The gear less flapping can be achieved by either piezo actuator or SMA (Shape Memory Alloy). The Piezo can be used to generate high frequency flapping but demands high voltage and also the displacement is low. This displacement can be amplified by means of some amplifying meshanism. In case of SMA the deflection is pretty good but the flapping frequency is low as the wire takes time to cool to retract back to its original position. Please find the attached images and videos on this page which might give you a better idea.