Investigation Into The Output Force And Tremor Characteristics Of Bionic Artificial Muscle Based On Freeze-drying Process

With the continuous development of robots and the birth of special polymer materials and smart materials,artificial muscles,which are the key to robots and intelligent mechanical systems,have become the focus of research in the field of bionics.As a new type of intelligent material with rapidly developing,bionic artificial muscles are constantly arousing the research upsurge of scientists all over the world,and have important application value in engineering fields such as aerospace,biomimetic robots and biomedical.However,it is found that biomimetic artificial muscle still has many problems that affect its practical needs,such as the milli-level output force greatly limit its application,and there is a "pathological tremor" phenomenon similar to human muscle in the process of force output,which can significantly affect the stability and performance of bionic artificial muscles in a certain range.Therefore,in order to promote the development of bionic artificial muscles in practical applications,it is urgent to conduct in-depth research on this tremor phenomenon.Aiming at the problem of improving the actuation performance and work instability caused by the output force tremor behavior of bionic artificial muscle in electric excitation experiments,the preparation method of bionic artificial muscle is proposed by using natural macromolecule sodium alginate as raw material and combining with freeze-drying process.The effect of water content on the output force performance and the output force tremor behavior of bionic artificial muscle are studied with glycerol as moisturizer.The effect of freeze-forming temperature on the output force performance and the tremor characteristics of bionic artificial muscle are studied by using the freezing forming temperature as the variable factor.In order to solve the problems of high cost of traditional bionic artificial muscles and toxicity of biological cross-linking,bio-crosslinking agent was used to cross-link the driving layer to study the influence of cross-linking ratio on the output force performance and the tremor characteristics of bionic artificial muscle.And the main research work is as follows.(1)A biomimetic artificial muscle is prepared by using natural polymer sodium alginate,and a preparation method of a bionic artificial muscle is proposed.The output force and displacement test system of bionic artificial muscle and the output force tremor evaluation system(mechanical properties,electrochemical performance,ion channel,water retention rate performance,etc.)of bionic artificial muscle are established.The effect of sodium alginate concentration on the performance of driving layer of bionic artificial muscle is studied,and the optimum concentration of sodium alginate for preparing bionic artificial muscle is determined.(2)Using glycerol as a moisturizer,the effects of driving layers with different moisturizers on the output force and its tremor characteristics of bionic artificial muscle are studied.The effects of moisturizers on the output force performance,response speed and tremor characteristics of bionic artificial muscle were studied by analyzing the effect of different moisturizers on the water content in the driving layer.The mechanism of the effect of the amount of moisturizer on the output force performance,response speed and tremor characteristics of bionic artificial muscle was explained,the molecular weight of moisturizer is small,which can be inserted into the molecular chain of sodium alginate and form hydrogen bonds.The hydrogen bonds formed between sodium alginate molecules are destroyed and the number of hydrogen bonds decreases,which increases the fluidity and slip ability of polymer chains.With the increase of water content in the driving layer,the hydrogen bond formed between macromolecules is reduced,the interaction force between macromolecules is weakened,and the activation energy required for the rotation of macromolecules in the chain is reduced,which makes it easy to produce deformation,thus enhancing the output force performance and response speed of the bionic artificial muscle.Too large amount of moisturizers does not significantly enhance the water content in the driving layer,but also increases the movement resistance of ions in the driving layer due to the viscous resistance of glycerol itself.(3)The bionic artificial muscles are prepared by the freezing process,and the output force,response speed and tremor characteristics behavior of bionic artificial muscle at different freezing temperature are studied.According to the performance test of the driving layer,the difference between the output force and its tremor characteristics of the bionic artificial muscle prepared at each freezing forming temperature is given,the optimal freezing temperature is determined,and the mechanism of improving the output force,response speed and tremor behavior of bionic artificial muscle by freezing forming temperature is clarified.The higher freezing temperature makes the crystal structure of the driving layer unstable,and the shrinkage is more serious and more defects after lyophilization,which is not conducive to the movement of ions inside the driving layer.The lower freezing temperature forms fine crystal grains,the interdiffusion between the crystal grains enhances their binding force and the connectivity of ion channels is enhanced,which provides a large diameter channel for the ions moving inside the driving layer.However,the crystallization temperature of the driving liquid is fixed,too low freezing temperature does not significantly improve the output force,response speed and tremor characteristics of bionic artificial muscle.(4)Bionic artificial muscles were prepared by using calcium chloride solution as cross-linking agent.The existence of cross-linked structure inside the driving layer was proved by Fourier transform infrared spectroscopy and microstructure of the driving layer.Through the experiment of different cross-linking agent ratios,the output performance,response speed and tremor characteristics of bionic artificial muscle output force are studied.Through the analysis of the output force and its tremor behavior of bionic artificial muscles by the performance experiments of driving layers with different cross-linking agent ratios,the improvement mechanism of biocrosslinking on the output force performance,response speed and tremor characteristics of bionic artificial muscles is clarified.Bio-crosslinking will produce cross-linking structure in the driving layer,which will change the spatial structure in the driving layer to a certain extent.Uncrosslinked driving layer will cause the loss of driving fluid and water due to the excessive internal ion channels,which is not conducive to the force output of bionic artificial muscle.The excessive cross-linking ratio may cause the connectivity between the ion channels inside the driving layer to be poor due to the agglomerated structure inside the driving layer,and the movement channel provided by the ions is limited,thereby making the inside of the driving layer Ion motion is bound.(5)Based on the predictive study of the output tremor behavior of bionic artificial muscles,combined with the characteristics of bionic artificial muscle output tremor,the main characteristics of gray prediction and the related theory of gray system,the gray prediction method is used to predict the tremor behavior of bionic artificial muscle output force.Based on GM(1,1)model,the predictive differential equation of output force tremor characteristics of bionic artificial muscle was established.The tremor time of bionic artificial muscle was predicted and analyzed when the amount of moisturizer was 4 ml.The GM(1,1)model is improved by adding sliding average calculation,monotonicity test and concave-convex judgment to improve the prediction accuracy of the model,and the mathematical model is verified by the experimental data.