The Carbonized SU-8 Elctrospun Nano-Fiber for an Electrode in the Energy Storage Device

The Nano-fiber has been used for many applications, such as tissue scaffolding, separator, due to the advantages of large surface area and superior mechanical performance. Currently, Electrospinning is the most important method to fabricate micro or nano fibers for mass production. SU-8, negative photo-resist is widely used in conventional lithography process and especially, the carbonized SU-8 is applied for C-MEMS, bio-MEMS. However, SU-8 is a new polymer solution which began to be studied only recently for electrospun fibers. The SU-8 photo-resist can be a cost-effective polymer solution for elctrospinning, since it can be made easily to be patterned carbon nano-fiber. A negative photo-resist, SU-8 2025 (Microchem Inc.) is used as a polymer solution for electrospinning. The setup for electrospinning system consists of a high voltage dc power supply (ESN-HV30, Nanonc, Inc., Korea), a syringe pump (KDS 100, KD Scientific, Inc., USA), a 5ml syringe with a tip which diameter is 0.4 mm. To investigate on the variation of diameters of electrospun fibers, the applied voltage and distance between the syringe tip and target were varied from 11 to 19kV and from 10 to 30 cm, respectively. The flow rate of syringe pump also was varied from 0.6 to 1.4 ml/h. For the lithography process, the electrospun fibers deposited on Si-Substrate were exposed for 100 seconds with 365nm UV exposure system (OS-1K, JSE, Inc., Korea). Pyrolysis process was undergone to 1173K under inert N2 atmosphere and the electrospun SU-8 nano-fibers were converted to carbon nano-fibers. The fiber diameter and surface are analyzed by FE-SEM (Sigma, Carl Zeiss, Inc., Germany) and XPS.