The ant is a marvel honed by millions of years of evolution. Lift loads that far exceed your own weight and work in groups with precise coordination. After exploring the environment and finding a food source, the chemical trail of a single specimen quickly guides the rest of the anthill to its position. Working together, these insects perform feats that on a human scale would amaze us. “Viewed as mechanical systems they are impressive. When we began to study them, we thought they could withstand a thousand times their weight, ”says Carlos Castro, professor of Aerospace Engineering at Ohio State University, in a biomechanics study. Reality? His team found that they withstand the pressure exerted by a weight of up to 5,000 times their body mass.
Apart from their strength, they are surprising for their speed: an ant travels three hundred meters in an hour. The secret, like that of other insects, lies as much in their surprising biology as in their size. Being so tiny has drawbacks (a footfall kills you), but many advantages. With a small body mass, it is easier to fly or stay attached to any surface, and great energy resources are not required to sustain prolonged activity .
Technology that mimics nature
Can we be inspired by these physical properties of insects to create electronic devices? Will our robots get better if we make them smaller instead of imitations of the human form? The answer is yes. To find proof, just visit Stanford University in California, where a team of researchers led by David Christensen and Elliot Hawkes has created the MicroTugs, miniature robots capable of dragging large objects.
The smallest of these machines, weighing nine grams, climbs a glass carrying a kilo on its back. The largest, twelve grams, drags twenty-kilo weights on a horizontal surface. They achieve this thanks to an adhesion mechanism that is impossible to reproduce in a larger-scale robot, a rubber that increases friction so much that it makes it possible to pull these objects with a thread wound around a spool and a small electric motor.
These devices are part of the family of micro-robots, devices often as advanced as the androids we see at tech shows or YouTube videos, but whose dimensions are measured in millimeters or a few centimeters. They take advantage of the small-scale world of insects and could play a determining role in our future. To be precise, the term microrobot defines machines with characteristic dimensions of less than one millimeter in length, although, in general, any device approximately the size of an insect – or with biomechanical properties similar to those of an insect – is considered as such. “Humans fight against gravity and friction to transport objects or move, but at smaller scales other properties and forces can be harnessed for the required tasks,” says engineer Christensen.
Some walk on water
Any automaton that operates on that plane belongs to the group of micro-robots, but we can keep going down the scale. Nanobotics is also a booming discipline, encompassing machines less than ten microns in size; a micrometer or micron is equal to one millionth of a meter. The difference is not only in size. If micro-robotics are designed to operate in a world of human dimensions, nano-robotics often focus on manipulation at the molecular level .
It achieves this using microelectromechanical systems, also known as MEMS, for its acronym in English. These are incredibly small gears, clamps and motors made of silicon or polymers and smart metals capable of reacting and moving in the presence of electrical currents. Finding a clear boundary between the two disciplines can be difficult. One of the smallest nanorobots is 130 microns long . It is a small filament of a thickness less than that of a human hair and moves through a surface of electrodes that provide it with the necessary energy. This striking experiment has come out of the laboratories of the University of Dartmouth (USA), and at the moment it does not have a clear function. But other similar Lilliputian mills do.
Scientists from the University of Hong Kong have created a robot of similar dimensions that carries drugs to specific areas within the human body. They have not yet developed a working prototype, but this genre of devices could help fight diseases that do not have an easy cure or require risky and high-precision surgery. The Nobel Prize in Chemistry awarded last October has endorsed this evidence. The award went to the British Fraser Stoddart, the Dutch Bernard Feringa and the French Jean-Pierre Sauvage for designing and producing molecular machines. These molecules controllable by the supply of light, heat, electrical charge or other form of energy combine, for example, to form interlocking shafts and rings that make up structures 50,000 times thinner than a hair, as Sauvage achieved, who also rotated a molecule in a controlled way around another.
Cars that can only be seen with a microscope
For their part, Feringa and his team created a nanocar that moved across a metal surface powered by four molecular wheels controlled by light and electricity. This opens the door to numerous applications. Feringa quotes one: “Tiny robots could be created that, once injected into the body, look for cancer cells to destroy them.” Computing or the manufacture of incredibly durable and small batteries are presented as two other possible utilities.
They are extreme cases. Most laboratories and companies focus their research on mechanical devices between one and ten centimeters in length, which offer several advantages over traditional robots. Their smaller size and weight allow them to walk on water and adhere to walls, among other physical feats , and at the same time it is possible to integrate more complex instruments and sensors, such as cameras or small manipulator arms.
