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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 4 — Feb. 24, 2014
  • pp: 4168–4179
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Stretchable optical waveguides

Jeroen Missinne, Sandeep Kalathimekkad, Bram Van Hoe, Erwin Bosman, Jan Vanfleteren, and Geert Van Steenberge  »View Author Affiliations


Optics Express, Vol. 22, Issue 4, pp. 4168-4179 (2014)
http://dx.doi.org/10.1364/OE.22.004168


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Abstract

We introduce the concept of mechanically stretchable optical waveguides. The technology to fabricate these waveguides is based on a cost-efficient replication method, employing commercially available polydimethylsiloxane (PDMS) materials. Furthermore, VCSELs (λ = 850 nm) and photodiodes, embedded in a flexible package, were integrated with the waveguides to obtain a truly bendable, stretchable and mechanically deformable optical link. Since these sources and detectors were integrated, it was possible to determine the influence of bending and stretching on the waveguide performance.

© 2014 Optical Society of America

1. Introduction

Stretchable material technologies have enabled an emerging range of applications that are impossible to achieve using conventional rigid or flexible technologies. Examples can be found in diverse application domains such as robotics and automation, health care and biomedical technologies, and consumer electronics. The ability to deform a functional substrate so that it can be wrapped around a curved or moving surface, allows for example creating an artificial (robot) skin [1

1. V. Lumelsky, M. Shur, and S. Wagner, “Sensitive Skin Workshop, Arlington, Virginia,” NSF, DARPA Sensitive Skin Workshop Report pp. 1–129 (1999).

], wearable on-body sensing systems [2

2. S. Cheng and Z. Wu, “A microfluidic, reversibly stretchable, large-area wireless strain sensor,” Adv. Funct. Mater. 21, 2282–2290 (2011). [CrossRef]

], or even monitoring moving machine parts or electronic systems that conform to their environment [3

3. Nokia, “The Morph Concept, “https://research.nokia.com/morph (accessed 2013).

].

A considerable amount of research has been performed on stretchable electronic systems in which, for example, non-stretchable islands are embedded in a stretchable material such as polydimethylsiloxane (PDMS), and joined with electrical interconnections. To make these interconnections mechanically stretchable, 2 approaches have been adopted. In a first approach, traditional conductors such as copper, gold or silicon are patterned as spring-like structures instead of straight lines [4

4. R. Verplancke, F. Bossuyt, D. Cuypers, and J. Vanfleteren, “Thin-film stretchable electronics technology based on meandering interconnections: fabrication and mechanical performance,” J. Micromech. Microeng. 22, 015002 (2012). [CrossRef]

7

7. J. A. Rogers, T. Someya, and Y. Huang, “Materials and mechanics for stretchable electronics,” Science 327, 1603–1607 (2010). [CrossRef] [PubMed]

]. In a second approach, an electrically conductive stretchable material itself is used to create the interconnections [8

8. T. Sekitani, Y. Noguchi, K. Hata, T. Fukushima, T. Aida, and T. Someya, “A rubberlike stretchable active matrix using elastic conductors,” Science 321, 1468–1472 (2008). [CrossRef] [PubMed]

]. Furthermore, not only the interconnections, but also electronic components themselves can be made flexible [9

9. D. Pham, H. Subbaraman, M. Chen, X. Xu, and R. Chen, “Self-aligned carbon nanotube thin-film transistors on flexible substrates with novel source -drain contact and multilayer metal interconnection,” IEEE Trans. Nanotechnol. 11, 44–50 (2012). [CrossRef]

] or stretchable [10

10. D.-H. Kim, J.-H. Ahn, W. M. Choi, H.-S. Kim, T.-H. Kim, J. Song, Y. Y. Huang, Z. Liu, C. Lu, and J. A. Rogers, “Stretchable and foldable silicon integrated circuits,” Science 320, 507–511 (2008). [CrossRef] [PubMed]

].

The majority of available PDMS materials is not suited for traditional photolithographic pattern definition. Although patterning of PDMS using wet chemical etching [12

12. J. Garra, T. Long, J. Currie, T. Schneider, R. White, and M. Paranjape, “Dry etching of polydimethylsiloxane for microfluidic systems,” J. Vac. Sci. Technol. A 20, 975–982 (2002). [CrossRef]

, 13

13. M. Schuettler, C. Henle, J. Ordonez, G. Suaning, N. Lovell, and T. Stieglitz, “Patterning of silicone rubber for micro-electrode array fabrication,” in Proceedings of International IEEE/EMBS Conference on Neural Engineering (Institute of Electrical and Electronics Engineers, New York, 1988), pp. 53–56.

