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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 14 — Jul. 4, 2011
  • pp: 13707–13713
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Powerless tunable photonic crystal with bistable color and millisecond switching

Chia-Tsung Chan and J. Andrew Yeh  »View Author Affiliations


Optics Express, Vol. 19, Issue 14, pp. 13707-13713 (2011)
http://dx.doi.org/10.1364/OE.19.013707


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Abstract

This study demonstrated a tunable photonic crystal (PhC) with 70 nm-wide spectral tuning (535 nm to 605 nm) and 3 ms of response time. The tunable PhC is based on reciprocal capillary action of liquid in the nanoscale PhC voids. By wetting the porous silicon PhC with ethanol and water, the PhC can be bistably switched respectively between liquid-filled state (orange color) and vapor-filled state (yellow color). Owing to the energy barrier between the two wetting states, the tunable PhC can remain at either of the two states with no external power consumption.

© 2011 OSA

1. Introduction

To overcome the obstacle, a tunable PhC featuring wide spectral tuning, fast response and powerless bistability was proposed. The driving mechanism for the tunable PhC was based on the reciprocal capillary action in the nanoscale PhC voids, which was disclosed in our earlier paper [9

9. C. T. Chan and J. A. Yeh, “Tunable photonic crystal based on capillary attraction and repulsion,” Opt. Express 18(20), 20894–20899 (2010). [CrossRef] [PubMed]

]. In this work, the porous silicon photonic crystal (PSiPhC) featuring hydrophobically modified void was tuned by alternately wetting its surface with ethanol and water. The wide spectral tuning results from a large refractive index change of the PSiPhC which is done by switching the PSiPhC between a vapor-filled state and a liquid-filled state via reciprocal capillary action. The fast response time is contributed by the enormous capillary pressure with a capillary radius at nanoscale. The powerless bistability is due to the energy barrier between the two wetting states. Table 1

Table 1. Tuning Range, Response Time and Powerless Bistability for Tunable PhCs at the Visible Range

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lists the comparisons of different tunable PhC method in tuning range, response time and powerless bistability.

2. Methodology

The color-changing method of the capillary-driven PSiPhC is shown in Fig. 1
Fig. 1 Schematic of the tunable PhC driven by reciprocal capillary action.
. All the tuning processes are carried out in 30% ethanol. Initially, the ambient 30% ethanol is unable to infiltrate the vapor-filled PSiPhC due to the strong hydrophobicity of the void surface (Fig. 1 a). After injecting a 99.5% ethanol jet, the low surface tension ethanol film wetted on the PSiPhC surface induces capillary attraction, which allows the 99.5% ethanol to infiltrate. Subsequently, the 99.5% ethanol gradually dissipates until the ethanol concentration in the voids reaches diffusion equilibrium with the outer 30% ethanol (Fig. 1 e). In contrast, the liquid-filled PSiPhC can be tuned again by injecting a water jet. Water is strongly repelled by FDTS coated silicon surface and has a 105° contact angle [9

9. C. T. Chan and J. A. Yeh, “Tunable photonic crystal based on capillary attraction and repulsion,” Opt. Express 18(20), 20894–20899 (2010). [CrossRef] [PubMed]

]. After the water diffused into the PSiPhC and diluted the void liquid, the increased surface tension of the void liquid induces capillary repulsion, which leads to the exfiltration of the void liquid. After that, the PSiPhC returns to its original vapor-filled state.

