Low-Cost Precision Patterning of Transparent Conductors and Failure Mode Analysis for Liquid Crystal Meandered Delay Lines

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DOI:

https://doi.org/10.4302/plp.v18i2.1365

Abstract

This letter details an optimized, low-cost process for the photolithographic patterning of Indium Tin Oxide (ITO) on glass and polycarbonate (PC) substrates for applications in microwave devices, such as liquid crystal-embedded meandered delay lines. A comprehensive fabrication protocol for both substrate types is presented, utilizing positive photoresists (AZ4562 and AZ5214E) and hydrochloric acid (HCl) etching. While high-fidelity patterning with sub-micron accuracy was achieved on glass substrates, the implementation on PC substrates revealed a critical failure mode: film cracking induced by thermal expansion coefficient mismatch. This study investigates the root cause of this cracking, linking it to the significant difference in the Coefficients of Thermal Expansion (CTE) between ITO (8.5 × 10⁻⁶ /K) and PC (70.2 × 10⁻⁶ /K). We demonstrate that replacing conventional thermal processing with room-temperature dehydration in a vacuum desiccator successfully mitigates this failure, enabling the fabrication of uniform and accurate ITO patterns on thermally sensitive polymer substrates.

 

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References

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Author Biography

Jinfeng Li, Beijing Institute of Technology

Prof. Jinfeng Li is a microwave engineer, a specialist in novel reconfigurable RF devices, as well as an authority on liquid crystals-based microwave and millimetre-wave technology. He received the Ph.D. degree in liquid crystals-based microwave and millimeter-wave electronics engineering from University of Cambridge. Prof. Li was a recipient of the IET Award, the AP Jarvis Prize (highest final-year-project honour in University of Birmingham), the AETiC Highly Cited Article Award 2023, the 2024 Top 1000 Reviewers Prize, and three Best Paper Awards at IEEE, IOP and IET conferences, respectively. He is recognised as among the World’s Top 2% Scientists List for 2025 by Stanford University and Elsevier (career-long and single recent year data - Top 2% Listed Years: 2025, 2024, 2023, 2022, 2021). He was a Cambridge Trust Scholar, Speaker at IEEE AP-S/URSI 2024 and the 50th & 46th European Microwave Conferences, Emerging Technologist with Barclays UK, Editorial Board member of three Science Citation Index journals, TPC and Session Chair of ten IEEE conferences, including IEEE ISAP (27th International Symposium on Antennas and Propagation), IEEE 15th International Conference on Microwave and Millimeter Wave Technology (ICMMT 2023), IEEE/IFAC 10th & 11th International Conference on Control, Decision and Information Technologies (CoDIT 2024 & CoDIT 2025), IEEE 17th ICSPS 2025, IEEE COINS 2024, IEEE VCC 2024, IEEE ICECET 2025, IEEE SNAMS 2019, and 5th China and International Young Scientist Terahertz Conference etc. He was elected Senior Member of the China Institute of Communications (CIC), Top 1% Reviewer on Publons (Web of Science), Reviewing Expert for the China Academic Degrees and Graduate Education Development Center, Grants Reviewer for the National Natural Science Foundation of China (NSFC), Newton Prize (£1m fund) reviewer for the UK National Commission for UNESCO, and Grants Reviewer for the Health and Social Care Delivery Research (HSDR) fund from National Institute for Health Research (NIHR), UK. Prof. Li is also an award-winning Concert Pianist and Composer with over 20 piano recitals across China and the UK (2004 - now). Recognised as a master of musical improvisation, he has captivated global audiences with his innovative reinterpretations of classical repertoire. With over one million followers across digital platforms, his performances bridge tradition and contemporary artistry. Pianist and scientist Jinfeng Li draws profound inspiration from his scientific research to inform his original musical compositions. He was elected National-level Young Talent in 2023. He teaches four undergraduate modules, including (1) States of the Arts in Liquid Crystals Millimetre-wave Technology for 6G; (2) Frontiers and Progress of Electrical and Computer Engineering; (3) States of the Arts in Piano; and (4) Frontiers of Electronic Science and Technology. He and his student won the Best Paper Award at IET GEn-CITy 2024. Electronics Letters (Wiley & IET) featured Prof. Li’s journal article in an Editor Pick in June 2025.

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Published

2026-07-01

How to Cite

[1]
J. Li, “Low-Cost Precision Patterning of Transparent Conductors and Failure Mode Analysis for Liquid Crystal Meandered Delay Lines”, Photonics Lett. Pol., vol. 18, no. 2, pp. 29–31, Jul. 2026.

Issue

Vol. 18 No. 2 (2026)

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Articles

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Copyright (c) 2026 Jinfeng Li

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