OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 11 — May. 26, 2008
  • pp: 8084–8093
« Show journal navigation

Liquid micro-lens array activated by selective electrowetting on lithium niobate substrates

S. Grilli, L. Miccio, V. Vespini, A. Finizio, S. De Nicola, and Pietro Ferraro  »View Author Affiliations


Optics Express, Vol. 16, Issue 11, pp. 8084-8093 (2008)
http://dx.doi.org/10.1364/OE.16.008084


View Full Text Article

Acrobat PDF (331 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Lens effect was obtained in an open microfluidic system by using a thin layer of liquid on a polar electric crystal like LiNbO3. An array of liquid micro-lenses was generated by electrowetting effect in pyroelectric periodically poled crystals. Compared to conventional electrowetting devices, the pyroelectric effect allowed to have an electrode-less and circuitless configuration. An interferometric technique was used to characterize the curvature of the micro-lenses and the corresponding results are presented and discussed. The preliminary results concerning the imaging capability of the micro-lens array are also reported.

© 2008 Optical Society of America

1. Introduction

This paper deals with the liquid lens effect obtainable by pyroelectrically activated electrowetting effect onto lithium niobate (LN) substrates. As described above, the operation of conventional electrowetting-based microfluidic devices demands more or less complex electrode geometries to actuate a liquid lens, thus requiring special technological steps and materials for the fabrication. The possibility to functionalize a specific and appropriate material to get a microfluidic lens array on a single chip is foreseen in this paper. This vision could lead to the realization in future of an optofluidic lens array on a microscopic scale.

2. Observation of lens effect

LN crystal substrates were used in this work to demonstrate the possibility to get a liquid lens array with variable curvature and focal length. LN is a very well known ferroelectric material widely used as a key element in optical modulators for fibre optic telecommunications [26

26. E. L. Wooten, K. M. Kissa, A. Yi-Yan, E. J. Murphy, D. A. Lafaw, P. F. Hallemeier, D. Maack, D. V. Attanasio, D. J. Fritz, G. J. McBrien, and D. E. Bossi, “A Review of Lithium Niobate Modulators for Fiber-Optic Communications Systems,” IEEE J. Sel. Top. Quantum Electron. 6, 69–82 (2000). [CrossRef]

] and in non-linear optic devices [27

27. R. L. Byer, “Nonlinear Optics and Solid-State Lasers:2000,” IEEE J. Sel. Top. Quantum Electron. 6, 911–930 (2000). [CrossRef]

]. To the best of our knowledge, the possibility to change the topography of a thin liquid film onto a microengineered LN substrate by the pyroelectric effect [28

28. F. Laurell, M. G. Roelofs, W. Bindloss, H. Hsiung, A. Suna, and J. D. Bierlein, “Detection of ferroelectric domain reversal in KTP waveguides,” J. Appl. Phys. 71, 4664–4670 (1992). [CrossRef]

,30

30. C. H. Bulmer, W. K. Burns, and S. C. Hiser, “Pyroelectric effects in LiNbO3 channel waveguide devices,” Appl. Phys. Lett. 48, 1036–1038 (1986). [CrossRef]

] was observed for the first time in this work. The topography variation allows to build-up a liquid microlens array activated by temperature gradients on the LN surface. The resulting structure can be considered as an open microfluidic system [18

18. R. Seemann, M. Brinkmann, E. J. Kramer, F. F. Lange, and R. Lipowsky, “Wetting morphologies at microstructured surfaces,” PNAS 102, 1848–1852 (2005). [CrossRef] [PubMed]

] exhibiting lens effect. In the past, regular arrays of liquid lenses have been observed by means of the electrowetting effect based on the spinodal dewetting theory [29

29. B. Sun and J. Heikenfeld “Observation and optical implications of oil dewetting patterns in electrowetting displays” J. Micromech. Microeng. 18, 025027 (2008) [CrossRef]

].

Fig. 1. Optical microscope image of two PPLN samples with a square array of reversed domains. The period of the structures is around 200 µm. A different mask was used for the two samples.

Figures 2(a)–2(b) show the optical microscope movies of the oil coated sample A under heating and cooling process, respectively.

