Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

An engineered anisotropic nanofilm with unidirectional wetting properties

Abstract

Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80 μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film’s anisotropic wetting behaviour as a function of measurable film morphology parameters.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: An overview of PPX nanofilm preparation and anisotropic wetting property.
Figure 2: Anisotropic wetting property of a PPX nanofilm.
Figure 3: Drop motion on a PPX nanofilm coated half-pipe.
Figure 4: Model of advancing and receding contact angles.

Similar content being viewed by others

References

  1. Huber, G. et al. Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements. Proc. Natl Acad. Sci. USA 102, 16293–16296 (2005).

    Article  CAS  Google Scholar 

  2. Bush, J. W. M., Hu, D. L. & Prakash, M. The integument of water-walking arthropods: Form and function. Adv. Insect Physiol. 34, 117–192 (2007).

    Article  Google Scholar 

  3. Zheng, Y. M., Gao, X. F. & Jiang, L. Directional adhesion of superhydrophobic butterfly wings. Soft Matter 3, 178–182 (2007).

    Article  CAS  Google Scholar 

  4. Oelschlägel, B., Gorb, S., Wanke, S. & Neinhuis, C. Structure and biomechanics of trapping flower trichomes and their role in the pollination biology of Aristolochia plants (Aristolochiaceae). New Phytol. 184, 988–1002 (2009).

    Article  Google Scholar 

  5. Extrand, C. W. Retention forces of a liquid slug in a rough capillary tube with symmetric or asymmetric features. Langmuir 23, 1867–1871 (2007).

    Article  CAS  Google Scholar 

  6. Berthier, J. Microdrops and Digital Microfluidics (William Andrew, 2008).

    Google Scholar 

  7. Pesika, N. S. et al. Gecko adhesion pad: A smart surface? J. Phys. Condens. Matter 21, 464132 (2009).

    Article  Google Scholar 

  8. Mahdavi, A. et al. A biodegradable and biocompatible gecko-inspired tissue adhesive. Proc. Natl Acad. Sci. USA 105, 2307–2312 (2008).

    Article  CAS  Google Scholar 

  9. de Gennes, P-G., Brochard-Wyart, F. & Quéré, D. Capillarity and Wetting Phenomena: Drops, Bubbles, Pearls, Waves (Springer, 2004).

    Book  Google Scholar 

  10. Khoo, H. S. & Tseng, F. G. Spontaneous high-speed transport of subnanoliter water droplet on gradient nanotextured surfaces. Appl. Phys. Lett. 95, 063108 (2009).

    Article  Google Scholar 

  11. Ichimura, K., Oh, S-K. & Nakagawa, M. Light-driven motion of liquids on a photoresponsive surface. Science 288, 1624–1626 (2000).

    Article  CAS  Google Scholar 

  12. Daniel, S., Sircar, S., Gliem, J. & Chaudhury, M. K. Ratcheting motion of liquid drops on gradient surfaces. Langmuir 20, 4085–4092 (2004).

    Article  CAS  Google Scholar 

  13. Sandre, O., Gorre-Talini, L., Ajdari, A., Prost, J. & Silberzan, P. Moving droplets on asymmetrically structured surfaces. Phys. Rev. E 60, 2964–2972 (1999).

    Article  CAS  Google Scholar 

  14. Shastry, A., Case, M. J. & Böhringer, K. F. Directing droplets using microstructured surfaces. Langmuir 22, 6161–6167 (2006).

    Article  CAS  Google Scholar 

  15. Linke, H. et al. Self-propelled Leidenfrost droplets. Phys. Rev. Lett. 96, 154502 (2006).

    Article  CAS  Google Scholar 

  16. Zhang, J., Cheng, Z., Zheng, Y. & Jiang, L. Ratchet-induced anisotropic behavior of superparamagnetic microdroplet. Appl. Phys. Lett. 94, 144104 (2009).

    Article  Google Scholar 

  17. So, E., Demirel, M. C. & Wahl, K. J. Mechanical anisotropy of nanostructured parylene films during sliding contact. J. Phys. D 43, 045403 (2010).

    Article  Google Scholar 

  18. Demirel, M. C., Cetinkaya, M., Singh, A. & Dressick, W. J. Noncovalent deposition of nanoporous Ni membranes on spatially organized poly(p-xylylene) film templates. Adv. Mater. 19, 4495–4499 (2007).

    Article  CAS  Google Scholar 

  19. Malvadkar, N. A., Sekeroglu, K., Dressick, W. J. & Demirel, M. C. Noncovalent mechanism for the conformal metallization of nanostructured parylene films. Langmuir 26, 4382–4391 (2010).

    Article  CAS  Google Scholar 

  20. Malvadkar, N. A., Dressick, W. J. & Demirel, M. C. Liquid phase deposition of titania onto nanostructured poly-p-xylylene thin films. J. Mater. Chem. 19, 4796–4804 (2009).