], reactive ion etching [12

12. J. Garra, T. Long, J. Currie, T. Schneider, R. White, and M. Paranjape, “Dry etching of polydimethylsiloxane for microfluidic systems,” J. Vac. Sci. Technol. A 20, 975–982 (2002). [CrossRef]

, 14

14. D. Szmigiel, K. Domanski, P. Prokaryn, and P. Grabiec, “Deep etching of biocompatible silicone rubber,” Microelectron. Eng. 83, 1178–1181 (2006). [CrossRef]

, 15

15. S. J. Hwang, D. J. Oh, P. G. Jung, S. M. Lee, J. S. Go, J.-H. Kim, K.-Y. Hwang, and J. S. Ko, “Dry etching of polydimethylsiloxane using microwave plasma,” J. Micromech. Microeng. 19, 095010 (2009). [CrossRef]

] and laser ablation [16

16. B. A. Fogarty, K. E. Heppert, T. J. Cory, K. R. Hulbutta, R. S. Martin, and S. M. Lunte, “Rapid fabrication of poly(dimethylsiloxane)-based microchip capillary electrophoresis devices using co2 laser ablation,” Analyst 130, 924–930 (2005). [CrossRef] [PubMed]

] has been reported, mainly replication based microfabrication techniques are used, and are generally referred to as ‘soft lithography’ [17

17. Y. Xia and G. M. Whitesides, “Soft lithography,” Annu. Rev. Mater. Sci. 28, 153–184 (1998). [CrossRef]

]. Specifically for fabricating waveguides in PDMS, several approaches have been reported differing in applied patterning technologies and methods to obtain the refractive index contrast required for waveguiding.

A first approach to introduce an index contrast is to use a single material, for example Sylgard®184 (Dow Corning) but differing the mixing ratios of prepolymer and curing agent or the (thermal) curing conditions [18

18. D. A. Chang-Yen, R. K. Eich, and B. K. Gale, “A monolithic PDMS waveguide system fabricated using soft-lithography techniques,” J. Lightwave Technol. 23, 2088 (2005). [CrossRef]

]. Alternatively, in [19

19. J. S. Kee, D. P. Poenar, P. Neuzil, and L. Yobas, “Monolithic integration of poly(dimethylsiloxane) waveguides and microfluidics for on-chip absorbance measurements,” Sensor. Actuat. B-Chem. 134, 532–538 (2008). [CrossRef]

], Sylgard®184 was mixed with a silicone oil (200®Fluid, Dow Corning) to increase the refractive index. Furthermore, PDMS can be chemically modified for example by incorporating phenyl groups in the side chains of the PDMS-backbone [20

20. S. Kopetz, D. Cai, E. Rabe, and A. Neyer, “PDMS-based optical waveguide layer for integration in electrical-optical circuit boards,” AEU-Int. J. Electron. Commun. 61, 163–167 (2007). [CrossRef]

] in order to obtain a new material with a different refractive index. It is clear that all these approaches require precise tuning of parameters or proprietary material development. However, recently, many types of optically transparent PDMS materials with a range of different refractive indexes have become commercially available and can directly be applied. This allows selecting 2 materials with a precise refractive index difference for the core and cladding, depending on the waveguide design.

To pattern waveguides in PDMS, a widely adopted approach is to precisely fill microchannels using a razor blade or squeegee [18

18. D. A. Chang-Yen, R. K. Eich, and B. K. Gale, “A monolithic PDMS waveguide system fabricated using soft-lithography techniques,” J. Lightwave Technol. 23, 2088 (2005). [CrossRef]

, 20

20. S. Kopetz, D. Cai, E. Rabe, and A. Neyer, “PDMS-based optical waveguide layer for integration in electrical-optical circuit boards,” AEU-Int. J. Electron. Commun. 61, 163–167 (2007). [CrossRef]

22

22. J. S. Kee, D. P. Poenar, P. Neuzil, and L. Yobas, “Design and fabrication of poly(dimethylsiloxane) single-mode rib waveguide,” Opt. Express 17, 11739–11746 (2009). [CrossRef] [PubMed]

