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Published February 14, 2019 | Submitted + Published
Journal Article Open

Differential Colorimetry Measurements of Fluctuation Growth in Nanofilms Exposed to Large Surface Thermal Gradients


Slender liquid nanofilms exposed to large surface thermal gradients are known to undergo thickness fluctuations, which rapidly self-organize into arrays of nanoprotrusions with a separation distance of tens of microns. We previously reported good agreement between measurements of the characteristic spacing and the wavelength of the most unstable mode predicted by a linear stability analysis based on a long wavelength thermocapillary model. Here, we focus on differential colorimetry measurements to quantify early time out-of-plane growth of protrusions for peak heights spanning 20 to 200 nm. Analysis of peak heights based on shape reconstruction reveals robust exponential growth. Good quantitative agreement of the growth rates with the thermocapillary model is obtained using a single fit constant to account for material parameters of nanofilms that could not be measured directly. These findings lend further support to the conjecture that the array protrusions uncovered almost two decades ago likely stem from a linear instability, whose growth rate is controlled by thermocapillary forces counterbalanced by capillary forces.

Additional Information

© 2019 Published under license by AIP Publishing. Submitted: 8 August 2018; Accepted: 24 January 2019; Published Online: 12 February 2019. The authors acknowledge the financial support from the National Science Foundation (NSF) (No. CBET 0701324) and a 2013 NASA Space Technology Research Fellowship to K. R. Fiedler (No. NNX13AN41H). We are also grateful for the use of instrumentation provided by the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology.

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Submitted - 1808.04693.pdf


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August 19, 2023
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