Lifepak defibrillator membrane switch

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By Duke Brekhus | Dec 18, 2019
Stryker Lifepad keypad

When Stryker created their Lifepak defibrillator, they knew how important it was for it to remain functional no matter the environment in which it was used. The device is used in hospitals, ambulances and everywhere in between where it might be subjected to tough conditions and repeated impact. With the original design consisting of an overlay directly over metal snap domes, little protection was offered to the domes themselves. Concerns were raised when they found that enough high-force impact could potentially invert these domes and possibly cause malfunctions.

While this didn’t cause any actual device failures, it was important to figure out a way to ensure that the potential issue wouldn’t ever lead to a malfunction in any of the defibrillators. Being used in such a critical industry, it was imperative that every button stayed functional for the life of the device. GMN’s experts revisited the original keypad design and began to devise ways to improve its durability.

Due to the way the keypad was designed to sit in the defibrillator, it had to retain the same dimensions and usability while still solving the potential dome inversion issue. The challenge became how to significantly improve high-impact resistance without altering any of the tactile feel, size or appearance of the keypad. Three different rounds of prototyping took place, each experimenting with different materials in various sizes and orientations below the keypad. The first round of prototypes worked on revisions to the original design, whereas the latter prototypes experimented with adding a layer of elastomer to aid with the energy dispersion from repeated impact.

GMN and Stryker eventually settled on a design where an elastomer layer and plastic frame rests between the printed circuit board assembly and the overlay. GMN had never combined elastomer with a plastic frame in this manner, but the new construction perfectly met the goal of improved impact resistance without affecting the feel of any of the buttons.

The new keypad construction was tested extensively to verify its functionality even in the toughest of circumstances. A one-pound weight was dropped multiple times from over 16” above the device on each of the buttons. While the old design might have struggled with the impact and failed, the new version held strong and worked consistently, even after dozens of repeated collisions.

The new design was not only incorporated in the current Lifepak defibrillator, but also found its way to other devices in the Stryker family. This unique keypad construction added a new design option to GMN’s toolbox for projects to come. This is yet another example of GMN’s ingenuity truly helping to optimize a product’s performance. To find out more about our design options or to discuss your manufacturing needs, set up a consultation with our experts.