The idea aims to generate more lift out of the traditional airfoil arrangement. The airfoil shape will contain a duct as shown in figure. The air inside the duct will again follow an airfoil contour only. Although the air flow to the main contour will get reduced, still the net lift will be increased because of increased contact area of divided flows. This can be easily shown using principles of fluid and flow mechanics. This will add up to the lift generated by main airfoil in accordance with Bernoulli's principle. So, now lift by both the contours will add up generating more lift than the traditional approach.
The duct can be opened by a flap, which can be manually controlled or automated based on certain considerations. It can be most useful during takeoffs when more lift is required and the air speed is lower. During normal flight, such a structure will generate high turbulence of wind and is not advisable. The flap design can be optimized to generate smoothest flow.
However, the main concern is the highly sensitive nature of airplane design, which already works with a factor of safety of around 1.1-1.2, to reduce the maximum weight. This design will cause changes in the wing, fuselage and related structure due to strength considerations, and hence the challenge.