Ultrasonic Liquid Penetration Measurement in Thin Sheets—Physical Mechanisms and Interpretation

Carina Waldner*, Ulrich Hirn*

*Corresponding author for this work

Research output: Contribution to journalArticle


Ultrasonic liquid penetration (ULP) measurements of porous sheets have been applied for a variety of purposes ranging from determining liquid absorption dynamics to surface characterization of substrates. Interpretation of ULP results, however, is complex as the ultrasound signal can be affected by several mechanisms: (1) air being replaced by the liquid in the substrate pores, (2) air bubbles forming during penetration, and (3) structural changes of the substrate due to swelling of the substrate material. Analyzing tailored liquids and substrates in combination with contact angle measurements we are demonstrating that the characteristic shape of the ULP measurement curves can be interpreted in terms of the regime of liquid uptake. A fast and direct decline of the curve corresponds to capillary penetration, the slope of the curve indicates the penetration speed. A slow decline after a previous maximum in the signal can be related to diffusive liquid transport and swelling of the substrate material
Original languageEnglish
Pages (from-to)2754
Issue number12
Publication statusPublished - 2020

Fields of Expertise

  • Advanced Materials Science

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