Preparation And Research Of Natural Polysaccharide Compound Hydrogel Actuator

Owing to their fascinating ability for programmable actuations in response to various stimuli?e.g.,temperature,pH,ion strength?IS?,light,etc.?and then change their volume or shape,self-shaping hydrogels hold many potential engineering and biomedical applications in drug delivery,tissue engineering,biomimetic actuators,medical devices,etc.Although considerable progress has been made recently in terms of the sophistication of the shapes and the diversity of the function for self-shaping hydrogels,their applications in biomedicine and engineering remain challenging.The major limitations include the unsatisfactory biocompatibility and biodegradation of synthetic polymers involved in existing hydrogel actuators.Natural polyelectrolytes are the ideal candidate materials for the hydrogel actuators.Besides of inherently prominent advantages of renewability,biocompatibility and biodegradability for nature polymers,they possess the ability of changing their own conformations in response to external stimuli?e.g.pH and IS?.To integrate polyelectrolytes into macroscopic materials,layer-by-layer?LBL?assembly is the most common used fabrication method,which is carried out by sequential adsorption of oppositely charge polyelectrolytes onto various substrates.However,the time-consuming LBL technique can only generate ultrathin films on a nanometers scale that can not be used as freestanding material unless by chemical post-treatment,and thus is inapplicable for the fabricating of biocompatible hydrogel actuators.It is still a great challenge now to integrate natural polyelectrolytes to form biocompatible hydrogel actuators in a green and facial way.In this contribution,we present a very simple approach for the fabrication of gradient all-polysaccharide polyelectrolyte complex?PEC?hydrogel actuators,which achieves multiple responses in temperature,pH,ionic strength,etc.,and we can obtained high sensitivity by adjusting the difference in gradient structure.1.An all-polysaccharide hydrogel film with gradient-structured was prepared by a driving-diffusion interface reaction?10 s?and using natural polyelectrolytes as raw material.The film thickness increased with the reaction time.Test results of FT-IR,SEM and XPS show that the forming of gradient-structured.Besides,the as-prepared complex films can address the challenge of simultaneously improving the mechanical properties?2.26 MPa?,response kinetics?2 s?and programmable locomotion capability for practical applications.Upon the trigger of salt and acid,the hydrogel sheet can undergo a distinct sequential double folding deformation behavior.Furthermore,the film enables various more sophisticated 2D and 3D shape transformations by Ca²⁺crosslinking of SA partly.2.A hydrogel with a larger gradient structures difference was prepared by adjusting the molecular weights of SA and CS and making the upper and lower molecules diffuse with each other,which has high sensitive response in a physiological environment?37°C 0.9%NaCl?.As the same time,the non-toxicity and biocompatibility of the hydrogel were verified by cytotoxicity tests.Thus,we prepared a hydrogel with biocompatibility in both the material and the stimulation environment.