How Slits Turn a Sheet into a Wing express
A flat sheet with slits in a flow of water or air behaves like self-adjusting blinds. The pressure opens the gaps, and each strip of material tilts, turning into a miniature wing. Thus, even a sheet placed perpendicular to the flow generates not only drag but also significant lateral lift.
By altering the cut pattern or material stiffness (e.g., carbon fiber), you can switch the surface between 'flight' and 'braking' modes without any moving parts. The aerodynamic function is encoded in the pattern itself, and the reversibility of the opening means that entropy barely increases, and the material doesn't wear out.
The term 'kirigami' comes from the Japanese words 'kiru' (to cut) and 'kami' (paper). Unlike origami, cuts are not only allowed here but are a key design element.