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September 26, 2002

6 Min Read
Design All Stars: Wearable monitor gathers data outside

Des_BodyMedia_front_back.jpg

  • Project: SenseWear Armband body monitor   

  • Concept: Unit worn on upper arm, more comfortable than a wristwatch   

  • Designers: BodyMedia and K Development   

  • Weight: 3 oz   

  • Appearance: High-tech look, more fitness-oriented than medical   

  • Materials: ABS, PC, TPU (elastomer)

A revolutionary new way to collect data from a patient wins accolades from the IDSA for its comfort, visual appeal, and portability.

One of the goals of lab research is to gather real-world data. Unfortunately, lab equipment that monitors sleep patterns or energy expenditure often requires that subjects be hooked up to less-than-portable devices. Designers at BodyMedia have overcome these limitations with the SenseWear Armband, a wearable monitor that supplements and can augment the findings of monitoring equipment currently found in hospitals or research labs.

“This product is the first of its kind to let researchers do tests outside the lab with multiple sensors,” says Chris Kasabach, VP, Industrial & Mechanical Design for BodyMedia. He explains that this is the first multiparameter body monitor for collecting clinically accurate data on energy expenditure (caloric burn), sleep quality, and activity levels in a free-living environment.

“Our requirements internally—that it be easier to put on and more comfortable than a watch—were met in the final design,” says Kasabach. Apparently, the armband met requirements for excellence as well, garnering a gold award in the 2002 IDEA competition, sponsored by the Industrial Design Society of America (IDSA) and BusinessWeek magazine.

It also meets IMM’s standards for a Design All Star. Not only is the product based on industrial design and IM plastics—polycarbonate, ABS, and TPU—but it was also produced in collaboration with K Development (Erie, PA), a plastics product design and development company. Molded by Nypro Carolina (Burlington, NC), the three main housing parts are contoured to feel comfortable on the user’s upper arm. In addition, the design aims for a low profile so that the unit can be worn undetected under clothing. In fact, it looks more like a fitness product than a medical one.

Des_BodyMedia_exploded.jpgDesigned to be worn for up to five days continuously, the armband consists of three main plastic parts that make up the housing as well as electromechanical contents. GSR and temperature sensors are insert molded into the housing parts.Keeping Tabs
One of the IDSA jurors, Louise St. Pierre, explained after the competition why the SenseWear armband won such acclaim. “This product is intelligent, not only in what it does, but also in how it has been designed. As developments of technology have advanced in recent years, it is increasingly rare that one finds a revolutionary application. This is one of those.”

What jurors found revolutionary is the way that the monitor allows researchers to collect patient data continuously over a period of five days. Says BodyMedia’s CEO Astro Teller, “SenseWear produces physiological records of the wearer, allowing researchers to peer continuously and accurately into the subjects’ lives over an extended time. Because it works outside the lab, researchers can view problems such as insomnia, obesity, and weight gain in the context of lifestyle patterns and make insights previously impossible in conventional labs.”

In addition to data gathering for sleep disorders and weight management, the armband is used for performance fitness purposes. For instance, a number of pro athletes wore them for insight into athletic performance. “In the future,” Teller says, “we’ll also look at other variables. The product can stay the same, but the data collected can be changed. The sensors are there already; it is just a question of having the computer science know-how to draw new conclusions.”

There are two ways to download data from the armband—a wireless connection or a cradle connected to PC, not unlike a PDA. Users just put the armband into the cradle and upload to BodyMedia’s PC-based Innerview software for viewing.

Design Details
Materials were integral to meeting needs for hypoallergenic use, comfort, durability, and reduced size. They included surgical grade, hypoallergenic stainless steel for sensors; FDA-approved copolyester for labels that touch the skin; UV-stabilized thermoplastic urethane for flexible “wings”; ABS; polycarbonate; and a custom developed, latex-free nylon/polyester blend for the adjustable strap.

The flexible wings were overmolded to the monitor top, and the TPU material flows between the pieces to form an integral gasket. All external sensors were insert molded into the bottom. The hourglass-shaped label covers the assembly screws, creating a smooth interface to the skin. These design elements made SenseWear water resistant and easy to clean.

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Plastics were essential in meeting appearance requirements that the device look more like a fitness product than a medical one.

Comfort was also a top priority. The issues of heat buildup, skin sensitivity, pinching, weight, and size were carefully considered to minimize allergic reactions, skin occlusion, and discomfort during continuous wear.

SenseWear also contains a large button for time-stamping important events. It was designed as an oversized feature so wearers could press it without seeing it. Audio and visual feedback was supplemented with tactile feedback in the event the wearer wants privacy. For example, the researcher can program an “alert” in SenseWear to tell the subject to take medication or wake up. In privacy mode, SenseWear will emit a short, undulating vibration instead of an audible alert.

Team Dynamics
Jason Williams, principal at K Development, worked integrally with mechanical engineers at BodyMedia to help create the product housing. “We were trying to shrink the envelope as much as possible, so that the final product size could be minimized. We worked closely with BodyMedia’s hardware team to reduce the size of the mechanicals and optimize component configurations, and then worked to shape the plastic parts around them.”

Together, the housing consists of three main plastic parts, each with a nominal wall thickness of 1.5 mm. Four screws attach the parts together on the side that touches the skin, but these are covered up with the copolyester label for comfort. “We were able to integrate parts,” says Williams, “by designing the overmolded TPU wings with an integral gasket.”

“SenseWear was designed to move with the body,” says Kasabach. “The gentle curves, stretch materials, smooth texture, and soft colors make the product feel more like a fitness monitor. The skin-touching sensor side was designed not to feel like the bottom of the product, but like the inside. Sensors are shaped to match the contours of the housing.”

Contact information
BodyMedia Inc., Pittsburgh, PA
Chris Kasabach
(412) 288-9901, ext. 1217
www.bodymedia.com
[email protected]

K Development Inc., Erie, PA
Jason Williams; (814) 866-0644
www.kdevelopment.com
[email protected]

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