Boisen, Anja

Matteucci, Marco

Schmidt, Michael Stenbæk

Thilsted, Anil H.

Viehrig, Marlitt

Metal-coated nanostructured surfaces have shown promise as substrates for surface-enhanced Raman spectroscopy (SERS) as they allow chemical trace detection with high sensitivity and rapid response. This sensitivity and specificity makes SERS especially interesting for environmental and biological analysis. Metal-capped silicon nanopillars, fabricated through a maskless ion etch, are state-of-the-art for on-chip SERS substrates. A dense cluster of high aspect ratio polymer nanocones was achieved by using high-throughput polymer injection moulding over a large area replicating a silicon nanopillar structure. Gold-capped polymer nanocones display similar SERS sensitivity as silicon nanopillars, while being easily integrable into a microfluidic chips

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Downloaded from orbit.dtu.dk on: Jan 01, 2018High-Throughput Fabrication of Nanocone Substrates through Polymer InjectionMoulding For SERS Analysis in Microfluidic SystemsViehrig, Marlitt; Matteucci, Marco; Thilsted, Anil H.; Schmidt, Michael Stenbæk; Boisen, AnjaPublication date:2017Document VersionPeer reviewed versionLink back to DTU OrbitCitation (APA):Viehrig, M., Matteucci, M., Thilsted, A. H., Schmidt, M. S., & Boisen, A. (2017). High-Throughput Fabrication ofNanocone Substrates through Polymer Injection Moulding For SERS Analysis in Microfluidic Systems. Abstractfrom 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, Savannah, UnitedStates.HIGH-THROUGHPUT FABRICATION OF NANOCONE SUBSTRATES THROUGH POLYMER INJECTION MOULDING FOR SERS ANALYSIS IN MICROFLUIDIC SYSTEMS Marlitt Viehrig1, *, Marco Matteucci1, Anil H. Thilsted2, Michael S. Schmidt1, and Anja Boisen1 1The Danish National Research Foundation and Villum Foundation’s Center for Intelligent Drug  Delivery and Sensing Using Microcontainers and Nanomechanics (IDUN), Department of  Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, Denmark. 2SpectroInlets, Kgs. Lyngby, Denmark. ABSTRACT Metal-coated nanostructured surfaces have shown promise as substrates for surface-enhanced Raman spectroscopy (SERS) as they allow chemical trace detection with high sensitivity and rapid response. This sensitivity and specificity makes SERS especially interesting for environmental and biological analysis. Metal-capped silicon nanopillars, fabricated through a maskless ion etch, are state-of-the-art for on-chip SERS substrates. A dense cluster of high aspect ratio polymer nanocones was achieved by using high-throughput polymer injection moulding over a large area replicating a silicon nanopillar structure. Gold-capped polymer nanocones display similar SERS sensitivity as silicon nanopillars, while being easily integrable into a microfluidic chips.  KEYWORDS: Lithography-free, Reactive Ion Etching, Polymer Injection, Nanopillars, SERS, Sensors  INTRODUCTION SERS utilizes noble metal nanostructures to amplify the Raman signal of small molecules through electromag-netic field enhancement by several orders of magnitude [1]. Maskless reactive ion etching (RIE) of silicon (Si) wafers produces uniform areas of free-standing nanopillars, which, after gold evaporation, result in isolated gold caps suitable for SERS detection [2]. This technique creates highly sensitive and reproducible plasmonic substrates in a scalable and cost-effective fashion. Our group has developed silicon nanopillar surfaces and applied them in the development of quantitative SERS sensors for biomedical sensing of hydrogen cyanide [3] and p-coumaric acid [4]. Subsequent integration of Si nanopillar chips into a centrifugal microfluidic platform for rapid and automated analysis of bacterial metabolites has been explored as well [5].  Microfluidic devices utilizing SERS often require an additional fabrication step or complex system integration strategies to allow SERS detection. Simplified integration of SERS sensing into microfluidic systems for multi-purpose Lab-on-a-Chip (LoC) applications is therefore highly sought after [6]. Injection moulding allows high-throughput fabrication of nanostructures for applications in the fields of superhydrophobic surfaces [7], as well as micro- and nanofluidic devices for biological sample handling [8]. Our work introduces the concept of utilizing high-throughput polymer injection moulding for the low-cost fabrication of  gold-capped polymer nanocones for SERS sensing replicated from nano-patterned silicon based shims.   EXPERIMENTAL Figure 1 illustrates the fabrication of polymer nanocones. We have developed a shim fabrication method that is based on maskless Si dry etching of microstructures to obtain Si nanocones (Fig. 1a).  