Research On Hybrid Magnetic Drive Microswimmer With Sporopollen Exine

The dimensions of microswimmers are generally in the sub-micron to micron level,and microswimmers can convert a variety of driving energy sources into controlled mechanical motion in the liquid environment.With the development of micro-nano technology,microswimmers have gradually been widely used in biomedical fields such as biochemical delivery,bio-sensing,targeted drugs delivery,and even pollution treatment in the environmental field.However,the traditional methods of manufacturing and assembling make it difficult to prepare microswimmers on a large scale.In addition,microswimmers are usually applied in the liquid environment,and limited by their own sizes,resulting in a very low Reynolds number.At this time,the inertial force can be ignored,and the viscous resistance is dominant,making the movement control very difficult.To apply the microswimmers in the biomedical fields,there are still a series of challenges,such as low biocompatibility,difficulty in the movement control,and obstacle avoidance.In order to solve the above problems,the microswimmer based on pollen grains is developed,and its control method and obstacle avoidance motion trajectory planning are studied.In this paper,a microswimmer with uniform size is prepared by biological hybridization method on a large scale.It adopts vacuum loading technology to make it have excellent magnetic characteristics,while maintaining the internal cavity structure of the microswimmer,which provides the possibility of loading drug.The dynamic analysis of the microswimmer provides theoretical support for its motion control.Then,the obstacle avoidance strategy based on the dynamic window algorithm is proposed.This method successfully makes the single microswimmer realize the autonomous avoidance of obstacle cells and attaining the targeted the cells.The main research contents include:Firstly,the natural sunflower pollen grains are used as the biological template for the microswimmer,and becoming a sporopollen shell with an urchin structure and a external cavity after chemical treatment.The vacuum loading method is used to make the magnetic particles enter the inside of the sporopollen shell to endow it with magnetic characteristics,and the morphology and magnetic characterization of the prepared microswimmer are carried out.Secondly,the dynamic analysis of the microswimmer under the magnetic field is carried out.The distribution of the fluid field around the microswimmer is simulated.And the influence of the surrounding physical obstacles on the movement of the microswimmer is determined.The corresponding dynamic model is constructed.Then the dynamic analysis result is verified by the relationship between speed and frequency,and the motion control accuracy of the microswimmer driven by the magnetic field is quantitatively analyzed.Thirdly,the obstacle avoidance strategy of the magnetically driven microswimmer based on the dynamic window method is proposed.Then the strategy is improved based on the simulation results of static obstacles and dynamic obstacles.Finally,a three-degree-of-freedom magnetic driving system is used to perform static obstacle avoidance experiments on the microswimmer,and the feasibility of this obstacle avoidance strategy is initially verified.The urchin-like microswimmer has uniform size with uniform structure and also has a large internal cavity as well as good biocompatibility,which is suitable for a drug carrier and cell packaging material.Its excellent paramagnetic properties make it possible to use the magnetic field for wireless motion control,and the obstacle avoidance strategy based on the dynamic window method can achieve autonomous obstacle avoidance,providing the possibility for cell micro-operations and targeted drugs delivery.