How can we explaine the adhesion force?

[NEMS]

Hello,

How can we explain the adhesion force between two different materials, for instance Glass and honey, or glass and water. if we put a droplet of honey why it does stick more firmly than a droblet of water? what are the forces reponsible on that ?
I'm looking to atomic scale explanation if it is possible.

the attached link gives an experiment on reducing the adhesion force, but I don't have any explanation .

ww.memsuniverse.com/?p=234

I would appreciate if you can help .

Many thanks.

NEMS

 

[Andy Resnick]

We do not yet have a good theory for wetting. That is different than adhesion, BTW. And neither has anything to do with viscosity.

Wetting behavior correlates with interfacial energy- we are unable to calculate interfacial energies from first principles, but there are some general chemical and physical principles we can use to manipulate the interfacial energy (chemical composition, temperature, etc).

 

[sir-pinski]

Hello NEMS,

The adhesion force between two materials is a result of intermolecular forces between the molecules of the two materials. These forces can be primarily attributed to three types of intermolecular forces: Van der Waals forces, hydrogen bonding, and electrostatic forces.

In the case of glass and honey, the adhesion force is primarily due to Van der Waals forces. These forces are weak interactions between molecules that arise due to temporary dipoles formed by the uneven distribution of electrons around atoms. In honey, the molecules are polar and have a slight positive and negative charge, allowing them to attract to the polar glass molecules. This attraction is stronger than the temporary dipoles formed between water and glass molecules, resulting in a stronger adhesion force.

On an atomic scale, the explanation for adhesion force can be further understood by looking at the surface energy of the materials. The surface energy is a measure of the energy required to break the bonds between molecules at the surface of a material. Materials with higher surface energy tend to have stronger adhesion forces as there are more bonding sites available for interactions with other materials.

The link you provided shows an experiment on reducing the adhesion force between two materials by using a thin layer of lubricant. This works because the lubricant reduces the surface energy of the material, making it less likely to adhere to other surfaces.

I hope this helps explain the adhesion force between different materials. Let me know if you have any further questions.