Short timescale wetting and penetration on porous sheets measured with ultrasound, direct absorption and contact angle

Research output: Contribution to journalArticleResearchpeer-review

Abstract

In this study the short timescale penetration and spreading of liquids on porous sheets is investigated. Three
measurement techniques are evaluated: ultrasonic liquid penetration measurement (ULP), contact angle
measurement (CA) and scanning absorptiometry (SA). With each of these techniques liquid penetration
as well as surface wetting can be measured. A quantitative comparison between the methods is carried
out. For our studies we are using model liquids with tuneable surface tension, viscosity and surface
energy which are the governing parameters for pore flow according to the Lucas–Washburn equation.
Scanning absorptiometry turns out to be an adequate tool for direct measurement for liquid penetration.
Ultrasonic liquid penetration showed a stable correlation (R2 ¼ 0.70) to SA and thus also gives a suitable
indication on the liquid penetration behaviour. Absorption of individual microliter drops measured in the
CA instrument showed different results than the other two measurements. For characterisation of the
wetting behaviour the measurement techniques gave substantially different results. We thus conclude
that ULP and SA do not capture the wetting behaviour of liquids on paper in the same way as
conventional contact angle measurement, it is unclear if their results are meaningful. Finally we are
proposing two parameters indicating a combination of liquid penetration and wetting, the slope of the
contact angle over time dq/dt and a contact angle calculated from SA. These two parameters are
moderately correlated, supporting the idea that they are indeed capturing a combination of liquid
penetration and wetting. While our investigations are restricted to paper, we believe that the methods
investigated here are generally applicable to study liquid absorption in thin porous media like
microfluidic paper based analytical devices, thin porous storage media, membranes and the like. Our
findings are highlighting the importance to have a match in timescale (time for penetration and wetting)
and size scale (liquid amount supplied) between the testing method and the actual use case of the
material, when analyzing wetting and penetration on porous materials.
Translated title of the contributionBenetzung und Penetration von Flüssigkeiten auf porösen Blättern, gemessen mit Ultraschall, direkter Absorption und Kontaktwinkel
LanguageEnglish
Pages12861–12869
Number of pages8
JournalRSC Advances
Volume8
Issue number23
DOIs
StatusPublished - 2018

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Contact angle
Wetting
Ultrasonics
Liquids
Scanning
Angle measurement
Porous materials
Interfacial energy
Microfluidics
Surface tension
Viscosity
Membranes

Keywords

    Fields of Expertise

    • Advanced Materials Science

    Cite this

    Short timescale wetting and penetration on porous sheets measured with ultrasound, direct absorption and contact angle. / Krainer, Sarah; Hirn, Ulrich.

    In: RSC Advances , Vol. 8, No. 23, 2018, p. 12861–12869.

    Research output: Contribution to journalArticleResearchpeer-review

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    abstract = "In this study the short timescale penetration and spreading of liquids on porous sheets is investigated. Threemeasurement techniques are evaluated: ultrasonic liquid penetration measurement (ULP), contact anglemeasurement (CA) and scanning absorptiometry (SA). With each of these techniques liquid penetrationas well as surface wetting can be measured. A quantitative comparison between the methods is carriedout. For our studies we are using model liquids with tuneable surface tension, viscosity and surfaceenergy which are the governing parameters for pore flow according to the Lucas–Washburn equation.Scanning absorptiometry turns out to be an adequate tool for direct measurement for liquid penetration.Ultrasonic liquid penetration showed a stable correlation (R2 ¼ 0.70) to SA and thus also gives a suitableindication on the liquid penetration behaviour. Absorption of individual microliter drops measured in theCA instrument showed different results than the other two measurements. For characterisation of thewetting behaviour the measurement techniques gave substantially different results. We thus concludethat ULP and SA do not capture the wetting behaviour of liquids on paper in the same way asconventional contact angle measurement, it is unclear if their results are meaningful. Finally we areproposing two parameters indicating a combination of liquid penetration and wetting, the slope of thecontact angle over time dq/dt and a contact angle calculated from SA. These two parameters aremoderately correlated, supporting the idea that they are indeed capturing a combination of liquidpenetration and wetting. While our investigations are restricted to paper, we believe that the methodsinvestigated here are generally applicable to study liquid absorption in thin porous media likemicrofluidic paper based analytical devices, thin porous storage media, membranes and the like. Ourfindings are highlighting the importance to have a match in timescale (time for penetration and wetting)and size scale (liquid amount supplied) between the testing method and the actual use case of thematerial, when analyzing wetting and penetration on porous materials.",
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    AU - Hirn,Ulrich

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    AB - In this study the short timescale penetration and spreading of liquids on porous sheets is investigated. Threemeasurement techniques are evaluated: ultrasonic liquid penetration measurement (ULP), contact anglemeasurement (CA) and scanning absorptiometry (SA). With each of these techniques liquid penetrationas well as surface wetting can be measured. A quantitative comparison between the methods is carriedout. For our studies we are using model liquids with tuneable surface tension, viscosity and surfaceenergy which are the governing parameters for pore flow according to the Lucas–Washburn equation.Scanning absorptiometry turns out to be an adequate tool for direct measurement for liquid penetration.Ultrasonic liquid penetration showed a stable correlation (R2 ¼ 0.70) to SA and thus also gives a suitableindication on the liquid penetration behaviour. Absorption of individual microliter drops measured in theCA instrument showed different results than the other two measurements. For characterisation of thewetting behaviour the measurement techniques gave substantially different results. We thus concludethat ULP and SA do not capture the wetting behaviour of liquids on paper in the same way asconventional contact angle measurement, it is unclear if their results are meaningful. Finally we areproposing two parameters indicating a combination of liquid penetration and wetting, the slope of thecontact angle over time dq/dt and a contact angle calculated from SA. These two parameters aremoderately correlated, supporting the idea that they are indeed capturing a combination of liquidpenetration and wetting. While our investigations are restricted to paper, we believe that the methodsinvestigated here are generally applicable to study liquid absorption in thin porous media likemicrofluidic paper based analytical devices, thin porous storage media, membranes and the like. Ourfindings are highlighting the importance to have a match in timescale (time for penetration and wetting)and size scale (liquid amount supplied) between the testing method and the actual use case of thematerial, when analyzing wetting and penetration on porous materials.

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    SP - 12861

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    T2 - RSC Advances

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    SN - 2046-2069

    IS - 23

    ER -