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Development Of Flexible Plasmonic Sensor Based On Imprinted Nanostructure Array On Plastics
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 2216–2221
www.materialstoday.com/proceedings
ICMS 2017
Development Of Flexible Plasmonic Sensor Based On Imprinted Nanostructure Array On Plastics Sudha Kumari,* Saswat Mohapatra, Rakesh S Moirangthem Nanophotonics Lab, Department of Applied Physics, Indian Institute of Technology (Indian school of Mines), Dhanbad, India-826004 *[email protected]
Abstract We present here flexible plastic based plasmonic sensor fabricated via nanoimprint lithography and metal sputtering. The goldcoated imprinted nanostructure on plastic served as plasmonic sensing chip that exhibits surface plasmon resonance (SPR) modes in the optical reflection spectra. The excitation of SPR mode on the sample was achieved via diffraction from the sub-wavelength metallic grating, which was confirmed with the theoretical calculation. Our proposed plastic based plasmonic sensor was tested for refractive index sensing, that yields the sensitivity about 800 nm/RIU. Thus, we believe that our presented plasmonic sensor could be used to develop a plastic sensor for detecting chemical and biological molecules at ultra-low concentration. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Second International Conference on Materials Science (ICMS2017). Keywords: Surface plasmons; plasmonics; nanoimprinting method; sensing.
1. Introduction The fabrication of plasmonic-based sensor devices has attracted an attention of flexible and portable devices. One of the major roadblocks in fabricating plasmonic nanostructures is the lack of low-cost, high throughput manufacturing technology. Since the fabrication through electron beam lithography is very time-consuming, expensive and low through-put and many more issues like resolution, reliability, and speed which are leading in the search for suitable methods [1-3].
* Corresponding author. Tel.: +91-326-2235116. E-mail address:[email protected] 2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Second International Conference on Materials Science (ICMS2017).
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
2217
Among these techniques, nanoimprinting lithography (NIL) represents a very promising cost-effective, highthroughput and high-resolution nanopatterning technique that can prepare nanostructure dimension down to 10 nm [3, 4 and 5]. Thermal nanoimprint lithography (T-NIL) has shown greater demand due to its potential and compatibility to replicate nanostructures in the thermoplastic polymer [6]. In this paper, we report a very simple approach for the fabrication procedure using easily available commercial thermal laminating pouches as a plastic substrate and optical discs as a template. By using commercially available optical discs (DVD), fabrication can be done in a very cost-effective way. DVD has surface plasmon resonance supported grating features which can be optically excited by shining the light [7-11]. The benefit of using lamination plastic here is that there is a thin film of polyethylene adhesive (polyethylene-vinyl acetate, PEVA) on the lamination plastic that acts as a thermal laminating film. Its glass transition temperature is very low. So in this T-NIL techniques, no any expensive resists or polymers are required for the coating that's so why the problem of surface sticking and non-uniformity is resolved here. 2. Experiment Here, we are using DVD as a master template for the fabrication. DVD has two polycarbonate layers which shield the grating with 740 nm as periodicity. These two layers are separated by the knife without damaging the grating structure. Transparent layer has the grating structure which is coated with the dye that was removed by soaking in isopropanol for five to ten minutes followed by drying with nitrogen gas. After completing the cleaning procedure, transparent discs layer was used as a master template for nanoimprinting. In the sample preparation, DVD nanograting pattern was initially replicated on polydimethylsiloxane (PDMS; Sylgard 184, Dow Corning) elastomer, followed by pouring the PDMS mixture (10:1) mixture on DVD template. After curing, the PDMS mold can be peeled off easily. The transferred pattern on PDMS mold is used for fabrication on cleaned laminating plastic by using thermal nanoimprinting method (T-NIL). The nanoimprinted sample was deposited with 80 nm gold thin film using a plasma sputtering unit. Fig.1. Shows a complete flowchart of steps involved in the fabrication process. (1)
Fig.1. Schematic illustration of the nanoimprinting process for fabricating nanograting on laminating plastic.
After fabrication and gold deposition, samples were analyzed by Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). All optical measurement and experiment were carried out with the help of setup shown in fig 2. Reflectance spectra were simultaneously recorded using a commercial CCD spectrometer and standard reflection probe, which consisted of seven optical fibers, six illumination fibers around one read fiber. The sample is mounted on the probe stand where white light is illuminated from the halogen lamp source [12].
