Cobalt complexes-based self-oscillating gels will become promising material for creation of actuators

Scientists from Immanuel Kant Baltic Federal University for the first time obtained cobalt complexes-based self-oscillating gels. Such gels can occasionally change their geometric parameters, thanks to that they can be used for creation of chemomechanical materials, that transform chemical energy into the energy of mechanical oscillations. The emergence of propagating chemical waves inside such gels enables to use material for creation of devices, processing information using cooperation of chemical waves. Results of the research are published in magazine Gels.

In chemistry, physics and robot engineering much more demanded become so-called self-oscillating polymer gels, properties of which—density, volume, color and others—occasionally change. For example, such gel can alternatively change its size, thanks to that it can be used in micropumps and actuators for transformation of chemical energy into mechanical one (movement). The ability of such materials to change condition, then return to initial one and change once more emerges thanks to a periodic oxidation-reduction Belousov–Zhabotinsky reaction in a gel. It has a complex mechanism, that consists of several tens of reactions, but in general can be presented as bromation and oxidation of organic substance (for example, malonic acid) by a bromate over catalyst in aqueous solution of mineral acid (for example, sulphuric). In the course of reaction, a catalyst occasionally changes its oxidation state and if it is connected with polymer matrix of gel, it leads to periodic changes of properties (color, size, transparency) of the whole gel.

Nowadays most self-oscillating gels are synthesized on the base of ruthenic complexes and their basic shortages are expensiveness, photosensitivity and complexity of synthesis. Thus, researchers are looking for more available alternatives.

Scientists from Kant Baltic Federal University (Kaliningrad) for the first time synthesized self-oscillating gels on the base of cheap, simple in synthesis and insensitive to light cobalt complexes. Obtained gels during Belousov–Zhabotinsky reaction in them generate and spread chemical waves, caused by oxidation-reduction proceedings of cobalt complexes.

Researchers elaborated two types of gels: the first one they obtained by means of including cobalt complexes into cation exchange polymer resins on the base of polyacrylamide; the second one was synthesized by copolymerization (sewing into long chains) of cobalt complexes with acrylamide.

During Belousov–Zhabotinsky reaction in both types of gel appeared and spread chemical waves, and thanks to that submillimeter (around tenths of a millimeter) parts of gel occasionally changed color.

Besides this one of gels apart from changing color (from yellow to orange) changed its volume, one moment shrinking and the next moment expanding. This property of a gel can be used for creation actuators for soft robots on its base.

In future authors are planning to continue investigation and research of self-oscillating gels on the base of cobalt components in order to achieve stronger mechanical oscillations of gels and learn to obtain them in the form of 3D shape of given sizes and forms, that is necessary for creation of actuators.

Provided by Immanuel Kant Baltic Federal University