3. Sample preparation

In Fig. 2 (a)
Fig. 2 (a) SEM images of the PSiPhC; the periodic structure from the cross section view (left) and the porous surface from the top view (right). (b) the PSiPhC partially immersed in water (left) and 99.5% ethanol (right) (c) the reflectivity spectra of the PSiPhC immersed in water (vapor-filled sate) and 99.5% ethanol (liquid-filled state).
, scanning electron microscopy (SEM) of the PSiPhC reveals the periodic structure in the cross section view (left image) with 1000 nm in thickness and the porous surface in the top view (right image) with 5 to 15 nm pore size distribution. In Fig. 2 (b), the hydrophobically modified PSiPhC shows unaltered yellow color when immersed in water (i.e. vapor-filled state for high surface tension liquid). In contrast, the color of the PSiPhC changed to orange when immersed in 99.5% ethanol (i.e. liquid-filled state for low surface tension liquid). Regarding the tuning range, Fig. 2 (c) shows the normal-incident reflectivity spectra of the PSiPhC immersed in water and ethanol, respectively. The wavelength at maximum intensity is 535 nm and 605 nm when immersed in water and ethanol respectively.

4. Experiments and discussions

Reversible patterning test and dynamic characterizations for the PSiPhC were performed in this work. Reversible pattering test was used to test the powerless bistability of the PSiPhC. The dynamic characterizations for the color-changing of the PSiPhC were performed using CCD camera imaging and response time measurement.

In the reversible pattering test, the PSiPhC was immersed in 30% ethanol. Two sets of needle and syringe were also immersed in the 30% ethanol and separately driven by two air-pulsed fluid dispensers. Each needle was aimed at the PSiPhC surface at approximately 45° incline angle. Figure 3
Fig. 3 Tunable PSiPhC with tic-tac-toe patterns; the orange tic-tac-toe was patterned by ethanol jet (from step 2 to 5). The yellow tic-tac-toe was patterned by water jet (from step 6 to 8).
shows how the color of the PSiPhC was tuned by wetting with ethanol and water. In step 1, the PSiPhC immersed in 30% ethanol appeared to be yellow. Then, an orange tic-tac-toe pattern was formed in step 2 and step 3 by repeatedly injecting and wetting the PSiPhC with ethanol. After the whole PSiPhC surface turned orange (see step 4 and step 5), another yellow tic-tac-toe pattern, shown in step 6 and step 7, was formed by repeatedly injecting and wetting the PSiPhC with water. In step 8, the whole PSiPhC surface returned to yellow again when wetted with water. The tic-tac-toe patterns formed in each step can permanently remain with no external power consumption.

In the CCD camera imaging, color changes of the PSiPhC were monitored with a 30 Hz video camera. More precise dynamic changes were monitored using a monochromatic high speed CCD camera (Motion Pro Y4, Integrated Design Tools, Inc.) operated at 300 Hz. The videos were captured while synchronizing the two dispensers to alternately inject ethanol and water in the same region on the PSiPhC surface. Each injection of ethanol and water separately took the first 20 ms of its 500 ms in a 1 Hz repetition.

The response time measurement was carried out with a laser diode and a monitor photodiode. The PSiPhC surface was irradiated by a 50 mW industrial 532 nm green laser with a near right angle incidence and a silicon PIN photodiode received and converted the reflected laser ray into electric current. The relative photocurrent intensity was monitored by a 500 MHz oscilloscope. Figure 6
Fig. 6 Response time measurement of the capillary attraction and the capillary repulsion.
shows the measured response time via laser irradiance and photodiode monitoring. With reference to the PSiPhC reflectivity at 532 nm in Fig. 2 (c) the higher photocurrent output at 9.9 depicts the higher reflectance of the vapor-filled PSiPhC (yellow color). Whereas the photocurrent output at 6.6 depicts the lower reflectance of the liquid-filled PSiPhC (orange color). The time constant is approximately 3 ms for both the capillary attraction and repulsion.

