The Study On Two-photon Microfabrication Of Hydrogels And Fabrication Of Different Morphologies Of Complex Hydrogels

Hydrogels are defined as water-swollen three-dimensional(3D)networks capable of imbibing water from an aqueous environment.They can provide a high resemblance to the extracellular matrix(ECM)and have good biocompatibility with living organisms.Therefore,hydrogels are widely used in biomedical field such as drug delivery and tissue engineering.To better simulate the microenvironment that the cell reside,hydrogels with more precise configuration are required.The resolution of hydrogels prepared by traditional microfabrication technologies is low.The twophoton polymerization microfabrication(TPPM)has the third-order nonlinear optical properties,and the polymerization only occurred in small volume.Therefore,TPPM can fabricate arbitrary 3D hydrogel microstructures with high resolution.However,the track of laser focus is defined because the focus is controlled by computer in TPPM.If the microstructure that has been processed deform due to insufficient stiffness,the complete microstructure can not be fabricated.Therefore,polymer with enough stiffness is beneficial to obtain high-precision 3D hydrogel in TPPM.Moreover,the stiffness of hydrogel has important influence on cell behavior.To solve these problem,the photoresist has been optimized.Then the optimized photoresist has been used to fabricated microstructures and the Young's modulus of these microstructures have been studied.In our present research,we determined the optimized photoresist through comparing the resolution of microstructures of different patterns fabricated by TPPM.The threshold of line fabrication with this photoresist was 3.50 mW,with the corresponding line width of 151 nm at the writing speed of 10 ?m/s.Moreover,the cubic microstructures with 30 ?m×30 ?m×5 ?m fabricated at various laser power,writing speed and layer distance have been used in Young's modulus study.The obtained value in air was 10~18 MPa,9.0~16.5 MPa and 8.7~28.8 MPa,respectively.The Young's modulus of microstructures at different layer distance in water was determined to be 3~6.5 MPa,close to that of cartilage tissue,which is expected to be used in bone tissue engineering.Finally,we fabricated different kinds of red blood cell microstructure in 30 °,45 °,60 ° and 90 °,and other complex hydrogel microstructures,which are expected to better simulate cell microenvironment.