Evaluation of the Electrode Design of an Integrated Bionic Microflapper for Improved Fluid Flow

Nature is often more resourceful than traditional technical approaches when it comes to finding efficient solutions to engineering problems. For example, the wavelike manner in which fish move—the so-called undulation—reveals the most energy-efficient way to transfer momentum from a solid to a fluid. This bionic principle can be made technically applicable, for example as an integrated cooling at chip-level, as a propulsion for microswimmers, or for efficient gas transport in lab-on-chip or gas sensing applications, to name just a few. The technical implementation of this concept is a thin and laterally extended monomorphic piezoelectric structure with segmented electrodes on top, which geometrically mimics a fish fin. The key of this concept is the phase-shifted excitation of the flapper by the segmented electrodes. To this end, various electrode designs and different fin geometries are evaluated with respect to their capability to generate undulation, which gives directly an estimate of the achievable mass flow. This is done by means of Laser Doppler Vibrometry. Additionally, these measurements serve as validation of coupled finite element models of momentum transfer between solid and fluid, which enable to evaluate the resulting flow field and to predict the achievable mass flow rates. This way, recommendations for the design of future MEMS flappers are derived and the most promising design variants are identified.