Transient self-assembly

Transient self-assembly is described as a state where the thousands of molecules which make up living materials cluster themselves together. This link, however, is only temporary, as some molecules deactivate and leave the cluster. Professor Jan van Esch from the TU Delft department of chemical engineering and researcher on the paper explained that to retain these clusters there has to be a continuous addition of new activated molecules to keep the cluster alive.

According to Van Esch this process takes place in nature, and is “an important mechanism in which chemical energy is used to carry out many important active functions within the living cell.” Until the publication of this paper earlier this month, there was no knowledge of how to achieve this process in the lab. The researchers at TU Delft were essentially able to exert kinetic control over a system by controlling the rate of chemical reactions, the rate at which new molecules, activated with a chemical fuel, enter and leave the cluster. This allows synthetic materials to act similarly to the cytoskeleton found in living cells.

It is the first time this activation has been successful with a fully synthetic system, an achievement that Van Esch and his colleagues are extremely happy with, however he emphasized that this research is just the beginning. While in the long term this transient self-assembly can potentially have applications in soft-robotics, his current focus is on the next step of the process, which is finding out whether these artificially created clusters can be used to carry out what he describes as ‘useful work’, such as moving or exerting a force on another object. A basic example of how energy is turned into work is the steam engine; heat is added to water to generate the steam, which drives motion. This is somewhat inefficient, however Van Esch hopes that by exerting molecular control, a similar process can be achieved using transient self-assembly. “If the chemical fuel that is put into the growth of these fibers could be used to move another object,” he said, “that would be a first example of transforming chemical energy directly into force, driven by a self-assembly process.”