Switching Chiral Microstructures Prepared By Femtosecond Laser Combined With Capillary Force Self-Assembly

Bottom-up technique is a method of constructing chiral micro/nano structures.Bottom-up method utilizes microscopic forces to realize self-assembly of molecules,particles or structures.Among various microscopic driving forces,capillary force is widely used in self-assembly due to its simplicity,scalability and low cost.However,the bottom-up method is weak in processing complex hierarchical structures because of its simple structure form.Therefore,the combination of top-down and bottom-up method has gradually become an alternative to complex hierarchical micro/nano structures.Based on the remarkable 3D processing characteristics of femtosecond laser,the femtosecond laser printing induced capillary force self-assembly(LPCS)method for preparing microstructures is developed.Many devices in daily life have a variety of function-rich micro/nano structures,such as electronic chips,microfluidic channels and integrated photonic devices.Among them,the chiral structure is a kind of unique hierarchical micro/nano structure.Chirality is a subtle and pervasive phenomenon in nature,such as DNA bimolecular chains,vines,and galaxies.Chiral structure itself has hand-light effect,which makes it of great value in biomolecular detection and other directions.Therefore,researchers are constantly exploring ways to prepare chiral micro/nano structures.Focusing on the LPCS,a novel preparation strategy combining stimulus response and LPCS technology is proposed in this paper,which successfully prepare reversible tunable chiral microstructures.The main contents are as follows:1.By studying the deformation characteristics of temperature-responsive hydrogels,driven by capillary force,reversible bidirectional assembly micropatterns are prepared by using different bending directions of hydrogel microstructure at different temperatures.A temperature-responsive micro-gripper with releasing and capturing ability is obtained.2.By using the cooperative design of anisotropic cross section and spatial distribution,chiral microstructures with switching rotation are prepared.The microstructure can switch different bending directions at different temperatures and finally form a chiral microstructure driven by capillary force.In addition,the effects of processing parameters on the assembly results and the chiral switching speed of the chiral microstructure are also investigated.3.By irradiating vortex light with different phase wavefronts on the opposite chiral assemblies,symmetrical vortical dichroism spectra are obtained,which proves that the prepared microstructure has good chiral tunability and shows its potential applications in chiral photonics.