True MEMS-scale hair-like flow sensors fabricated via hybrid projection micro-stereolithography and aerosol jet printing

In this work, we introduce a hybrid microfabrication<br/>method for developing 3D MEMS-scale sensors that<br/>combines aerosol jet printing (AJP) and projection microstereolithography<br/>(PμSL). By reaching sub-10 μm<br/>resolution in fabrication, PμSL enables fabrication of<br/>geometrically intricate overhanging structures such as<br/>perforated surfaces, cavities, and multi-DOF geometries.<br/>Piezoresistive sensing elements can be seamlessly<br/>integrated on printed MEMS designs through AJP by direct<br/>deposition of conductive nanomaterials. Cantilever-based<br/>and cilia-inspired MEMS sensors were fabricated and<br/>tested through electromechanical testing and wind flow<br/>characterization, respectively. Consistent<br/>electromechanical performance and a highly linear flow<br/>response between 0 to 35 m/s (R² = 0.9886) were<br/>demonstrated with the results. Beyond the limitations of<br/>planar silicon processing, the proposed hybrid 3D printing<br/>method provides a flexible route towards realizing complex<br/>MEMS devices.