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Researchers at the University of the West of England have used 3D printing to create a spherical rover that can be powered entirely using photosynthesis.
Composed of an algae ball housed inside a PLA casing, this Marimo Actuated Rover System or ‘MARS’ device, is capable of accumulating sufficient oxygen in a given area to enable it to roll in that direction. Using this ‘rotational torque’ phenomenon, the team say that their system can move autonomously, potentially making it ideal for carrying sensors into habitats which humans can’t otherwise reach.
Photosynthetic power sourcing
According to the researchers, many of the conventional rovers used to access challenging environments suffer from issues around their “robustness and autonomous operation in uncertain conditions.” One potential way the team has identified of improving upon existing designs, is to make their power sources more self-sufficient, with solar energy representing a promising alternative.
In the natural world, photosynthesis is used to organically gather this solar energy, as organisms convert the photons gathered from sunlight into glucose, oxygen and water via reactions that take place in their respective electron transport systems, that make them ideal as a power source for rovers requiring reliable propulsion.
However, the scientists say that the chloroplasts used to achieve this in green plants have a maximum photosynthetic efficiency of 36%. In order to fully-optimize the photosynthetic process, the team therefore propose “combining it with human engineering,” in a way that yields a novel autonomous rover with the ability to not only navigate remotely, but do so without constantly needing to be refueled.
Introducing the ‘MARS’ Marimo Ball
Essentially, the researchers’ approach to autonomous travel revolves around the Marimo algae, which naturally congregates into balls in freshwater rivers. In its typical environment, the plantlife observably rises and falls between currents, as its filamentous structure and naturally-occurring internal compartments attract bubbles that periodically lift it to the surface before dissipating, causing it to sink.
When integrated into partially-Ultimaker S5-3D printed spheres, filled with a lower density of air than water, the photosynthetic process of these balls can therefore be used to generate enough oxygen asymmetrically, to shift the device’s center of mass, causing it to move.
“If the rover is spherical, this facilitates freedom to move in three dimensions,” explain the scientists in their paper. “The low density of gas compared to water means the gas rises in the form of bubbles to minimize its overall Potential Energy (PE). As the volume of trapped gas increases over time the peak rotational torque increases until motion is achieved.”
Inside the MARS rover, such Marimo balls are held in place by 3D printed enclosures, initially designed to feature a range of shapes, to allow the team to identify the geometry and tessellation factor for achieving the optimal energy yield. Interestingly, during testing, in which each of four prototypes were deployed underwater in a pool, those with the largest integrated ‘vents’ performed best.
In their paper, the team theorized that this was due to the need for “reliable bubble release,” which meant that the number, location and size of each prototype’s vents “had a significant impact on [their] speed and smoothness of rotation.”
Likewise, the researchers discovered that those containing split Marimo balls in pentagonal enclosures achieved the best gas release, while their fastest iteration was capable of traveling at up to 275mm per hour. Given these demonstrable autonomous drive capabilities, the scientists say that the MARS could be deployed in future Antarctic expeditions, where self-sufficiency is more vital than speed.
“Potential applications for the MARS platform can be found in situations where speed of operation is not imperative but device longevity is,” concluded the scientists in their paper. “For example, strategic water sampling and water quality monitoring, inspection of deep underground mines, mediating interactions between underwater animals, studies and control of fish groups or ecological studies.”
Autonomous 3D printed vehicles
As 3D printing’s compatibility with ultra-resistant materials continues to grow, so does the technology’s application in the production of all-terrain vehicles, designed to be robust enough to tackle anything nature can throw at them.
In one such use case, late last year, Lockheed Martin used MakerBot 3D printing to develop and test elements of an AI-powered lunar rover. Designed for deployment during NASA’s mission to return to the Moon, the vehicle’s system housings and sensor mounts were made from durable ABS, in a way that was said to make them UV, heat and moisture-resistant.
At China’s Tianjin University, meanwhile, researchers have come up with a 3D printed pipe climbing robot, developed for applications here on terra firma. Featuring a series of soft bending mechanisms and modular grippers, the tiny bot is capable of climbing oddly-shaped infrastructure, and fixing piping that would otherwise be tricky to access.
The researchers’ findings are detailed in their paper titled “Marimo actuated rover systems,” which was co-authored by Neil Phillips, Thomas C. Draper, Richard Mayne, Darren M. Reynolds and Andrew Adamatzky.
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Featured image shows the researchers’ 3D printed ‘MARS’ rover. Image via the University of the West of England.