Patterning over the inner curved surface is important because it allows to obtain seamless flexible imprinting stamps. However, most of the available methods now are suitable for the roller mold with small size. In this study, a completely modified lithography technique is proposed to fabricate microstructure on a hollow mold with 200 mm in inner diameter and 150 mm in length. A spray coating method is adopted. A photoresist film with thickness varying from 5.0 to 6.0 µm is achieved. After that, excimer laser machining method is employed to fabricate a slender photo-mask which can be implemented for UV patterning on the inner surface of a hollow cylinder. On this photo-mask, array hexagonal grids with 30 µm linewidth and totally 145 mm long are prepared. Finally, a 405 nm UV laser diode scans with constant speed over the photo-mask and hence transfer the pattern on the photomask to the resist film. The exposure step is relatively time-saving. If the scanning speed is 30 mms-1, it takes more than one hour a little to pattern the whole roller mold (around 940 cm2 area). Although a seamless flexible stamp has still not achieved, this study demonstrates the potential and possibility of the proposed technique.

[1] Weaver, Peter. The Technique of Lithography. London: B.T. Batsfold, p. 49, 1964.
[2] Tan, Hua. "Applications of Nanoimprint Lithography to Nano-Photonic". PhD diss., Princeton University, pp. 1, 2004.
[3] Haatainen, Tomi. “Stamp fabrication by step and stamp nanoimprinting”. PhD diss., Aalto University, pp. 29, 2011.
[4] Tan, Hua, Andrew Gilbertson, and Stephen Y. Chou. "Roller nanoimprint lithography." Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 16, no. 6 (1998): 3926-3928..
[5] Ahn, Se Hyun, and L. Jay Guo. "Large-area roll-to-roll and roll-to-plate nanoimprint lithography: a step toward high-throughput application of continuous nanoimprinting." ACS nano 3, no. 8: 2304-2310, 2009.
[6] Ok, Jong G., et al. "Continuous and scalable fabrication of flexible metamaterial films via roll-to-roll nanoimprint process for broadband plasmonic infrared filters." Applied Physics Letters 101.22: 223102, 2012.
[7] Mäkelä, Tapio, Tomi Haatainen, Päivi Majander, Jouni Ahopelto, and Vito Lambertini. "Continuous double-sided roll-to-roll imprinting of polymer film." Japanese journal of applied physics 47, no. 6S: 5142, 2008.
[8] Rogers, John A., Zhenan Bao, Anita Makhija, and Paul Braun. "Printing process suitable for reel-to-reel production of high-performance organic transistors and circuits." Advanced materials 11, no. 9: 741-745, 1999.
[9] Ahn, Se Hyun, and L. Jay Guo. "High‐speed roll‐to‐roll nanoimprint lithography on flexible plastic substrates." Advanced materials 20.11: 2044-2049, 2008.
[10] Nietner, Larissa F., and David E. Hardt. "Direct-Write Photolithography for Cylindrical Tooling Fabrication in Roll-to-Roll Microcontact Printing." Journal of Micro and Nano-Manufacturing 3, no. 3: 031006, 2015.
[11] Taniguchi, Jun, and Masao Aratani. "Fabrication of a seamless roll mold by direct writing with an electron beam on a rotating cylindrical substrate." Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 27, no. 6: 2841-2845, 2009.
[12] Chen, Lien-Sheng, Jia-Yush Yen, Yung-Pin Chen, Lon A. Wang, Tien-Tung Chung, Hung-I. Lin, Ping-Hung Chen, and Shu-Hung Chang. "Longitudinal stitching of sub-micron periodic fringes on a roller." Microelectronic Engineering 88, no. 11: 3235-3243, 2011.
 
[13] Microchemicals GmbH. Last accessed 2017. “Dip coating of Photoresists”. Last modified: 2013-11-07. http://www.microchemicals.com/technical_information/dip_coating_photoresist.pdf.
[14] Lee, Yung-Chun, Hong-Wei Chen, and Fei-Bin Hsiao. "Fabrication of seamless roller mold for continuous roller imprinting of microlens array films." Journal of Microelectromechanical Systems 21, no. 2: 316-323, 2012.
[15] Tsai, Sung-Wen, Po-Yu Chen, Shr-Ren Huang, and Yung-Chun Lee. "Fabrication of seamless roller mold with 3D micropatterns using inner curved surface photolithography." Microelectronic Engineering 150: 19-25, 2016.
[16] Tsai, Sung-Wen, Po-Yu Chen, and Yung-Chun Lee. "Fabrication of a seamless roller mold with wavy microstructures using mask-less curved surface beam pen lithography." Journal of Micromechanics and Microengineering 24, no. 4: 045022, 2014.
[17] Joseph E. Petrzelka, David E. Hardt, “Laser direct write system for fabricating seamless roll-to-roll lithography tools”. Proc. SPIE Int Conference: MOEMS-MEMS, vol. 8612, Micromachining and Microfabrication Process Technology XVIII, 861205, 2013.
[18] Tsai, Sung-Wen, and Yung-Chun Lee. "Fabrication of ball-strip convex microlens array using seamless roller mold patterned by curved surface lithography technique." Journal of Micromechanics and Microengineering 24, no. 1: 015014, 2013.
[19] Petrzelka, Joseph E. "Contact region fidelity, sensitivity, and control in roll-based soft lithography." PhD diss., Massachusetts Institute of Technology, pp. 216, 2012.
[20] SanyoDenki Global. Last accessed 2017. “SANMOTION_Model_No_PB_M0008554B”. https://db.sanyodenki.co.jp/downfile/products_e/sanmotion/manuals/sanmotion_pb.html
[21] Graco. Last accessed 2017. “313869L, AirPro EFX Automatic Spray Gun, Instructions/Parts, English”. http://www.graco.com/us/en/products/finishing/airpro-efx-automatic-air-spray-gun.html
[22] Tsung-Lun Wen, Yung-Chun Lee. “Fabrication of seamless roller mold using curved surface beam pen lithography and step-and-rotate lithography”. Master diss, National Cheng Kung University, pp. 67-68, 2015.
[23] Smith, D. Y., E. Shiles, Mitio Inokuti, and E. D. Palik. "Handbook of optical constants of solids." Handbook of Optical Constants of Solids 1: 369-406, 1985.
[24] Chi-Chen Chiu, Yung-Chun Lee. “Development of excimer laser micromachining system for fabricating microlens array and its application.” PhD diss., National Cheng Kung University, pp. 31-37, 2012. 
[25] Hoechst, Last accessed 2017. “AZ® 4000 series photoresist for thick film applications”. http://mfc.engr.arizona.edu/documents/Lithography%20Information/ResistData/AZ_4000_thick.pdf
[26] Zhen-Hao Luo, Yung-Chun Lee. “A digital fabrication system of roller molds based on optical fiber arrays”. Master diss., National Cheng Kung University, pp. 57-58, 2016.