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Sensors 2017, 17(12), 2825;

Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy

Research Group of Food Safety, Korea Food Research Institute, 245, Nongsaengmyeong-ro, Iseo-myeon, Wanju-gun, Jeollabuk-do 55365, Korea
Department of Molecular Science and Technology, Ajou University, Suwon 16499, Korea
Author to whom correspondence should be addressed.
Received: 24 October 2017 / Revised: 28 November 2017 / Accepted: 4 December 2017 / Published: 6 December 2017
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [1327 KB, uploaded 6 December 2017]   |  


We experimentally modulate the refractive index and the absorption coefficient of an SU-8 dry film in the terahertz region by UV light (362 nm) exposure with time dependency. Consequently, the refractive index of SU-8 film is increased by approximately 6% after UV light exposure. Moreover, the absorption coefficient also changes significantly. Using the reflective terahertz imaging technique, in addition, we can read security information printed by UV treatment on an SU-8 film that is transparent in the visible spectrum. From these results, we successfully demonstrate security printing and reading by using photoresist materials and the terahertz technique. This investigation would provide a new insight into anti-counterfeiting applications in fields that need security. View Full-Text
Keywords: terahertz spectroscopy; anti-counterfeiting; security; photoresist material terahertz spectroscopy; anti-counterfeiting; security; photoresist material

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Shin, H.J.; Lim, M.-C.; Park, K.; Kim, S.-H.; Choi, S.-W.; Ok, G. Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy. Sensors 2017, 17, 2825.

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