Fig. 2. Optical microscope movies of the oil coated sample A (a) under heating [3.3MB] and (b) cooling process [4.4MB]. [Media 2] [Media 3]

The heating process was performed by increasing the temperature from 40 °C up to 100 °C. The cooling was achieved by letting the temperature to decrease from 100 °C down to 40 °C, thus with an approximate rate of 12 °C/min. The whole process took about 5 minutes and the liquid lens array kept stable topography for about 30 minutes at 40 °C, after its formation. The evolution of the oil film topography is clearly visible in both movies and, in particular, the lens effect is more pronounced in case of the cooling process. This is reasonably due to the different nature of the surface charges generating the electric potential modulation on the substrate, as discussed in the following section. The liquid microlenses were formed in correspondence of the hexagonal domains and thus with a lateral dimension of about 100 µm. Practical limitations to the fabrication of smaller lenses is not expected because reversed domains with lateral dimensions down to tens of micron can be reliably obtained in LN substrates. Anyway, the performance of the smaller lenses would be dramatically affected by the consequent enhancement of the diffraction effects due to the fact that the lens aperture became comparable with wavelength. It is important to note that the response of the liquid lens array was quite fast. In fact, the lens array was formed about 1 s after the temperature started to decrease.

Moreover, the lens formation followed faithfully the domain grating, thus exhibiting perfect homogeneity over the whole patterned region. In principle, liquid microlens arrays would be possible with areas as large as desirable depending basically on the area obtainable by the lithographic process used for the domain inversion process. In fact, Fig. 2 shows clearly the degree of uniformity obtainable by the technique, with a field of view including 42 lens elements corresponding to an area of about (1.4×1.2) mm2. The limited field of view corresponding to the chosen magnification prevented to report larger view images.

3. Interpretation of the phenomenon

It is well known that LN is a rhombohedral crystal belonging to the point group 3m at room temperature [36

36. R. S. Weis and T. K. Gaylord, “Lithium Niobate: Summary of Physical Properties and Crystal Structure,” Appl. Phys. A 37, 191–203 (1985). [CrossRef]

]. The lack of inversion symmetry induces different effects including the pyroelectricity. This is the manifestation of the spontaneous polarization change ΔPs following to a temperature variation ΔT, according to ΔPi=piΔT, where ΔP i is the coefficient of the polarization vector and pi is the pyroelectric coefficient. At equilibrium, all Ps in the crystal are fully screened by the external screening charge and no electric field exists [37

37. E. M. Bourim, C.-W. Moon, S.-W. Lee, and I. K. Yoo, “Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals,” Phys. B 383, 171–182 (2006). [CrossRef]

]. The change of the polarization, occurring with temperature variation, perturbs such equilibrium, causing a lack or excess of surface screening charge. Consequently, an electrostatic state appears and generates a high electric field at the crystal surface [38

38. B. Rosenblum, P. Bräunlich, and J. P. Carrico, “Thermally stimulated field emission from pyroelectric LiNbO3,” Appl. Phys. Lett. 25, 17–19 (1974). [CrossRef]

,39

39. G. Rosenman, D. Shur, Y. E. Krasik, and A. Dunaevsky, “Electron emission from ferroelectrics,” J. Appl. Phys. 88, 6109–6161 (2000). [CrossRef]

]. Figures 3(a)–3(b) show the schematic view of the PPLN sample cross section with the charge distribution occurring at the equilibrium state and in case of heating/cooling treatment, respectively. The arrows indicate the orientation of the ferroelectric domains.

Fig. 3. Schematic view of the PPLN sample cross section with the charge distribution exhibited (a) at the equilibrium state; (b) in case of heating (top) and (bottom) cooling process.

γsl+γlgcosϑ=γsg
(1)

where ϑ corresponds to the contact angle of the droplet. The charges at the solid-liquid interface reduce the surface tension according to the Lippman equation [41

41. M. G. Lippmann, Ann. Chim. Phys.5, 494 (1875).

]:

γsl(V)=γsl012cV2
(2)

where γsl0 corresponds to zero charge condition and c is the capacitance per unit area assuming that the charge layer can be modelled as a symmetric Helmholtz capacitor [15

15. E. Colgate and H. Matsumoto, “An investigation of electrowetting-based micro actuation,” J. Vac. Sci. Technol. A 8, 3625–3633 (1990). [CrossRef]

]. It is important to note that in the present work the surface was not a metal and the liquid was not an electrolyte, as basically assumed by the double charge model [15

15. E. Colgate and H. Matsumoto, “An investigation of electrowetting-based micro actuation,” J. Vac. Sci. Technol. A 8, 3625–3633 (1990). [CrossRef]

,40

40. F. Beunis, F. Strubbe, M. Marescaux, K. Neyts, and A. R. M. Verschueren, “Diffuse double layer charging in nonpolar liquids,” Appl. Phys. Lett. 91, 182911-3 (2007). [CrossRef]