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Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
Fig. 2. The experimental setup used for measuring the reflectance spectra through grating samples.
3. Results and discussion The surface morphology and height profile of the imprinted nanograting sample were characterized using scanning electron microscopy and atomic force microscopy. Fig 3(a)-(b) shows that SEM and AFM images of the original DVD disc and fig. 3(d)-(e) shows the corresponding images of imprinted nanograting on laminating plastic. It can be seen from fig. 3(d)-(e) that the surface morphology of imprinted nanograting structure is very smooth and uniform without defects.
Fig.3. (a) and (d) shows the SEM image of the DVD master template and imprinted nanograting on laminating plastics, (b) and (e) show the corresponding AFM images of the DVD master template and imprinted sample, (c) and (f) are the line profiles of the AFM image shown in (b) and (e).
Their corresponding height profile as shown in fig. 3(f) gives a value of 140 nm, which is close to the height of DVD master template having 160 nm. The periodicity of nanograting obtained from SEM image was approximately 730 nm. This implies that there is a successful transfer of nanograting structure from PDMS mold to laminating plastic. Further, nanograting sample was used as a plasmonic chip after depositing a gold film of
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
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thickness 80 nm. The reflectance spectrum of the plasmonic chip was recorded in ambient air under at normal incidence. Thus, gold coated nanograting sample exhibits SPR mode appeared a dip around 748 nm in the reflectance spectrum as shown in fig.3(a). The simulation was performed in order to investigate the surface plasmon excitation of the fabricated nanostructure using finite element Modelling (FEM) method. The commercially available FEM modeling package COMSOL Multiphysics 5 with radio frequency (RF) module was used to calculate reflectance spectra and electric field distributions at normal incidence.
Fig.4 (a) shows the experimental (solid black line) and (b) shows the calculated (black dotted line) reflectance spectra obtained from gold coated nanograting on laminating plastic under normal incidence in ambient air, (c) calculated normalized total electric field profile of the excited SPR mode.
For the simulation, the parameters of nanogratings such as height, width, and periodicity having values 140 nm, 530 nm, and 730 nm respectively. The thickness of the gold thin film was considered as 80 nm. 2D simulation was carried out for transverse-magnetic (TM) the polarization of light, which was normally incident on gold coated nanograting structure in the air medium. The calculated reflectance spectrum (fig. 4(a)) gives a very close agreement with the experimental result (fig. 4(b)). The corresponding normalized total electric field profile associated with excited SPR mode at 748 nm along the x-y plane is shown in fig.4(c). The optical field profile shows that surface plasmon waves are excited on gold coated nanograting surface and the surface plasmon waves are mostly confined to the gold surface. Hence, it can be exploited as a plasmonic sensor to sense the changing surrounding dielectric medium. The bulk sensitivity of the proposed plasmonic plastic sensor was investigated by loading glycerol-water mixtures of different refractive indices on the sensor surface attached to the flow cell. To demonstrate gold coated nanostructures as a plasmonic refractive index sensor, different refractive index (RI) solutions were prepared by mixing glycerol with DI water at different ratios and have values 1.333, 1.344, 1.357, 1.370, 1.384, and 1.398 respectively [13].
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Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
Fig 5(a). The response of surface plasmon modes upon exposing different glycerol-water mixtures of different refractive indices on the gold coated nanostructure surface (b) Linear relation showing the variation of the surface plasmon resonance wavelength with changing refractive indices of the liquid.
