Conventional robots have rigid underlying structures which limit their ability to interact with their environment. Their manipulators have rigid links and can manipulate objects using only their specialized end effectors. Such robots often have trouble navigating in unstructured and congested environments.

Animals and plants exhibit complex movement with soft structures which lack rigid parts. Muscular hydrostats (such as octopus arms or elephant trunks) are composed of muscle and connective tissue; and plant cells can alter shapes when pressurized by osmosis. For some time, researchers have been inspired by biology to conceive “soft robots”. Equipped with a soft structure and surplus of freedom, these robots can be used for difficult tasks in unstructured situations. Let’s explore a few.

The “green cross”

This robot was developed by researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and could pave the way to fully untethered robots for space exploration, search and rescue systems, biomimetics, medical surgery, rehabilitation and other applications.

The new soft robot, powered by pressurized air, replaces multiple control systems with one input, reducing the number, weight and complexity of the components required to power it.

“Simplifying soft robots” by Harvard John A. Paulson School of Engineering and Applied Sciences, YouTube.

“Before this research, we couldn’t build fluidic soft robots without independently controlling each actuator through separate input lines and pressure supplies and a complex actuation process,” stated Nikolaos Vasios, a graduate student at SEAS, and the first author of the research. “Now, we can embed the functionality of fluidic soft robots in their design, allowing for a substantial simplification in their actuation.” he added.

EuMoBot

Inspired by euglenoids (one of the best-known groups of swimming flagellates), Krishna Manaswi Digumarti and co-workers at the Department of Engineering and Mathematics at the University of Bristol (UK) presented the design and development of EuMoBot, a multi-segmented soft robot. The biomimetic robot could replicate large body deformations for locomotion. In the study, the scientists engineered two robots at different sizes to operate with a constant internal volume.

“Fabrication of the multi-segment soft robot by bonding together three HEB actuators.” Credit: RSIF, doi: 10.1098/rsif.2018.0301 (Fair Use).

The engineering protocol utilized the hyperelasticity of fluid-filled elastomeric chambers to replicate the movement of euglenoids. The smaller robot moved at a speed of 1/5 body lengths per cycle, whereas the larger robot moved at a speed of 1/10 body lengths per cycle. The study showed as to how soft robots could be employed to change shape and replicate biological motion, while acting as a tool to study biomimetics (synthetic methods which mimic biochemical processes).

LEeCH

Engineers from the Toyohashi University of Technology in Japan and the University of Cambridge have built the Longitudinally Extensible Continuum-robot (LEeCH) which is inspired by the Hirudinea species (also known as leeches) that have suckers at either end of their flexible bodies.

“Wall-climbing robot Inspired by a leech” by Toyohashi University of Technology, YouTube.

“I came up with the idea in the bathroom of my house. The shower hose went wild as if it had a life when I inadvertently turned on the faucet at maximum,” says Ayato Kanada, lead author of the study. “Then an idea occurred to me that if I could manipulate a hose, I might be able to make a robot with the dynamic movement of a living creature.” he added. LEeCH can climb straight up vertical walls, move over obstacles such as steps, or jump from one wall to another.

It is composed of three flexible tubes connected parallelly that can bend or extend by controlling the length of each flexible tube fed by the gear. A suction cup at either end of its long, flexible body gives LEeCH a strong grip as it climbs against gravity. With their light and soft bodies, such robots can survive dangerous falls.

Snakeskin robot

This soft robot (again courtesy of Harvard University — SEAS) is basically a silicone rubber tube. What’s special about it is its “skin”: a thin, stretchable plastic sheet cut with a laser.

“Snakeskin Robot” by Harvard University, YouTube.

The cuts, shaped liked triangles or circles, were made to resemble the scales of snakeskin. When air is pumped into the tube, the robot expands and contracts, enabling the scales to “pop up”, lodge in the surface, and pull the robot forward. In a study published in Science Robotics, scientists showed that the artificial snakeskins work against unrefined surfaces such as asphalt and concrete. Such robots could be scaled down and utilized to deliver drugs inside arteries, or for disaster situations when there is a great need to crawl inside narrow spaces.

Yes, the future of robotics could well be soft (pun intended of course). 🐙