Fabrication of Solution-Based Cylindrical Microlens with High Aspect Ratio

고종횡비를 갖는 용액기반 원통형 마이크로렌즈 제조

  • Jeon, Kyungjun (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Lee, Jinyoung (Interdisciplinary Program in Creative Engineering, Korea University of Technology and Education) ;
  • Park, Jongwoon (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
  • 전경준 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 이진영 (한국기술교육대학교 창의융합공학협동과정) ;
  • 박종운 (한국기술교육대학교 전기.전자.통신공학부)
  • Received : 2021.03.09
  • Accepted : 2021.03.15
  • Published : 2021.03.31


A cylindrical microlens (CML) has been widely used as an optical element for organic light-emitting diodes (OLEDs), light diffusers, image sensors, 3D imaging, etc. To fabricate high-performance optoelectronic devices, the CML with high aspect ratio is demanded. In this work, we report on facile solution-based processes (i.e., slot-die and needle coatings) to fabricate the CML using poly(methyl methacrylate) (PMMA). It is found that compared with needle coating, slot-die coating provides the CML with lower aspect ratio due to the wide spread of solution along the hydrophilic head lip. Although needle coating provides the CML with high aspect ratio, it requires a high precision needle array module. To demonstrate that the aspect ratio of CML can be enhanced using slot-die coating, we have varied the molecular weight of PMMA. We can achieve the CML with higher aspect ratio using PMMA with lower molecular weight at a fixed viscosity because of the higher concentration of PMMA solute in the solution. We have also shown that the aspect ratio of CML can be further boosted by coating it repeatedly. With this scheme, we have fabricated the CML with the width of 252 ㎛ and the thickness of 5.95 ㎛ (aspect ratio=0.024). To visualize its light diffusion property, we have irradiated a laser beam to the CML and observed that the laser beam spreads widely in the vertical direction of the CML.


  1. Stellmacher, A. et al., "Fast and cost effective fabrication of microlens arrays for enhancing light out-coupling of organic light-emitting diodes", Mater. Lett., Vol. 252, pp. 268-271, 2019. https://doi.org/10.1016/j.matlet.2019.05.133
  2. Shan, T., Liu, T., Mohaime, M., Salam, B., and Liu, Y., "Large format cylindrical lens films formed by roll-to-roll ultraviolet embossing and applications as diffusion films", J. Micromech. Microeng., Vol. 25, 035029, 2015. https://doi.org/10.1088/0960-1317/25/3/035029
  3. Luo, Z. et al., "Rapid fabrication of cylindrical microlens array by shaped femtosecond laser direct writing", Appl. Phys. A, Vol. 122, pp. 1-5, 2016.
  4. Qiu, J., Li, M., Ye, H., Yang, C., and Shi, C., "Fabrication of high fill factor cylindrical microlens array with isolated thermal reflow", Appl. Opt., Vol. 57, pp. 7296-7302, 2018. https://doi.org/10.1364/AO.57.007296
  5. Dutta, R., Kan, J., Bettiol, A., and Watt, F., "Polymer microlens replication by Nanoimprint Lithography using proton beam fabricated Ni stamp", Nucl. Instrum. Methods Phys. Res. B., Vol. 260, pp. 464-467, 2007. https://doi.org/10.1016/j.nimb.2007.02.064
  6. Lee, J., and Park. J., "Fabrication of Cylindrical Microlens Using Slot-die Coating and Thermal Reflow Method", J. of The Korean Society of Semiconductor & Display Technology, Vol. 19, pp. 30-35, 2020.
  7. Ding, X., Liu, J., and Harris, T., "A review of the operating limits in slot die coating processes", AIChE J., Vol. 62, pp. 2508-2524, 2016. https://doi.org/10.1002/aic.15268
  8. Lee, K., Liu, L., and Liu, T., "Minimum Wet Thickness in Extrusion Slot Coating", Chem. Eng. Sci. Vol. 47, pp. 1703-1713, 1992. https://doi.org/10.1016/0009-2509(92)85018-7
  9. Choi, I., and Kim, J., "A pneumatically driven inkjet printing system for highly viscous microdroplet formation", Micro Nanosyst. Lett., Vol. 4, 2016.
  10. Baruah, S. D., and Laskar, N. C., "Relationship between Molecular Weight and Viscosity for Polydispersed Poly(n-docosyl acrylate)", Polym. J., Vol. 28, pp. 893-895, 1996. https://doi.org/10.1295/polymj.28.893
  11. Liu, C., Lin, Y., Lai, W., and Huang, W., "Improved performance of inkjet-printed Ag source/drain electrodes for organic thin-film transistors by overcoming the coffee ring effects", AIP Adv., Vol. 7, 115008, 2017. https://doi.org/10.1063/1.5004136