Inkjet-printed 2D electric field sensor array for microwave NDE of thin dielectric composites

In this paper, a printed multilayer paper substrate microwave sensor array is introduced, offering a novel approach to microwave non-destructive evaluation (NDE) of composite materials. The sensor array is meticulously crafted, comprising five layers of intricately printed sensor elements, a precision-engineered 3D printed sensor holder, and an Arduino-based data acquisition system, collectively forming an integrated system for material assessment. The approach involves illuminating the composite material under investigation into a locally uniform plane wave emitted by a spot-focusing horn antenna. The plane wave scattered by the composite material is interrogated by the printed sensor array with 75 sensor elements distributed across its five layers. Each layer accommodates 15 sensor elements positioned to maximize the measurement coverage. Individual sensor elements are linked to zero-bias Schottky diodes to capture the electric field strength associated with the incident plane wave. Resistive transmission lines and conductive sensor elements in the sensor array were printed with precision using inks with conductivities of 777 and 3300 S/m, respectively, for signal transmission in the array. Preliminary measurements of composite panels with defects indicate the ability of the printed sensor to provide an instantaneous map of local field perturbation in the presence of defects.