Elastic interfacial tension

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The surface stress (or surface loading), to a solid surface work per area that is needed elastic to stretch . So in such a way that the distance between the surface atoms changes, but not the number of surface atoms. The elastic interfacial tension is often referred to as the surface tension of the solid surface . In the case of solids, however, this quantity is not always clearly defined: there is a risk of confusion with the work per change in area, also known as surface tension , if the number of surface atoms is changed, as is usually the case with liquid interfaces.

Definition of the elastic interfacial tension

If the area A of a solid surface is changed by a small amount d A by elastic stretching while the number of surface atoms remains the same, the elastic interfacial tension f is given by the work d W that is performed during the reversible stretching, divided by the change in the area , d A :

f = d W / d A .

At the same time, f is also the force per unit length to elastically stretch a surface. Strictly speaking, f is a tensor, similar to the stress tensor for describing stresses in the interior of solids.

Determination of interfacial tensions and their changes

Measurements of absolute values ​​of the interfacial tension are difficult, therefore corresponding values ​​are calculated for the single crystal surfaces of metals.

Changes in the elastic interfacial tension, for example caused by adsorbates, can be determined using the substrate curvature method.

application

Sensitive measurements of changes in the elastic interfacial tension caused by adsorbates can be used for sensor applications . For example, antibiotics can be determined in the blood serum in the research laboratory.

Historical

Josiah Willard Gibbs was the first to recognize that, for solid surfaces, a distinction must be made between the work to recreate a surface and the work to elastically stretch an existing surface.

Individual evidence

  1. ↑ G. Angenheister, A. Busemann, O. Föppl, JW Geckeler, A. Nadai: Mechanics of elastic bodies . Springer-Verlag, 2013, ISBN 978-3-642-48543-5 ( google.com [accessed on August 31, 2016]).
  2. ↑ Dirk Sander: Surface stress: implications and measurements . In: Current Opinion in Solid State and Materials Scienc . tape 7 , no. 1 , February 2003, p. 51–57 , doi : 10.1016 / S1359-0286 (02) 00137-7 ( online on the MPI Halle website [PDF]).
  3. ^ Hans-Jürgen Butt: A Sensitive Method to Measure Changes in the Surface Stress of Solids . In: Journal of Colloid and Interface Science . tape 180 , no. 1 , June 1996, p. 251-260 , doi : 10.1006 / jcis.1996.0297 .
  4. ↑ Roberto Raiteri, Hans-Jürgen Butt, Massimo Grattarola: Changes in surface stress at the liquid / solid interface Measured with a microcantilever . In: Electrochimica Acta . tape 46 , no. 2-3 , November 2000, pp. 157–163 , doi : 10.1016 / S0013-4686 (00) 00569-7 ( online on the MIT Media Lab website [PDF]).
  5. ↑ Joseph W. Ndieyira, Natascha Kappeler, Stephen Logan, Matthew A. Cooper, Chris Abell, Rachel A. McKendry, Gabriel Aeppli: Surface-stress sensors for rapid and ultrasensitive detection of active free drugs in human serum . In: Nature Nanotechnology . tape 9 , no. 3 , 2013, p. 225–232 , doi : 10.1038 / nnano.2014.33 .
  6. ^ Josiah Willard Gibbs: The Scientific Papers of J. Willard Gibbs . Volume I Thermodynamics. Longmans, Green, and Co., London, New York and Bombay 1906, OCLC 61574355 , III. On the Equilibrium of Heterogeneous Substances, p. 315 ( online at archive.org - The Internet Archive ).