Research-oriented experimental teaching design and practice based on the adhesion properties of magnetically controlled surfaces
[Objective]To effectively improve students'learning of mechanical theory and comprehensive innovation ability,the structural design and mechanical performance analysis of intelligent materials is an important part of the course of design mechanics.The intelligent adhesive surface is the key component of wearable design and underwater robot adsorption mechanisms.Research on the adhesion properties of magnetically controlled surfaces is integrated into the design mechanics course as an exploratory,innovative,experimental teaching project.Adhesion behavior,as a special function or survival ability acquired by organisms in the long-term evolution process,usually has dynamic and adaptive characteristics to adapt to the complex and changing living environment and can realize the rapid transformation of adhesion and motion state through real-time sensing contact.However,the wet adhesive contact interface is a more complex multiscale contact problem,which involves many factors,such as liquid motion,solid surface microstructure deformation,and liquid-solid interface interaction.Thus,the development of intelligent wet adhesive surfaces in the engineering field is difficult,and the underlying mechanisms of the liquid-solid regulations at the wet adhesion interface have not been sufficiently revealed.Adhesion behavior,as a special function or survival ability of organisms,usually has dynamic and adaptive characteristics to adapt to the complex and changing living environment and can realize the rapid transformation of adhesion and motion state.[Methods]To address the challenge of controlling adhesion in wet environments,we designed a magnetic control wet adhesive surface inspired by the precise microstructures and unique movement of a gecko's toe pad.This surface consists of a microcolumn array made from polydimethylsiloxane and carbonyl iron particles.Then,a self-made adhesion tester was designed,and adhesion measurements were conducted.The coupling effect of preload and external stimuli on the wet adhesion performance between a solid substrate and the developed surface,which was an intelligent surface with magnetic field control,simple preparation,and adjustable adhesion,was analyzed.The wet adhesion experimental device was designed,and the mechanical analysis of this surface was conducted.The variations of the adhesion properties of the magnetically controlled surfaces under different magnetic field and load conditions were systematically investigated from the experimental and theoretical points of view,and the solid-liquid-solid surface contact state and control mechanism under the coupling effect of magnetic field and load were analyzed.[Results]The results indicated that the differences in adhesion performance with different magnetic field strengths,orientations,or preload magnitudes primarily stem from variations in the surface microstructure,thereby leading to the distinct wetting behavior of liquid droplets on the surface,manifesting as low-adhesion and high-adhesion states.In situ observation and analysis of theoretical models demonstrated that changes in adhesive force with different magnetic field strengths,orientations,or preload magnitudes are mainly caused by the length of the liquid bridge and the apparent contact angle of the developed surface.Benefiting from the magnetic field adjustment effect of the magnetic microcolumn and the synergistic effect of the external load,the results indicated that adhesion switching between 170 μN and 53 μN can be achieved by changing the magnetic field intensity and the transition from 53 μN to 114 μN can be achieved by changing the direction of the magnetic field.Furthermore,changing the preload can adjust the adhesion force change between 31 μN and 141 μN.[Conclusions]This magnetic response surface provides not only a novel interface for microfluidic control and droplet transport but also a new method for the development of intelligent adhesive surfaces.This design and analysis of magnetically controlled surfaces provide not only a novel interface for microfluidic control and droplet transport but also a new method for the development of intelligent adhesive surfaces.In addition,the experimental teaching and practice based on the adhesion properties of magnetically controlled surfaces help students further understand the concept of intelligent adhesion and improve students'innovative and practical ability.
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