A robot that mimics the way salamanders walk and swim could become a useful tool in developing neuroprosthetic devices for paraplegic patients and amputees.
The robot - dubbed ‘Pleurobot’ - is based on X-ray videos of salamanders in motion and was developed by a team at Ecole Polytechnique Fédérale de Lausanne in Switzerland.
The robot features 3D-printed bones, motorized joints and electronic circuitry as its ‘nervous system’.
Inspired by the salamander species Pleurodeles waltl, ‘Pleurobot’ can walk, crawl, and even swim underwater.
Although the team has built salamander robots before, this is the first time they have built a robot that is accurately based on the 3D motion of the animal’s skeleton.
X-ray videos of a salamander from the top and the side were used, tracking up to 64 points along its skeleton while it performed different types of motion in water and on the ground.
"What is new is really our approach to building Pleurobot," said Auke Ijspeert who led the team. "It involves striking a balance between designing a simplified bone structure and replicating the salamander's gait in three dimensions."
Pleurobot was designed with fewer bones and joints than the real-life creature and features only 27 motors and 11 segments along its spine in contrast to the amphibian’s 40 vertebrae and multiple joints, some of which can even rotate freely and move side-to-side or up and down.
In the design process, the researchers identified the minimum number of motorized segments required, as well as the optimal placement along the robot’s body. As a result, it could replicate many of the salamander’s types of movement.
"Animal locomotion is an inherently complex process," said Kostas Karakasilliotis who designed the first versions of the Pleurobot. "Modern tools like cineradiography, 3D printing and fast computing help us draw closer and closer to understanding and replicating it."
Vertebrate locomotion is a sophisticated interplay between the spinal cord, the body and the environment. It is the spinal cord that controls motion, not the brain, so mimicking the salamander's movement gives insight into how the spinal cord works and how it interacts with the body.
A robot that so closely mimics the biomechanical properties of the body can become a useful scientific tool to investigate these interactions.
Neurobiologists have shown that electrical stimulation of the spinal cord is what determines whether the salamander walks, crawls or swims.
At the lowest level of stimulation, the salamander walks; with higher stimulation, its pace increases, and beyond some threshold the salamander begins to swim. Pleurobot is programmed to accurately mimic all of these functions.
Ijspeert believes that understanding the fundamentals of this interplay between the spinal cord and the body's locomotion will help with the development of future therapies and neuroprosthetic devices for paraplegic patients and amputees. He also thinks that the design methodology used for the Pleurobot can help develop other types of “biorobots”, which will become important tools in neuroscience and biomechanics.
Meanwhile a small, squishy vehicle that is equipped with soft wheels in order to allow it to roll easily over rough terrain and run underwater has been demonstrated by its creators at Rutgers University
Future versions of the vehicle are being cited as suitable for search and rescue missions after disasters, as well as deep space and planet exploration, and manipulating objects during magnetic resonance imaging (MRI).
It features a soft motor that provides torque without bending or extending its housing.
"The introduction of a wheel and axle assembly in soft robotics should enable vast improvement in the manipulation and mobility of devices," said Aaron Mazzeo who worked on the project. "We would very much like to continue developing soft motors for future applications and develop the science to understand the requirements that improve their performance."
The soft, metal-free motors are touted as being suitable for harsh environments with electromagnetic fields, while being able to withstand strong impacts – it survived a fall eight times its height.
It is also capable of braking the motor and holding it in a fixed position without the need for extra power.
To create the vehicle, the Rutgers engineers used silicone rubber that is nearly one million times softer than aluminium.
"If you build a robot or vehicle with hard components, you have to have many sophisticated joints so the whole body can handle complex or rocky terrain," said Xiangyu Gong who also worked on the project. "For us, the whole design is very simple, but it works very well because the whole body is soft and can negotiate complex terrain."
The team predicts that future uses for the technology include amphibious vehicles that could traverse rugged lakebeds; search and rescue missions in extreme environments and varied terrains, such as irregular tunnels; shock-absorbing vehicles that could be used as landers equipped with parachutes; and elbow-like systems with limbs on either side.
"We think these robots also would be useful for working around children or animals and you could envision them being helpful in hospitals," Mazzeo said. "There are opportunities also for toys and for creating educational science or engineering kits."