The obvious solution was to adapt the toroidal shape for a PC fan. He was familiar with the idea from similar screws on boats that are commercially available. You can see his tests in the video below.

A team at MIT’s Lincoln Lab has developed a new propeller shape that significantly reduces ... researchers iterated on various toroidal propeller geometries until arriving at one that ...

He proposed the toroidal shape (like a donut) as a potential solution for navigating viscous environments. However, despite ...

Jinlin and colleagues wanted to determine whether observed radio source asymmetries indicate that magnetic fields in the galactic halo still have a toroidal shape when the effects of the ...