    Article  CAS  Google Scholar 

  21. Malvadkar, N. A., Park, S., Urquidi-MacDonald, M., Wang, H. & Demirel, M. C. Catalytic activity of cobalt deposited on nanostructured poly(p-xylylene) films. J. Power Sources 182, 323–328 (2008).

    Article  CAS  Google Scholar 

  22. Demirel, M. C. et al. Bio-organism sensing via surface enhanced Raman spectroscopy on controlled metal/polymer nanostructured substrates. Biointerphases 4, 35–41 (2009).

    Article  CAS  Google Scholar 

  23. Boduroglu, S., Cetinkaya, M., Dressick, W. J., Singh, A. & Demirel, M. C. Controlling the wettability and adhesion of nanostructured poly-(p-xylylene) films. Langmuir 23, 11391–11395 (2007).

    Article  CAS  Google Scholar 

  24. Lee, W. et al. Nanostructure-dependent water-droplet adhesiveness change in superhydrophobic anodic aluminum oxide surfaces: From highly adhesive to self-cleanable. Langmuir 26, 1412–1415 (2010).

    Article  CAS  Google Scholar 

  25. Cheng, Z., Gao, J. & Jiang, L. Tip geometry controls adhesive states of superhydrophobic surfaces. Langmuir 26, 8233–8238 (2010).

    Article  CAS  Google Scholar 

  26. Quéré, D. Wetting and roughness. Ann. Rev. Mater. Res. 38, 16.1–16.29 (2008).

    Article  Google Scholar 

  27. Dussan V, E. B. & Chow, R. T-P. On the ability of drops or bubbles to stick to non-horizontal surfaces of solids. J. Fluid Mech. 137, 1–29 (1983).

    Article  CAS  Google Scholar 

  28. Extrand, C. W. & Kumagai, Y. Liquid drops on an inclined plane: The relation between contact angles, drop shape, and retentive force. J. Colloid Interface Sci. 170, 515–521 (1995).

    Article  CAS  Google Scholar 

  29. Nadkarni, G. D. & Garoff, S. An investigation of microscopic aspects of contact angle hysteresis: Pinning of the contact line on a single defect. Europhys. Lett. 20, 523–528 (1992).

    Article  CAS  Google Scholar 

  30. de Gennes, P. G. Wetting: Statics and dynamics. Rev. Mod. Phys. 57, 827–863 (1985).

    Article  CAS  Google Scholar 

  31. Michael, D. H. Meniscus stability. Ann. Rev. Fluid Mech. 13, 189–216 (1981).

    Article  Google Scholar 

  32. Gao, L. & McCarthy, T. J. Wetting 101°. Langmuir 25, 14105–14115 (2009).

    Article  CAS  Google Scholar 

  33. Extrand, C. W. Model for contact angles and hysteresis on rough and ultraphobic surfaces. Langmuir 18, 7991–7999 (2002).

    Article  CAS  Google Scholar 

  34. ElSherbini, A. I. & Jacobi, A. M. Retention forces and contact angles for critical liquid drops on non-horizontal surfaces. J. Colloid Interface Sci. 299, 841–849 (2006).

    Article  CAS  Google Scholar 

  35. Prakash, M., Quéré, D. & Bush, J. W. M. Surface tension transport of prey by feeding shorebirds: the capillary ratchet. Science 320, 931–934 (2008).

    Article  CAS  Google Scholar 

  36. Renvoisé, P., Bush, J. W. M., Prakash, M. & Quéré, D. Drop propulsion in tapered tubes. Europhys. Lett. 86, 64003 (2009).

    Article  Google Scholar 

  37. Courbin, L. et al. Imbibition by polygonal spreading on microdecorated surfaces. Nature Mater. 6, 661–664 (2007).

    Article  CAS  Google Scholar 

  38. Chu, K. H., Xiao, R. & Wang, E. N. Uni-directional liquid spreading on asymmetric nanostructured surfaces. Nature Mater. 9, 413–417 (2010).

    Article  CAS  Google Scholar 

Download references

Acknowledgements

We gratefully acknowledge financial support for this work from the Pennsylvania State University and the Office of Naval Research under the Naval Research Laboratory Core 6.1 Research Program and the Young Investigator Program. We thank J. Bush for a number of useful discussions.

Author information

Authors and Affiliations

Authors

Contributions

M.C.D. and W.J.D. planned the research, and M.C.D. supervised the research. M.C.D., N.A.M. and K.S. carried out the experiments. M.J.H. developed the theoretical model. All authors contributed to writing and revising the manuscript, and agreed on its final contents.

Corresponding author

Correspondence to Melik C. Demirel.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 475 kb)

Supplementary Information

Supplementary Movie 1 (MOV 969 kb)

Supplementary Information

Supplementary Movie 2 (MOV 1673 kb)

Supplementary Information

Supplementary Information (PDF 4465 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Malvadkar, N., Hancock, M., Sekeroglu, K. et al. An engineered anisotropic nanofilm with unidirectional wetting properties. Nature Mater 9, 1023–1028 (2010). https://doi.org/10.1038/nmat2864

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat2864

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing