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Title: Nano-Imprint of Photonic-Plasmonic Nanostructures on Novel Polymers

Participants: Boston University – Dianmian Lin (MS ’11) and Professor Luca Dal Negro

Tufts University – Professors David Kaplan and Fiorenzo Omenetto

Funding: Air Force (via the Optical Food Sensing program)

Background: Nanostructure has been extensively exploited to construct photonics and plasmonic devices for light emission enhancement and optical biosensing. Current optical platforms are based on widely used substrate such as silicon, quartz and PDMS. Novel polymers, such as silk biopolymer and organic material have emerged to improve the performance of photonics devices by adding new functions. However, the nanofabrication of photonic-plasmonic nanostructures on the top of these solvent-sensitive polymers pose unique challenges.

Current lithographic methods require energy radiation, elevated-temperature processing, high pressure, wet chemical or aggressive plasma etching during resist processing. The solvents involved, as well as the harsh processing requirements, limit the application to organic material, environment and biomedical engineering, such as OLED, implantable devices and environmental monitors.

Description: In this project, in collaboration with Professors Fiorenzo Omenetto and David Kaplan at Tufts University, we demonstrated a rapid nanoimprint method to fabricate both the nanohole pattern and gold nanoparticle pattern on protein-based biopolymer-silk. Nanohole structures are imprinted at room temperature with mold of Si pillars, while gold nanoparticle patterns are predefined on a donor mold, and then transfer imprinted onto the surface of the silk film. By this approach, various patterns with feature sizes down to 25 nano-meter scale can be fabricated over several square centimeters on one substrate.

Results: The SEM images below show imprinted nanostructures on silk and actively doped (luminescent) polymer layers. They demonstrate that a mold can be completely replicated into a silk substrate with high fidelity. Nano-imprintThis technique provides an attractive approach to fabricating large-area nanostructures on the surface of solvent sensitive polymer at great precision and at low cost. Since the imprint procedure relies on mechanical deformation, it preserves the biological, chemical and physical properties of biopolymer. Also, the advantage of chemical/solvent free provides flexibility in choosing organic materials for improved device performance.


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