Equal volume mixtures of small and large polytetrafluorethylene (PTFE)
spheres are shaken in an atmosphere of controlled humidity which allows to also
control their tribo-charging. We find that the contact numbers are
charge-dependent: as the charge density of the beads increases, the number of
same-type contacts decreases and the number of opposite-type contacts
increases. This change is not caused by a global segregation of the sample.
Hence, tribo-charging can be a way to tune the local composition of a granular
material.Comment: 7 Pages, 5 Figure
