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Electrofluidic displays using Young–Laplace transposition of brilliant pigment dispersions

Nature Photonics volume 3, pages 292–296 (2009)Cite this article

Abstract

Conventional electrowetting displays reconfigure the contact angle of a coloured oil film on a planar hydrophobic surface. We report on electrofluidic displays, in particular a three-dimensional microfluidic display device that provides a direct view of brilliantly coloured pigment dispersions. Electromechanical pressure is used to pull the aqueous dispersion from a reservoir of small viewable area (<10%) into a surface channel of large viewable area (>90%). The hydrophobic channel and reservoir respectively impart a small or large radius of curvature on the dispersion. Therefore, with no voltage, Young–Laplace pressure forces the dispersion to retract into the reservoir. Preliminary prototypes exhibit ∼55% white reflectance, and future development points towards a reflectance of ∼85%. Uniquely, compared to electrowetting pixels, the electrofluidic pixels reduce the visible area of the coloured fluid by an additional two to three times (improving contrast), are potentially bistable, are as thin as ∼15 µm (giving potential for rollable displays), and can be miniaturized without increased operating voltage.

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Figure 1: The three-dimensional pixel structure and basic pixel operation.
Figure 2: Images of electrofluidic displays and pixels.
Figure 3: Voltage and time response of electrofluidic pixel characteristics.
Figure 4: Colour filtering techniques and materials that are required for full-colour electrofluidic displays.
Figure 5: The liquids in electrofluidic displays can be dosed by means of self-assembly.

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Acknowledgements

The authors acknowledge partial financial support for Cincinnati's general program in displays by Sun Chemical Corp., Motorola (K. Dean), Polymer Vision (E. Huitema), ITRI Taiwan (W. Cheng), Air Force Research Labs (R. Naik), Air Force Office of Scientific Research (AFOSR) Young Investigator Award no. 06NE223 (K. Reinhardt), and an National Science Foundation (NSF) CAREER Award no. 0640964 (Electronics Photonics & Device Technologies (EPDT)). The authors thank R. Fair of Duke University for discussion on switching speed in microscale electrowetting cavities.

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Authors and Affiliations

  1. Department of Electrical and Computer Engineering, Novel Devices Laboratory, University of Cincinnati, Cincinnati, 45221, Ohio, USA

    J. Heikenfeld, K. Zhou, E. Kreit, B. Raj & S. Yang

  2. Sun Chemical Corporation, Cincinnati, 45232, Ohio, USA

    B. Sun, A. Milarcik, L. Clapp & R. Schwartz

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  1. J. Heikenfeld
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Correspondence to J. Heikenfeld.

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Competing interests

Both Sun Chemical and PolymerVision are corporate sponsors of this work and have commercial interest in the outcome of the research performed at the University of Cincinnati.

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Heikenfeld, J., Zhou, K., Kreit, E. et al. Electrofluidic displays using Young–Laplace transposition of brilliant pigment dispersions. Nature Photon 3, 292–296 (2009). https://doi.org/10.1038/nphoton.2009.68

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