSi Mobile to meet the IPX7 standard.
The housing components use a two-shot injection moulding process that combines Versaflex TPE with an Eastman Tritan copolyester substrate. Insert-moulded Versaflex also is used to hold cables in place on the four device connectors. This material provides firm adhesion to the cable assembly and strain relief properties.
For the charging station housing, Edgetek XT, based on the Eastman Tritan copolyester, delivers high impact and durability along with UL 94-V0 flame retardance, enhanced melt flow, and chemical resistance.