The air molecules at the surface of a wing are effectively stationary (see the no-slip condition).
Attempts have been made over the years to delay the onset of this flow separation by careful design and smooth surfaces.
As flow separation results from the velocity deficit that is characteristic of boundary layers, suction attempts to remove the boundary layer from the surface before it can separate.
The technology was first developed by Werner Pfenninger in the Second World War and has been researched almost continuously since.
However, about 500 watts of power would be needed to drive the pumps which would mean covering the glider with solar panels and would increase the cost greatly.