]. However, a similar model can be as well invoked even in case of dielectric surfaces [25

25. F. Mugele and J.-C. Baret, “Electrowetting: from basics to applications,” J. Phys. Condens. Matter 17, R705–R774 (2005). [CrossRef]

]. Therefore, in the case investigated here, the presence of the net electric charge underneath the crystal surface (see bottom drawing in Fig. 2(b)), generated pyroelectrically, lowers the surface tension due to the repulsion between like charges that make the work for expanding the surface area [39

39. G. Rosenman, D. Shur, Y. E. Krasik, and A. Dunaevsky, “Electron emission from ferroelectrics,” J. Appl. Phys. 88, 6109–6161 (2000). [CrossRef]

]. The air-liquid interface exhibits a waviness profile to minimize the energy of the whole system. Simulations of the electric potential distribution, generated pyroelectrically, were performed by a finite element based calculation and Fig. 4(a) shows the result. The plot refers to a section along a diagonal direction (direction b in Fig. 1).

Fig. 4. (a). Schematic view of the sample cross section with the simulated electric potential distribution generated pyroelectrically; (b) (top) surface tension profile and (bottom) the schematic view of the corresponding oil film topography. The black arrows indicate the orientation of the spontaneous polarization.

The simulation clearly shows that the electric potential is modulated according to the domain structure, thus exhibiting minimum value in correspondence of the hexagon centres. The surface tension profile was then calculated by using Eq. (2) and the corresponding behaviour, in accordance with the experimental results, is shown in Fig. 4(b). In fact, the solid-liquid interface tension appears to be modulated according to the electric potential. It is important to consider that the number of charges between two consecutive hexagons is higher along the b direction compared to the horizontal or vertical direction. Therefore, the work done by the charges along the b direction produces a stronger hydrostatic pressure towards hexagon centres, thus leading to the formation of liquid micro lenses in correspondence of the hexagons.

4. Characterization of the liquid micro-lens array by an interferometric method

The microfluidic system was observed and investigated during the cooling process by an interferometric apparatus based on Digital Holography [42

42. P. Ferraro, S. De Nicola, and G. Coppola, “Digital holography: recent advancements and prospective improvements for applications in microscopy” in Optical Imaging Sensors and Systems for Homeland Security Applications, vol. 2 of Advanced Sciences and Technologies for Security Applications seriesB. Javidi ed., (Springer, 2005), pp. 47–84.

]. The schematic view of the optical set-up used for the acquisition of the images is shown in Fig. 5.

Fig. 5. Schematic view of the interferometric configuration. A sequence of digital holograms have been recorded on the CCD plane. An additional lens was used (not shown in the figure to simplify the drawing) and located between the lens-array and the CCD plane to magnify the image of the lens array.
Fig. 6. Movie [4MB] of the evolving two-dimensional distribution of the wrapped phase map, modulo 2π, corresponding to 3×4 lens elements on the incoming collimated beam, during cooling in case of the sample B. The phase map was reconstructed at a distance of 156 mm. [Media 1]

The wavefront modifications induced by the micro-lens array onto a collimated laser beam (plane wavefront) were analysed. The phase-map of the transmitted wavefront at the exit pupil of the microlens array can be obtained by the numerical reconstruction of digital holograms, which consists in reconstructing the complex wavefront transmitted by the microlens array by back-propagating the diffraction field. Amplitude and phase maps of the object wavefront can be retrieved from the complex wavefront. Numerical methods and the principle of operation to get wavefront reconstruction are reported in refs. [32

32. S. Grilli, M. Paturzo, L. Miccio, and P. Ferraro, “In situ investigation of periodic poling in congruent LiNbO3 by quantitative interference microscopy,” Meas. Sci. Technol. (in press).

] and [42

42. P. Ferraro, S. De Nicola, and G. Coppola, “Digital holography: recent advancements and prospective improvements for applications in microscopy” in Optical Imaging Sensors and Systems for Homeland Security Applications, vol. 2 of Advanced Sciences and Technologies for Security Applications seriesB. Javidi ed., (Springer, 2005), pp. 47–84.

