Humidity Dependence of Adhesion for Silane Coated Microcantilevers

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This study examines adhesion between silane-coated micromachined surfaces that are exposed to humid conditions. Our quantitative values for interfacial adhesion energies are determined from an in-situ optical measurement of deformations in partly-adhered cantilever beams. We coated micromachined cantilevers with either ODTS (C{sub 18}H{sub 37}SiCl{sub 3}) or FDTS (C{sub 8}F{sub 17}C{sub 2}H{sub 4}SiCl{sub 3}) with the objective of creating hydrophobic surfaces whose adhesion would be independent of humidity. In both cases, the adhesion energy is significantly lower than for uncoated, hydrophilic surfaces. For relative humidities (RH) less than 95% (ODTS) and 80% (FDTS) the adhesion energy was extremely low and constant. ... continued below

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34 p.

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DE BOER,MAARTEN P.; MAYER,THOMAS M.; CARPICK,ROBERT W.; MICHALSKE,TERRY A.; SRINIVASAN,U. & MABOUDIAN,R. November 9, 1999.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Description

This study examines adhesion between silane-coated micromachined surfaces that are exposed to humid conditions. Our quantitative values for interfacial adhesion energies are determined from an in-situ optical measurement of deformations in partly-adhered cantilever beams. We coated micromachined cantilevers with either ODTS (C{sub 18}H{sub 37}SiCl{sub 3}) or FDTS (C{sub 8}F{sub 17}C{sub 2}H{sub 4}SiCl{sub 3}) with the objective of creating hydrophobic surfaces whose adhesion would be independent of humidity. In both cases, the adhesion energy is significantly lower than for uncoated, hydrophilic surfaces. For relative humidities (RH) less than 95% (ODTS) and 80% (FDTS) the adhesion energy was extremely low and constant. In fact, ODTS-coated beams exposed to saturated humidity conditions and long (48 hour) exposures showed only a factor of two increase in adhesion energy. Surprisingly, FDTS coated beams, which initially have a higher contact angle (115{degree}) with water than do ODTS coated beams (112{degree}), proved to be much more sensitive to humidity. The FDTS coated surfaces showed a factor of one hundred increase in adhesion energy after a seven hour exposure to 90% RH. Atomic force microscopy revealed agglomerated coating material after exposed to high RH, suggesting a redistribution of the monolayer film. This agglomeration was more prominent for FDTS than ODTS. These findings suggest a new mechanism for uptake of moisture under high humidity conditions. At high humidities, the silane coatings can reconfigure from a surface to a bulk phase leaving behind locally hydrophilic sites which increase the average measured adhesion energy. In order for the adhesion increase to be observed, a significant fraction of the monolayer must be converted from the surface to the bulk phase.

Physical Description

34 p.

Notes

OSTI as DE00014828

Medium: P; Size: 34 pages

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  • Journal Name: Langmuir; Other Information: Submitted to Langmuir

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  • Report No.: SAND99-2950J
  • Grant Number: AC04-94AL85000
  • Office of Scientific & Technical Information Report Number: 14828
  • Archival Resource Key: ark:/67531/metadc620309

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  • November 9, 1999

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • April 12, 2017, 1:41 p.m.

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DE BOER,MAARTEN P.; MAYER,THOMAS M.; CARPICK,ROBERT W.; MICHALSKE,TERRY A.; SRINIVASAN,U. & MABOUDIAN,R. Humidity Dependence of Adhesion for Silane Coated Microcantilevers, article, November 9, 1999; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc620309/: accessed November 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.