Simplified Ground-type Single-plate Electrowetting Device for Droplet Transport

  • Received : 2010.11.19
  • Accepted : 2011.03.31
  • Published : 2011.05.02


The current paper describes a simpler ground-type, single-plate electrowetting configuration for droplet transport in digital microfluidics without performance degradation. The simplified fabrication process is achieved with two photolithography steps. The first step simultaneously patterns both a control electrode array and a reference electrode on a substrate. The second step patterns a dielectric layer at the top to expose the reference electrode for grounding the liquid droplet. In the experiment, a $5{\mu}m$ thick photo-imageable polyimide, with a 3.3 dielectric constant, is used as the dielectric layer. A 10 nm Teflon-AF is coated to obtain a hydrophobic surface with a high water advancing angle of $116^{\circ}$ and a small contact angle hysteresis of $5^{\circ}$. The droplet movement of 1 mM methylene blue on this simplified device is successfully demonstrated at control voltages above the required 45 V to overcome the contact angle hysteresis.


  1. L. Malic, D. Brassard, T. Veres, and M. Tabrizian, "Integration and detection of biochemical assays in digital microfluidic LOC devices," Lab Chip, vol. 10, no. 4, pp. 418-431, 2010.
  2. M. Abdelgawad and A. R. Wheeler, "The digital revolution: A new paradigm for microfluidics," Adv. Mater., vol. 21, no. 8, pp. 920-925, February 2009.
  3. J. Heikenfeld, K. Zhou, E. Kreit, B. Raj, S. Yang, B. Sun, A. Milarcik, L. Clapp, and R. Schwartz, "Electrofluidic displays using Young-Laplace transposition of brilliant pigment dispersions," Nat. Photonics, vol. 3, no. 5, pp. 292-296, May 2009.
  4. R. Shamai, D. Andelman, B. Berge, and R. Hayes, "Water, electricity, and between... On electrowetting and its applications," Soft Matter, vol. 4, no. 1, pp. 38-45, January 2008.
  5. M. G. Pollack, A. D. Shenderov, and R. B. Fair, "Electrowetting-based actuation of droplets for integrated microfluidics," Lab Chip, vol. 2, no. 2, pp. 96-101, May 2002.
  6. M. Abdelgawad, P. Park, and A. R. Wheeler, "Optimization of device geometry in single-plate digital microfluidics," J. Appl. Phys., vol. 105, no. 9, p. 094506, May 2009.
  7. Y. J. Liu, D. J. Yao, H. C. Lin, W. Y. Chang, and H. Y. Chang, "DNA ligation of ultramicro volume using an EWOD microfluidic system with coplanar electrodes," J. Micromech. Microeng., vol. 18, no. 4, 2008.
  8. R. B. Fair, A. Khlystov, T. D. Tailor, V. Ivanov, R. D. Evans, V. Srinivasan, V. K. Pamula, M. G. Pollack, P. B. Griffin, and J. Zhou, "Chemical and biological applications of digital-microfluidic devices," IEEE Des. Test Comput., vol. 24, no. 1, pp. 10-24, 2007.
  9. Y. Li, M. Yoshio, L. Haworth, W. Parkes, M. Kubota, and A. J. Walton, "Test structure for characterizing low voltage coplanar EWOD system," IEEE Trans. Semicond. Manuf., vol. 22, no. 1, pp. 88-95, 2009.
  10. M. Washizu, "Electrostatic actuation of liquid droplets for micro-reactor applications," IEEE Trans. Ind. Appl., vol. 34, no. 4, pp. 732-737, 1998.
  11. A. Torkkeli, J. Saarilahti, A. Haara, H. Harma, T. Soukka, and P. Tolonen, "Electrostatic transportation of water droplets on superhydrophobic surfaces," in Proceedings of 14th IEEE International Conference on Micro Electro Mechanical Systems, Interlaken, Switzerland, 21–25 January 2001, pp. 475-478.
  12. U.-C. Yi and C.-J. Kim, "Characterization of electrowetting actuation on addressable single-side coplanar electrodes," J. Micromech. Microeng., vol. 16, no. 10, pp. 2053-2059, 2006.
  13. I. Moon and J. Kim, "Using EWOD (electrowettingon-dielectric) actuation in a micro conveyor system," Sens. Actuators A, vol. 130-131, pp. 537-544, 2006.
  14. S.-K. Fan, H. Yang, T.-T. Wang, and W. Hsu, "Asymmetric electrowetting–moving droplets by a square wave," Lab Chip, vol. 7, no. 10, pp. 1330-1335, 2007.
  15. K. H. Kang, "How electrostatic fields change contact angle in electrowetting," Langmuir, vol. 18, no. 26, p. 10318, 2002.
  16. Y. Fouillet and J.-L. Achard, "Microfluidique discrete et biotechnologie," C. R. Phys., vol. 5, no. 5, pp. 577-588, 2004.
  17. R. B. Fair, A. Khlystov, V. Srinivasan, V. K. Pamula, and K. N. Weaver, "Integrated chemical/biochemical sample collection, pre-concentration, and analysis on a digital microfluidic lab-on-a-chip platform," Proc. SPIE, vol. 5591, pp. 113-124, 2004.
  18. C. Cooney, C.-Y. Chen, M. Emerling, A. Nadim, and J. Sterling, "Electrowetting droplet microfluidics on a single planar surface," Microfluid. Nanofluid., vol. 2, no. 5, pp. 435-446, September 2006.
  19. J. Berthier, P. Dubois, P. Clementz, P. Claustre, C. Peponnet, and Y. Fouillet, "Actuation potentials and capillary forces in electrowetting based microsystems," Sens. Actuators A, vol. 134, no. 2, pp. 471-479, March 2007.
  20. H. Moon, S. K. Cho, R. L. Garrell, and C.-J. Kim, "Low voltage electrowetting-on-dielectric," J. Appl. Phys., vol. 92, no. 7, pp. 4080-4087, October 2002.
  21. S. Berry, J. Kedzierski, and B. Abedian, "Low voltage electrowetting using thin fluoroploymer films," J. Colloid Interface Sci., vol. 303, no. 2, pp. 517-524, November 2006.
  22. Y. Li, W. Parkes, L. I. Haworth, A. W. S. Ross, J. T. M. Stevenson, and A. J. Walton, "Room-temperature fabrication of anodic tantalum pentoxide for lowvoltage electrowetting on dielectric (EWOD)," J. Microelectromech. Syst., vol. 17, no. 6, pp. 1481-1488, December 2008.
  23. J.-H. Chang, D. Y. Choi, S. Han, and J. J. Pak, "Driving characteristics of the electrowetting-ondielectric device using atomic-layer-deposited aluminum oxide as the dielectric," Microfluid. Nanofluid., vol. 8, no. 2, pp. 269-273, February 2010.
  24. P. Y. Paik, V. K. Pamula, and K. Chakrabarty, "Adaptive cooling of integrated circuits using digital microfluidics," IEEE Trans. Very Large Scale Integr. (VLSI) Syst., vol. 16, no. 4, pp. 432-443, 2008.

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