3D Printed Silicones With Shape Morphing And Low-temperature Ultraelasticity

As an emerging manufacturing technology,3D printing provides a perfect solution to the problems such as difficult personalization,complexity and large amount of consumables in the traditional cutting process.However,with the development of various engineering fields,people begin to pursue the intellectualization of products,and static products formed by 3D printing are difficult to meet the needs.Therefore,3D printing deformable smart materials come into people’s field of vision.In this paper,deformable silicon foams were prepared based on direct writing 3D printing technology,and the mechanical properties of the subsequent multi-scale pore foams were investigated at low temperature.It provides a simple and effective method for preparing dynamic functional structures,which complements the deficiency of foam elastomer research in the direction of low temperature,and is expected to play a role in polar scientific research,aviation and other advanced industries.The main research content of this topic is as follows:（1）Based on the direct writing 3D printing technology,self-made silicone rubber ink was used as the printing paste,sodium chloride particles were mixed into the paste,and the unique osmotic pressure driven deformation mechanism was used to realize the direct writing3D printing of deformable intelligent materials.The preparation process and deformation mechanism were explored.Firstly,the rheological properties and mechanical strength of the printing stock are analyzed,and the printability of the ink is expounded.The deformation mechanism of single-layer structure was studied,and the double-layer structure with bending deformation was prepared.The influence of water temperature,linear width combination,sodium chloride content and modulus on bending deformation was studied.The results showed that:1)in the preparation of printing paste,the mechanical strength of the vapor phase silica was obviously improved,and polyether siloxane could effectively improve the shape retention.2)In the study of deformation effect,the size of single-layer structure increases first and then gradually decreases to close to the initial size in the process of deformation.The increase of water temperature can accelerate the deformation rate,and the deformation result is affected by the linear width,sodium chloride content and modulus.3)In the aspect of application exploration,solid splines that can bear 24 times of its own weight are printed,and the sensitivity of piezoresistive sensor prepared by osmotic pressure mechanism can reach 54.56 k Pa^-1.Through the above experiments,the deformation mechanism and law are clarified,and the application is explored.（2）Sodium chloride particles were used as sacrificed-template to construct micro-nano pores,and direct writing 3D printing technology was used to construct millimeter-scale uniform pores,so as to realize the preparation of multi-scale porous silicon foam.The density is as low as 0.29 g/cm³,and the total porosity is as high as 75.9%.At the same time,the phenyl functional group was introduced into the base glue to prepare the silicon foam with low temperature resistance and high elasticity.The mechanical properties of foam were investigated,including the maximum stress,strain loss,compressive work and energy dissipation coefficient at room temperature/low temperature.The results show that:1)the foam has excellent ultimate compression performance,can withstand 85%compression strain,and still has good resilience when the load exceeds 66000 times of its own weight;In the multi-cycle compression experiment,it can still maintain elasticity in the environment of25℃to-60℃,and the four parameters almost remain unchanged in the cycle,with good fatigue resistance.The foams with different porosity can be prepared effectively by controlling the content of sodium chloride,and their compressive properties are obviously different.2)In the aspect of sensor application,the sensitivity of piezoresistive sensor can be effectively improved by mixing conductive filler into the print paste and multi-scale pores,and the sensitivity of the preliminary design structure can reach 19.93 k Pa^-1.Through the above experiments,the high elasticity of silicon foam in low temperature environment is clarified,and the application is explored.