]. Hereby, the challenge is to remove the excess material to avoid a residual layer between the different waveguide cores since this may cause cross-talk between neighboring channels. As an alternative, closed microchannels can be patterned in cladding material and subsequently capillary filled with another material that forms the core of the waveguide [23

23. V. Lien, Y. Berdichevsky, and Y.-H. Lo, “A prealigned process of integrating optical waveguides with microfluidic devices,” IEEE Photon. Technol. Lett. 16, 1525–1527 (2004). [CrossRef]

, 24

24. V. Lien, K. Zhao, Y. Berdichevsky, and Y.-H. Lo, “High-sensitivity cytometric detection using fluidic-photonic integrated circuits with array waveguides,” IEEE J. Sel. Top. Quantum Electron. 11, 827–834 (2005). [CrossRef]

].

2. Fabrication methods

2.1. Waveguide design and materials

The waveguides consist of 6 cm long multimode channels with a cross-section of 50 μm × 50 μm. These are typical dimensions for multimode waveguides providing 1dB alignment tolerances larger than ±10 μm for in- and outcoupling [25

25. N. Bamiedakis, R. Penty, and I. White, “Compact multimode polymer waveguide bends for board-level optical interconnects,” J. Lightwave Technol. 31, 2370–2375 (2013). [CrossRef]

]. To maximize the light confinement, the refractive index contrast between cladding and core was chosen as large as possible within the limits of available materials. Therefore, Sylgard®184 (Dow Corning, refractive index ncladding = 1.41) was used as cladding and LS-6257 (Nusil, refractive index ncore = 1.57) was used as core material, resulting in a waveguide numerical aperture (NA) of ncore2ncladding2=0.69. The higher this value, the smaller bending radii are possible, which is important when designing deformable waveguides. As operating wavelength, 850 nm was selected, for which optoelectronic sources and detectors are available and the intrinsic losses of both materials are low. According to the product specifications, the intrinsic loss of the LS-6257 material is below 0.05 dB/cm [26

26. B. Riegler and R. Thomaier, “Index matching silicone for optoelectronic applications,” in New Developments in Optomechanics, A. E. Hatheway, eds., Proc. SPIE 6665, 666508 (2007). [CrossRef]

] and based on internal experience, Sylgard®184 is expected to exhibit a similar intrinsic loss value.

2.2. Waveguide fabrication

The multimode waveguides were patterned using a replication technique, see Fig. 1. First, a master mold was fabricated by defining 50 μm × 50 μm SU-8 ribs on a 250 μm pitch using UV lithography on a silicon wafer. This master mold was over-coated with Sylgard®184 (Dow Corning), which was subsequently thermally cured (15 minutes at 100°C on a hotplate) and then released. This layer forms the bottom cladding of the waveguides. Another, temporary, 10 cm × 10 cm glass substrate was covered with a spin-coated release layer of a 4% weight/volume polyvinyl alcohol solution in water (PVA, molecular weight between 31k and 50k, Sigma Aldrich). Then, a 25 μm thick layer of Sylgard®184 was spin-coated onto this release layer, forming the top cladding of the waveguides. Both the patterned and unpatterned cladding substrates were plasma treated (Diener Pico, 0.8 mbar, 24 s, 190 W 40 kHz generator, gas used: air) and subsequently brought in contact to form channels. This plasma treatment creates silanol groups on the surface forming an irreversible Si-O-Si bond upon contact [27

27. S. Bhattacharya, A. Datta, J. Berg, and S. Gangopadhyay, “Studies on surface wettability of poly(dimethyl) siloxane (PDMS) and glass under oxygen-plasma treatment and correlation with bond strength,” J. Microelectromech. Syst. 14, 590–597 (2005). [CrossRef]

]. Then, a drop of another type of PDMS, LS-6257 (Nusil) was applied at the inlet of the channels, filling them using the capillary action. After complete filling of the channels, the material was thermally cured for 14 hours in an oven at 80°C, realizing the waveguides. Finally, the waveguide substrate was immersed in deionized water for 1 hour to dissolve the PVA layer and obtain the freestanding, stretchable waveguides.

