Meeting the Challenge of Wearable Medical Device Design

Advances on several technology fronts have led to an explosion of new wearable medical and health devices. From smart watches that count steps and measure blood oxygen content, to hearing aids and insulin pumps, more people than ever before rely on these devices.

Designing these devices is more challenging than most other consumer products. They have data input and output, they must work in harsh environments, and generally speaking must fit and be inconspicuous. From an engineering standpoint, packaging, mechanics, and electronics must all work together. Bi-directional informational flow is also a key issue.

“This type of device is extremely challenging to design, and extremely iterative in nature,” says Stephen Endersby, director of product portfolio management for Dassault Systemès SOLIDWORKS brand. “The eCAD people are fighting the industrial designers, and the poor mechanical guys are caught in the middle trying to keep everybody happy.”

“Electrical and electronic engineers on these projects ‘hold the whip,’” adds Endersby. “If it isn’t functional it won’t sell.” Despite that, Endersby says “the overwhelming design concern in wearable medical devices mostly comes down to packaging.”

Wearable medical devices can be divided into four categories, each more complicated than the previous. Passive monitors only record data. Surveillance devices record and report data, either on a schedule or in real-time. Diagnostic devices make decisions such as when to alert the user or to “call home” to medical professionals. Therapeutic devices treat a specific condition. Diagnostic and therapeutic devices come with higher legal risk and more lengthy regulatory review cycles than passive monitors and surveillance devices.

The design process is highly iterative. “Industrial ID and eCAD are packaged up into a version, then you start hammering on it for product performance in terms of simulations. EMC, electromagnetics and antenna design, and heat/shock/thermal are all part of it,” says Endersby.

Designers must also take into consideration whether the device is a health device or a medical device, notes Endersby. “Take an insulin pump,” he says. “It’s not real high tech but it must deliver a set amount of the drug at a set time and a set rate. The medical impact of something going wrong with a drug delivery device is an order of magnitude worse than a health device losing your jogging data.” The requirements of medical devices for traceability, approvals, testing, and more “make the importance of a collaboration platform to be much more stringent,” he adds.

Engineering teams working on wearable medical devices often spend more time on documenting the design process than actually designing. Anything that helps shorten design review and compliance cycles are valuable.

Collaboration platforms such as the Dassault Systemès 3DEXPERIENCE platform can transform such a complicated design process. Each project requires the input of multiple engineering disciplines, plus product managers, specification authors, standards compliance test engineers, and executive and government officials. When all these solutions are accessible on a common platform, design is more efficient.

Consider a typical workflow in which a design team starts with a form factor for the wearable. Mechanical engineers and industrial designers collaborate to model that form factor in the mechanical environment. From there the electronics engineer derives the PCB outline and gets to work on the layout. If the mechanical team later realizes something about the enclosure needs to change, that team can make the change and the electronics engineer can then pull in that change downstream. As the design develops, stress and thermal simulations can be performed on the PCB within the enclosure, uncovering aspects of the design that need to be adjusted and optimized for cooling or durability.

Traditionally, the use of simulation in medical device design has been a polarizing subject among engineers. The increased use of cloud-based collaboration is making it easier to incorporate simulation as part of the design process instead of waiting for a complete design to be referred to an analyst.

An effective simulation of a wearable medical device requires two prerequisites. First, the study needs to be set up correctly, including accurate models and proper boundary conditions. Second, the engineer or designer needs to have an expectation of what the result should be. The expectation is important. If there is no preliminary expectation of what the simulation should produce, there is no way to ensure goals are met. If a team expects a simulation to produce a design solution, disappointment is often the result.

Endersby believes the collaboration platform approach to product design is especially helpful for simulation. “Companies who need to develop these tools all have the same challenges — packaging, power consumption, EMC, and more. If things go wrong, it’s diffcult to backtrack”

The traditional siloed approach is just too inefficient, Endersby notes. “If the mechanical guys are working in one system and they pass a neutral format to electrical, and then electrical does the same to simulation, it doesn’t work.”

A common data language is required. “Antennas need a common data model and a common language,” says Endersby. “So when mechanical and electrical are set up, they can take it all to simulation.” It is all about the “pain-free exchange of information” between hardware, software, mechanical, design, and prototyping. “All that information must be as frictionless as possible. Where there is friction there is area for mistakes. We believe the platform approach is where companies will start to win.”

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