One of the recurring themes in the presentations at the IDTechEx conference was the need to for wearable Health Tech devices to “disappear” into our daily lives. These products can’t be intrusive, but rather become a part of our normal day-to-day habits. One important key to helping these devices merge into the background of our lives is the development of electronic circuits that are not simply flexible, but that can be stretched repeatedly as well. The photos above are of prototype technologies that have already been demonstrated (some of which have been covered here in Health Tech Insider), mentioned by Anwar Mohammed from Flextronics. The company develops a wide range of technology, including printed electronics.
Silver inks are a mainstay in printed electronics and already are in widespread use for low-cost RFID (radio frequence identification) tags for a variety of applications. Silver is brittle, however, and does not hold up well to stretching. The metal traces fracture which makes it more difficult for electrons to find a path to complete an electrical circuit, resulting in higher resistance. Flextronics researchers have developed silver inks that are composed of nano-flakes of the metal. Where the flakes overlap, they create a path for the electrical current. By printing the silver traces on a stretchable plastic substrate, the arrangement of the of the flakes is altered, and new connections are made. The result is that the resistance does not increase nearly as much as with traditional silver inks.
Further research has demonstrated that using flakes of different sizes increases the chances of connections in the stretched and relaxed states. Flextronics has developed an assortment of circuit patterns that hold up to stretching without separating from the plastic substrate. They have also been able to create stretchable traces as small as 50 microns wide using screen printing techniques. The company is continuing to study stretchable circuitry, which will lead to better and more “invisible” wearable devices in the future.