Research On 4D Printed Shape Memory Polymers And Their Adaptive Dynamic Devices

Shape memory polymer(SMP)is an intelligent material with inherent characteristics such as large deformability,excellent flexibility,light weight,easy processing,and biodegradability.The emergence of smart materials weakens the boundary between functional materials and structural materials and shows good application prospects in the fields of tissue engineering,biomedicine,and smart structures.With the development of 3D printing technology,material processing methods have achieved rapid changes from two-dimensional to three-dimensional,and the concept of 4D printing has also emerged.4D printing technology is to realize the transformation of shape or other properties of 3D printed structures under specific stimuli by means of 3D printing of smart materials.However,intelligent materials suitable for 4D printing are rarely involved in current research.Based on this,this paper first develops two SMP suitable for 4D printing and explores their respective application potential.The main research contents and conclusions are as follows:(1)Epoxy vinyl ester was used to equip a strong and tough shape memory polymer printing ink with UV curing function,and a high-precision model was printed by a DLP 3D photo-curing printer.The microstructure under the SEM image reached the micron level.In addition,a series of shape memory performance characterizations prove the excellent shape memory performance and toughness of the material.The printed classic Eiffel Tower model can make 90° bending without cracks,which is more powerful to prove the toughness of the material.The difference of thermodynamic properties of materials under different treatment methods was also explored.The difference of thermodynamic properties of materials under different treatment methods was also explored.Moreover,the heat-treated material can achieve a strain increase of300 ～ 400 % at 15-20 degrees above the glass transition temperature.(2)a UV-curable shape memory polymer printing ink with higher toughness and strength was prepared by using PEG400 DA,8413 and HEMA.In order to select the optimal system,a series of shape memory polymer systems were prepared by using different amounts of functional crosslinking agents,and the effects of different crosslinking agents on the thermodynamic properties of the materials were investigated.Subsequently,the gradient printing of the material can be realized by gray-scale exposure,and the hydrophilic groups of PEG400 DA and HEMA can realize the underwater development effect by combining the performance differences of different gradient materials.Finally,combined with the inherent shape memory function of the material,the dual encryption function is realized,and it is found that two different encryption effects are obtained according to different processing methods:permanent encryption or permanent decryption.