Fig. 1 Simplified concept of the PDMS waveguide fabrication process based on a capillary filling technique: (a) Bonding of 2 PDMS layers forming covered channels, (b) Applying a drop of liquid core material at the inlet, (c) Curing the core material once the channels are filled.

To interface the waveguides and create end-faces, a precise cut was made perpendicular to the waveguides using a thin razor blade. A photo of such a cut is shown in Fig. 2 also illustrating the dimensions of the waveguides. Due to the softness of the PDMS materials (Durometer, Shore A 50 for Sylgard®184 and Shore A 40 for LS-6257), polishing of the waveguide end-faces is difficult and was therefore not applied.

Fig. 2 Razor blade cross-section of the PDMS waveguides fabricated using capillary filling.

2.3. Integration of light sources and detectors

In order to characterize waveguides, interfacing with sources and detectors is needed. Usually, waveguides are characterized using actively aligned optical fibers at the input and output. However, for investigating the behavior of waveguides under mechanical bending, and especially stretching, this method becomes difficult, if not impossible. Therefore, a process was developed to integrate light sources and detectors with the waveguides [28

28. B. Van Hoe, E. Bosman, J. Missinne, S. Kalathimekkad, G. Van Steenberge, and P. Van Daele, “Novel coupling and packaging approaches for optical interconnects,” in Optoelectronic Interconnects XII, A. L. Glebov and R. T. Chen, eds., Proc. SPIE 8267, 82670T–82670T–11 (2012). [CrossRef]

], as illustrated in Fig. 3.

Fig. 3 Fabrication steps for integrating optoelectronic components with stretchable waveguides; the procedure is identical for integrating VCSELs or photodiodes.

As a starting point for this process, the technology for embedding thinned, bare die VCSELs (850 nm, multimode 1×4 array, ULM Photonics ULM850-05-TT) and photodiodes (GaAs, 100 μm circular active area, 1×4 array, Enablence, PDCA04-100-GS) in 40 μm thick, flexible polyimide foils was used. A 100 μm thick 45° deflecting micro mirror plug (material: polyimide) with a 120 nm evaporated gold coating was aligned with the active areas of these embedded optoelectronic components using a Dr. Tresky flip-chip bonder and subsequently glued using XS8455-48 adhesive (Namics corporation). The divergence angle of the VCSEL (20°, full width 1/e2 at 5 mA driving current) is small enough and the active area of the photodiode is large enough to ensure efficient coupling to the 50 μm × 50 μm waveguides after bridging the 100 μm distance between active area, mirror plug and waveguide end-face.

Subsequently, this complete assembly was aligned and bonded with the PDMS-based optical waveguides. To ensure proper vertical alignment, the waveguides top cladding thickness was precisely controlled to 25 μm, while the lateral positioning was performed using marks on the polyimide substrate which were aligned to the waveguides using a modified mask aligner. For achieving precise bonding of the PDMS and the polyimide substrate, a ‘dry bonding’ technique was used. Therefore, a 50 nm SiO2 layer was coated on the polyimide substrate, and then the PDMS and the coated polyimide substrate were plasma treated (Diener Pico, 0.8 mbar, 24 s, 190 W 40 kHz generator, gas used: air) creating silanol groups on both substrates. When the silanol groups on these 2 treated surfaces are brought into contact, an irreversible Si-O-Si bond is formed [27

27. S. Bhattacharya, A. Datta, J. Berg, and S. Gangopadhyay, “Studies on surface wettability of poly(dimethyl) siloxane (PDMS) and glass under oxygen-plasma treatment and correlation with bond strength,” J. Microelectromech. Syst. 14, 590–597 (2005). [CrossRef]

].

After this process, a small drop of Sylgard®184 was dispensed to fill the air gap between the waveguide end-faces and the mirror plug, acting as index matching material. This drop of material was left curing at room temperature in order not to induce thermal stress which may shift the components and affect the optical alignment.

Fig. 4 Embedded 1×4 VCSEL array coupled to 4 PDMS waveguides using the process shown in Fig. 3. The optoelectronic component is covered by the mirror plug and can therefore not be seen.
Fig. 5 Photo of the complete stretchable optical link including embedded VCSELs and photodiodes integrated with PDMS waveguides.

3. Characterization methods

The stretchable waveguides were characterized in terms of propagation losses, bending losses, stretching losses and reliability.