]. Several holograms were recorded at a rate of 1 image per second. The movie in Fig. 6 shows the wrapped phase maps modulus 2π corresponding to 3×4 lens elements on the incoming collimated beam during the system cool down. The phase curvature indicates the existence of the lens effect. In fact, the curvature of the oil-air interface changes while the sample is cooling, as can be clearly noticed into the movie reported in Fig. 6. This effect could be exploited for having an array of microlenses with variable focus. The number of fringes decreases during the cooling, indicating that the liquid layer is returning back to its initial condition corresponding to a completely erased waviness and thus to an infinite focal length.

Figure 7 shows a portion of the mod 2π unwrapped phase map corresponding to a single frame of the movie in Fig. 6 and allows to estimate the wavefront curvature in correspondence of 2×2 micro-lenses of the array.

Fig. 7. Unwrapped phase map corresponding to a portion of the image in Fig. 6 for a fixed temperature during cooling.

Fitted parabolic profiles, calculated during cooling, indicate the presence of variable defocus, namely a variable focal length as shown in Fig. 8(a), where the phase profiles of the transmitted wavefront, corresponding to different time frames (1s, 3s, 5s, 7s, 9s, 11s, 13s, 14s) during cooling, are reported. The slight tilt of the sample, respect to the microscope objective into the interferometric set-up, is revealed by the asymmetry of the curves in Fig. 8(a). The focal length f of the liquid lenses can be retrieved by fitting the unwrapped phase map Φ(x, y) to a 2nd order polynomial according to

Φ(x,y)=2πλ(x2+y2)2f
(3)

Figure 8(b) shows the variation of the focal length (from 1.75 mm up to 2.1 mm) corresponding to the time frames of Fig. 8(a) during the cooling process. This effect could be used to have an array of microlenses with variable focus. Moreover, an imaging experiment was also performed in order to show the possibility to use this kind of variable focus microlens array for integrated microscope applications.

Fig. 8. (a). Phase profiles of the transmitted wavefront calculated for different frames during cooling; (b) focal length values calculated as function of time during the cooling process.

Figure 9 shows the imaging capability of the microlens array on a portion of USAF photo-target. The LN substrate, with the microlens array, was positioned over the target and observed under the optical microscope. The images in Figs. 9(a)–9(b) were acquired at two different focal planes corresponding to focusing the target through the regions outside and inside the aperture of the microlenses, respectively.

Fig. 9. Optical microscope images of the target “8” observed through the microlens array at two different focal planes imaging the target (a) through the region outside the lenses and (b) through the up-right microlens, where the focusing capability of the microlenses is clearly visible.

Furthermore, different oils with variable densities, such as paraffin oil, primed oil and sweet almond oil, were also used for analogous experiments and the lens effect appeared to work even though exhibiting slight different behaviours depending essentially on the oil density properties.

5. Conclusions and further developments

Acknowledgments

The research leading to these results has received funding from the European Community’s Seventh Framework Programme FP7/2007-2013 under grant agreement n° 216105 “Real 3D”. The authors thank Mr. Gregory Genta Jouve for the chemical characterization of the oil sample.

References and links

1.

P. Ferraro, “What breaks the shadow of the tube?” The Physics Teacher 36, 542–543 (1998). [CrossRef]

2.

B. Berge and J. Peseux, “Variable focal lens controlled by an external voltage: an application of electrowetting,” Eur. Phys. J. E 3, 159–163 (2000) [CrossRef]

3.

D. Grahan-Rowen, “Liquid lenses make a splash,” Nat. PhotonicsVolume sample, 2–4 (2006). [CrossRef]

4.

G. Beni and M. A. Tenan, “Dynamics of electrowetting displays,” J. Appl. Phys. 52, 6011–6015 (1981). [CrossRef]

5.

R. Hayes and D. J. Feenstra, “Video-Speed electronic paper based on electrowetting,” Nature 425, 383–385 (2003). [CrossRef] [PubMed]

6.

S. Kuiper and B. H. W. Hendriks, “Variable-focus liquid lens for miniature cameras,” Appl. Phys. Lett. 85, 1128–1130 (2004). [CrossRef]

7.

L. Dong, A. K. Argawal, D. J. Beebe, and H. Jiang, “Adaptive liquid microlenses activated by stimuliresponsive hydrogels,” Nature 442, 551–554 (2006). [CrossRef] [PubMed]

8.

C. C. Cheng and J. A. Yeh, “Dieletrically actuated liquid lens,” Opt. Express 15, 7140–7145 (2007). [CrossRef] [PubMed]

9.

D. Psaltis, S. R. Quache, and C. Yang, “Developing optofluidic technology through the fusion of microfluidics and optics,” Nature 442, 381–386 (2006). [CrossRef] [PubMed]

10.

