Discovered factors for the propulsion of microrobots

TEM image of hollow silica microcapsules / IBEC 

A study led by researchers from the Institute of Bioengineering of Catalonia opens the door to the mobility of new microscopic objects using a whole library of enzymes. According to experts, these micro-robots can be used in the near future for environmental and biomedical purposes.

Ingesting a pill to cure a serious illness, or adding a pinch of a synthetic powder to make water drinkable, seemed like science fiction concepts until only a few generations ago. However, the emergence of new disciplines such as bioengineering, is raising the level of sophistication and specialization of new materials to unsuspected limits.

An example of this is the group of Intelligent Nanobio Devices led by Samuel Sánchez, ICREA researcher at the Institute of Bioengineering of Catalonia (IBEC).

After years developing devices of the size of one thousandth of the thickness of a hair for technological and biomedical applications, Sánchez's group, in multidisciplinary collaboration with a team of computational chemistry, has taken a significant new leap in their research: understanding the processes molecular level that allow so-called micromotors to propel themselves into a liquid.

In the study, which is published in the journal Nature Communications , Sánchez and his colleagues describe what until now was a mystery for the scientific community: how was it possible that enzymes, which are catalytic machines in the nanoscale, could propel particles huge in relation to them?

And, while most of the research groups focused their efforts on equipping microrobots with propellants based on an enzyme called urease, IBEC researchers have managed to adhere and test the mobility of these microscopic objects with a whole new series of enzymes.

Xavier Arqué, a PhD student at the IBEC and first author of the study, states: "The secret of the mobility of these micro-robots lies in the properties of the enzymes themselves."

A new door towards self-propelled microrobots

While enzymes such as urease and acetylcholinesterase could change their internal structure, this process being related to a higher reaction rate (known as conformation in scientific terminology), and generating the propulsion of micromotors, other more rigid enzymes with lower speed of reaction were not able to generate such mobility.

In the words of Sánchez himself: "This is the first time that we can predict if an enzyme is going to be useful for propelling microscopic objects."

To carry out their discovery, the researchers combined the most advanced techniques of computer simulation with experimental techniques, thanks to the collaboration with the group of Sílvia Osuna, ICREA professor at the University of Girona.

This discovery opens the door to a whole new series of self-propelled micro-robots with applications in medicine, water treatment and biotechnology.

Bibliographic reference:  Reference article: Xavier Arqué , Adrian Romero-Rivera , Ferran Feixas , Tania Patiño , Sílvia Osuna & Samuel Sánchez (2019) " Intrinsic enzymatic properties modulate the self-propulsion of micromotors "  Nature Communications 10, 2826.