Innovative Hydraulic Retraction for a Cool Lightsaber Effect

The lightsaber is arguably the most iconic fictional weapon in film history. Yes, it is just a sci-fi sword. But a lightsaber is so much cooler than that would imply. And a big reason for the world’s fascination with lightsabers is the awesome extension and retraction effect. But it isn’t possible to recreate that in the real world — at least not with light alone. So hobbyists, enthusiasts, and cosplayers come up with ways to simulate the effect, and Marb may have developed the most innovative method with this hydraulic lightsaber effect.

The goal, of course, was to make a cylinder of light extend from the handle to a predetermined length, like a lightsaber in a Star Wars film. A common way to achieve that is with a telescoping translucent tube that slides into the hilt when the lightsaber is off. But Marb’s technique is much more fluid — because it relies on fluid.

When Marb’s lightsaber turns on, a syringe pumps liquid glycerin into a transparent tube. A small laser shines blue light into the glycerin, which refracts and scatters the light. The result is what appears to be a cylinder of glowing blue light that extends from the handle. Though we do have to use some selective vision to ignore the transparent tube until the lightsaber is turned on.

To pump the glycerin from a reservoir into the tube, Marb modified a large syringe with 3D-printed mounts to work with a linear actuator. As the linear actuator extends, it pushes on the syringe and forces the fluid into the tube.

There are, however, a couple of issues with this beyond the visible tube. Marb thinks it would benefit from a faster linear actuator, which would make the whole effect happen more quickly. He also says that degassing the glycerin would help to remove the trapped air that forms bubbles. But while it isn’t perfect, we have to give this project points for being a very creative solution to a problem many of have tried to solve.