Three-dimensional photolithography technology for a fiber substrate using a microfabricated exposure module

This paper proposes a new three-dimensional (3D) photolithography technology for a high-resolution micropatterning process on a fiber substrate. A brief review on the lithography technology of the non-planar surface is also presented. The proposed technology mainly comprises the microfabrication of the 3D exposure module and the spray deposition of thin resist films on the fiber. The 3D exposure module is successfully prepared by the wet etching of a quartz substrate and the projection exposure method. The chief advantages of the 3D exposure module are long service life, low cost, narrow print gap and thus high resolution. A novel spray coating system has been developed for the preparation of uniform and thin resist films on the fibers, which are necessary for the high-resolution micropatterning process. The spray deposition process on the 125 µm in-diameter optical fiber has been systematically investigated. The viscosity and volatility of the resist solutions have complicated effects because the spray-coating deposition process on the fiber mainly consisted of the impinging region. The uniform and thin resist film down to 1 µm thick had been successfully achieved. Fine patterns with the line width down to 6 µm were successfully formed on the optical fiber by using the microfabricated exposure module. Preliminary photolithography experiments confirmed that the new 3D photolithography technology is one attractive low-cost solution to the integration of micro transducers onto the fibers for various applications. The 3D exposure module could also enable the continuous photolithography process on the fibers.