3d-printed underwater propulsion

[rhoenix]

hen searching for a novel solution to a problem, sometimes the best bet is to look to nature first. Evolution has had uncountable eons to come up with efficient workarounds, so why not borrow some concepts? Researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation are doing just that in the search for a silent underwater propulsion system. It turns out cephalopods have that figured out.

This class of sea creatures, which include both squid and octopus, get around through a variety of means. One commonality among most members of the class is water jet propulsion. This is the aspect that intrigued the research team, but it’s not a simple process — there are a lot of moving parts.

The animal sucks water into a specialized cavity in its mantle and closes off the opening when it’s time to move. The water is then put under pressure and expelled through a siphon. The direction of the siphon can be changed to allow the creature to steer very accurately. This underwater jet propulsion can be used to avoid danger with quick bursts of speed.

Reproducing this system has proven challenging, but things are starting to come together with the help of 3D printing. The octopod-inspired propulsion system consists of four bulbs made from a flexible plastic polymer (sometimes called elastomer). Water is sucked into each bulb with an actuator. Whereas a squid or octopus has a muscular closure to seal water in the mantle, the synthetic reproduction uses a recirculation valve to keep water from flowing back out of the bulb. A hydraulic piston contracts the bulb via an integrated cable and the water is expelled with great force.

To make this contraption in any way effective, scientists needed an efficient way to produce it, and that’s where 3D printing comes in. With the exception of the hydraulic piston, the entire structure of the jets can be built in a single step. Like most 3D printing, this is accomplished with fused deposition modeling. A thermoplastic like polyurethane is heated, then extruded layer-by-layer to create complex 3D shapes.

Cephalopods run the size gamut from almost microscopic to gigantic, and researchers have found this nature-inspired propulsion system is similarly scalable. The current design could provide efficient propulsion with bulbs up to two meters in diameter — double what current production facilities allow. Researchers are investigating the possibility of using multiple robotic 3D printing extrusion heads to build a larger version of this system.

The jet bulbs are sufficient for powering small boats and various types of watercraft, but larger versions could power more massive ships. The main advantage of this system would be low cost and easy replacement of components via a 3D printer, but it would also be a much safer method of propulsion in general. Propellers are a hazard to sea life, not to mention any humans that might happen to tumble off the back of a boat.

Well, I'm intrigued. If this has the same or greater propulsive potential than standard propellers do, then I'm all for it.