Optofluidics [Draft review]

Communities Digital Biology
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Here’s a literature review I did several years ago on opto-electrowetting (or opto-EWOD). I think this would make a great collaborative open-hardware project. This technique is particularly interesting because it solves many of the problems with other types of DMF (e.g., EWOD). I made this post a wiki, so edits/contributions are welcome and encouraged!

These are the reasons why opto-EWOD is interesting:

  1. You get millions of addressable fluxels from a projector that fits in your pocket and costs <$200 (and getting cheaper every year).
  2. You only need 2 electrical connections (GND and HV). Connectors are one of the biggest challenges and biggest expenses for traditional DMF platforms.
  3. Fabrication of the devices is 1D vs 3D. For DMF, you need a to fabricate an electrode pattern at <100um resolution (2D), then you need to build up the z-layer stack (dielectric, hydrophobic layers) with a surface roughness of 0.1-1um. It’s possible, but it pushes the limits of all of the technologies involved. For opto-EWOD, fabrication is as easy as it gets; you can choose from a selection of simple printing and lamination processes. The only trick is materials science, but there seem to be practical materials available right now; it’s just that the processes and tricks are not as widely known in the community.
  4. I’m not 100% sure about the patent landscape, but the first patent I am aware of is from 2004, which means that it is due to expire in the very near future.

Primary research papers:

  1. Chiou, P. Y., Moon, H., Toshiyoshi, H., Kim, C.-J. & Wu, M. C. Light actuation of liquid by optoelectrowetting. Sens. Actuators Phys. 104, 222–228 (2003). [cited by 226]
  2. P. Y. Chiou, Z. Chang, and M. C. Wu, “Droplet Manipulation With Light on Optoelectrowetting Device,” J. Microelectromechanical Syst., vol. 17, no. 1, pp. 133–138, Feb. 2008. [cited by 58]
  3. P. Y. Chiou, S.-Y. Park, and M. C. Wu, “Continuous optoelectrowetting for picoliter droplet manipulation,” Appl. Phys*. Lett.*, Dec. 2008. [cited by 46]
  4. Pei, S. N. et al. Light-actuated digital microfluidics for large-scale, parallel manipulation of arbitrarily sized droplets. in 2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS) 252–255 (2010). doi:10.1109/MEMSYS.2010.5442519 [cited by 25]
  5. J. K. Valley, S. NingPei, A. Jamshidi, H.-Y. Hsu, and M. C. Wu, “A unified platform for optoelectrowetting and optoelectronic tweezers,” Lab. Chip, vol. 11, no. 7, pp. 1292–1297, Apr. 2011. [cited by 32]

Theses:

1. S. N. Pei, “Optofluidic Devices for Droplet and Cell Manipulation,” 2015.

  • This is an excellent thesis and provides a lot of optimization information on light power, color, photoconductor thickness, etc.
  • Optimizes OEW process so that it can be controlled via a DLP projector instead of a laser

Patents:

1. P. Y. Chiou, “Systems and methods for optical actuation of microfluidics based on opto-electrowetting,” WO2004012848 A2, 12-Feb-2004.

Academic labs:

1. Ming Wu, UC Berkley

Companies:

1. Berkley Lights

DLP Projectors

1. DELL 4210X (used in Pei, 2015)

  • 3500 Lumens, contrast ratio 2000:1
  • Available used on ebay for $200-300

2. Texas Instruments DLP Pico Projection (DLP4710 reference design)

  • 600 Lumens
  • $999 USD for reference design kit

3. Joyhero Mini Portable

4. ERISAN WiFi Wireless Projector

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This is definitely cool technology! I looked through some of those papers, and it seems like it requires deposition of the photoconductor and dielectric layers. Are you considering this easy – I guess it is when you have the right lab equipment! – or are you thinking of another process?

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I think there are also organic photoconductors that can be applied via liquid deposition. I mean it’s not easy, but relative to DMF – where you need to do those same types of depositions plus 2D patterning – it’s quite attractive.

The manufacturing equipment isn’t widely available, but it should be simple to DIY.