Molecular Robotics | Shogo Hamada
Tiny robots, mighty potential
One of the remarkable features of life is how we build ourselves. Living systems are designed in a bottom-up fashion by synthesizing and self-assembling molecules. Learning from this fascinating process in nature, molecular robotics aims to build up robotic systems from the nanoscale, molecular level. Such a bottom-up fabrication allows various potential benefits compared to the current top-down fabrication strategy in robotics. For instance, molecular robots can achieve a precisely identical structure due to their strictly defined design at the molecular level. In addition, the robots can be synthesized and assembled in the scale of Avogadro’s numbers, which can easily exceed the scale allowed by the top-down approach. Finally, self-assembly allows an autonomous construction of the robots without manipulation. These characteristics could open a new frontier in robotics by ultimately overcoming the fundamental limitations of the conventional strategy.
Figure 1: A history and recent advancements in molecular robotics. Adapted from Molecular Robotics. Encyclopedia of Robotics. Springer (2021). 
History-wise, a precursor to molecular robotics can be traced back to nanotechnology (Fig. 1). A vision to build machines at the nanoscale ultimately led to the idea of creating robotic systems from molecules. Currently, researchers tackle this new field in robotics by mainly two approaches. One is chemistry-based, creating molecular machines by synthesizing novel molecules with mechanical capabilities. Another is nano-bioengineering-based, which emphasizes building systems by utilizing various kinds of biomolecules and biochemical reactions. Two approaches are now starting to converge under the common goal of creating robotic systems from molecules. For instance, researchers in Japan launched the “Molecular Cybernetics” project this year . The project aims to create a “chemical AI” by integrating various technologies spanning both approaches.
Notably, thanks to the recent advancements in DNA nanotechnology, we are now witnessing a “Cambrian explosion” of molecular robots made by biomolecules. Various classes of biomolecular machines and robots have been recently invented, ranging from nanoscale even up to mesoscale (sub-millimeter size) [3-11]. Biomolecular robots use biomolecules as materials, such as DNA, RNA, proteins, and lipids. The molecules are designed, synthesized, and assembled into devices and then integrated as one system. Indeed, all devices and structures comprising a robot, such as sensors, processors, actuators, and chassis, can be constructed especially by using DNA. Although such systems are created from biomolecules, they do not rely on life, which allows a design without any “black box” of living systems.
Future biomolecular robots could be applied to various fields, from materials to healthcare. For instance, a new class of smart materials could be made from a swarm of molecular robots. The approach could realize active, programmable, and responsive materials designed from the molecular level. In addition, a molecular robot that can carry drugs with sophisticated information processing capabilities could be used for theranostics. Pioneering studies already suggest practical uses of biomolecular robots for such intelligent drug delivery systems working inside living bodies .
Towards “life-like” molecular robots
Recent examples also attempt to mimic forms and even characteristics of life. For instance, an amoeba-like robot is created by mimicking the shape of a single cell . The robot can deform its body by switching the linkage between molecular motors and liposome-based chassis. Our team created a mesoscale, slime-like machine powered by artificial metabolism . The machine can keep regenerating its bodies analogous to the living systems by coupling synthesis and assembly of DNA. Complex robotic behaviors, such as locomotion, racing, and even selection, were achieved by programming its dynamic capabilities. Such examples indicate the feasibility of creating further “life-like” molecular robots from biomolecules. As a next step, our group is currently working on the development of molecular robots that can think and evolve. The best is yet to come!
For further information:
An overview of the field, including its history and details of the latest examples, is described in Molecular Robotics (Encyclopedia of Robotics, Springer, 2021) . The encyclopedia is currently adding more entries related to molecular robotics, from materials to devices and design frameworks.
Furthermore, SN Applied Sciences launched a Topical Collection on Molecular Robotics. The collection welcomes submission on a broad spectrum of topics contributing to the advancement of molecular robotics, such as experimental, theoretical, and social aspects of the field.
 Hamada, S. Molecular Robotics. Encyclopedia of Robotics. Springer. (2021)
 Molecular Cybernetics Project. https://molcyber.org. (Accessed on 2021/09/20)
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Dr. Shogo Hamada is a Specially Appointed Lecturer in the Department of Robotics at Tohoku University, Japan. He received his Dr.Eng. at the Tokyo Institute of Technology (Japan). After working as Assistant Professor in the Department of Bioengineering and Robotics at Tohoku University, he became a Kavli Postdoctoral Fellow in the Kavli Institute at Cornell for Nanoscale Science, then appointed as Research Associate and Lecturer in the Department of Biological and Environmental Engineering at Cornell University (USA). His research interest lies at the intersection between robotics and nano-bioengineering, especially molecular robotics.