F. Mugele and S. Herminghaus, “Electrostatic stabilization of fluid microstructures,” Appl. Phys. Lett. 81, 2303–2305 (2002). [CrossRef]

11.

T. Beerling, “Liquid metal switch employing an electrically isolated control element,” US Patent N. 7,053,323 (2006).

12.

P. M. Moran, S. Dharmatilleke, A. H. Khaw, K. W. Tan, M. L. Chan, and I. Rodriguez, “Fluidic lenses with variable focal length,” Appl. Phys. Lett. 88, 041120-3 (2006). [CrossRef]

13.

H. Ren, D. Fox, P. A. Anderson, B. Wu, and S.-T. Wu, “Tunable-focus liquid lens controlled using a servo motor,” Opt. Express 14, 8031–8036 (2006). [CrossRef] [PubMed]

14.

B. S. Gallardo, V. K. Gupta, F. D. Eagerton, L. I. Jong, V. S. Craig, R. R. Shah, and N. L. Abbott, “Electrochemical principles for active control of liquids on submillimeter scales,” Sci. 283, 57–60 (1999). [CrossRef]

15.

E. Colgate and H. Matsumoto, “An investigation of electrowetting-based micro actuation,” J. Vac. Sci. Technol. A 8, 3625–3633 (1990). [CrossRef]

16.

A. Sharma and R. Khanna, “Pattern formation in unstable thin liquid films,” Phys. Rev. Lett. 81, 3463–3466 (1998). [CrossRef]

17.

D. E. Kataoka and S. M. Troian, “Patterning liquid flow on the microscopic scale,” Nature 402, 794–797 (1999). [CrossRef]

18.

R. Seemann, M. Brinkmann, E. J. Kramer, F. F. Lange, and R. Lipowsky, “Wetting morphologies at microstructured surfaces,” PNAS 102, 1848–1852 (2005). [CrossRef] [PubMed]

19.

H. Moon, S. K. Cho, R. L. Garrell, and C.-J. Kim, “Low voltage electrowetting-on-dielectric,” J. Appl. Phys. 92, 4080–4087 (2002). [CrossRef]

20.

D. Aronov, G. Rosenman, A. Karlov, and A. Shashkin, “Wettability patterning of hydroxyapatite nanobioceramics induced by surface potential modification,” Appl. Phys. Lett. 88, 163902-3 (2006). [CrossRef]

21.

D. B. Wang, R. Szoszkiewicz, M. Lucas, E. Riedo, T. Okada, S. C. Jones, S. R. Marder, J. Lee, and W. P. King, “Local wettability modification by thermochemical nanolithography with write-read-overwrite capability,” Appl. Phys. Lett. 91, 243104-3 (2007). [CrossRef]

22.

M. W. J. Prinse, W. J. J. Welters, and J. W. Weekamp, “Fluid control in multichannel structures by electrocapillary pressure,” Sci. 291, 277–280 (2001). [CrossRef]

23.

C. W. Monroe, L. I. Daikhin, M. Urbakh, and A. A. Kornyshev, “Electrowetting with electrolytes,” Phys. Rev. Lett. 97, 136102-4 (2006). [CrossRef] [PubMed]

24.

P. Lazar and H. Riegler, “Reversible self propelled droplet movement: a new driving mechanism,” Phys. Rev. Lett. 95, 136103-4 (2005). [CrossRef] [PubMed]

25.

F. Mugele and J.-C. Baret, “Electrowetting: from basics to applications,” J. Phys. Condens. Matter 17, R705–R774 (2005). [CrossRef]

26.

E. L. Wooten, K. M. Kissa, A. Yi-Yan, E. J. Murphy, D. A. Lafaw, P. F. Hallemeier, D. Maack, D. V. Attanasio, D. J. Fritz, G. J. McBrien, and D. E. Bossi, “A Review of Lithium Niobate Modulators for Fiber-Optic Communications Systems,” IEEE J. Sel. Top. Quantum Electron. 6, 69–82 (2000). [CrossRef]

27.

R. L. Byer, “Nonlinear Optics and Solid-State Lasers:2000,” IEEE J. Sel. Top. Quantum Electron. 6, 911–930 (2000). [CrossRef]

28.

F. Laurell, M. G. Roelofs, W. Bindloss, H. Hsiung, A. Suna, and J. D. Bierlein, “Detection of ferroelectric domain reversal in KTP waveguides,” J. Appl. Phys. 71, 4664–4670 (1992). [CrossRef]

29.

