Rods, beads and glue float to the desired position as if held by a magic hand: Researchers have developed a construction system that can build complex 3D structures without contact. The secret of “LeviPrint” is a sophisticated implementation of so-called acoustic levitation: the components are held in suspension by a complex field of sound waves, which is generated by an element at the end of a movable robot arm. The prototype has already impressively demonstrated its “tinkering” talent. According to the developers, this indicates interesting application potential.
Sometimes we can actually feel loud music from a loudspeaker in our bones and it can make small objects like polystyrene balls dance. The forces that sound waves can exert on matter become clear. This effect is specifically exploited in the process of acoustic levitation. Specially positioned speakers generate ultrasound, creating a field of standing waves. At junctions, it creates dynamics that can keep objects in limbo in a controlled manner. This method has been used for some time for the non-contact manipulation of small objects such as water droplets or plastic beads. But now the researchers led by Asier Marzo from the Public University of Navarre in Pamplona are presenting a further development that could significantly expand the application potential of the process.
Rods in an acoustic spell
Their system, called LeviPrint, is based on a sophisticated optimization of the acoustic load-bearing capacity: the scientists have succeeded in keeping both spherical and elongated objects in suspension through the combination of innovative loudspeaker units and control by special algorithms. Acoustic field configurations are formed that exert a firm spell on the rods. The effect is so intense that it is retained even when the field is moved: the object then moves with it and can also be rotated. For their prototype, the scientists installed this system at the end of a robotic arm that can be moved flexibly. “In order to be able to produce complex objects without contact, we developed a levitator in combination with a robotic arm and a liquid dispenser,” says Marzo.
As the tests show, the system can hold objects securely in its “acoustic hand”, move and rotate them and thus position them without contact. With the robot arm, it is possible to construct a variety of 3D structures from rods, particles and glue, the developers explain. For example, they built small cubes or a bridge with the LeviPrint system for demonstration purposes. The largest balsa stick units were eight centimeters long and weighed 16 milligrams.
Contactless designed 3D structures
After the “acoustic hand” has positioned such a component for the construction, it picks up a droplet of adhesive from a dispenser and transports it to the connection points of the elements while it is floating. A UV light then ensures that the adhesive hardens at the connections between the components. In addition to rod constructions, structures can also be built up from several plastic beads. The adhesive alone can also serve as a building material: the demonstrations show that structures can be created that consist only of adhesive elements that are applied one after the other and cured by UV radiation.
The scientists now see considerable potential for applications in their LeviPrint system. “There is no contamination because the manipulator does not touch the material. In addition, the system enables manufacturing techniques that are not possible with other methods, such as construction in closed containers from the outside,” explains first author Iñigo Ezcurdia from the Public University of Navarre. Because the ultrasonic field can also penetrate certain materials, the researchers report. For example, they built a small ship inside a wireframe by levitating materials from the outside through an opening to the small construction site.
“We hope that this technique can inspire new manufacturing processes – such as areas such as the microfabrication of electromechanical components,” the scientists write. According to them, further developments of the concept could even expand the potential significantly: “If LeviPrint can be adapted to work in aqueous media, it could perhaps also build complex structures in cell culture media or even in living beings,” the team says.
Source: Elhuyar Foundation, Preprint of the work
Video: © UpnaLab