Thanks to millions of years of evolution, nature has built molecular devices and machines capable of performing complex and essential functions for the life of organisms. Instead, only one hundred and fifty years have passed since the birth of the Periodic Table of the Elements, an icon of chemistry. About sixty years ago Richard Feynman started talking (jokingly) about nanotechnology, and less than forty years ago the tunneling scanning microscope was invented, which allows one to see and manipulate single molecules.
Chemists have been designing, building and studying artificial nanomachines for about three decades. First they developed very simple and rudimentary systems; then, once the fundamental principles governing the movement of objects at the nanometer scale were understood, and the necessary modeling and experimental tools were acquired, they moved on to more sophisticated devices. Researchers are now learning to integrate molecular machines into organized structures and to make them interact appropriately with the environment in which they are located, so as to obtain useful functions.
Although the systems studied so far are enormously less complex and with very modest performances compared to natural nanomachines, research in recent years shows that with artificial molecular machines it is possible to process information, convert energy, synthesize other molecules, deliver drugs and build mechanical actuators. It is worth mentioning in this regard the concluding reflection contained in the motivation of the 2016 Nobel Prize for Chemistry:
Compared with the machines that changed our world following the industrial revolution of the nineteenth century, molecular machinery is still in a phase of growth. However, just as the world stood perplexed before the early machines, such as the first electric motors and steam engines, there is the potential for a similar explosive development of molecular machines. In a sense, we are at the dawn of a new industrial revolution of the twenty-first century, and the future will show how molecular machinery can become an integral part of our lives. The advances made have also led to the first steps towards creating truly programmable machines, and it can be envisaged that molecular robotics will be one of the next major scientific areas (Ramström 2016).
If at the moment we can hypothesize that in the near future molecular machines can be used in practice in some sectors of technology and medicine, perhaps the most innovative applications are still beyond the reach of our imagination. Apart from these certainly important aspects, research on molecular machines already has many scientific and cultural merits. First of all it has awakened curiosity, sharpened the ingenuity and stimulated the creativity of scientists (in particular chemists), many of whom have discovered to be, in fact, real molecular engineers.
Secondly, since the study of molecular machines involves areas of chemistry and biology, but also of physics, mathematics, engineer-ing and medicine, scientists from different disciplines, even apparently distant from each other, have begun to talk to each other – something by no means automatic and banal – and to interact. These “unconventional” collaborations will allow us to face important challenges, both at the borders between the disciplines and within them. In solving open problems, new ones will also be identified, thus nurturing the virtuous circle at the base of scientific and cultural progress, in which curiosity, research and discovery follow each other without interruption. The scientist is a lucky person because he works in this cycle that nobody can interrupt: there will always be something new to discover, something unexpected will always happen, someone will always have a new idea. Precisely for this reason the scientist is also a humble person: he knows that the world is a mystery that dominates him. Joseph Priestley, the first scientist to investigate photosynthesis, expressed this condition in an admirable way:
The greater is the circle of light, the greater is the boundary of the darkness by which it is confined. But, notwithstanding this, the more light we get, the more thankful we ought to be, for by this means we have the greater range for satisfactory contemplation. In time the bounds of light will be still farther extended; and from the infinity of the divine nature, and the divine works, we may promise ourselves and endless progress in our investigation of them: a prospect truly sublime and glorious (Priestley 1779).
Finally, it should be remembered that frontier research such as that on nanomachines is almost always carried out in collaboration between laboratories in different countries in various parts of the world. Among human activities, scientific research is among the longest and most widely globalized ones. In science, not only ideas but also people circulate with great freedom on a planetary scale. In our laboratories, for example, European, American, Indian, Iranian, Chinese, Japanese and Australian researchers have worked and are still working together. This is undoubtedly a positive globalization, which has a particular value in a historical period like the one we are going through, characterized by the closure of borders and the construction of walls.
Scientists, in virtue of their privileged positions, are called to work for the progress of humanity. Which means to develop science, but also to protect the environment and to fight social injustice. A scientist cannot hide behind the hypocrisy of neutral science. A responsible scientist must be concerned that his research is used for peaceful purposes and not for war, for alleviating poverty and not for increasing privileges, and for taking care of our fragile planet, the only place where we can live. As said by Albert Einstein: «Concern for man himself and his fate must always constitute the chief objective of all technological endeavors; never forget this in the midst of your diagrams and equations.»
This recommendation, of course, also applies to molecular machines.
We wish to express our gratitude to the members of our research group, with whom we shared the enthusiasm and effort in research on molecular machines. A special thanks goes to Margherita Venturi and Serena Silvi for having critically read the manuscript, and to our families for never letting us miss their support.