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Smart Microrobots can self-reconfigure, merge, split, and heal themselves

We are on the verge of new transitions that will transform robotics. One is already underway—the miniaturization of robots, to the point where invisible, microscopic robots could be around us and inside us, performing monitoring or even life-saving functions. We have seen systematic bio-inspired efforts to create microbe-like, microscopic robots. They are a part of a new trend in what is called “tiny robot” research.

 

The range of technologies and uses for tiny robots is broad, from drones to pills, and from surveillance and rescue to biomedicine. The trend has parallels with miniaturization in the electronics industry, where exponentially smaller and more energy-efficient units have been produced each generation.

 

Microrobots are usually smaller than a millimetre but as large as a micron — that’s between a 1,000th of a metre to a millionth of a metre in size.

 

Recently, a team of researchers from Stanford University, California, achieved the first milestone towards the development of 7.8mm wide origami robots: a proof-of- concept prototype. They dubbed it a millirobot. The robot uses the folding/unfolding of Kresling origami to roll, flip and spin. These robots are operated wirelessly using magnetic fields to move in narrow spaces and morph their shape for medical tasks, such as disease diagnosis, drug delivery, and even surgery.

 

 

 

Challenges

For biomedical applications, the synthesis of micro/nanorobots integrating respective
functions at the microscopic scale is essential. Achieving effective actuation, transportation
and wireless manipulation on small scales has been a major challenge. Due to their unique
size and dynamics, there are many micro/nanofluidic problems involved in the propulsion
and application of swimming micro/nanorobots.

 

Considering that micro/nanoscale objects in the movement are limited by Brownian motion as well as low Reynolds numbers (the ratio of inertial forces over viscous forces), designs based on classical mechanics are no longer applicable to micro/nanorobots.

 

In addition, individual robot shows limited ability in executing tasks. As the need for biomedical application scenarios grows, micro/nanorobots are expected to perform in a cluster manner. There will be greater opportunities for application if the individual robot can self-assemble into cluster form and interact with each other to carry out specified tasks cooperatively.

 

 

Sustainability and energy efficiency are front-and-center issues as robotics becomes more useful, more affordable, and therefore more ubiquitous. This is especially true of microscopic robots that would be too small and cheap to collect and recycle traditionally. All current microelectronics and most micro-robots rely heavily on lithography for their manufacturing. This top-down method, though extremely precise, is rather wasteful. For highly integrated chips, a 20 g chip requires 1.7 kg of materials inputs. Bottom-up sustainable approaches can mitigate/eliminate such waste.

 

To put this statement in context, examples already include magnetic microswimmer robots, employing bacterial modes of locomotion, which are biocompatible, and potentially ready for integration within our bodies. They require lithography to create clever microscopic screw-type structures, enough to produce the cork-screw swimming movement. Such micro-robots have encapsulated, picked, and delivered cells, protecting them from shear forces in fluids, while others have captured non-motile sperm, propelled them, and ultimately fertilized an egg.

 

Organisms in nature have inspired researchers with the solution to the above mentioned problems. Tiny single-celled microorganism can actively swim, sense their surroundings, and react to external stimuli. Artificial micro/nanorobots have been developed by imitating the structure and propulsion principles of biological microswimmers. Replicating the structure design of microorganisms enables the artificial microrobots to propel. Moreover, the exploration of a working principle in a collective manner of robots is noteworthy. Most individual organisms in nature can associate with each other and live in a swarm to perform biological activities efficiently

 

 

MIT researchers create world’s smallest robot for medical, industrial application

Researchers at U.S. Massachusetts Institute of Technology (MIT) have created the world’s smallest robots that can be used for medical diagnosis or industrial application such as detection of oil or gas leakage, a study said Monday.

 

According to the study published in the journal Nature Nanotechnology, the tiny robots are devices about the size of a human egg cell, which consist of tiny electronic circuits made of two-dimensional materials, piggybacking on minuscule particles called colloids.

 

They are insoluble particles or molecules anywhere from a billionth to a millionth of a meter across, and they can stay afloat indefinitely in a liquid or in air.

 

The self-powered cell-size robots don’t need any external power source or even internal batteries. Their circuits get the trickle of electricity from a photodiode to power their computation and memory circuits.

