Recently discovered Sharrow boat props. Apparently the guy who invented them first developed the the concept for reducing noise from drones filming orchestras. I'm surprised we aren't seeing more widespread availability yet of "tipless" drone propellers.
There may have been new attempts, but when I last looked into these types of drone propellers, nobody seems to have been successfully able to demonstrate they actually offer significant improvements (either noise or efficiency) over traditional designs.
To be fair, the limiting factor might be manufacturing capabilities, given most attempts were using 3d printed propellers which results in terrible surface finish, compared to injection molding.
To be fair, the limiting factor might be manufacturing capabilities, given most attempts were using 3d printed propellers which results in terrible surface finish, compared to injection molding.