Research On Femtosecond Laser Bionic 4D Printing Based On Environmental Response Tunable Hydrogel

Since the 4D printing technology capable of programming and controlling the structural shape has been proposed in 2013,it has been widely used in various fields such as micromechanics and biomedicine.Hydrogel with excellent biocompatibility and deformation ability is an excellent 4D printing material.However,the current 4D printing structures based on hydrogel materials have large scales,which are all on the order of millimeters,and the response speed is more than a few seconds.Therefore,the hydrogel 4D printing technology has further room for improvement on both the spatial and temporal scales.The femtosecond laser two-photon polymerization direct writing technology has powerful processing capabilities,high processing accuracy,and can realize micro-nano-scale three-dimensional processing.This paper proposes a pH-tuned environmentally-responsive hydrogel femtosecond laser 4D biomimetic printing technology,which enables 4D printing with fast response in the micrometer scale.Through this technology,multiple-degree-of-freedom complex deformation of leaf-like microstructures is achieved,and the technology is finally applied to aspects such as particle capture and magnetron transfer.In addition,in terms of improving the efficiency of the femtosecond laser processing system,a part of the high-efficiency processing method for rapidly processing the even-lobed bifurcated micro oblique cylinder by vortex light superposition using a spatial light modulator is also introduced,which greatly improves the efficiency of fabricating microstructures by femtosecond laser direct writing.In this paper,the femtosecond laser two-photon polymerization direct writing technology is used to process the pH-tuned hydrogel.By adjusting the processing parameters,the deformation control of the micro-scale leaf structure can be achieved,including expansion and contraction,torsion,twist and shrinkage.Deformation effects such as various degrees of freedom of movement,and the response time does not exceed 0.5 s.Previously reported work on hydrogel 4D printing has reduced the structural scale and response speed by at least two and one order of magnitude,respectively.By using the size difference of the pores on the microcage structure processed by the pH-tuned hydrogel during expansion and contraction,the capture and release of the microparticles are realized.Through the magnetic nanoparticle adsorption on the microcage structure,the capture and release of the microparticles and the magnetron transfer were realized.