Additively Manufactured Degradable Piezoelectric Microsystems for Sensing and Actuating

The global overabundance of electronic waste and ever-increasing concerns regarding the energy-and material-intensive manufacturing processes associated with traditional electronics are driving the development of solution-processed, degradable electronics. Of note, the industry-dominating prevalence of harmful lead-based materials in sensing and actuating devices drives the push for more eco-friendly solution-processed piezoelectric systems. Yet current ecofriendly multi-material printing processes are limited by both the conventional challenges of multilayer processes as well as the low-temperature thermal constraints of biodegradable materials. Herein, a novel approach for fabricating fully printed, sustainable piezoelectric transducers on paper substrates is presented. Low-temperature screen-printing processes are used to integrate non-toxic KNbO3 layers with degradable carbon- or zinc-based conductive inks into devices. The influence of electrode material on device characteristics is assessed, with effective piezoelectric coefficients reported as high as 4.6 pC N−1 and 5.1 pC N−1 for devices with carbon and zinc electrodes respectively. The potential of the developed technology is then demonstrated through the first-ever instance of fully printed piezoelectric force sensors and acoustic speakers comprised entirely of green materials. By demonstrating entirely printable green piezoelectric devices compatible with various electrode materials, this work serves as a step towards developing more complex sustainable piezoelectric technologies in the future.