Femtosecond Laser Two-Photon Direct Writing On Polyimide Film

With the rapid development of flexible electronic technology,integrated technology and micro-nano processing technology have been used to manufacture new flexible electronic components that integrate sensing,filtering,data storage and other functions on flexible materials.Flexible electronic technology has been widely used in various fields and has attracted of attention.As one of the flexible materials with the best comprehensive performance,polyimide film has gradually become an excellent candidate material for manufacturing flexible electronic devices due to its good thermal stability,radiation resistance,and non-toxic characteristics.In recent years,with the development of laser,laser direct writing micro-nano processing technology has become a popular choice for manufacturing flexible electronic devices.Especially,the femtosecond laser two-photon direct writing micro-nano processing technology which is based on the two-photon absorption principle and can break through the optical diffraction limit,has attracted researchers' attention.The micro-nano devices manufactured by this technology have been widely used in biology,medical,chemical and other fields.In this thesis,we firstly introduce the concept of flexible electronics,the development and application of flexible electronic devices.Then we introduce the characteristics of laser direct writing processing technology and its applications in manufacturing flexible electronic devices.We focus on the femtosecond laser two-photon direct writing technology based on the principle of two-photon absorption,and its applications in fabricating micro-nano devices;Finally,the basic properties and application fields of polyimide films are introduced.This thesis focuses on femtosecond laser two-photon direct writing of positive and negative photoresist on polyimide film substrate for fabricating microstructures.The main points of the thesis are listed as follows:1.Experimental setup and sample preparation: The femtosecond pulse laser oscillator was used to construct the optical setup two-photon laser direct writing experiments.The polyimide film with radiation resistance,high temperature resistance and excellent flexibility is selected as the substrate,and positive and negative photoresists are selected and spin coated on the polyimide film respectively.2.Femtosecond laser two-photon direct writing negative photoresist on polyimide: Microstructures were prepared by using femtosecond laser two-photon direct writing negative photoresist AR-N 4340 on the substrate of polyimide film.The influences of laser power and scanning speed on the fabrication resolution were studied respectively,and the best fabricated line resolution of 115 nm and the microstructure of IOE letters were obtained on the polyimide film substrate.The flexibility test showed that the sub-wavelength lines fabricated on the polyimide film possessed good flexibility.This research proves the feasibility of femtosecond laser two-photon direct write negative photoresist on polyimide film,and provides experimental basis for the its potential application in the manufacture of flexible electronic device.3.Femtosecond laser two-photon direct writing positive photoresist on polyimide: On the substrate of polyimide film,microstructures were fabricated by using femtosecond laser two-photon direct writing positive photoresist SUN-140 P.The influences of laser power and scanning speed on the processing resolution were studied.A best line resolution of 252 nm,the logo of Zhengzhou University and the pattern of Bauhinia were fabricated on the polyimide film substrate.The flexibility test showed that the sub-wavelength lines prepared on the polyimide film possessed good flexibility.This research proves the feasibility of femtosecond laser two-photon direct writing positive photoresist on polyimide film.It also provides experimental basis for its future application in manufacturing flexible electronic devices.