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Tradeoff Control of Multi-exposure Lithography for SU-8 Photochemical Reaction Channel Formation

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Abstract

A method involving multi-exposure with low-power is presented to fabricate an SU-8 mold based on a digital micromirror device (DMD) maskless lithography with an LED source at a wavelength of 405 nm. The SU-8 mold is used for the fabrication of a PDMS concentration gradient generator (CGG). During a one-time exposure, it is easy to over-expose at the top and under-expose at the bottom of a thick SU-8, which then forms a T-shaped structure. This is more obvious for high-absorption coefficients such as 365 nm. We found that by taking advantage of the partially absorbed and partially transmissive characteristics of the 405-nm wavelength, multi-exposure can form an effective photochemical reaction channel in SU-8 and can solve the problem mentioned above. However, excessive exposure will cause the linewidth to increase, therefore, it is necessary to find a tradeoff for the number of multi-exposure times. For a 55-µm thick SU-8, the tradeoff threshold is found to be 25. Three types of SU-8 CGG molds were fabricated at this threshold. The results indicate that the actual profile of the SU-8 mold shows good agreement with the design profile without any T-shaped structures.

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Acknowledgements

This work was funded by Research and Development planning project in key areas of Guangdong Province (grant no. 2020B090924 001) and Guangzhou Science and Technology planning project (202002030210). The authors would like to thank the Analysis and Test center of GDUT for use of its LSCM facility and thank Editage [www.editage.cn] for English language polishing.

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Authors and Affiliations

  1. School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou, 510006, People’s Republic of China

    Qi-Ming Chen, Jin-Yun Zhou, Yi-Ming Hu & Qi Zheng

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  1. Qi-Ming Chen
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  2. Jin-Yun Zhou
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  3. Yi-Ming Hu
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Correspondence to Jin-Yun Zhou.

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Chen, QM., Zhou, JY., Hu, YM. et al. Tradeoff Control of Multi-exposure Lithography for SU-8 Photochemical Reaction Channel Formation. BioChip J 14, 369–380 (2020). https://doi.org/10.1007/s13206-020-4405-y

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  • DOI: https://doi.org/10.1007/s13206-020-4405-y

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