B. Sun and J. Heikenfeld “Observation and optical implications of oil dewetting patterns in electrowetting displays” J. Micromech. Microeng. 18, 025027 (2008) [CrossRef]

30.

C. H. Bulmer, W. K. Burns, and S. C. Hiser, “Pyroelectric effects in LiNbO3 channel waveguide devices,” Appl. Phys. Lett. 48, 1036–1038 (1986). [CrossRef]

31.

M. Yamada, N. Nada, M. Saitoh, and K. Watanabe, “First-order quasi-phase matched LiNbO3 waveguide periodically poled by applying an external field for efficient blue second-harmonic generation,” Appl. Phys. Lett. 62, 435–436 (1993). [CrossRef]

32.

S. Grilli, M. Paturzo, L. Miccio, and P. Ferraro, “In situ investigation of periodic poling in congruent LiNbO3 by quantitative interference microscopy,” Meas. Sci. Technol. (in press).

33.

K. Nassau, H. J. Levinstein, and G. M. Loiacono, “The domain structure and etching of ferroelectric lithium niobate,” Appl. Phys. Lett. 6, 228–229 (1965). [CrossRef]

34.

S. Grilli, P. Ferraro, P. De Natale, B. Tiribilli, and M. Vassalli, “Surface nanoscale periodic structures in congruent lithium niobate by domain reversal patterning and differential etching,” Appl. Phys. Lett. 87, 233106-3 (2005). [CrossRef]

35.

V. Gopalan and T. E. Mitchell, “In situ video observation of 180° domain switching in LiTaO3 by electro-optic imaging microscopy,” J. Appl. Phys. 85, 2304–2311 (1999). [CrossRef]

36.

R. S. Weis and T. K. Gaylord, “Lithium Niobate: Summary of Physical Properties and Crystal Structure,” Appl. Phys. A 37, 191–203 (1985). [CrossRef]

37.

E. M. Bourim, C.-W. Moon, S.-W. Lee, and I. K. Yoo, “Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals,” Phys. B 383, 171–182 (2006). [CrossRef]

38.

B. Rosenblum, P. Bräunlich, and J. P. Carrico, “Thermally stimulated field emission from pyroelectric LiNbO3,” Appl. Phys. Lett. 25, 17–19 (1974). [CrossRef]

39.

G. Rosenman, D. Shur, Y. E. Krasik, and A. Dunaevsky, “Electron emission from ferroelectrics,” J. Appl. Phys. 88, 6109–6161 (2000). [CrossRef]

40.

F. Beunis, F. Strubbe, M. Marescaux, K. Neyts, and A. R. M. Verschueren, “Diffuse double layer charging in nonpolar liquids,” Appl. Phys. Lett. 91, 182911-3 (2007). [CrossRef]

41.

M. G. Lippmann, Ann. Chim. Phys.5, 494 (1875).

42.

P. Ferraro, S. De Nicola, and G. Coppola, “Digital holography: recent advancements and prospective improvements for applications in microscopy” in Optical Imaging Sensors and Systems for Homeland Security Applications, vol. 2 of Advanced Sciences and Technologies for Security Applications seriesB. Javidi ed., (Springer, 2005), pp. 47–84.

OCIS Codes
(090.0090) Holography : Holography
(220.2560) Optical design and fabrication : Propagating methods
(220.3630) Optical design and fabrication : Lenses
(110.1080) Imaging systems : Active or adaptive optics

ToC Category:
Optical Design and Fabrication

History
Original Manuscript: February 11, 2008
Revised Manuscript: March 18, 2008
Manuscript Accepted: March 23, 2008
Published: May 20, 2008

Virtual Issues
Vol. 3, Iss. 6 Virtual Journal for Biomedical Optics

Citation
S. Grilli, L. Miccio, V. Vespini, A. Finizio, S. De Nicola, and Pietro Ferraro, "Liquid micro-lens array activated by selective electrowetting on lithium niobate substrates," Opt. Express 16, 8084-8093 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-11-8084