 

That’s powerful enough for the tiny robots to sense information about their environment, store data in their memory, and make it possible to retrieve data upon mission completed.

 

MIT scientists hope their efforts can lay the groundwork for the tiny robotic devices to be used in the medical sector like the diagnosis in human digestive system, where they pass through the digestive tract searching for signs of inflammation or other disease indicators.

 

“Colloids can access environments and travel in ways that other materials can’t,” said Michael Strano, a professor of Chemical Engineering at MIT and a senior author of the study.

 

The researchers also want the tiny robots to be used for detection of oil or gas leakages in pipelines or waft through air to measure compounds inside a chemical processor or refinery.

 

In an industrial scenario, the robots can be inserted into one end of a pipeline and flow along toward the other end while checking for the presence of contaminants that indicate where potential problems are located. Such devices could ultimately be a boon for the oil and gas industry, Strano said.

 

Smart microrobots that can adapt to their surroundings

The University of Brussels Researchers Nithin Mathews, Anders Lyhne Christensen, Rehan O’Grady, Francesco Mondada & Marco Dorigo have developed modular robots — made up of many different units — that can merge, split, and reconfigure themselves: all while maintaining sensory control. They call them mergeable nervous system robots (MNS robots). One individual robot acts as a centralized decision-making robot, referred to as the brain units — but additional robots can autonomously join the brain unit as and when needed, to change the shape and structure of the overall system. They can heal themselves by replacing malfunctioning parts — even when a brain unit malfunctions.

 

In an article appearing in Science Advances (“Adaptive locomotion of artificial microswimmers”), the scientists describe the method they have developed for “programming” the robot’s shape so that it can easily travel through fluids that are dense, viscous or moving at rapid speeds.

 

 

They are made of hydrogel nanocomposites that contain magnetic nanoparticles allowing them to be controlled via an electromagnetic field.

Embodied intelligence

When we think of robots, we generally think of bulky machines equipped with complex systems of electronics, sensors, batteries and actuators. But on a microscopic scale, robots are entirely different. Fabricating miniaturized robots presents a host of challenges, which the scientists addressed using an origami-based folding method. Their novel locomotion strategy employs embodied intelligence, which is an alternative to the classical computation paradigm that is performed by embedded electronic systems.

 

Our robots have a special composition and structure that allow them to adapt to the characteristics of the fluid they are moving through. For instance, if they encounter a change in viscosity or osmotic concentration, they modify their shape to maintain their speed and maneuverability without losing control of the direction of motion,” says Sakar. These deformations can be “programmed” in advance so as to maximize performance without the use of cumbersome sensors or actuators. The robots can be either controlled using an electromagnetic field or left to navigate on their own through cavities by utilizing fluid flow. Either way, they will automatically morph into the most efficient shape.

Inspired by nature

“Nature has evolved a multitude of microorganisms that change shape as their environmental conditions change. This basic principle inspired our microrobot design. The key challenge for us was to develop the physics that describe the types of changes we were interested in, and then to integrate this with new fabrication technologies,” says Nelson.

 

In addition to offering enhanced effectiveness, these miniaturized soft robots can also be manufactured easily at a reasonable cost. For now, the research team is working on improving the performance for swimming through complex fluids like those found in the human body.

 

New modular robots can merge, split, and even heal themselves

The crucial point of this research is in the logic control system that the robots use. Previous systems for sensory and motor control were closely linked to the body shape and type of the robots: proprioception had to be reprogrammed for each new robotic body. The brain centrally sends out commands to the various parts of the body; but since the shape of that body is built-in, it’s not a very flexible nervous system. This system has a different approach: the commands are given to the brain unit with a higher level of logic. It can then, by merging and splitting the robot units, adapt its body to respond in an appropriate way to its environment.

 

The researchers hope that more flexible robotics systems will be able to solve many of the problems they encounter, relying on vast computing power to mimic the process of evolution that adapts natural bodies to their environments. In the paper from Nature Communications that describes the research, they conclude:

 

“Our vision is that, in the future, robots will no longer be designed and built for a particular task. Instead, we will design composable robotic units that give robots the flexibility to autonomously adapt their capabilities, shape and size to changing task requirements.” Currently, the system is ten fairly small units that can cooperate with each other. But perhaps, in the future, we won’t need to create twenty specialized robots for twenty different tasks: we’ll only need one.