Fig. 6 Setup for investigating the effect of bending on the waveguide losses. The part of the sample where coupling between the optoelectronic components and the waveguides is performed was immobilized to exclude effects from changing coupling conditions as much as possible.

Then, the waveguides were subjected to mechanical stretching. In a first experiment, the waveguides were elongated for 30 % using a dedicated setup, see Fig. 7. The stretching mechanism consisted of a fixed and a moving holder positioned on guiding pins. Using a spindle, this moving holder was connected to a precision stepper motor, of which the direction of movement and speed was addressed by a commercial driving circuit, controlled by a programmable micro-controller unit. To limit the effect of changing coupling conditions, the waveguides were fixed away from the coupling region. Furthermore, a thicker block of PDMS was attached (using the ‘dry bonding’ technique explained above) on both sides of the waveguides to hold the sample without applying clamping pressure on the waveguides themselves, see Fig. 7.

Fig. 7 Setup for investigating the effect of stretching on the waveguide losses: (a) the waveguide link mounted on the setup and (b) a close-up on the thicker PDMS protruding blocks attached on both sides allowing fixation without direct clamping on the waveguides themselves.

All bending and stretching experiments were performed on waveguide samples with index matching PDMS between the waveguide end-faces and optoelectronic components.

4. Results and discussion

4.1. Waveguide link loss

Fig. 8 Optical power detected by the photodiode, measured for 3 waveguide links. The dashed lines represent the case without, and the solid lines with index matching PDMS applied. The dotted curve represents the emitted VCSEL power.

It is clear that application of the index matching PDMS significantly increases the amount of power detected by the photodiode. This can be explained by the lower divergence angle of the light beam in PDMS as compared to air, by the lower reflection losses and furthermore by the reduced influence of the waveguide end-face roughness on the coupling loss.

Fig. 9 Total optical loss in the waveguide link (in dB), measured for 3 waveguide links. The dashed lines represent the case without, and the solid lines with index matching PDMS applied.

4.2. Influence of waveguide bending

Fig. 10 Additional bending losses as a function of bending radius measured for 3 different waveguide links (depicted using different colors). The 3 separate experiments per link are depicted using different line styles (solid, dashed and dotted).

Due to the thickness of the PDMS blocks attached to the sample, it was not possible to measure bending radii smaller than 4 mm. However, it can be seen in Fig. 10 that the bending loss for two 90° bends becomes higher than 0.5dB (i.e. 0.25dB per 90° bend) when the bending radius becomes smaller than 4 mm. This corresponds with the results in [25

25. N. Bamiedakis, R. Penty, and I. White, “Compact multimode polymer waveguide bends for board-level optical interconnects,” J. Lightwave Technol. 31, 2370–2375 (2013). [CrossRef]

], in which the bending losses of 50 μm × 50 μm waveguides (with an NA of 0.25 and 1.14) were simulated using ray tracing simulations. It was found that the bending loss of a single 90° bend becomes higher than 0.25dB for bending radii between 3 and 9 mm, depending on the incoupling conditions and the numerical aperture of the simulated waveguide.

4.3. Influence of waveguide stretching

Fig. 11 Additional losses recorded when subjecting the waveguides to 9 cycli of 30 % elongation (8.3 s per cycle, waveguides unstretched at t=0 s). The experimental data for 3 different optical links is displayed in the 3 subplots showing link 1 to 3 from top to bottom. Within each subplot, the results for 3 different VCSEL driving currents are displayed using different line styles (solid, dashed and dotted).

The waveguides can easily be stretched more than 30 %, but then it becomes difficult to maintain stability of the coupling region. Nevertheless, the waveguide substrate can be stretched up to 140 % before the PDMS material breaks.

4.4. Influence of long-term waveguide stretching

Fig. 12 Long-term optical link reliability testing: inter-cycle insertion loss variation of 3 optical links (data averaged over 50 cycles). These 3 optical links were present on the same substrate and therefore subjected to identical stretching conditions.

Although the loss variations during one cycle fluctuate between 0.2 and 0.7 dB, the long-term average insertion loss is very stable which indicates that the stretching does not introduce noticeable degradation. It can also be seen that the variations occur in a similar fashion for the different links, indicating possible effects of environmental influences. The test was eventually stopped at 80000 stretching cycles without a clear indication that degradation or failure would occur.

