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Title: Humidity Dependence of Adhesion for Silane Coated Microcantilevers

Abstract

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 FDTSmore » 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.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
14828
Report Number(s):
SAND99-2950J
TRN: AH200130%%37
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
Langmuir
Additional Journal Information:
Other Information: Submitted to Langmuir; PBD: 9 Nov 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ADHESION; COATINGS; HUMIDITY; MOISTURE; SILANES; MECHANICAL STRUCTURES; MINIATURIZATION; INTERFACES; WETTABILITY

Citation Formats

DE BOER, MAARTEN P, MAYER, THOMAS M, CARPICK, ROBERT W, MICHALSKE, TERRY A, SRINIVASAN, U, and MABOUDIAN, R. Humidity Dependence of Adhesion for Silane Coated Microcantilevers. United States: N. p., 1999. Web.
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. United States.
DE BOER, MAARTEN P, MAYER, THOMAS M, CARPICK, ROBERT W, MICHALSKE, TERRY A, SRINIVASAN, U, and MABOUDIAN, R. Tue . "Humidity Dependence of Adhesion for Silane Coated Microcantilevers". United States. https://www.osti.gov/servlets/purl/14828.
@article{osti_14828,
title = {Humidity Dependence of Adhesion for Silane Coated Microcantilevers},
author = {DE BOER, MAARTEN P and MAYER, THOMAS M and CARPICK, ROBERT W and MICHALSKE, TERRY A and SRINIVASAN, U and MABOUDIAN, R},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/14828}, journal = {Langmuir},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {11}
}