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All-water-based electron-beam lithography using silk as a resist

Nature Nanotechnology volume 9, pages 306–310 (2014)Cite this article

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Abstract

Traditional nanofabrication techniques often require complex lithographic steps and the use of toxic chemicals. To move from the laboratory scale to large scales, nanofabrication should be carried out using alternative procedures that are simple, inexpensive and use non-toxic solvents. Recent efforts have focused on nanoimprinting and the use of organic resists (such as quantum dot–polymer hybrids, DNA and poly(ethylene glycol)), which still require, for the most part, noxious chemicals for processing. Significant advances have been achieved using ‘green’ resists that can be developed with water, but so far these approaches have suffered from low electron sensitivity, line edge roughness and scalability constraints. Here, we present the use of silk as a natural and biofunctional resist for electron-beam lithography. The process is entirely water-based, starting with the silk aqueous solution and ending with simple development of the exposed silk film in water. Because of its polymorphic crystalline structure, silk can be used either as a positive or negative resist through interactions with an electron beam. Moreover, silk can be easily modified, thereby enabling a variety of ‘functional resists’, including biologically active versions. As a proof of principle of the viability of all-water-based silk electron-beam lithography (EBL), we fabricate nanoscale photonic lattices using both neat silk and silk doped with quantum dots, green fluorescent proteins (GFPs) or horseradish peroxidase (HRP).

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Figure 1: Working principle of all-water-based electron-beam patterning on a silk film.
Figure 2: Silk nanostructures generated by EBL.
Figure 3: Effect of EBL on silk polymorphism.
Figure 4: Use of functionalized silk resists and resulting assessment of fluorescence enhancement and biological activity of electron-beam-written nanostructures.

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Acknowledgements

The authors acknowledge support from the National Science Foundation (NSF) (DMR-1242240), ONR (N00014-13-1-0596) and AFOSR (FA9950-10-1-0172). SEM images were obtained at the Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Infrastructure Network (NNIN), which is supported by the NSF (award no. ECS-0335765). CNS is part of the Faculty of Arts and Sciences at Harvard University. M.A.B. and A.N.M. acknowledge the ASEE for their support under the NDSEG fellowship.

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Author notes

  1. Sunghwan Kim & Konstantinos Tsioris

    Present address: Present address: Department of Physics & Division of Energy Systems Research, Ajou University, Suwon 443-749, Republic of Korea (S.K.), Koch Institute of Integrative Cancer Research, MIT, 77 Massachusetts Avenue, Building 76–253, Cambridge, Massachusetts 02139, USA (K.T.),

  2. Sunghwan Kim and Benedetto Marelli: These authors contributed equally to this work

Authors and Affiliations

  1. Department of Biomedical Engineering, Tufts University, 4 Colby Street, Medford, 02155, Massachusetts, USA

    Sunghwan Kim, Benedetto Marelli, Mark A. Brenckle, Alexander N. Mitropoulos, Eun-Seok Gil, Konstantinos Tsioris, Hu Tao, David L. Kaplan & Fiorenzo G. Omenetto

  2. Department of Physics, Tufts University, 4 Colby Street, Medford, 02155, Massachusetts, USA

    Fiorenzo G. Omenetto

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Contributions

S.K., B.M., M.A.B., H.T., D.L.K. and F.G.O. conceived and designed the experiments. S.K., B.M, E.G., A.N.M., K.T., M.A.B. and H.T. performed the experiments. S.K., B.M, M.A.B. and F.G.O. analysed the data. S.K., B.M., E.G., A.N.M., K.T., M.A.B and H.T. contributed materials/analysis tools. S.K., B.M., M.A.B. and F.G.O. co-wrote the paper. All authors discussed the results and commented on the manuscript.

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Correspondence to Fiorenzo G. Omenetto.

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Kim, S., Marelli, B., Brenckle, M. et al. All-water-based electron-beam lithography using silk as a resist. Nature Nanotech 9, 306–310 (2014). https://doi.org/10.1038/nnano.2014.47

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