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Building Molecular Machines

Building Molecular Machines

Joseph Wang

Department of Nanoengineering, University of California, San Diego, USA

Three pioneers in the development of nanomachines—Jean-Pierre Sauvage (University of Strasbourg), J. Fraser Stoddart (Northwestern University), and Bernard Feringa (University of Groningen)—were awarded the 2016 Nobel Prize in Chemistry by the Royal Swedish Academy of Sciences. The Nobel committee described the tools developed by these chemists as the “world’s smallest machines.” The first step toward building such tiny machines was taken by Jean-Pierre Sauvage in 1983, when he linked two ring-shaped molecules together to form a chain, allowing one component to move freely around the other. The development of synthetic nanoscale motors, capable of converting energy into movement and forces, represents one of the most fascinating topics of nanotechnology. Inspired by protein nanomotors in living organisms, synthetic molecular machines can produce mechanical motion and be cycled between states, in response to different external stimuli, such a light or pH change. Such reversible switching between two or more stable conformations mimics the intracellular movement of protein biomotors. Understanding the remarkable operation of nature’s biomotors has provided researchers with new insights into how to impart greater sophistication onto the performance of man-made nanomachines. Such artificial nanomachines consist of molecular components that resemble large-scale machines. These include molecular wheels, rotors, cars, and elevators, developed by the Nobel trio, that have considerable potential as components of molecular machinery.

Synthetic molecular machines and their microscale counterparts are currently a research area of intense activity. Recent efforts have led to a variety of powerful man-made micro/nanoscale machines, with advanced motion control and new functions, that are capable of performing different tasks.  Similar to natural biomotors that ferry materials around cells, artificial microscale motors have been shown useful to load, transport, and release a variety of cargos at well-defined positions. Such new capabilities have led to numerous potential applications. Since molecular machines are still fragile and difficult to scale up, many of these practical applications have relied on “larger” microscale machines. For example, recent studies have illustrated the ability of microscale machines to write, image, and repair nanoscale structures.

Inspired by the movie Fantastic Voyage, recent advances indicate considerable promise of using micro/nanoscale machines to biomedical applications, including drug delivery, diagnostics, nanosurgery, and biopsies of hard-to-reach tumors. After two decades of basic research on designing tiny artificial machines in test tubes, the field has recently reached a new milestone where the functionality of these tiny machines was evaluated in live bodies. Artificial micro/nanoscale machines are no longer fantastical science fiction of the far future. These tiny machines are expected to revolutionize many aspects of technology and medicine, leading eventually to major improvements in the quality of our lives.