Charging changes contact composition in binary sphere packings

Area of Science:

• Granular physics
• Triboelectricity
• Materials science

Background:

• Granular materials exhibit complex behaviors influenced by particle properties and interactions.
• Tribocharging, the transfer of electric charge through contact and separation, is a common phenomenon in granular systems.

Purpose of the Study:

• To investigate the effect of tribocharging on the contact behavior of granular materials.
• To determine if controlled tribocharging can be used to tune the local composition of granular mixtures.

Main Methods:

• Mixtures of small and large polytetrafluoroethylene (PTFE) spheres were prepared in equal volumes.
• The PTFE spheres were subjected to controlled humidity to induce and control tribocharging.
• Contact numbers between spheres of the same and opposite types were analyzed as a function of charge density.

Main Results:

• Contact numbers were found to be dependent on the charge density of the PTFE beads.
• As charge density increased, the number of same-type contacts decreased.
• Conversely, the number of opposite-type contacts increased with increasing charge density.
• This phenomenon was not attributed to global segregation of the granular sample.

Conclusions:

• Tribocharging significantly influences the local contact interactions within granular materials.
• Controlled tribocharging offers a method to tune the local composition of granular mixtures by altering particle contact preferences.