Table 2

Table 2. Transition Times for the Capillary-Driven Tunable PhC

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illustrates transition times for the three types of tuning processes described in section 2. For capillary action, the dynamics for both attraction and repulsion in fluidic channels can be resolved by the modified Lucas-Washburn equation [15

15. D. I. Dimitrov, A. Milchev, and K. Binder, “Capillary rise in nanopores: molecular dynamics evidence for the Lucas-Washburn equation,” Phys. Rev. Lett. 99(5), 054501–054504 (2007). [CrossRef] [PubMed]

] as Eq. (1). The estimated time scale for capillary attraction is 1 × 10−5 to 2 × 10−5 s (e.g. 5 nm in radius and 1000 nm in height) and the time for capillary repulsion is even shorter for the liquid slippage on hydrophobic boundary [16

16. C. H. Choi, K. Johan, A. Westin, and K. S. Breuer, “Apparent slip flows in hydrophilic and hydrophobic microchannels,” Phys. Fluids 15(10), 2897–2902 (2003). [CrossRef]

,17

17. D. C. Tretheway and C. D. Meinhart, “A generating mechanism for apparent fluid slip in hydrophobic microchannels,” Phys. Fluids 16(5), 1509–1515 (2004). [CrossRef]

]. For liquid diffusion, the estimated time scale is 2 × 10−4 to 7 × 10−4 s based on Fick's second law of diffusion with reference to the mutual diffusion coefficient of water and ethanol [18

18. K. C. Pratt and W. A. Wakeham, “The mutual diffusion coefficient of ethanol-water mixtures: determination by a rapid, new method,” Proc. R. Soc. Lond. A Math. Phys. Sci. 336(1606), 393–406 (1974). [CrossRef]

] as Eq. (2). For liquid injection, estimated time scale for millimeter traveling of the liquid jet front adjacent to the needle outlet is roughly 2 × 10−3 to 3 × 10−3 s based on the dynamic pressure and Hagen-Poiseuille law as Eq. (3) and Eq. (4), respectively. The injection flow rate in the liquid injection process is the key limit on response time owing to the expansion and deceleration of liquid jet from the needle outlet.

5. Conclusion

In summary, the wide spectral tuning, fast response, and powerless bistability of the capillary-driven tunable PhC are demonstrated. First, the powerless bistable color states of the PSiPhC have been verified via reversible patterning test. Second, high speed imaging and response time measurement revealed the millisecond response time of the tunable PSiPhC. Future works include shortening the response time by scaling down the dimensions. To expand spectral tuning range, introducing new materials to enhance the refractive index contrast of liquids and PhC solid is necessary.

References and links

1.

A. C. Arsenault, D. P. Puzzo, I. Manners, and G. A. Ozin, “Photonic-crystal full-colour displays,” Nat. Photonics 1(8), 468–472 (2007). [CrossRef]

2.

J. J. Walish, Y. Kang, R. A. Mickiewicz, and E. L. Thomas, “Bioinspired electrochemically tunable block copolymer full color pixels,” Adv. Mater. (Deerfield Beach Fla.) 21(30), 3078–3081 (2009). [CrossRef]

3.

H. Kim, J. Ge, J. Kim, S. Choi, H. Lee, H. Lee, W. Park, Y. Yin, and S. Kwon, “Structural colour printing using a magnetically tunable and lithographically fixable photonic crystal,” Nat. Photonics 3(9), 534–540 (2009). [CrossRef]

4.

Y. Shimoda, M. Ozaki, and K. Yoshino, “Electric field tuning of a stop band in a reflection spectrum of synthetic opal infiltrated with nematic liquid crystal,” Appl. Phys. Lett. 79(22), 3627–3629 (2001). [CrossRef]

5.

K. L. Jim, D. Wang, D. C. Leung, C. Choy, and H. L. W. Chan, “One-dimensional tunable ferroelectric photonic crystals based on Ba0.7Sr0.3TiO3/MgO multilayer thin films,” J. Appl. Phys. 103(8), 1–6 (2008). [CrossRef]

6.

T. Tanaka and D. J. Fillmore, “Kinetics of swelling of gels,” J. Chem. Phys. 70(3), 1214–1218 (1979). [CrossRef]

7.

Y. Li and T. Tanaka, “Kinetics of swelling and shrinking of gels,” J. Chem. Phys. 92(2), 1365–1371 (1990). [CrossRef]

8.

