First Approach Using Fluidic Force Microscopy (FluidFM®) to Measure Adhesion Forces between Droplets and Flat/Rough Surfaces Immersed in Water.

By guest author Laura Schwan.

L. Schwan^1,* and U. Bröckel¹

¹Institute of Micro-Process-Engineering and Particle Technology (IMiP), University of Applied Sciences Trier, Environmental Campus Birkenfeld,P.O. Box 1380, D-55761 Birkenfeld, Germany.

*Email: L.Schwan@umwelt-campus.de

Link to publication: First Approach Using Fluidic Force Microscopy (FluidFM®) to Measure Adhesion Forces between Droplets and Flat/Rough Surfaces Immersed in Water

#Done with a FLEX: The Flexible Research AFM

Our research project addresses the complex field of battery recycling and deals with the difficult task of recovering valuable metals such as cobalt, nickel and lithium from the residues of pyrometallurgical recycling processes. The Priority Programme SPP2315, funded by the German Research Foundation (DFG), focuses on the concept of Engineered Artificial Minerals (EnAM) in the slag phase of pyrometallurgical processes. These EnAM are present in the form of crystals, whose formation is thermodynamically dependent. The EnAM act as a reservoir for the critical elements in the slag and are therefore worthy recycling [1,2].

Figure 1: Selective wet agglomeration principle.

However, a major scientific challenge has been to accurately quantify the wetting properties and adhesion force between EnAM crystals or more generally, particles and binding liquid droplets. To overcome this challenge, the FlexAFM in combination with the FluidFM® (Fluidic Force Microscopy) has proven to be a highly accurate tool that provides insight into the dynamics of wetting and adhesion at the microscale. In our work, an experimental setup is described that includes the formation of binding liquid droplets and initial measurements of adhesion forces between binding liquid droplets and standard flat and rough surfaces simulated by borosilicate glass and silicon carbide abrasive paper, respectively. Liquid paraffin oil is used as the binding liquid and measurements are performed in deionised water as the suspension liquid (continuous phase). An inverted microscope and a rectangular prism are used for optical control of the droplet formation (figure 2 a). It also allows the behaviour of the droplet to be studied during the measurement (figure 2 b and c).

Figure 2: a) Schematic representation of the experimental setup, FluidFM® Cantilever with droplet seen through prism and inverted microscope during adhesion force measurement b) on a flat surface and c) on a rough surface.

The pressure control system of the FluidFM® technology is used to generate the paraffin oil droplet on the cantilever tip (Ø_droplet ≈ 40 µm). After droplet formation, force distance curves are generated and the size of the droplet is checked after each measurement with the help of the optical setup. The results of these adhesion force measurements are discussed in detail in [5].

This work establishes a methodology for the future evaluation of the wetting properties of EnAM crystals in relation to the selective wet agglomeration process. The versatility of the FluidFM® system also allows the study of changes in parameters such as the pH of the continuous phase and the influence of surfactants on the adhesion forces. This offers the possibility of a deeper understanding of interparticular interactions and description of wetting characteristics, paving the way for potential applications in a wide range of fields.

References:

[1] Elwert, T.; Strauss, K.; Schirmer, T.; Goldmann, D. Phase composition of high lithium slags from the recycling of lithium ion batteries. World Metall. -Erzmetall 2012, 65, 163–171.

[2] Velázquez-Martínez, O.; Valio, J.; Santasalo-Aarnio, A.; Reuter, M.; Serna-Guerrero, R. A Critical Review of Lithium-Ion Battery Recycling Processes from a Circular Economy Perspective. Batteries 2019, 5, 68.

[3] Cattermole, A.E. Classification of the metallic constituents of ores 1904, 76359.

[4] Schreier J.; Bröckel U. Multidimensional separation due to selective spherical agglomeration-Evidence of shape separation via X-ray microtomography. Particuology 2021, 58, 316-323. https://doi.org/10.1016/j.partic.2021.04.003 

[5] Schwan, L.; Bröckel U. First Approach Using Fluidic Force Microscopy (FluidFM®) to Measure Adhesion Forces between Droplets and Flat/Rough Surfaces Immersed in Water. Processes 2024, 12, 99. https://doi.org/10.3390/pr12010099 .

To read more:

Determining mass of individual micron-sized particles using PicoBalance and FluidFM® probes