When most people think of wearable devices, they think of smart watches, smart glasses, fitness trackers, and smart clothing. These devices have two things in common: they all need an external power source and they all require exacting manufacturing processes.
Using the new hybrid printing process, the team demonstrated stretchable piezoelectric sensors, conformable to human skin, with integrated tellurium nanowire piezoelectric materials, silver nanowire electrodes, and silicone films. The printed devices were then attached to a human wrist, accurately detecting hand gestures, and to an individual's neck, detecting the individual's heartbeat. Neither of the devices used an external power source.
Piezoelectric materials are some of the most promising materials in the manufacture of wearable electronics and sensors because they generate their own electrical charge from applied mechanical stress instead of from a power source. Yet printing piezoelectric devices is challenging because it often requires high electric fields for poling and high sintering temperatures. This adds to the time and cost of the printing process and can be detrimental to surrounding materials during sensor integration.
The biggest advantage of the hybrid printing method is the ability to integrate a wide range of functional and structural materials in one platform, streamlining the processes, reducing the time and energy needed to fabricate a device, and ensuring the performance of printed devices.
Vital to the design are nanostructured materials with piezoelectric properties, which eliminate the need for poling or sintering, and the highly stretchable silver nanowire electrodes, which are important for wearable devices attached to bodies in motion.