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Optofluidics is a research and technology area that combines the advantages of fluidics (in particular microfluidics) and optics. Applications of the technology include displays, biosensors, lab-on-chip devices, lenses, and molecular imaging tools and energy.

History

The idea of fluid-optical devices can be traced back at least as far as the 18th century, when spinning pools of mercury were proposed (and eventually developed) as liquid-mirror telescopes. In the 20th century new technologies such as dye lasers and liquid-core waveguides were developed that took advantage of the tunability and physical adaptability that liquids provided to these newly emerging photonic systems. The field of optofluidics formally began to emerge in the mid-2000s as the fields of microfluidics and nanophotonics were maturing and researchers began to look for synergies between these two areas. One of the primary applications of the field is for lab-on-a-chip and biophotonic products.

Companies and technology transfer

Optofluidic and related research has led to the formation of a number of new products and start-up companies. Varioptic specializes in the development of electrowetting based lenses for numerous applications. Optofluidics, Inc. was launched in 2011 from Cornell University in order to develop tools for molecular trapping and disease diagnosis based on photonic resonator technology. Liquilume from UC Santa Cruz specializes in molecular diagnostics based on arrow waveguides.

In 2012, the European Commission has launched a new COST framework that is concerned solely with optofluidic technology and their application.

Examples of Specific Applications

Given the broad range of technologies that have already been developed in the field of microfluidics and the many potential applications of integrating optical components into these systems, the range of applications for optofluidic technology is vast.

Laminar Flow Based Optofluidic Waveguides

Optofluidic waveguides are based on principles of traditional optical waveguides and microfluidic techniques used to maintain gradients or boundaries between flowing fluids. Yang et al. used microfluidic techniques based on laminar flow to generate fluid-based gradient-indices of refraction. This was implemented by flowing two cladding layers of deionized water (${\displaystyle n=1.33}$) around a core layer of ethylene glycol (${\displaystyle n=1.43}$). Using traditional microfluidic techniques to generate and maintain gradients of fluids, Yang et al. were able maintain refractive index profiles ranging from step-index profiles to depth-varying gradient-index profiles. This allowed for the novel and dynamic generation of complex waveguides.

Optofluidic Photonic Crystal Fibers

Optofluidic Photonic-crystal fibers (PCFs) are traditional PFCs modified with microfluidic techniques. Photonic-crystal fibers are a type of fiber optic waveguide with cladding layers arranged in a crystalline fashion in their cross-sectional areas. Traditionally, these structured cladding layers are filled with a solid-state material with a different refractive indices or are hollow. Each cladded core then acts as a single mode fiber passing multiple light paths in parallel. Traditional PCFs are also limited to using hollow or solid-state cores that must be filled at the time of construction. This means that the material properties the PCFs were set at the time of construction and were limited to the material properties of solid-state materials.

Viewig et al. used microfluidic technology to selectively fill sections of photonic crystal fibers with fluids that exhibit a high degree of Kerr nonlinearity such as toluene and carbon tetrachloride. Selectively filling hollow PFCs with fluid allows for control over thermal diffusion via spatial segregation and allows for the ability to pattern multiple different types of fluid. Using non-linear fluids, Vieweg et al. were able to generate a soliton continuum which has many applications for imaging and communications.

See also

• List of optofluidics researchers

References

1. Psaltis, D.; Quake, S. R.; Yang, C. (2006). "Developing optofluidic technology through the fusion of microfluidics and optics". Nature. 442 (7101): 381–386. Bibcode:2006Natur.442..381P. doi:10.1038/nature05060. PMID 16871205. S2CID 1729058.
2. Zahn, p. 185.
3. Boas, Gary (June 2011). "Optofluidics and the Real World: Technologies Evolve to Meet 21st Century Challenges". Photonics Spectra. Retrieved 2011-06-26.
4. "Optofluidics: Optofluidics can create small, cheap biophotonic devices". Jul 1, 2006. Retrieved 2011-06-26.
5. "COST Action MP1205 Advances in Optofluidics: Integration of Optical Control and Photonics with Microfluidics". Archived from the original on 2017-11-26. Retrieved 2017-02-14.
6. Yang, Y.; Liu, A.Q.; Chin, L.K.; Zhang, X.M.; Tsai, D.P.; Lin, C.L.; Lu, C.; Wang, G.P.; Zheludev, N.I. (January 2012). "Optofluidic waveguide as a transformation optics device for lightwave bending and manipulation". Nature Communications. 3 (1): 651. Bibcode:2012NatCo...3..651Y. doi:10.1038/ncomms1662. ISSN 2041-1723. PMC 3272574. PMID 22337129.
7. Azizipour, Neda; Avazpour, Rahi; Rosenzweig, Derek H.; Sawan, Mohamad; Ajji, Abdellah (2020-06-18). "Evolution of Biochip Technology: A Review from Lab-on-a-Chip to Organ-on-a-Chip". Micromachines. 11 (6): 599. doi:10.3390/mi11060599. ISSN 2072-666X. PMC 7345732. PMID 32570945.
8. ^ Tu, Haohua; Boppart, Stephen A. (2012-07-23). "Coherent fiber supercontinuum for biophotonics". Laser & Photonics Reviews. 7 (5): 628–645. doi:10.1002/lpor.201200014. ISSN 1863-8880. PMC 3864867. PMID 24358056.
9. ^ Vieweg, M.; Gissibl, T.; Pricking, S.; Kuhlmey, B. T.; Wu, D. C.; Eggleton, B. J.; Giessen, H. (2010-11-17). "Ultrafast nonlinear optofluidics in selectively liquid-filled photonic crystal fibers". Optics Express. 18 (24): 25232–25240. Bibcode:2010OExpr..1825232V. doi:10.1364/oe.18.025232. ISSN 1094-4087. PMID 21164870.
10. Shao, Liyang; Liu, Zhengyong; Hu, Jie; Gunawardena, Dinusha; Tam, Hwa-Yaw (2018-03-24). "Optofluidics in Microstructured Optical Fibers". Micromachines. 9 (4): 145. doi:10.3390/mi9040145. ISSN 2072-666X. PMC 6187474. PMID 30424079.

Further reading

• Fainman, Yeshaiahu; Psaltis, Demetri (18 September 2009). Optofluidics: fundamentals, devices, and applications. McGraw Hill Professional. ISBN 978-0-07-160156-6. Retrieved 26 June 2011.
• Zahn, Jeffrey D. (31 October 2009). Methods in bioengineering: biomicrofabrication and biomicrofluidics. Artech House. ISBN 978-1-59693-400-9. Retrieved 26 June 2011.
• Ferreira M, Leça J (1 December 2022). "Real-Time Measurement of Refractive Index Using 3D-Printed Optofluidic Fiber Sensors". Sensors. 22 (23): 9377. Bibcode:2022Senso..22.9377L. doi:10.3390/s22239377. PMC 9739723. PMID 36502090.

• Optofluidics