23 Apr Developing Wearable Electronics with Conductive Inks
Of the many ways that COVID-19 is changing the world around us, it emphasized a need for connected patient monitoring devices that require minimal clinician involvement. Whether you look at the Phillips BX100 Biosensor, Enfucell Wearable Temperature Tag, or Ontex smart adult diapers they all promise to provide us new monitoring abilities and improve outcomes. Conductive inks which make many of these products possible have been around for decades but are just now picking up steam for flexible, stretchable, wearable applications as materials are improved. Intersected with the decades-long trend of miniaturization and cost reduction in electronics, this is leading to an explosion of interest in wearable monitoring devices for hospital and at-home environments.
Conductive inks are typically made of a conductive material (silver, carbon) inside of a polymer carrier that is mixed with a solvent to allow the ink to be applied and cured on a final design. In principle, they are no different than circuit board traces or wires, but can be applied on all sorts of films and substrates necessary for a low-cost wearable device. Key Tech has experience working with these technologies and has learned a thing or two in the process; our tips for developing wearable electronics with conductive inks are:
- De-risk early and incrementally – Don’t let their small size or apparent simplicity fool you, wearable electronics with conductive inks are complex systems with loads of material science, mechanical, electrical, and firmware engineering involved. Because performance is so application-specific and nothing is guaranteed we recommend identifying core challenges early and incrementally de-risking these aspects of the design rather than trying it all at once. The best place to start is on the application-specific wearable, conductive parts and work backwards towards the conventional electronic components.
- Find the right printing partner – Conductive inks can be applied through inkjet, screen printing, or roll-roll manufacturing. Inkjet printing is convenient but only the latter two are suitable for volume manufacturing and offer the most options for inks. Doing it right requires a lot of capital-intensive equipment and hard-earned experience to get features reliably printed and adhering to your substrate. Key Tech partners with experienced printers to produce our prototypes.
- Mind the flex – Just because they can flex and stretch doesn’t mean you want them to. Materials like Dupont’s Intexar series inks and substrates are only becoming more robust, but they still will degrade under continual mechanical stress. First try to eliminate stretching of conductors, look to minimize flexing/twisting, then de-risk your design in those conditions.
- Develop resilient designs and algorithms – Unlike a conventional circuit board you cannot count on conductive ink features to be excellent conductors or to be consistent from device to device. From the start, Key Tech recommends designs and algorithms that are insensitive to conductive ink variabilities and are minimally impacted by the additional series resistance of the ink.
Wearables require a strong interdisciplinary design team. Drop us a line at TalkToUs@keytechinc.com to learn about what our team can do for your unique challenges.
Ward received his B.S. in Electrical Engineering from Bucknell University where he co-authored publications on both a river water quality monitoring system and an animatronic vulture. In his free time, he enjoys cycling, backpacking, and baking artisan bread.
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