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. P. Ferraro, "What breaks the shadow of the tube?" The Physics Teacher 36, 542-543 (1998). [CrossRef]
  2. B. Berge and J. Peseux, "Variable focal lens controlled by an external voltage: an application of electrowetting," Eur. Phys. J. E 3, 159-163 (2000) [CrossRef]
  3. D. Grahan-Rowen, "Liquid lenses make a splash," Nat. Photonics Volume sample, 2-4 (2006). [CrossRef]
  4. G. Beni and M. A. Tenan, "Dynamics of electrowetting displays," J. Appl. Phys. 52,6011-6015 (1981). [CrossRef]
  5. R. Hayes and D. J. Feenstra, "Video-Speed electronic paper based on electrowetting," Nature 425, 383-385 (2003). [CrossRef] [PubMed]
  6. S. Kuiper and B. H. W. Hendriks, "Variable-focus liquid lens for miniature cameras," Appl. Phys. Lett. 85,1128-1130 (2004). [CrossRef]
  7. L. Dong, A. K. Argawal. D. J. Beebe, and H. Jiang, "Adaptive liquid microlenses activated by stimuli-responsive hydrogels," Nature 442, 551-554 (2006). [CrossRef] [PubMed]
  8. C. C. Cheng and J. A. Yeh, "Dieletrically actuated liquid lens," Opt. Express 15, 7140-7145 (2007). [CrossRef] [PubMed]
  9. D. Psaltis, S. R. Quache, and C. Yang, "Developing optofluidic technology through the fusion of microfluidics and optics," Nature 442, 381-386 (2006). [CrossRef] [PubMed]
  10. F. Mugele and S. Herminghaus, "Electrostatic stabilization of fluid microstructures," Appl. Phys. Lett. 81,2303-2305 (2002). [CrossRef]
  11. T. Beerling, "Liquid metal switch employing an electrically isolated control element," US Patent N. 7,053,323 (2006).
  12. P. M. Moran, S. Dharmatilleke, A. H. Khaw, K. W. Tan, M. L. Chan, and I. Rodriguez, "Fluidic lenses with variable focal length," Appl. Phys. Lett. 88,041120-3 (2006). [CrossRef]
  13. H. Ren, D. Fox, P. A. Anderson, B. Wu, S.-T. Wu, "Tunable-focus liquid lens controlled using a servo motor," Opt. Express 14, 8031-8036 (2006). [CrossRef] [PubMed]
  14. B. S. Gallardo, V. K. Gupta, F. D. Eagerton, L. I. Jong, V. S. Craig, R. R. Shah, and N. L. Abbott, "Electrochemical principles for active control of liquids on submillimeter scales," Sci. 283, 57-60 (1999). [CrossRef]
  15. E. Colgate and H. Matsumoto, "An investigation of electrowetting-based micro actuation," J. Vac. Sci. Technol. A 8, 3625-3633 (1990). [CrossRef]
  16. A. Sharma and R. Khanna, "Pattern formation in unstable thin liquid films," Phys. Rev. Lett. 81,3463-3466 (1998). [CrossRef]
  17. D. E. Kataoka and S. M. Troian, "Patterning liquid flow on the microscopic scale," Nature 402, 794-797 (1999). [CrossRef]
  18. R. Seemann, M. Brinkmann, E. J. Kramer, F. F. Lange, and R. Lipowsky, "Wetting morphologies at microstructured surfaces," PNAS 102, 1848-1852 (2005). [CrossRef] [PubMed]
  19. H. Moon, S. K. Cho, R. L. Garrell, and C.-J. Kim, "Low voltage electrowetting-on-dielectric," J. Appl. Phys. 92, 4080-4087 (2002). [CrossRef]
  20. D. Aronov, G. Rosenman, A. Karlov, and A. Shashkin, "Wettability patterning of hydroxyapatite nanobioceramics induced by surface potential modification," Appl. Phys. Lett. 88, 163902-3 (2006). [CrossRef]
  21. D. B. Wang, R. Szoszkiewicz, M. Lucas, E. Riedo, T. Okada, S. C. Jones, S. R. Marder, J. Lee, and W. P. King, "Local wettability modification by thermochemical nanolithography with write-read-overwrite capability," Appl. Phys. Lett. 91, 243104-3 (2007). [CrossRef]
  22. M. W. J. Prinse, W. J. J. Welters, and J. W. Weekamp, "Fluid control in multichannel structures by electrocapillary pressure," Sci. 291, 277-280 (2001). [CrossRef]
  23. C. W. Monroe, L. I. Daikhin, M. Urbakh, and A. A. Kornyshev, "Electrowetting with electrolytes," Phys. Rev. Lett. 97, 136102-4 (2006). [CrossRef] [PubMed]
