Collective Motion And Control Of Self-Oscillating Gel

Active matter is a broad definition,including single cell,living individual and other self-driven non-living groups.It can transform energy on the molecular level into collective behavior and movement function on the macro scale.The importance of the research on the collective motion of active matter stems from the theoretical prediction and experimental exploration of the self-organizing structure that is ubiquitous in the system,and the application of its mechanism to the design of bionic materials.Related research has important prospects for ecological governance,medical surgery,sensing and robot engineering.However,a comprehensive understanding of the mechanism and control of collective motion is lacking,and it remains a challenge to construct robust,fault-tolerant and flexible active population systems that can better adapt to environmental changes.In this dissertation,in this dissertation,the general laws of such active collective behavior,i.e.,internal dynamical processes,are investigated with chemically active self-oscillating gel motors.The main research contents are as follows:Firstly,the parameter effect of BZ chemical wave,the driving force source of BZ gel,was studied.Chemical wavelength is the key parameter limiting the size of gel motor.The modulation law with reaction temperature and reactant concentration of one-dimensional pulse wavelength in the reaction-diffusion system was studied.Controlling the reaction temperature and reactant concentration,it was found that decreasing the hydrogen ion and bromate concentrations and increasing the reaction temperature and malonic acid concentration were conducive to the shortening of the chemical wavelength,where the temperature and malonic acid were effective in reducing the pulse wave wavelength to the submicron scale.The combined adjustment of the four reaction variables achieved an order of magnitude shortening of the chemical wavelength,with the shortest wavelength reaching 0.04 cm.Secondly,the general law of directional locomotion of gel motor was explored in a single small-scale gel.According to the relationship between the locomotion direction of gel and the propagation direction of chemical wave,the motion mode of gel was changed by adjusting the length of gel,that is,the gel undergoes direct wave locomotion when the gel length is 60 grid points and retrograde wave locomotion when the length is 90 grid points under fixed parameters.The dynamic analysis of the chemical wave reveals that the force of the gel is position dependent: the push force that induces the direct wave locomotion of the gel appears in the front and middle sections of the gel;the pull force that induces the retrograde wave locomotion of the gel mainly appears in the end section of the gel.The increase of the gel length causes the amplitude of BZ oscillation in the end section of the gel to increase,resulting in the increase of the pull force of the chemical waveback and the retrograde wave locomotion of the gel.Thirdly,the relationship between the motion pattern of the small-scale BZ gel group and the internal heterogeneity was studied.Heterogeneity exists widely in life groups,which shapes social structure,leadership,movement motivation and collective performance of groups.Although the effect of heterogeneity can be observed in real populations,it is rarely considered in theoretical and simulation studies.In this thesis,the effect of the number and location of heterogeneous individuals is investigated by setting individual activity differences in nine BZ gel group.An ordered unidirectional motion is generated when a single heterogeneous individual is present.When two heterogeneous individuals are present,the population forms a split motion with an orientation angle greater than 90° and a curved motion with an orientation angle less than or equal to 90°.The individual heterogeneity was quantified based on activity differences,and different motion patterns of the group were realized by changing the activity differences of heterogeneous individuals,including irregular motion when activity difference Δε = 0-0.0014,swing-forward motion when Δε = 0.0021-0.007,and circular motion when Δε ≥ 0.0077.The group motion was analyzed based on the phase difference and dispersion.The corresponding relationship between the chemical bifurcation of gel oscillation and the bifurcation of the order parameter of group motion is obtained.Finally,the environmental adaptive motion pattern transformation of heterogeneous group was studied.Due to the photosensitivity of BZ gel,by applying light to the nine-gel system containing two heterogeneous individuals,the general rule of heterogeneity changing with light under fixed activity difference was obtained,that is,the increase of ambient light intensity led to the increase of heterogeneity,which was manifested by the increase of oscillation frequency difference and phase difference of BZ gels.The law was used to realize the motion patterns under different light intensities,i.e.,swing-forward motion,circular motion,and splitting motion.The light intensity was controlled to realize the adaptive transformation of gel motion patterns and collective functions,including group capture,escape,and release,according to the net displacement magnitude of different motion patterns.In this thesis,the dynamic control method of active gel from individual to group level is obtained,especially in the modulation of group motion pattern.This thesis emphasizes that heterogeneity is the important origin of collective motion.The results of this thesis can not only be used to realize the design of soft robots and intelligent materials,but also help to promote the related research and analysis of biological group processes.