Researchers at Cornell University have achieved a significant milestone in robotics by developing the world’s smallest walking robot, measuring between two to five microns across. To put this into perspective, over 30,000 of these minuscule robots could be accommodated on the sharp tip of a needle. This unprecedented size opens the door to a wide array of applications in medical fields and materials science, primarily because these robots can engage with light on a scale that corresponds with the light’s wavelength. The ability to manipulate light at such a minute level presents exciting new opportunities for imaging and sensor technologies that were previously unattainable.
The breakthrough, according to Paul McEuen, the lead researcher and emeritus professor of physical science at Cornell, lies in the concept of diffractive robotics. This term refers to untethered robots equipped with imaging capabilities suited for extreme micro-scales. The robots operate based on the principles of visible light diffraction—which is the bending of light waves when they encounter an opening or barrier. McEuen stated that this development effectively places a microscope’s lens into the microworld, allowing for unprecedented close-up imaging capabilities not feasible with conventional microscopes. This perspective is invaluable in scientific research and diagnostics, enabling more sophisticated investigations at the cellular and molecular levels.
To comprehend the dimensions of these robots, one must note that they span only five microns in width, equivalent to 5,000 nanometers. For context, if a nanometer were likened to a marble, a micron would compare to a basketball. The wavelengths of visible light, situated between 400 and 700 nanometers, allow these robots to include imaging structures that can operate on the nano-scale. Co-author Francesco Monticone emphasized that miniaturization technology has now progressed to a point where mechanical systems can effectively interact with and reshape light at sizes drastically smaller than a meter—specifically, a million times smaller.
Achieving movement in these robots was another challenge the research team faced, especially given their size and the non-existence of traditional power supplies like batteries. Rather than “walking” in the expected sense of the word, these tiny robots navigate through their environment using magnetic fields. Each robot is embedded with numerous nano-scale magnets, both long and thin and short and stout, which allows magnetic field manipulation to induce movement. Study co-author Itai Cohen explained how varying the intensity of the magnetic field can control the direction and movement style of these robots, producing a unique inch-worm-like wriggle or swimming action through fluids to reach imaging targets effectively.
For imaging purposes, these micro-robots can adjust their diffractive components, enabling them to interact with larger microscope lenses or function independently. Techniques leveraging visible light diffraction have versatile applications, including optical microscopy for cell and tissue studies, interferometry for assessing surface imperfections, and super-resolution microscopy for investigating proteins and cellular mechanisms. Thus, the inclusion of micro-scale robots could revolutionize existing imaging methodologies, facilitating deeper insights into complex biological systems and material properties.
In conclusion, the implications of this research extend well beyond basic robotic functionalities; they herald a new era combining robotics with optical engineering at incredibly small scales. Monticone envisions a future where swarms of these diffractive microbots could autonomously perform complex tasks such as super-resolution microscopy and other sensory functions while navigating through samples. This pioneering work by Cornell researchers is only the beginning of understanding the potential and practical applications this new class of micro-robotics may offer, encouraging further exploration and innovation in both scientific and industrial realms.