5. Conclusion

References and links

1.

V. Lumelsky, M. Shur, and S. Wagner, “Sensitive Skin Workshop, Arlington, Virginia,” NSF, DARPA Sensitive Skin Workshop Report pp. 1–129 (1999).

2.

S. Cheng and Z. Wu, “A microfluidic, reversibly stretchable, large-area wireless strain sensor,” Adv. Funct. Mater. 21, 2282–2290 (2011). [CrossRef]

3.

Nokia, “The Morph Concept, “https://research.nokia.com/morph (accessed 2013).

4.

R. Verplancke, F. Bossuyt, D. Cuypers, and J. Vanfleteren, “Thin-film stretchable electronics technology based on meandering interconnections: fabrication and mechanical performance,” J. Micromech. Microeng. 22, 015002 (2012). [CrossRef]

5.

F. Bossuyt, T. Vervust, and J. Vanfleteren, “Stretchable electronics technology for large area applications: fabrication and mechanical characterization,” IEEE Trans. Comp. Pack. Man. 3, 229–235 (2013).

6.

T. Li, Z. Huang, Z. Suo, S. P. Lacour, and S. Wagner, “Stretchability of thin metal films on elastomer substrates,” Appl. Phys. Lett. 85, 3435–3437 (2004). [CrossRef]

7.

J. A. Rogers, T. Someya, and Y. Huang, “Materials and mechanics for stretchable electronics,” Science 327, 1603–1607 (2010). [CrossRef] [PubMed]

8.

T. Sekitani, Y. Noguchi, K. Hata, T. Fukushima, T. Aida, and T. Someya, “A rubberlike stretchable active matrix using elastic conductors,” Science 321, 1468–1472 (2008). [CrossRef] [PubMed]

9.

D. Pham, H. Subbaraman, M. Chen, X. Xu, and R. Chen, “Self-aligned carbon nanotube thin-film transistors on flexible substrates with novel source -drain contact and multilayer metal interconnection,” IEEE Trans. Nanotechnol. 11, 44–50 (2012). [CrossRef]

10.

D.-H. Kim, J.-H. Ahn, W. M. Choi, H.-S. Kim, T.-H. Kim, J. Song, Y. Y. Huang, Z. Liu, C. Lu, and J. A. Rogers, “Stretchable and foldable silicon integrated circuits,” Science 320, 507–511 (2008). [CrossRef] [PubMed]

11.

B. Van Hoe, G. Van Steenberge, E. Bosman, J. Missinne, T. Geernaert, F. Berghmans, D. Webb, and P. Van Daele, “Optical fiber sensors embedded in flexible polymer foils,” in Optical Sensing and Detection, F. Berghmans, A. G. Mignani, and C. A. van Hoof, eds., Proc. SPIE 7726, 72603 (2010).

12.

J. Garra, T. Long, J. Currie, T. Schneider, R. White, and M. Paranjape, “Dry etching of polydimethylsiloxane for microfluidic systems,” J. Vac. Sci. Technol. A 20, 975–982 (2002). [CrossRef]

13.

M. Schuettler, C. Henle, J. Ordonez, G. Suaning, N. Lovell, and T. Stieglitz, “Patterning of silicone rubber for micro-electrode array fabrication,” in Proceedings of International IEEE/EMBS Conference on Neural Engineering (Institute of Electrical and Electronics Engineers, New York, 1988), pp. 53–56.

14.

D. Szmigiel, K. Domanski, P. Prokaryn, and P. Grabiec, “Deep etching of biocompatible silicone rubber,” Microelectron. Eng. 83, 1178–1181 (2006). [CrossRef]

15.

S. J. Hwang, D. J. Oh, P. G. Jung, S. M. Lee, J. S. Go, J.-H. Kim, K.-Y. Hwang, and J. S. Ko, “Dry etching of polydimethylsiloxane using microwave plasma,” J. Micromech. Microeng. 19, 095010 (2009). [CrossRef]

16.

B. A. Fogarty, K. E. Heppert, T. J. Cory, K. R. Hulbutta, R. S. Martin, and S. M. Lunte, “Rapid fabrication of poly(dimethylsiloxane)-based microchip capillary electrophoresis devices using co2 laser ablation,” Analyst 130, 924–930 (2005). [CrossRef] [PubMed]

17.