For this experiment, the custom-made flow cell was used. Sample chip was properly sealed with the flow cell with the help of glue. The momentum of surface plasmon wave is dependent on the surrounding dielectric medium (εd). Fig. 5(a) shows the reflectance spectra of gold coated nanograting sample after passing different RI solutions. The subsequent passage of aqueous solutions with increasing RI from n=1.333 to n=1.398 on the sensor surface, SPR dip shifted from 992 nm to 1050 nm. The error bars in fig. 5(b) show the variation in sensor response for each liquid solution obtained from four different samples. The slope (δλ/δn) with standard deviation provides the bulk RI sensitivity of 800 ± 27 nm/RIU (refractive index unit). It is worth to mention that the broad line width of SPR mode in reflectance spectra might be associated with DVD nanograting features, which can be improved by optimizing the nanostructures. 4. Conclusions In summary, we have proposed a cost effective and easily available simple design SPR based refractive index sensor. Lamination plastic is introduced here as a thermoplastic substrate. Thermal imprinting lithography method provides the easiest way and high-throughput for the large-scale production of cost-effective plasmonic refractive index sensors. The obtained bulk sensitivity is 800 nm/RIU. Hence, the fabricated gold grating structure has potency for biosensor applications.We believe that our proposed refractive index sensor has the potential for developing simple, economical, portable and label-free biosensor with high sensitivity. Acknowledgements The authors acknowledge the Indian Institute of Technology (ISM), Dhanbad for providing financial support and all the research facilities. . Reference [1] [2] [3] [4] [5] [6]
M Geissler andY Xi Adv. Mater. 16 (2004)1249–69. F Watt, A A Bettiol, J A Van Kan, E J Teo and M B H Breese Int. J. Nanosci. 4 (2005) 269–86. S Y Chou, P R Krauss and P J Renstrom Appl. Phys. Lett. 67 (1995) 3114–6. S Y Chou, P R Krauss, W Zhang, L Guo and L Zhuang J. Vac. Sci. Technol. B 15 (1997) 2897–904 S Y Chou, P R Krauss and P J Renstrom Science 272 (1996) 85–7. B Choi, X Dou, Y Fang, B M Phillips and P Jiang Phys. Chem. Chem. Phys. 18 (2016) 26078–87.
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221 [7] [8] [9] [10] [11] [12] [13]
H Schift and A Kristensen Handbook of Nanotechnology vol 9, 3rd edn (Berlin: Springer) pp 2010 271. B Kaplan, H Guner, O Senlik K Gurel, M Bayindir and A Dana Plasmonics 4 (2009) 237–4. X Dou, P Y Chung, J L Dai and P Jiang Appl. Phys Lett. 100 (2012) 041116–20. K Gurel, B Kaplan, H Guner, M Bayindir and A Dana Appl. Phys. Lett. 94 (2009) 233102–5. X Dou, B M Phillips, P Y Chung and P Jiang Optoelectron. Lett. 37 (2012) 3681–3. B K Singh and A C Hillier Anal. Chem.78 (2006) 2009-2018. L F HoytInd. Eng. Chem. Res. 26 (1932) 329-332.
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ScienceDirect Materials Today: Proceedings 5 (2018) 2216–2221
www.materialstoday.com/proceedings
ICMS 2017
Development Of Flexible Plasmonic Sensor Based On Imprinted Nanostructure Array On Plastics Sudha Kumari,* Saswat Mohapatra, Rakesh S Moirangthem Nanophotonics Lab, Department of Applied Physics, Indian Institute of Technology (Indian school of Mines), Dhanbad, India-826004 *[email protected]
Abstract We present here flexible plastic based plasmonic sensor fabricated via nanoimprint lithography and metal sputtering. The goldcoated imprinted nanostructure on plastic served as plasmonic sensing chip that exhibits surface plasmon resonance (SPR) modes in the optical reflection spectra. The excitation of SPR mode on the sample was achieved via diffraction from the sub-wavelength metallic grating, which was confirmed with the theoretical calculation. Our proposed plastic based plasmonic sensor was tested for refractive index sensing, that yields the sensitivity about 800 nm/RIU. Thus, we believe that our presented plasmonic sensor could be used to develop a plastic sensor for detecting chemical and biological molecules at ultra-low concentration. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Second International Conference on Materials Science (ICMS2017). Keywords: Surface plasmons; plasmonics; nanoimprinting method; sensing.
1. Introduction The fabrication of plasmonic-based sensor devices has attracted an attention of flexible and portable devices. One of the major roadblocks in fabricating plasmonic nanostructures is the lack of low-cost, high throughput manufacturing technology. Since the fabrication through electron beam lithography is very time-consuming, expensive and low through-put and many more issues like resolution, reliability, and speed which are leading in the search for suitable methods [1-3].
* Corresponding author. Tel.: +91-326-2235116. E-mail address:[email protected] 2214-7853© 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Second International Conference on Materials Science (ICMS2017).
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
2217
Among these techniques, nanoimprinting lithography (NIL) represents a very promising cost-effective, highthroughput and high-resolution nanopatterning technique that can prepare nanostructure dimension down to 10 nm [3, 4 and 5]. Thermal nanoimprint lithography (T-NIL) has shown greater demand due to its potential and compatibility to replicate nanostructures in the thermoplastic polymer [6]. In this paper, we report a very simple approach for the fabrication procedure using easily available commercial thermal laminating pouches as a plastic substrate and optical discs as a template. By using commercially available optical discs (DVD), fabrication can be done in a very cost-effective way. DVD has surface plasmon resonance supported grating features which can be optically excited by shining the light [7-11]. The benefit of using lamination plastic here is that there is a thin film of polyethylene adhesive (polyethylene-vinyl acetate, PEVA) on the lamination plastic that acts as a thermal laminating film. Its glass transition temperature is very low. So in this T-NIL techniques, no any expensive resists or polymers are required for the coating that's so why the problem of surface sticking and non-uniformity is resolved here. 2. Experiment Here, we are using DVD as a master template for the fabrication. DVD has two polycarbonate layers which shield the grating with 740 nm as periodicity. These two layers are separated by the knife without damaging the grating structure. Transparent layer has the grating structure which is coated with the dye that was removed by soaking in isopropanol for five to ten minutes followed by drying with nitrogen gas. After completing the cleaning procedure, transparent discs layer was used as a master template for nanoimprinting. In the sample preparation, DVD nanograting pattern was initially replicated on polydimethylsiloxane (PDMS; Sylgard 184, Dow Corning) elastomer, followed by pouring the PDMS mixture (10:1) mixture on DVD template. After curing, the PDMS mold can be peeled off easily. The transferred pattern on PDMS mold is used for fabrication on cleaned laminating plastic by using thermal nanoimprinting method (T-NIL). The nanoimprinted sample was deposited with 80 nm gold thin film using a plasma sputtering unit. Fig.1. Shows a complete flowchart of steps involved in the fabrication process. (1)
Fig.1. Schematic illustration of the nanoimprinting process for fabricating nanograting on laminating plastic.
After fabrication and gold deposition, samples were analyzed by Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). All optical measurement and experiment were carried out with the help of setup shown in fig 2. Reflectance spectra were simultaneously recorded using a commercial CCD spectrometer and standard reflection probe, which consisted of seven optical fibers, six illumination fibers around one read fiber. The sample is mounted on the probe stand where white light is illuminated from the halogen lamp source [12].
2218
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
Fig. 2. The experimental setup used for measuring the reflectance spectra through grating samples.
3. Results and discussion The surface morphology and height profile of the imprinted nanograting sample were characterized using scanning electron microscopy and atomic force microscopy. Fig 3(a)-(b) shows that SEM and AFM images of the original DVD disc and fig. 3(d)-(e) shows the corresponding images of imprinted nanograting on laminating plastic. It can be seen from fig. 3(d)-(e) that the surface morphology of imprinted nanograting structure is very smooth and uniform without defects.
Fig.3. (a) and (d) shows the SEM image of the DVD master template and imprinted nanograting on laminating plastics, (b) and (e) show the corresponding AFM images of the DVD master template and imprinted sample, (c) and (f) are the line profiles of the AFM image shown in (b) and (e).
Their corresponding height profile as shown in fig. 3(f) gives a value of 140 nm, which is close to the height of DVD master template having 160 nm. The periodicity of nanograting obtained from SEM image was approximately 730 nm. This implies that there is a successful transfer of nanograting structure from PDMS mold to laminating plastic. Further, nanograting sample was used as a plasmonic chip after depositing a gold film of
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
2219
thickness 80 nm. The reflectance spectrum of the plasmonic chip was recorded in ambient air under at normal incidence. Thus, gold coated nanograting sample exhibits SPR mode appeared a dip around 748 nm in the reflectance spectrum as shown in fig.3(a). The simulation was performed in order to investigate the surface plasmon excitation of the fabricated nanostructure using finite element Modelling (FEM) method. The commercially available FEM modeling package COMSOL Multiphysics 5 with radio frequency (RF) module was used to calculate reflectance spectra and electric field distributions at normal incidence.
Fig.4 (a) shows the experimental (solid black line) and (b) shows the calculated (black dotted line) reflectance spectra obtained from gold coated nanograting on laminating plastic under normal incidence in ambient air, (c) calculated normalized total electric field profile of the excited SPR mode.
For the simulation, the parameters of nanogratings such as height, width, and periodicity having values 140 nm, 530 nm, and 730 nm respectively. The thickness of the gold thin film was considered as 80 nm. 2D simulation was carried out for transverse-magnetic (TM) the polarization of light, which was normally incident on gold coated nanograting structure in the air medium. The calculated reflectance spectrum (fig. 4(a)) gives a very close agreement with the experimental result (fig. 4(b)). The corresponding normalized total electric field profile associated with excited SPR mode at 748 nm along the x-y plane is shown in fig.4(c). The optical field profile shows that surface plasmon waves are excited on gold coated nanograting surface and the surface plasmon waves are mostly confined to the gold surface. Hence, it can be exploited as a plasmonic sensor to sense the changing surrounding dielectric medium. The bulk sensitivity of the proposed plasmonic plastic sensor was investigated by loading glycerol-water mixtures of different refractive indices on the sensor surface attached to the flow cell. To demonstrate gold coated nanostructures as a plasmonic refractive index sensor, different refractive index (RI) solutions were prepared by mixing glycerol with DI water at different ratios and have values 1.333, 1.344, 1.357, 1.370, 1.384, and 1.398 respectively [13].
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Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221
Fig 5(a). The response of surface plasmon modes upon exposing different glycerol-water mixtures of different refractive indices on the gold coated nanostructure surface (b) Linear relation showing the variation of the surface plasmon resonance wavelength with changing refractive indices of the liquid.
For this experiment, the custom-made flow cell was used. Sample chip was properly sealed with the flow cell with the help of glue. The momentum of surface plasmon wave is dependent on the surrounding dielectric medium (εd). Fig. 5(a) shows the reflectance spectra of gold coated nanograting sample after passing different RI solutions. The subsequent passage of aqueous solutions with increasing RI from n=1.333 to n=1.398 on the sensor surface, SPR dip shifted from 992 nm to 1050 nm. The error bars in fig. 5(b) show the variation in sensor response for each liquid solution obtained from four different samples. The slope (δλ/δn) with standard deviation provides the bulk RI sensitivity of 800 ± 27 nm/RIU (refractive index unit). It is worth to mention that the broad line width of SPR mode in reflectance spectra might be associated with DVD nanograting features, which can be improved by optimizing the nanostructures. 4. Conclusions In summary, we have proposed a cost effective and easily available simple design SPR based refractive index sensor. Lamination plastic is introduced here as a thermoplastic substrate. Thermal imprinting lithography method provides the easiest way and high-throughput for the large-scale production of cost-effective plasmonic refractive index sensors. The obtained bulk sensitivity is 800 nm/RIU. Hence, the fabricated gold grating structure has potency for biosensor applications.We believe that our proposed refractive index sensor has the potential for developing simple, economical, portable and label-free biosensor with high sensitivity. Acknowledgements The authors acknowledge the Indian Institute of Technology (ISM), Dhanbad for providing financial support and all the research facilities. . Reference [1] [2] [3] [4] [5] [6]
M Geissler andY Xi Adv. Mater. 16 (2004)1249–69. F Watt, A A Bettiol, J A Van Kan, E J Teo and M B H Breese Int. J. Nanosci. 4 (2005) 269–86. S Y Chou, P R Krauss and P J Renstrom Appl. Phys. Lett. 67 (1995) 3114–6. S Y Chou, P R Krauss, W Zhang, L Guo and L Zhuang J. Vac. Sci. Technol. B 15 (1997) 2897–904 S Y Chou, P R Krauss and P J Renstrom Science 272 (1996) 85–7. B Choi, X Dou, Y Fang, B M Phillips and P Jiang Phys. Chem. Chem. Phys. 18 (2016) 26078–87.
Sudha Kumari / Materials Today: Proceedings 5 (2018) 2216–2221 [7] [8] [9] [10] [11] [12] [13]
H Schift and A Kristensen Handbook of Nanotechnology vol 9, 3rd edn (Berlin: Springer) pp 2010 271. B Kaplan, H Guner, O Senlik K Gurel, M Bayindir and A Dana Plasmonics 4 (2009) 237–4. X Dou, P Y Chung, J L Dai and P Jiang Appl. Phys Lett. 100 (2012) 041116–20. K Gurel, B Kaplan, H Guner, M Bayindir and A Dana Appl. Phys. Lett. 94 (2009) 233102–5. X Dou, B M Phillips, P Y Chung and P Jiang Optoelectron. Lett. 37 (2012) 3681–3. B K Singh and A C Hillier Anal. Chem.78 (2006) 2009-2018. L F HoytInd. Eng. Chem. Res. 26 (1932) 329-332.
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