Multiple Stimuli-responsive Hydrogel Actuators With Multiple Functions

Stimuli-responsive hydrogel actuators,one of the most important intelligent materials,have the ability to generate reversible shape deformation or variation of mechanical properties upon the trigger of certain stimuli.It has been considered as one of the most anticipated candidates as biomimetic material because of the high content of water and low modulus.Recently,diverse type of hydrogel actuators have been fabricated with bilayer,gradient,patterned,and oriented structure,but the existing hydrogel actuators still respond to only one external stimulus and produce simple deformation such as bending.These shortcoming have greatly restricted the development and application of hydrogel actuators.In order to achieving multi-responsiveness and broadening the application fields of hydrogels actuators,the main works have been done and listed as follow:?1?Boronic acid groups were introduced into hydrogel bulks,which can be bonded by PVA?polyvinyl alcohol?through the formation of PBA-diol ester bonds under alkaline condition.Using PVA as supermolecular glue,two hydrogel bulk with boronic acid groups were assembled stably.In addition,a bilayer multi-responsive hydrogel actuator was fabricated by the combination of cationic monomer methacryloxyethyltrimethyl ammonium chloride?METAC?and N-isopropyl acrylamide?NIPAM?in one system.Various 2D and 3D morphologies can be achieved by selectively changing the bonding positions.Finally,the soft grippers with tunable grip force have been fabricated.?2?A novel fluorescent hydrogel actuator with p H and thermo dual responsiveness has been presented.The fluorescent molecule?perylene tetracarboxylic acid,PTCA?was introduced into the gradient structure of PNIPAm/PAAm hydrogel,and the hydrogel exhibited stable thermoresponsive shape deformation and switchable fluorescence performance upon p H trigger.Therefore,fluorescence quenching-based and actuation-based information could be decrypted when exposed to UV light and immersed into warm water,respectively.Moreover,the thermoresponsive actuating behavior can be applied to further encrypt the fluorescence quenching-based information,realizing dual information encryption.?3?Based on Ca²⁺-alginate coordination,a gelatin core with Ca²⁺was placed in the solution of alginate,hydrogel would grow from the core and finally hollow hydrogel could be obtained by dissolving the gelatin core.Using 3D printing and hydrogel assembly,various 3D shape gelatins were prepared,and diverse complex hollow hydrogels were fabricated by the same way base on the 3D gelatin.The obtained hollow hydrogels could be used as pneumatic/hydraulic actuators.Moreover,the capacity that could allow small molecules to pass through render the alginate hollow hydrogels ideal candidates for matter transportation,and reaction containers that could regulate the reaction speed have been demonstrated.In addition,functional polymers or nanoparticles have been introduced into the hydrogel wall,and functional hollow hydrogels have been developed.In summary,this thesis has done related research about the multi-responsive hydrogel actuators.Based on the design of anisotropic structure and chemical components,various multi-responsive hydrogel actuators have been prepared and diverse complex deformation have been achieved.Besides,the fluorescence property has been incorporated into hydrogel network,and dual information encryption was realized by combining of actuating and fluorescence properties.Finally,the multi-functionalization of hydrogel actuators has been achieved by the hollow structure of hydrogel.