In the episode of MBC’s popular entertainment program “Infinite Challenge,” Park Myung-soo takes a part-time job washing the windows of Building 63, and explains how biomimetic robots that mimic the characteristics of cockroaches and geckos could take over this task.
In the “Extreme Part-Time Job” episode of MBC’s popular entertainment program “Infinite Challenge,” Park Myung-soo is shown washing the windows of Building 63. Although the work is done on a gondola, the fear of heights and anxiety about safety is evident on the novice window washer’s face, making viewers nervous. Wouldn’t it be great if a robot could take over such a difficult task, where one mistake could lead to a major accident?
When you think of a robot cleaning the windows of a skyscraper for a human, it’s easy to imagine a human-shaped robot holding a cleaning tool and diligently washing the windows. However, the consensus is that a robot with a cleaning module mounted on a body that can climb up and down building walls would be more efficient than a human-shaped robot. In order to realize the ability to climb up and down building walls, robots that mimic the basic structures, principles, and mechanisms of animals and plants are called biomimetic robots.
One such robot that has achieved remarkable results in climbing up and down building walls is Spinybot. Spinybot utilizes the principle of how cockroaches climb up and down walls. Cockroaches use the delicate hairs on their feet as hooks to climb up and down walls. Walls are made up of small, bumpy bends in the surface, and these bends have the potential to touch the cockroach’s hairs from many directions. If one of these hairs touches the bend in a direction that supports the roach’s weight, the hair has a small force that supports the roach’s weight. While the force of a single hair is small, the combined force of multiple hairs can generate enough force to support the roach’s weight. Spinybot’s feet also have small but numerous claws, which use the same principle to support the robot’s weight as it climbs up and down walls. However, this method relies on the probability of claw-to-wall contact, which makes it impossible to attach to smooth walls like glass.
One robot that has overcome this limitation is Stickybot, a robot that mimics the plantar structure of a gecko’s foot. Geckos are able to walk on ceilings and walls without the need for adhesive substances, and the secret lies in the millions of microscopic hairs on the soles of their feet. You might be wondering how something with so many tiny hairs on the bottom of its feet can stick to walls, but the van der Waals force makes it possible.
Van der Waals forces are small electrical forces that act between molecules and are caused by the momentary deflection of electrons inside a non-polar molecule. When there is a momentary electron deflection inside a non-polar molecule, the side where the electrons are oriented has a (-) pole and the side where the electrons are relatively free has a (+) pole. The molecule that experiences this electron bias will also affect its neighbors. The (-) pole pushes the electrons inside the neighboring molecule to the opposite side, making the side where the electrons have escaped a (+) pole and the opposite side where the electrons are relatively clustered a (-) pole. This (-) pole then affects the neighboring molecules, and the chain reaction causes all molecules to become instantaneously polarized. This instantaneous polarization creates an electrostatic attraction between the molecules, which is called the van der Waals force. The van der Waals force generated by a single cilia is very small, but when millions of microscopic cilia clump together, the force is enough to support the lizard’s weight. If the same phenomenon that occurs in the soles of a gecko’s feet were to occur in the palm of a human hand, the force would be non-negligible, with a human palm capable of supporting a weight of about 40 kilograms. Stickybot also uses urethane pads with a microscopic hair structure to attach the robot to walls using van der Waals forces. Because it uses electrical forces rather than physical contact, it can move on smooth walls like glass.
In addition to van der Waals forces, the gecko’s cilia have another peculiarity: they are directional. These cilia have the property of gaining great adhesion when applied in one direction, but easily falling off when applied in the opposite direction. Stickybot’s microscopic hairs are also directional, which means that they have a large adhesive force downward, where the robot’s weight is acting, but it doesn’t take much effort to pull them off in the opposite direction.
Both Spinybot, which uses the characteristics of cockroaches, and Stickybot, which uses the characteristics of geckos, are good examples of biomimetic robots that can climb building walls, but both methods are still time-consuming. To solve this problem, researchers are exploring different approaches to develop faster and more efficient wall climbing techniques.
There are millions of species of animals and plants on Earth, and they all have their own ways to adapt to their environment and survive. For example, the surface of a robot can be improved by mimicking the scale structure of a fish that swims well underwater, or a new type of attachment system can be developed by referencing the hand and foot structure of a monkey that climbs trees. This kind of research will enable biomimetic robots to have more diverse and innovative capabilities. There may be animals and plants that have not yet been studied that have solutions for quickly climbing building walls. The more diverse the flora and fauna, the more possibilities there are for biomimetic robots. With further research and technological advancements, the world of biomimetic robots will only get more amazing.
