The first 3D-printed and wet-metallized three-axis accelerometer with differential capacitive sensing

In this paper, the innovative fabrication process for electro-mechanical sensors, born from the smart combination of 3D-printing and wet-metallization and previously demonstrated in a $z$ -axis accelerometer, is employed to fabricate a fully 3D three-axis accelerometer. Thanks to the three-dimensionality of the printing process, a central symmetry along the three axes can be obtained by design, unlike in common 2D-like microfabrication processes. Electrostatic differential sensing is obtained through the metallization procedure and the subsequent mounting of fixed electrodes on an external frame of the mechanical structure. Experimental tests under accelerations show good agreement with theoretical predictions. With relatively small dimensions (features as low as $450~\mu \text{m}$ ), very high capacitive sensitivity (> 200 fF/g) and low theoretical thermo-mechanical noise, the proposed three-axis accelerometer represents a further step towards the development of an innovative fabrication process for high-performance, customizable, and low-cost electro-mechanical devices.