Y. Xia and G. M. Whitesides, “Soft lithography,” Annu. Rev. Mater. Sci. 28, 153–184 (1998). [CrossRef]

18.

D. A. Chang-Yen, R. K. Eich, and B. K. Gale, “A monolithic PDMS waveguide system fabricated using soft-lithography techniques,” J. Lightwave Technol. 23, 2088 (2005). [CrossRef]

19.

J. S. Kee, D. P. Poenar, P. Neuzil, and L. Yobas, “Monolithic integration of poly(dimethylsiloxane) waveguides and microfluidics for on-chip absorbance measurements,” Sensor. Actuat. B-Chem. 134, 532–538 (2008). [CrossRef]

20.

S. Kopetz, D. Cai, E. Rabe, and A. Neyer, “PDMS-based optical waveguide layer for integration in electrical-optical circuit boards,” AEU-Int. J. Electron. Commun. 61, 163–167 (2007). [CrossRef]

21.

K. S. Ryu, X. Wang, K. Shaikh, and C. Liu, “A method for precision patterning of silicone elastomer and its applications,” J. Microelectromech. Syst. 13, 568–575 (2004). [CrossRef]

22.

J. S. Kee, D. P. Poenar, P. Neuzil, and L. Yobas, “Design and fabrication of poly(dimethylsiloxane) single-mode rib waveguide,” Opt. Express 17, 11739–11746 (2009). [CrossRef] [PubMed]

23.

V. Lien, Y. Berdichevsky, and Y.-H. Lo, “A prealigned process of integrating optical waveguides with microfluidic devices,” IEEE Photon. Technol. Lett. 16, 1525–1527 (2004). [CrossRef]

24.

V. Lien, K. Zhao, Y. Berdichevsky, and Y.-H. Lo, “High-sensitivity cytometric detection using fluidic-photonic integrated circuits with array waveguides,” IEEE J. Sel. Top. Quantum Electron. 11, 827–834 (2005). [CrossRef]

25.

N. Bamiedakis, R. Penty, and I. White, “Compact multimode polymer waveguide bends for board-level optical interconnects,” J. Lightwave Technol. 31, 2370–2375 (2013). [CrossRef]

26.

B. Riegler and R. Thomaier, “Index matching silicone for optoelectronic applications,” in New Developments in Optomechanics, A. E. Hatheway, eds., Proc. SPIE 6665, 666508 (2007). [CrossRef]

27.

S. Bhattacharya, A. Datta, J. Berg, and S. Gangopadhyay, “Studies on surface wettability of poly(dimethyl) siloxane (PDMS) and glass under oxygen-plasma treatment and correlation with bond strength,” J. Microelectromech. Syst. 14, 590–597 (2005). [CrossRef]

28.

B. Van Hoe, E. Bosman, J. Missinne, S. Kalathimekkad, G. Van Steenberge, and P. Van Daele, “Novel coupling and packaging approaches for optical interconnects,” in Optoelectronic Interconnects XII, A. L. Glebov and R. T. Chen, eds., Proc. SPIE 8267, 82670T–82670T–11 (2012). [CrossRef]

OCIS Codes
(230.0230) Optical devices : Optical devices
(230.3120) Optical devices : Integrated optics devices
(250.0250) Optoelectronics : Optoelectronics
(250.5460) Optoelectronics : Polymer waveguides

ToC Category:
Integrated Optics

History
Original Manuscript: November 8, 2013
Revised Manuscript: December 13, 2013
Manuscript Accepted: December 16, 2013
Published: February 18, 2014

Citation
Jeroen Missinne, Sandeep Kalathimekkad, Bram Van Hoe, Erwin Bosman, Jan Vanfleteren, and Geert Van Steenberge, "Stretchable optical waveguides," Opt. Express 22, 4168-4179 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-4-4168


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References

  1. V. Lumelsky, M. Shur, S. Wagner, “Sensitive Skin Workshop, Arlington, Virginia,” NSF, DARPA Sensitive Skin Workshop Report pp. 1–129 (1999).
  2. S. Cheng, Z. Wu, “A microfluidic, reversibly stretchable, large-area wireless strain sensor,” Adv. Funct. Mater. 21, 2282–2290 (2011). [CrossRef]
  3. Nokia, “The Morph Concept, “ https://research.nokia.com/morph (accessed 2013).
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