Surface electric fields of apatite electret promote biological responses

The measurement of contact angle revealed that the wettability of the polarized HA was higher than that of normal HA, showing that both the N-HA and P-HA were more hydrophilic than that of the HA. Wettability has been reported to depend on surface roughness or crystallinity on a solid surface. Considering these factors, the present study employed HA specimens with almost equal surface roughness, crystallinity, and constituent elements at the surface. Thus, the improved wettability of the HA surfaces resulted from other factors. The possible explanation for the improved surface wettability by polarization is the surface energy modification because of polar interaction energy with water.