Polymer structures were then fabricated via injection moulding (Fig. 1c) from nickel shims (Fig. 1b) obtained from the Si templates. Subsequent gold evaporation resulted in the formation of metal nanocaps on the injection moulded nanocone tips, as illustrated in Figure 1d. The SERS capability of polymer nanocones compared to Si nanopillars was assessed utilizing Trans-l,2-bis(4-pyridyl)ethylene (BPE) as the benchmark analyte.   RESULTS AND DISCUSSION Figure 2 shows gold-capped nanopillar structures on flat silicon substrates (Fig. 2a) as well as polymer injection moulded nanocones Figure 1: Fabrication procedure for polymer SERS substrates from Si nanocones through pol-ymer-injection moulding of inverted structures with subsequent metal nanocap formation. Figure 2: Gold-capped silicon nanopillars (a) and polymer nanocones (b) show comparable morphology. BPE signal of silicon nanopillars and polymer nanocones in comparison (c) illustrate comparable SERS functionalities. Polymeric nano-cones can be utilized in injection-moulded microfluidics for SERS analysis (d).   on flat polymer (Fig. 2b). Both substrates present morphological similarity over large areas. The SERS functionality of polymer nanocones, illustrated by depositing droplets of 100µM BPE as analyte  in Fig. 2c, show comparable enhancement to Si nanopillars at relatively high analyte concentrations. The achieved polymer structures are com-patible and can be easily integrated into microfluidic chips, as illustrated in Fig. 2d.       CONCLUSION We successfully fabricated gold-capped polymer nanocones from Si nanopillars utilizing high-throughput polymer injection moulding. Polymer nanocones display high density morphologies with a high aspect ratio. The structures can be utilized for SERS sensing of trace molecules with a similar sensitivity than Si nanopillars at high analyte concentrations. Integration in a LoC systems in a straight-forward manner is possible due to the polymeric nature of the substrate.   ACKNOWLEDGEMENTS This work was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP7/2007–2013) Grant no. 320535-HERMES and the IDUN Center of Excellence funded by the Danish National Research Foundation (grant no. DNRF122) and the Villum Fonden (Grant No. 9301).  REFERENCES [1] K. Kneipp, H. Kneipp, I. Itzkan, R. R. Dasari, and M. S. Feld, “Surface-enhanced Raman scattering and biophysics,” J. Phys. Condens. Matter, vol. 14, no. 18, p. 202, May 2002. [2] M. S. Schmidt, J. Hübner, and A. Boisen, “Large Area Fabrication of Leaning Silicon Nanopillars for Surface Enhanced Raman Spectroscopy,” Adv. Mater., vol. 24, no. 10, p. OP11-OP18, Mar. 2012. [3] R. K. Lauridsen, L. M. Sommer, H. K. Johansen, T. Rindzevicius, S. Molin, L. Jelsbak, S. B. Engelsen, and A. Boisen, “SERS detection of the biomarker hydrogen cyanide from Pseudomonas aeruginosa cultures isolated from cystic fibrosis patients.,” Sci. Rep., vol. 7, p. 45264, Mar. 2017. [4] L. Morelli, K. Zór, C. B. Jendresen, T. Rindzevicius, M. S. Schmidt, A. T. Nielsen, and A. Boisen, “Surface Enhanced Raman Scattering for Quantification of p-Coumaric Acid Produced by Escherichia coli.,” Anal. Chem., vol. 89, no. 7, pp. 3981–3987, Apr. 2017. [5] O. Durucan, L. Morelli, M. S. Schmidt, R. Burger, T. Rindzevicius, and A. Boisen, “Detection of bacterial metabolites through dynamic acquisition from surface enhanced raman spectroscopy substrates integtrated in a centrifugal microfluidic platform.” Chemical and Biological Microsystems Society, 2015. [6] Q. Zhou and T. Kim, “Review of microfluidic approaches for surface-enhanced Raman scattering,” Sensors Actuators B Chem., vol. 227, pp. 504–514, 2016. [7] S.-M. Lee and T. H. Kwon, “Mass-producible replication of highly hydrophobic surfaces from plant leaves,” Nanotechnology, vol. 17, no. 13, pp. 3189–3196, Jul. 2006. [8] K. Kistrup, C. E. Poulsen, P. F. Østergaard, K. B. Haugshøj, R. Taboryski, A. Wolff, and M. F. Hansen, “Fabrication and modelling of injection moulded all-polymer capillary microvalves for passive microfluidic control,” J. Micromechanics Microengineering, vol. 24, no. 12, p. 125007, Dec. 2014.  CONTACT * Department of Micro- and Nanotechnology, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Phone: +45 45255745; mvie@nanotech.dtu.dk 

High-Throughput Fabrication of Nanocone Substrates through Polymer Injection Moulding For SERS Analysis in Microfluidic Systems

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High-Throughput Fabrication of Nanocone Substrates through Polymer Injection Moulding For SERS Analysis in Microfluidic Systems

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