 

Self-reconfigurable modular robots

Modular self-reconfiguring robotic systems or self-reconfigurable modular robots are autonomous kinematic machines with variable morphology. Beyond conventional actuation, sensing and control typically found in fixed-morphology robots, self-reconfiguring robots are also able to deliberately change their own shape by rearranging the connectivity of their parts, in order to adapt to new circumstances, perform new tasks, or recover from damage.

 

For example, a robot made of such components could assume a worm-like shape to move through a narrow pipe, reassemble into something with spider-like legs to cross uneven terrain, then form a third arbitrary object (like a ball or wheel that can spin itself) to move quickly over a fairly flat terrain; it can also be used for making “fixed” objects, such as walls, shelters, or buildings.

Nanotech pioneer J. Storrs Hall’s original concept, the Utility Fog, consists of a swarm of nanobots (“Foglets”) that can take the shape of virtually anything, and change shape on the fly. Researchers from many universities including  MIT, Lausanne, and the University of Brussels are developing modular robots. Various teams of researchers are working, for instance, on paper-like robots that can fold themselves origami-style.

Daniela Rus, director of the computer science and artificial intelligence laboratory at the Massachusetts Institute of Technology, envisions origami bots that can shape themselves into tools to perform medical procedures or deliver drugs inside the body. In a demonstration by her team in May 2016, a tiny origami bot made from pig intestine was able to unfold itself from a swallowed capsule in a simulated stomach and move across the stomach wall with the help of an external magnet.

Structure and control

Modular robots are usually composed of multiple building blocks of a relatively small repertoire, with uniform docking interfaces that allow transfer of mechanical forces and moments, electrical power and communication throughout the robot.

 

The modular building blocks usually consist of some primary structural actuated unit, and potentially additional specialized units such as grippers, feet, wheels, cameras, payload and energy storage and generation.

 

In some cases this involves each module having 2 or more connectors for connecting several together. They can contain electronics, sensors, computer processors, memory and power supplies; they can also contain actuators that are used for manipulating their location in the environment and in relation with each other. A feature found in some cases is the ability of the modules to automatically connect and disconnect themselves to and from each other, and to form into many objects or perform many tasks moving or manipulating the environment.

 

 

A taxonomy of architectures

Modular self-reconfiguring robotic systems can be generally classified into several architectural groups by the geometric arrangement of their unit (lattice vs. chain). Several systems exhibit hybrid properties, and modular robots have also been classified into the two categories of Mobile Configuration Change (MCC) and Whole Body Locomotion (WBL).

 

Lattice architecture have their units connecting their docking interfaces at points into virtual cells of some regular grid. This network of docking points can be compared to atoms in a crystal and the grid to the lattice of that crystal. Therefore, the kinematical features of lattice robots can be characterized by their corresponding crystallographic displacement groups (chiral space groups).

 

Usually few units are sufficient to accomplish a reconfiguration step. Lattice architectures allows a simpler mechanical design and a simpler computational representation and reconfiguration planning that can be more easily scaled to complex systems.

 

Chain architecture do not use a virtual network of docking points for their units. The units are able to reach any point in the space and are therefore more versatile, but a chain of many units may be necessary to reach a point making it usually more difficult to accomplish a reconfiguration step. Such systems are also more computationally difficult to represent and analyze.

 

Hybrid architecture takes advantages of both previous architectures. Control and mechanism are designed for lattice reconfiguration but also allow to reach any point in the space

 

Military applications

A swarm of small robots that can assemble and disassemble on command might be deployed to do reconnaissance in a combat zone or to survey damage after a natural disaster. And if one component gets damaged or destroyed in the process, the rest would be able to reassemble and carry on.

 

The ability to develop nano based micro-sensors that could be scattered on the ocean floor to detect enemy submarines could lead to a paradigm shift in the Navy’s undersea warfare systems and capabilities. The same concept can be tailored for detecting enemy mines in the littorals. These furturistic nano based sensors will be networked and can be laid/controlled from distant locations.

 

 

 

 

 

References and Resources also include:

https://en.wikipedia.org/wiki/Self-reconfiguring_modular_robot

http://www.xinhuanet.com/english/2018-07/24/c_137345174.htm

https://www.nanowerk.com/nanotechnology-news2/newsid=51929.php

 

 

About Rajesh Uppal

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