So, to quote pterosaur.net:
Unlike the wings of birds, the wings of pterosaurs would have tended to change shape under aerodynamic load - something often referred to as 'passive cambering'. Camber refers to the curvature of a wing in cross section. Because pterosaurs possessed membrane wings, the wing would have been elastic (though we do not know exactly how compliant the wing would have been) and this would have allowed the wing to stretch slightly when producing fluid forces (i.e. lift and drag). This stretching would result in a slight upward "bowing" of the wing membrane, thereby increasing camber. At the same time, it is plausible that active mechanisms (i.e. muscular actions) in the wing membrane could have limited passive cambering or allowed different regions of the wing to differ in their response to external forces - thereby producing variable camber over the wing. The compliance and shape of the pterosaur wing was likely capable of producing very large lift coefficients. Work by Colin Palmer and others has demonstrated that a pterosaur wing allowed to camber completely passively during flight might very well have achieved lift coefficients of nearly 2.0 for short periods of time, which is quite high for a large flying animal (by way of comparison, large birds usually max out at a CL of about 1.6).
However, feathered wings have a neat little mechanism that allows them to reduce the air resistance of the wing in the upstroke and also redirect the air flow under the bird for some extra lift.
Each feather has a major (greater) side and a minor (lesser) side, meaning that the shaft or rachis does not run down the center of the feather. Rather it runs longitudinally of center with the lesser or minor side to the front and the greater or major side to the rear of the feather. This feather anatomy, during flight and flapping of the wings, causes a rotation of the feather in its follicle. The rotation occurs in the up motion of the wing. The greater side points down, letting air slip through the wing. This essentially breaks the integrity of the wing, allowing for a much easier movement in the up direction. The integrity of the wing is reestablished in the down movement, which allows for part of the lift inherent in bird wings. This function is most important in taking off or achieving lift at very low or slow speeds where the bird is reaching up and grabbing air and pulling itself up. At high speeds the air foil function of the wing provides most of the lift needed to stay in flight.
But would it be theoretically possible for a living creature to have a wing that's capable of both tricks? If yes, how would it work?