Locomotion And Light Effect Of Self-oscillating BZ Gels

The adaptive locomotion of living organisms plays an important role in their survival and reproduction.Accordingly,the general mechanism and systematic design for the functional locomotion of bionic materials are hot issues in the field of active matter.Most of the artificial bio-inspired systems reported previously are difficult to achieve simultaneously controllable locomotion and environmental adaptability.In various artificial systems,the self-oscillating gel is an ideal research system because of its advantages of internal-drive and controllable motion direction.By using experimental and analysis methods such as the synthesis and characterization of polymer hydrogels,CCD-based tracking system and Fourier transformation,the locomotion and light effect of the self-oscillating BZ gels were studied systematically based on the mechanisms of photosensitive Belousov-Zhabotinsky(BZ)reaction,the nonmonotonic relationship between the oscillatory frequency and the light intensity for the photosensitive BZ reaction,the highest-frequency dominant principle of chemical wave' propagation,and the theory of direct and retrograde wave locomotion.Research progress has been made in three aspects:1.The capillarity-induced propagation reversal of chemical waves in a self-oscillating gel was observed and its mechanism was proposed.Unidirectional chemical waves generated by the BZ reaction can drive locomotion,which results from the difference between the push and pull forces in the wavefront and waveback,respectively.A self-oscillating gel was subject not only to the asymmetric forces engendered by the propagation of the chemical waves,but also to the additional forces originating from the capillary effect in the polymer skeleton.The directions of wave-driven forces at two ends of a gel were the same,while the additional forces were opposite.On the basis of the force balance equation of the self-oscillating gel(relationship between the stress tensor and the motion velocity of the gel),it was certain that the one ends of a self-oscillating gel in a tube were squeezed unequally during unidirectional motion,exiting new waves of higher frequency and ultimately giving rise to reversal of the direction of chemical waves' propagation.With the reversal of the direction of chemical wave propagation,the direction of asymmetric forces reversed and gave rise to a nonmonotonic evolution of the gel locomotion velocity.Further studies show that the time required for chemical waves reversal can be shortened by increasing the concentration of malonic acid and bromate.2.According to the I-f relationship of self-oscillating gels and the theory of direct wave and retrograde wave locomotion,the direct and retrograde wave locomotion of self-oscillating gels were realized and a new region of direct wave locomotion at low light intensity was found in experiments.The oscillatory dynamics of homogeneous reaction system and self-oscillating gels system were compared.It was found that with the increase of light intensity,the homogeneous reaction system only shows simple oscillatory dynamics,while the oscillatory dynamics of the gels system transit from simple oscillations to complex oscillations via bifurcation.The effect of parameter ?(a Oregonator model parameter of the BZ reaction,used to describe the concentration of BZ reaction substrates)on the oscillatory dynamics of the gels system was studied: when 0.0820 ? ? ? 0.1478,the oscillation dynamics of the gels system underwent bifurcation and displayed complex oscillations.when ? ? 0.1805 or? ? 0.0492,there were only simple oscillations without bifurcation.when ? = 0.1478,an unreported complex oscillatory region at low light intensity was found.The relationship between the locomotion modes and the local oscillatory dynamics of self-oscillating gels was obtained.The retrograde wave locomotion of self-oscillating gels took place in the simple oscillatory region,while the direct wave locomotion took place in the complex oscillatory region.3.The systematic design of self-oscillating gels' phototactic locomotion was proposed According to the I-f relationship of self-oscillating gels,and the relationship between the locomotion modes of gels and light intensity,a design scheme of phototactic locomotion of self-oscillating gels was proposed by establishing the spatial difference of light intensity,the direction of chemical waves' propagation and the determination of the mode of gel locomotion.The positive phototactic locomotion of gel via direct and retrograde waves,the negative phototactic locomotion of gel via direct and retrograde waves,and the double-way phototactic locomotion of self-oscillating gels were designed systematically in the same type and different types of dynamic region of the I-f relationship,respectively.There are 71 figures,9 tables and 128 references in this thesis.