Micro Electro Kinetic Actuator (MEKA) arrays for active sublayer control of turbulent boundary layers

Recent progress is summarized in the development of microactuator arrays that function on the electrokinetic principle to permit active control of streamwise sublayer vortical structures in turbulent boundary layers. Electrokinetic microactuator arrays induce volume displacement in the sublayer by electrokinetic pumping under an impulsively applied electric field. Individual microchannels are formed in a substrate and filed with a 1 μm-scale doped porous polymer matrix material that provides the required ζ-potential when wetted by the corresponding electrolyte. The resulting microactuator arrays have many characteristics that make them potentially suited for practical sublayer control on full-scale aeronautical and hydronautical vehicles. Essentially loss-less frequency response has been demonstrated to 10 kHz. Several such micro electrokinetic actuator (MEKA) arrays have been fabricated from a three-layer design leading to the MEKA-5 full-scale hydronautical array, composed of 25,600 individual electrokinetic microactuators with 350 um center-to-center spacings, arranged in a 40 x 40 pattern of unit cells, each composed of a 4 x 4 matrix of actuators; this array was successfully fabricated in a 7 x 7 cm² tile in 250 um thick mylar substrate material. MEMS design and fabrication processes were used to produce a top layer for the MEKA-5 hydronautical- scale array; the functionality incorporated in this top layer fabrication demonstrates the complete elements needed for microscale electrokinetic actuator arrays for sublayer control.