Complex sentence: Molecular propeller is a molecule that propels fluids when rotated, due to its designed shape that is analogous to macroscopic propellers: it has several molecular-scale blades attached at a certain pitch angle around the circumference of a shaft, aligned along the rotational axis.
Split into simpler sentences: Molecular propeller is a molecule that propels fluids when rotated, due to its special shape. It can be designed in analogy to macroscopic propellers, as a molecular system with several blades attached at a certain pitch angle around the circumference of a shaft, aligned along the rotational axis.