The first step in assembling a machine is usually the design: what we want the machine to look like, where each part should go. If the project is based on a living organism, the focus will be on imitating a functionality of that being. Inspired by the flight of birds, we invented aircraft. Interested in the locomotion power of horses, we create land vehicles. Curious about the brain’s memory and thinking capacity, we made computers. Our need for planning stems from the fact that computers, automobiles and aircraft do not assemble themselves.
However, birds, horses and brains do not need human planning to exist. This observation suggests a new paradigm of technology construction: self-assembly and self-innovation. A bird’s wings, for example, assemble themselves, as they develop the exact shape for the bird’s flight without a human design that foreshadows the ordering of bones, muscles, and feathers. The ability to fly is also an example of self-innovation, given that the first single-celled organisms on Earth did not have the physiological structures to do so. Mastering a portion of this sophisticated self-assembly and self-innovation technology of the living world required scientific advances.
In 2018, Frances H. Arnold was recognized by the Nobel Prize in Chemistry for having discovered the so-called directed evolution of enzymes, including producing unprecedented examples in the biological world. This means manipulating the evolutionary principles that allow for self-innovation. Thus, it is possible to induce living organisms (bacteria) to build molecular machines (enzymes) of human interest; for example, biocatalysts that replace their more toxic industrial equivalents. In 2020, it was the turn of Emmanuelle Charpentier and Jennifer A. Doudna to be awarded the Nobel, also in chemistry, for discovering a method of genomic editing using the immune system of bacteria. The molecular scissors found by the researchers make it possible to control the self-assembly processes of living cells and, who knows, open the way for new therapies against cancer and for the cure of hereditary diseases.
The next phase of the paradigm shift attracts not only chemists but physicists as well. One limitation of self-assembly technology is the use, from the start, of the genetic code and other biochemical mechanisms that have evolved over about three billion years. How did this genetic code and the first biochemical processes self-organize, having only simpler molecules as an initial resource? The question is intended to be broader than a search for the origin of life. The idea is to discover a variety of self-assembling, self-repairing, adaptable and, if possible, self-innovating machines, from abundant basic components. The aim is to learn the general physical principles that resulted in the transition from inanimate to living matter. In other words, the challenge is to find technologies inspired by the emergence of life.
While chemists research the appearance of behavior similar to that of living organisms in aggregates of molecules, physicists want to test even more diverse systems – photons, electrons, atoms and macroscopic objects. In 2015, Dilip Kondepudi led an illustrative experiment in this line. He gathered a dozen millimeter metallic spheres immersed in a viscous oil. The team of researchers showed that, if an electrical current generated by an external source passed through these spheres, they organized themselves in the form of worms, and moved as such. The metal worms also moved towards the source of energy, reminding us of the intentionality of a living being in its search for a source of food. In this sense, the experiment can be interpreted as a kind of metabolism created on its own. The system still healed autonomously in response to mechanical injuries. Although they demonstrate self-assembly inspired by living beings, experiments like this still do not present spontaneous innovations such as those that give rise to new biological species.
On the theoretical front, there are promising hypotheses and models under debate. Also in 2015, physicist Jeremy England proposed the concept of dissipative adaptation, a thermodynamic principle to describe how matter, when fed by certain sources of energy, can become as organized and complex as the particles that make up the cell of a bacterium or the body of a bird. It is known that when the external power supply to any physical system is interrupted, be it a machine or a living being, the tendency is for this system to reach the so-called thermodynamic equilibrium, a state of matter that best describes the inert air in a room. closed than the wind that comes in through an open window. If an organism is in a state of thermal equilibrium, it is certainly not alive. But when a system is excited by external forces and receives energy capable of removing it from equilibrium, exceptional phenomena can occur. In particular, atoms can participate in the internal motions that characterize a living system. The challenge remains to refine current hypotheses and models, and to confront them with practice.
Technologies inspired by the transition from non-living to living matter are a bold idea with the potential to advance fundamental science. Whether we can achieve them or not, that is the question.
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Daniel Valente is a physicist and professor at the Federal University of Mato Grosso (UFMT).
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