AsiaIndustrial NetNews: Using a soft, flexible body can makeRobotgetting better and better. There are many good reasons to do so: Compliant robots can work more safely and can take advantage of many unique locomotion patterns.
In the last week or so, two new approaches to soft robotic locomotion have emerged: one uses an external magnetic field, while the other uses an electric field to drive fluttering fins.
The robotic rays, developed at Zhejiang University in Hangzhou, China, are propelled by soft wings made of dielectric elastomers that bend when electricity is applied to them. Dielectric elastomers are very responsive and move relatively fast, but they require very high voltages (around 10 kV) to make them work. Traditionally, dielectric elastomers are covered in insulating layers, but for this aquatic application, the researchers just submerged all of the insulating layers in water, relying on the water as the electrodes and electric field.
There are several other reasons why this design is notable. First, it’s almost completely transparent. Full see-through of body, fins, tail and elastomeric muscles. When adding the electronics and battery required for phone-free operation, the effect is slightly damaged, but in fact a 450mAh 3.7V battery will keep swimming at 1.1 solid for 3 hours and 15 minutes and is even portable a small camera. With a maximum unrestricted speed of 6.4 cm/s, the robotic fish will swim happily in water temperatures ranging from just above freezing to nearly 75°C.
The overall efficiency of this Robot is comparable to that of rainbow trout, as a 25 cm long trout consumes about 0.03 watts to move at a speed of 10 cm/s. Of course, real trout can move faster and more dynamically, but for robots, the biological level of efficiency is much higher. The researchers aren’t ready to come up with any specific applications for robotics, so it’s probably best to simply take a look at how these technologies work, leaving practical robots for the next generation.
Meanwhile, at North Carolina State University, Raleigh, researchers have been working on a more fundamental actuation technique with the potential for soft robotics. They’re not exactly at the robotics stage, but they’ve managed to turn polymer membranes into muscles that can be remotely actuated with magnetic fields. The researchers introduced iron particles into a liquid polymer mixture and then applied a magnetic field to the magnetic beads, aligning the particles themselves with the parallel chains. When dried and cut into strips, the chains persist, and when another magnetic field is applied to them, the chains align with and work with the polymer.
By changing the strength and direction of the magnetic field and tweaking the structure of the polymer, the researchers were able to create a set of potentially very useful soft actuators, including a cantilever that can lift up to 50 times its own weight, extending and contracting accordion structures like muscles Likewise, a tube with traveling compressional waves acts as a peristaltic pump.
These actuators seem to be inexpensive and easy to construct, and while they are only constrained in response to external forces, they will work well in the context of tiny robots inside your body or deployable robotic structures that don’t require constant activation .
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