M. A. Hayes, N. A. Polson, and A. A. Garcia, “Active control of dynamic supraparticle structures in microchannels,” Langmuir 17(9), 2866–2871 (2001). [CrossRef]

9.

C. T. Chan and J. A. Yeh, “Tunable photonic crystal based on capillary attraction and repulsion,” Opt. Express 18(20), 20894–20899 (2010). [CrossRef] [PubMed]

10.

V. Lehmann, R. Stengl, and A. Luigart, “On the morphology and the electrochemical formation mechanism of mesoporous silicon,” Mater. Sci. Eng. B 69–70, 11–22 (2000). [CrossRef]

11.

J. Y. Chyan, W. C. Hsu, and J. A. Yeh, “Broadband antireflective poly-Si nanosponge for thin film solar cells,” Opt. Express 17(6), 4646–4651 (2009). [CrossRef] [PubMed]

12.

Y. X. Zhuang, O. Hansen, T. Knieling, C. Wang, P. Rombach, W. Lang, W. Benecke, M. Kehlenbeck, and J. Koblitz, “Vapor-phase self-assembled monolayers for anti-stiction applications in MEMS,” J. Microelectromech. Syst. 16(6), 1451–1460 (2007). [CrossRef]

13.

Z. H. Yang, C. Y. Chiu, J. T. Yang, and J. A. Yeh, “Investigation and application of an artificially hybridstructured surface with ultrahydrophobic and anti-sticking character,” J. Micromech. Microeng. 19, 085022–085033 (2009). [CrossRef]

14.

C. Y. Yang, L. Y. Huang, T. L. Shen, and J. A. Yeh, “Cell adhesion, morphology and biochemistry on nano-topographic oxidized silicon surfaces,” Eur. Cell. Mater. 20, 415–430 (2010). [PubMed]

15.

D. I. Dimitrov, A. Milchev, and K. Binder, “Capillary rise in nanopores: molecular dynamics evidence for the Lucas-Washburn equation,” Phys. Rev. Lett. 99(5), 054501–054504 (2007). [CrossRef] [PubMed]

16.

C. H. Choi, K. Johan, A. Westin, and K. S. Breuer, “Apparent slip flows in hydrophilic and hydrophobic microchannels,” Phys. Fluids 15(10), 2897–2902 (2003). [CrossRef]

17.

D. C. Tretheway and C. D. Meinhart, “A generating mechanism for apparent fluid slip in hydrophobic microchannels,” Phys. Fluids 16(5), 1509–1515 (2004). [CrossRef]

18.

K. C. Pratt and W. A. Wakeham, “The mutual diffusion coefficient of ethanol-water mixtures: determination by a rapid, new method,” Proc. R. Soc. Lond. A Math. Phys. Sci. 336(1606), 393–406 (1974). [CrossRef]

OCIS Codes
(350.4238) Other areas of optics : Nanophotonics and photonic crystals
(050.5298) Diffraction and gratings : Photonic crystals

ToC Category:
Photonic Crystals

History
Original Manuscript: May 4, 2011
Revised Manuscript: June 12, 2011
Manuscript Accepted: June 12, 2011
Published: June 30, 2011

Citation
Chia-Tsung Chan and J. Andrew Yeh, "Powerless tunable photonic crystal with bistable color and millisecond switching," Opt. Express 19, 13707-13713 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-14-13707