The idea of making tiny robots is not new and, as is often the case in technology, has its roots in science fiction. In imagining a world populated by mechanical humanoids, many writers ended up exploring concepts such as robotic animals, and, by extension, insects. Books and movies such as The Amazing Journey (1966), in which scientists reduce themselves to an almost molecular scale to penetrate the body of a patient, sparked interest in the possibility of making tiny machines. The arrival of semiconductors, integrated circuits and miniaturization techniques at the end of the last century made it possible to take the first steps in that direction. Today, micro-robotics is one of the engineering disciplines with the greatest projection.
More sustainable, faster and cheaper
We are in a field that interests the military, biotech companies and even construction companies, for various reasons. These machines consume less energy than the larger ones and are cheaper to manufacture, because they require fewer materials and are assembled in series. It is possible to equip them with new systems of propulsion and senseless locomotion in bulky devices, such as magnetic or electrostatic adhesion, and ultralight wings in the form of a membrane similar to those of bees, dragonflies, flies and mosquitoes.
They can also take advantage of new forms of power, such as small solar panels or thermoelectric generators that create current if there are minimal variations in temperature, or long-range wireless charging sources that would be unable to drive a large motor or power a conventional microprocessor; and their smallness makes them ideal in medicine, since they can act within the body without resorting to surgery.
The greatest advantage of these robots, apart from the difficulties of their construction, which we will deal with in the next part of the dossier, is not in what they achieve individually, but by working together. “The precision that can be achieved in their control enables them to collaborate with minimal redundancy and add their capabilities in a linear fashion,” says Christensen. Synchronized, two dozen of his MicroTugs manage to pull a midsize car.
They will be able to self-heal
These possibilities have changed the vision of many scientists, who no longer see future robotics as a universe of androids that help us in the most strenuous or dangerous tasks, but as an environment populated by swarms of small automata of all kinds that will perform jobs that we are unable to perform, or require a great investment of time and effort, from the transport of medicines to the parts of the body affected by a disease to the construction of buildings.
These robots will make copies of themselves, recycle and take advantage of nearby materials, and compensate for any breakdown that occurs in a unit . If a factory’s mechanical arm breaks down today, for example, the assembly line must be stopped until it is repaired. In a future of micro-robots, production would continue without interruption, because the robots themselves would repair their partner or a new one would take its place in a few seconds.
How close are we to this vision? Several obstacles remain to be overcome. The most important, autonomy. Such a machine can only integrate a very small battery , and, although there are techniques that could alleviate the energy needs of certain models, it is a field in which large investments will have to be made. In this, the smaller robots look a lot like the larger ones.
Another important problem is that of communications. Only in recent years have we begun to consider the difficulties associated with collective behavior in swarms and to work on software models that allow these types of machines to coordinate with each other. It is an issue with large-scale applications as well. If one day we have autonomous cars driving on the streets, it will be necessary for them to talk to each other and coordinate their movements to ensure maximum safety and efficiency.
However, there are very specific situations in which micro-robots can already be used as an alternative to larger machines. MIT engineers, in collaboration with the University of Sheffield, in the United Kingdom, and the Tokyo Institute of Technology, in Japan, have created a device that is taken as a pill and is capable of recovering in a few hours a battery ingested by a child , a frequent problem that only in North America affects more than 3,500 children a year and that requires a complex surgical intervention. The robot folds like an origami sheet into the capsule, but once in the stomach it moves to find and retrieve the battery before it does irreparable damage.
Put them together, activate them and go to sleep
Construction and other industries will also benefit from these advances. SRI International has a fabrication platform that uses microrobots a few millimeters long to erect structures . The key to their development is an intelligent surface that feeds them and moves them to the desired position. Thanks to it, automatons do not need their own battery to work. On this surface dozens of these devices are distributed, each one equipped with the necessary work tools and programmed for a specific task, such as building a scaffold or handling small amounts of liquids. If necessary, they can even create tools.
Advances in component miniaturization and new materials will soon make it possible to build more efficient automatons suitable for more complex tasks. Part of the charm of the challenge lies in seeing how far we will go, what uses we will find for the most fascinating instruments we have created. As physicist Richard Feynman said in his famous 1959 talk There is a lot of room in the background, ” these micro-machines will be more or less useful in the end, but they will definitely be a lot of fun to make .”
Images: Bae Systems / Greg Campbell – Stanford University / Technion
