A new concept for humidity sensing using curved micro-beams

There are number of common humidity sensing methods in MEMS. They include capacitive, resistive, and thermal methods. Among these methods, capacitive sensing is considered the most common in MEMS. In this method, changes of a capacitor dielectric constant, due to the absorption of air water vapor into a coating layer is correlated to humidity. The slow sensor time response and the degradation of the coating material over time are the major limitations of this method. Humidity have recently been studied as significant sources for environmental noise that, if ignored while operating a typical MEMS sensor, may lead to poor performance. In this work, we propose the utilization of this effect to overcome the challenging limitations of the humidity capacitive sensing. Specifically, we propose the use of an uncoated arch micro-beam to detect changes in the thermal properties of air due to humidity. Found to amplify these changes by orders of magnitude due to the richness of its nonlinear dynamics, an arch beam was selected for this investigation. These amplified effects become the measurements of interest, rather than being treated as noise. This new way of sensing humidity, can eliminate the need for the coating layer and significantly decrease the sensor response time.