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Patterned direct-write and screen-printing of NIR-to-visible upconverting inks for security applications
Tyler Blumenthal1, Jeevan Meruga, P Stanley May
1Department of Materials and Metallurgical Engineering, South Dakota School of Mines and Technology, 501 St Joseph Street, Rapid City, SD 57701, USA.
Nanotechnology
|April 14, 2012
Summary
Direct-write printing creates polymer security features using luminescent nanocrystals. These covert, upconverting phosphors are visible under laser light, enabling advanced anti-counterfeiting applications.
Area of Science:
- Materials Science
- Optics and Photonics
- Nanotechnology
Background:
- Security printing demands advanced anti-counterfeiting measures.
- Luminescent materials offer unique properties for covert features.
- Upconversion phosphors convert lower energy light to higher energy visible light.
Purpose of the Study:
- To develop direct-write printing methods for polymer-based security features.
- To incorporate luminescent upconversion nanocrystals into printable polymer films.
- To evaluate the feasibility of these features for covert and forensic security applications.
Main Methods:
- Utilized direct-write printing of atomized material and screen-printing techniques.
- Dispersed oleic acid-capped lanthanide-doped nanocrystals (β-NaYF₄:3%Er, 17%Yb) within polymer films.
- Excited printed features with a 980 nm laser to observe visible upconversion emission (540 nm and 660 nm).
Main Results:
- Successfully printed polymer structures with highly resolved features, including text.
- Achieved efficient upconversion luminescence from the nanocrystal-impregnated polymer films.
- Demonstrated printing on various substrates: paper, Kapton®, and glass.
Conclusions:
- Direct-write printing is a viable method for creating advanced security features using upconversion phosphors.
- The printed features are covert and invisible to the naked eye at low concentrations.
- These technologies hold significant potential for anti-counterfeiting and forensic applications.
