Abstract
The project is aimed at solving the problems of creating universal soft robots using 3D printing, whose movement is controlled by various external stimuli, such as magnetic and electric fields, UV radiation, pressure, etc., for widespread use in medicine, various fields of science and national economy. The main objectives of the project are to create (a) a block copolymer thermoplastic polymer matrix that provides the desired melt rheology and physical and mechanical properties of finished products, and (b) a set of fillers that perform the functions of susceptibility to one or another external control influence, and (c) development of theoretical models of a composite material to identify the fundamental relationship between its composition and properties and optimize its parameters.
Research done during the first year of the project
In the first stage of the project, the main attention was paid to the preparation of polysiloxane-urethane matrices and magnetically active materials based on them. A new synthetic approach was developed to obtain linear copolymers based on polyorganosiloxanes and urethanes. The new synthetic approach is based on the azide-alkyne cycloaddition reaction, which allows easy control of the synthesis process under simple conditions. Copolymers with different lengths of the siloxane block were synthesized, characterized by modern physical methods and their rheological properties were studied. The resulting materials were used for the first time in the process of 3D printing with thermoplastic polymers. The possibility of high-quality 3D printing of standard structures of varying complexity using the developed materials was demonstrated. A technique for introducing carbonyl iron magnetic particles into synthesized copolymer matrices was developed, and magnetic-polymer composites were obtained whose rheological properties can be controlled by a magnetic field.
Thermoplastic matrices of polyurea-siloxane have been synthesized by the polycondensation method using different commercially available products. The synthesis was scaled up and the influence of various factors on it was studied: stirring intensity, type of solvent, ratio of initial reagents involved in the polycondensation; optimal conditions for carrying out the synthesis were determined. 10 g of polysiloxaneurea was prepared for further introduction of a magnetic filler. Methods were developed to modify the surface of the carbonyl iron microparticles to improve compatibility with the polymer matrix. 50 g of carbonyl iron with a shell of aminopropyltriethoxysilane and 50 g of carbonyl iron with a shell of methyltriethoxysilane were obtained. The presence of the shell was confirmed by scanning electron microscopy with energy dispersive microanalysis. Based on polysiloxaneurea matrices and modified iron particles, samples of magnetic-polymer composites were obtained, their magnetorheological properties were studied and it was shown that they are regulated by an external magnetic field.
Together with Chinese colleagues, magnetically active materials have been developed based on commercially available thermoplastic polyurethane filled with microparticles of a magnetically hard neodymium-iron-boron alloy. The results of 3D printing soft robots using this material will be analyzed. In addition, soft bending actuators have been developed and fabricated by the Chinese project team using 3D printing technology with plain and conductive thermoplastic polyurethane filaments.
A theoretical study of the properties of polymer composites was carried out based on the consideration of mesoscopic cells of the material volume containing one or more filler particles. Using finite element modeling, a three-dimensional cubic cell of the material containing spherical, cubic, cylindrical and ellipsoidal inclusions was considered. To study the influence of filler parameters on the mechanical characteristics of a polymer composite, boundary value problems of uniaxial compression of a material cell and filler particle rotation were considered. It was shown that substantial control over the mechanical properties of composites using fillers with different Young’s moduli is possible only for fillers made from soft materials, the Young’s modulus of which is no more than 100 times higher than the Young’s modulus of the polymer matrix. In order to study the effect of surface treatment of filler particles on the properties of a polymer composite and improve the convergence of numerical solutions of mesoscopic mechanics problems, material cells containing inclusions surrounded by soft shells were constructed. It was demonstrated that even at low filler concentrations for the case of soft polymer matrices, it is possible to obtain the widest range of changes in the elastic modulus of a material cell (about 10%) using relatively soft shells around the filler particles. The results obtained during the modeling process will allow us to describe new ways to fine-tune the mechanical properties of polymer composites.
Based on the results of the work, three collaborative papers have been written, one of which has been accepted for publication in the highly rated first quartile journal Bio-Design and Manufacturing, and the other two are under review.