Fan device

A fan device, comprising:

• a hub comprising a central shaft and an outer periphery, wherein the outer periphery surrounds the central shaft;
• and
• a plurality of fan blades arranged on the outer periphery at equal angles, wherein each of the fan blades extends in a direction away from the central shaft, each of the fan blades comprises a driving surface, and the driving surface comprises:
• a first tooth column comprising a plurality of first skin-tooth units, wherein the first skin-tooth units are arranged side by side in the direction away from the central shaft, each of the first skin-tooth units comprises a first body, a first middle ridge and two first side ridges protrude from a surface of the first body, two first flow directing channels are formed between the first middle ridge and the two first side ridges, and a groove is formed between two adjacent first skin-tooth units;
• and
• a second tooth column comprising a plurality of second skin-tooth units, wherein the second skin-tooth units are arranged side by side in the direction away from the central shaft, each of the second skin-tooth units comprises a second body and an extension element, a second middle ridge and two second side ridges protrude from a surface of the second body, two second flow directing channels are formed between the second middle ridge and the two second side ridges, the extension element is located in the groove and comprises an extension rib, one end of the extension rib is connected to the second middle ridge, and an other end of the extension rib extends to a position between the two adjacent first side ridges of the two adjacent first skin-tooth units.