Buckling response of electrothermally actuated micro-beams to parallel and transverse flow

We explore both theoretically and experimentally the role of the flow direction on the performance of a novel flow sensor based on post buckling deflection monitoring of electro-thermally actuated double-clamped micro beams. Single crystal Si beams were buckled by a compressive stress arising due to Joule's heating. In the case of a flow directed along the beam, increase of the stream velocity resulted in decrease of the deflection due to the cooling of the beam by conductive heat transfer and convection. In the case of a transverse flow the drag force acting on the structure had a competing effect and deflection decrease was less pronounced. In the case of parallel flow, the deflection sensitivity of 1.5 μm/(m/s) and the critical current sensitivity of 0.4 mA/(m/s) were registered in the experiments. The results were qualitatively consistent with the predictions of the coupled nonlinear reduced order structural, fluidic and heat transfer models.