Photon-modulated wettability changes on spiropyran-coated surfaces

Rohit Rosario, Devens Gust, Mark Hayes, Frank Jahnke, Joseph Springer, Antonio Garcia

Research output: Contribution to journalArticlepeer-review

242 Scopus citations


A coating of photoresponsive spiropyran molecules covalently bound to a glass surface along with a mixture of organosilanes to control the surface environment was prepared. The relatively nonpolar spiropyran can be reversibly switched to a polar, zwitterionic merocyanine isomer that has a much larger dipole moment by UV light, and back again by visible light. The contact angle was 11°-14° lower for dry, spiropyran-coated surfaces after irradiation with UV than that for dry, spiropyran-coated surfaces after irradiation with visible light. The light-induced changes observed in the surface energy were correlated to the switching of the surface-bound spiropyran molecule between polar and nonpolar forms by means of fluorescence spectroscopy and epifluorescence microscopy. Water in capillary tubes coated with the photosensitive layer was observed to rise when the wavelength of incident light was switched from visible to UV. The UV-induced rise was of the order of 2.8 mm for a 500 μm diameter capillary. This microfluidic actuation of water in an enclosed capillary or microchannel using light is termed "photocapillarity". Contact angle hysteresis prevented the water from flowing back clown the capillary when the light was switched from LTV back to visible.

Original languageEnglish (US)
Pages (from-to)8062-8069
Number of pages8
Issue number21
StatePublished - Oct 15 2002

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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