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References

  1. A. C. Arsenault, D. P. Puzzo, I. Manners, and G. A. Ozin, “Photonic-crystal full-colour displays,” Nat. Photonics 1(8), 468–472 (2007). [CrossRef]
  2. J. J. Walish, Y. Kang, R. A. Mickiewicz, and E. L. Thomas, “Bioinspired electrochemically tunable block copolymer full color pixels,” Adv. Mater. (Deerfield Beach Fla.) 21(30), 3078–3081 (2009). [CrossRef]
  3. H. Kim, J. Ge, J. Kim, S. Choi, H. Lee, H. Lee, W. Park, Y. Yin, and S. Kwon, “Structural colour printing using a magnetically tunable and lithographically fixable photonic crystal,” Nat. Photonics 3(9), 534–540 (2009). [CrossRef]
  4. Y. Shimoda, M. Ozaki, and K. Yoshino, “Electric field tuning of a stop band in a reflection spectrum of synthetic opal infiltrated with nematic liquid crystal,” Appl. Phys. Lett. 79(22), 3627–3629 (2001). [CrossRef]
  5. K. L. Jim, D. Wang, D. C. Leung, C. Choy, and H. L. W. Chan, “One-dimensional tunable ferroelectric photonic crystals based on Ba0.7Sr0.3TiO3/MgO multilayer thin films,” J. Appl. Phys. 103(8), 1–6 (2008). [CrossRef]
  6. T. Tanaka and D. J. Fillmore, “Kinetics of swelling of gels,” J. Chem. Phys. 70(3), 1214–1218 (1979). [CrossRef]
  7. Y. Li and T. Tanaka, “Kinetics of swelling and shrinking of gels,” J. Chem. Phys. 92(2), 1365–1371 (1990). [CrossRef]
  8. M. A. Hayes, N. A. Polson, and A. A. Garcia, “Active control of dynamic supraparticle structures in microchannels,” Langmuir 17(9), 2866–2871 (2001). [CrossRef]
  9. C. T. Chan and J. A. Yeh, “Tunable photonic crystal based on capillary attraction and repulsion,” Opt. Express 18(20), 20894–20899 (2010). [CrossRef] [PubMed]
  10. V. Lehmann, R. Stengl, and A. Luigart, “On the morphology and the electrochemical formation mechanism of mesoporous silicon,” Mater. Sci. Eng. B 69–70, 11–22 (2000). [CrossRef]
  11. J. Y. Chyan, W. C. Hsu, and J. A. Yeh, “Broadband antireflective poly-Si nanosponge for thin film solar cells,” Opt. Express 17(6), 4646–4651 (2009). [CrossRef] [PubMed]
  12. Y. X. Zhuang, O. Hansen, T. Knieling, C. Wang, P. Rombach, W. Lang, W. Benecke, M. Kehlenbeck, and J. Koblitz, “Vapor-phase self-assembled monolayers for anti-stiction applications in MEMS,” J. Microelectromech. Syst. 16(6), 1451–1460 (2007). [CrossRef]
  13. Z. H. Yang, C. Y. Chiu, J. T. Yang, and J. A. Yeh, “Investigation and application of an artificially hybridstructured surface with ultrahydrophobic and anti-sticking character,” J. Micromech. Microeng. 19, 085022–085033 (2009). [CrossRef]
  14. C. Y. Yang, L. Y. Huang, T. L. Shen, and J. A. Yeh, “Cell adhesion, morphology and biochemistry on nano-topographic oxidized silicon surfaces,” Eur. Cell. Mater. 20, 415–430 (2010). [PubMed]
  15. D. I. Dimitrov, A. Milchev, and K. Binder, “Capillary rise in nanopores: molecular dynamics evidence for the Lucas-Washburn equation,” Phys. Rev. Lett. 99(5), 054501–054504 (2007). [CrossRef] [PubMed]
  16. C. H. Choi, K. Johan, A. Westin, and K. S. Breuer, “Apparent slip flows in hydrophilic and hydrophobic microchannels,” Phys. Fluids 15(10), 2897–2902 (2003). [CrossRef]
  17. D. C. Tretheway and C. D. Meinhart, “A generating mechanism for apparent fluid slip in hydrophobic microchannels,” Phys. Fluids 16(5), 1509–1515 (2004). [CrossRef]
  18. K. C. Pratt and W. A. Wakeham, “The mutual diffusion coefficient of ethanol-water mixtures: determination by a rapid, new method,” Proc. R. Soc. Lond. A Math. Phys. Sci. 336(1606), 393–406 (1974). [CrossRef]

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