  24. P. Lazar and H. Riegler, "Reversible self propelled droplet movement: a new driving mechanism," Phys. Rev. Lett. 95, 136103-4 (2005). [CrossRef] [PubMed]
  25. F. Mugele and J.-C. Baret, "Electrowetting: from basics to applications," J. Phys. Condens. Matter 17, R705-R774 (2005). [CrossRef]
  26. E. L. Wooten, K. M. Kissa, A. Yi-Yan, E. J. Murphy, D. A. Lafaw, P. F. Hallemeier, D. Maack, D. V. Attanasio, D. J. Fritz, G. J. McBrien, and D. E. Bossi, "A Review of Lithium Niobate Modulators for Fiber-Optic Communications Systems," IEEE J. Sel. Top. Quantum Electron. 6, 69-82 (2000). [CrossRef]
  27. R. L. Byer, "Nonlinear Optics and Solid-State Lasers:2000," IEEE J. Sel. Top. Quantum Electron. 6, 911-930 (2000). [CrossRef]
  28. F. Laurell, M. G. Roelofs, W. Bindloss, H. Hsiung, A. Suna, and J. D. Bierlein, "Detection of ferroelectric domain reversal in KTP waveguides," J. Appl. Phys. 71,4664-4670 (1992). [CrossRef]
  29. B. Sun and J. Heikenfeld "Observation and optical implications of oil dewetting patterns in electrowetting displays" J. Micromech. Microeng. 18,025027 (2008) [CrossRef]
  30. C. H. Bulmer, W. K. Burns, and S. C. Hiser, "Pyroelectric effects in LiNbO3 channel waveguide devices," Appl. Phys. Lett. 48,1036-1038 (1986). [CrossRef]
  31. M. Yamada, N. Nada, M. Saitoh, and K. Watanabe, "First-order quasi-phase matched LiNbO3 waveguide periodically poled by applying an external field for efficient blue second-harmonic generation," Appl. Phys. Lett. 62, 435-436 (1993). [CrossRef]
  32. S. Grilli, M. Paturzo, L. Miccio, and P. Ferraro, "In situ investigation of periodic poling in congruent LiNbO3 by quantitative interference microscopy," Meas. Sci. Technol. (in press).
  33. K. Nassau, H. J. Levinstein, and G. M. Loiacono, "The domain structure and etching of ferroelectric lithium niobate," Appl. Phys. Lett. 6, 228-229 (1965). [CrossRef]
  34. S. Grilli, P. Ferraro, P. De Natale, B. Tiribilli, and M. Vassalli, "Surface nanoscale periodic structures in congruent lithium niobate by domain reversal patterning and differential etching," Appl. Phys. Lett. 87, 233106-3 (2005). [CrossRef]
  35. V. Gopalan and T. E. Mitchell, "In situ video observation of 180° domain switching in LiTaO3 by electro-optic imaging microscopy," J. Appl. Phys. 85, 2304-2311 (1999). [CrossRef]
  36. R. S. Weis and T. K. Gaylord, "Lithium Niobate: Summary of Physical Properties and Crystal Structure," Appl. Phys. A 37, 191-203 (1985). [CrossRef]
  37. E. M. Bourim, C.-W. Moon, S.-W. Lee, and I. K. Yoo, "Investigation of pyroelectric electron emission from monodomain lithium niobate single crystals," Phys. B 383, 171-182 (2006). [CrossRef]
  38. B. Rosenblum, P. Bräunlich, and J. P. Carrico, "Thermally stimulated field emission from pyroelectric LiNbO3," Appl. Phys. Lett. 25, 17-19 (1974). [CrossRef]
  39. G. Rosenman, D. Shur, Y. E. Krasik, and A. Dunaevsky, "Electron emission from ferroelectrics," J. Appl. Phys. 88, 6109-6161 (2000). [CrossRef]
  40. F. Beunis, F. Strubbe, M. Marescaux, K. Neyts, and A. R. M. Verschueren, "Diffuse double layer charging in nonpolar liquids," Appl. Phys. Lett. 91, 182911-3 (2007). [CrossRef]
  41. M. G. Lippmann, Ann. Chim. Phys. 5, 494 (1875).
  42. P. Ferraro, S. De Nicola, and G. Coppola, "Digital holography: recent advancements and prospective improvements for applications in microscopy" in Optical Imaging Sensors and Systems for Homeland Security Applications, vol. 2 of Advanced Sciences and Technologies for Security Applications series B. Javidi ed., (Springer, 2005), pp. 47-84.

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Multimedia

Multimedia FilesRecommended Software
» Media 1: MOV (4083 KB)     
» Media 2: MOV (3408 KB)     
» Media 3: MOV (4517 KB)     

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited