A team of researchers at Delft University of Technology has discovered a new process that could help mimic life in non-living materials, such as robots. The new process relies on fuel to control non-living materials in a similar fashion to what living cells do.
The team says the reaction cycle could be applied to a wide range of materials. Its rate can also be controlled, opening up many opportunities in this emerging field. The new development could also play a big role in future soft robotics, with soft machines sensing their environment and responding appropriately.
The team’s findings were published in Nature Communications.
Mimicking Chemical Reactions in Living Cells
Chemist Rienk Eelkema and his team work on mimicking the chemical reactions in living cells, which provide the fuel needed to control the cell. These reactions drive non-living materials in the same way, but they are limited.
“Up to now, there are only about five types of reaction that are widely used by researchers,” Eelkema says. “Those reactions have two major drawbacks: their rate is difficult to control and they only work on a specific set of molecules.”
Along with Benjamin Klemm, lead author of the study, the pair discovered a new type of reaction whose rate can be effectively controlled. This reaction works on a wide range of materials.
“The essence of the reaction cycle is that it can switch between an uncharged and a charged particle by adding a chemical fuel to it,” Eelkema continues. “This allows us to change materials and thus modify the structures of those materials, because equal charges repel each other and different charges attract each other. The type and amount of fuel determines the reaction rate, and therefore how long a charge and thus a given structure exists.”
One of the things the team did was use their reaction cycle to charge a hydrogel, which resulted in the charges repelling each other and the gel swelling.
Role in Building Soft Robots
The researchers say that the cycle of chemical reactions could play a role in building soft robots.
“Soft robots do already exist, for example microparticles controlled externally through magnetic or electric fields. But ultimately you’d want a robot to be able to control itself: to see for itself where it is and what is happening and then respond accordingly,” Eelkema says. “You can program our cycle into a particle in advance, then leave it alone, and it performs its function independently as soon as it encounters a signal to do so.”
Eelkema will now look to add signal processing to the process, which will link it to the environment.
“For example, a polymer particle could contain some components of such a cycle,” he says. “When it encounters the last part of the reaction, the cycle is completed, serving as a signal to disintegrate or swell up, for example.”
The cells in humans and other organisms rely on energy to function.
“That is also the reason why we humans need to eat,” Eelkema explains. “That linking of energy to function takes place through chemical reactions and is what defines living beings. It enables cells to control when and where structures are formed or processes take place, locally and for a limited time.”
On the other hand, non-living material can function without an energy supply and exist forever. It wasn’t until ten years ago that processes existed that could use a chemical fuel to drive interactions in non-living materials.
“We introduced that here in Delft, along with a few other places, and since then the field has exploded,” Eelkema concluded.