Unraveling the Path of Trajectoids: A Leap in Physics and Algorithmic Design

PRMJ
5 min readNov 2, 2023

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In a groundbreaking study published in Nature, a team of physicists and mathematicians from the Institute for Basic Science’s Center for Soft and Living Matter in South Korea, along with a colleague from the University of Geneva, have unveiled a novel algorithm. This algorithm is not just another addition to the vast field of physics; it’s a pioneering tool that paves the way for objects to follow a predestined path down a ramp, a concept straight out of a science fiction narrative. This remarkable innovation has been further elaborated in a News & Views piece by Elisabetta Matsumoto and Henry Segerman from the Georgia Institute of Technology and Oklahoma State University, respectively.

3D-printed Trajectoids with internal metal ball bearings to stabilize the center of gravity

Envisioning the Unseen: The Concept of Trajectoids

The journey begins with a simple yet intriguing puzzle: a sphere rolling down a ramp. Imagine this sphere made of clay, being deformed as it rolls, adapting itself to trace a given path. This physical alteration in shape, once rolled down the ramp again, compels the sphere to follow the initial path, thanks to its new deformities. This realization opened up a world of possibilities for the researchers, leading to the core question: Can these deformations be mathematically correlated with the sphere’s path?

The Algorithm: Bridging Physics and Mathematics

The answer, delightfully, was yes. The team employed mathematics and physics to derive formulas that link deformations of an object with its designated path on an inclined plane. This theoretical framework was then transformed into a tangible reality via a computer program, designed to create such objects using 3D printing technology.

The Birth of Trajectoids

The researchers developed an algorithm to craft trajectoids for predefined paths. Starting with a spherical shape, they divided the path into segments. At each point, they subtly modified the contact point to guide the shape to the next segment. This process, repeated across all segments, results in a trajectoid tailored to the desired path.

Experimental validation came through 3D-printed trajectoids with internal metal ball bearings to stabilize the center of gravity and granting it the necessary weight to maintain its path-following behavior. Remarkably, these shapes adhered to their designed paths, even navigating uphill sections.

Trajectoid programmed to follow a pre-desired path

The innovation didn’t stop there; the team went a step further to develop “two-period trajectoids” that could traverse a given path not once but twice, showcasing an advanced level of path design. Two-period trajectoids are designed to traverse their designated path twice in a single descent. This means that the trajectoid not only reaches the end of its path but continues to roll back over the path, ending up again at the start point. Creating a two-period trajectoid involves more sophisticated geometric adjustments than a single-period trajectoid. The shape must be precisely altered to ensure that its center of gravity and surface features align perfectly with the path not only on the first pass but also on the second.

The development of two-period trajectoids necessitated the creation of more complex mathematical models. These models account for additional variables and conditions that dictate the object’s motion over two periods of the path, such as the angle of the slope, the friction coefficient, and the precise topography of the trajectoid.

This innovation provides deeper insights into the dynamics of rolling motion and the interaction between an object’s shape and its trajectory. It extends our understanding of how subtle changes in an object’s surface can significantly impact its path of motion.

Beyond the Laboratory: Expanded Applications and Future Prospects

The groundbreaking research on trajectoids has far-reaching implications that extend beyond the confines of a laboratory. This innovative algorithm, designed to predict and control the path of objects, promises to revolutionize various fields, ranging from robotics to quantum computing.

In Robotics: Pioneering Movement and Efficiency

In the realm of robotics, the application of trajectoid principles could lead to significant advancements. Imagine robotic parts that can adapt and move with unprecedented precision and efficiency. This could lead to the development of more sophisticated and versatile robots, capable of performing complex tasks with greater accuracy. In industries like manufacturing, such advancements could optimize production processes, minimize errors, and enhance safety. Furthermore, in medical robotics, the precise control offered by trajectoid technology could improve the accuracy of surgical robots, leading to better patient outcomes.

In Physics Research: Unlocking New Understandings

The study’s contribution to physics research is particularly noteworthy in the context of electron angular momentum. Understanding the nuances of electron behavior is crucial for developing new materials and technologies. By applying trajectoid principles, physicists could gain deeper insights into electron dynamics, potentially leading to breakthroughs in materials science and electronics. This could pave the way for the creation of new materials with unique properties, influencing everything from energy storage to computing.

In Quantum Computing: Advancing the Quantum Frontier

Perhaps one of the most exciting prospects of this research lies in its application to quantum computing. The control over motion and path as demonstrated by trajectoids could be instrumental in the study and manipulation of quantum bits or qubits. Qubits are the fundamental building blocks of quantum computers, and their precise control is key to realizing the full potential of quantum computing. By applying trajectoid principles, researchers could develop new methods for qubit manipulation, potentially leading to more stable and efficient quantum computers. This advancement could accelerate the development of powerful computational tools capable of solving complex problems that are currently beyond the reach of classical computers.

A Multidisciplinary Marvel

The research is thanks to the power of interdisciplinary collaboration, merging physics, mathematics, and technology. The trajectoid algorithm could help understand how objects move and interact in both mechanical and quantum realms.

References

This article was inspired by the groundbreaking research detailed in the study “Solid-body trajectoids shaped to roll along desired pathways” by Y.I. Sobolev, R. Dong, T. Tlusty, and colleagues, published in Nature, Volume 620, pages 310–315 (2023), available at https://doi.org/10.1038/s41586-023-06306-y.

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