3D printable multi-directional piezoelectric sensor

The electromechanical coupling behaviors of the piezoelectric materials enable their wide applications in sensing systems. However, the comprehensive measurement of the stress tensor presented significant challenges for current piezoelectric sensing devices. Notably, the evaluation of the surface shear stress requires complicated structural designs along with intricate fabrication processes. Herein, we present the design methodology and manufacturing route to simultaneously extracting all individual components of the stress tensor. Our scheme is based on manipulating the deformation mechanism of each individual ligament within the piezoelectric micro-lattice structures. We implement our design principle via three-dimensional printing of free-form, piezo-active feedstock with high-resolution micro-architectures. The presented piezoelectric multi-mode sensor owns the capability of isolating the target stress components when subjecting to multiple external inputs. Innovated by these findings, the applicability of the multi-mode sensors is demonstrated by embedding them to the gas-solid interface as the conformal, flexible airflow sensor that is able to monitor the status of the airflow, as well as a self-sensing fluid pipe for liquid velocity field mapping.