Abstract: A heat pipe includes a casing, a main wick structure received in the casing, an auxiliary wick structure received in the main wick structure, and a working fluid contained in the casing. The main wick structure is attached to an inner surface of the casing. An inner peripheral surface of the main wick structure and an outer peripheral surface of the auxiliary wick structure cooperatively define a vapor channel. The auxiliary wick structure is hollow, and extends along a longitudinal direction of the casing. A liquid channel is defined in the auxiliary wick structure. Two ends of the auxiliary wick structure are both fixed on the two ends of the casing. The working fluid is saturated in the main wick structure and the auxiliary wick structure.

Abstract: A heat pipe includes a casing and a plurality of wick layers. The casing has an inner wall. The wick layers stack at an inner surface of the casing in turn. The wick layers respectively define a plurality of pores therein. Diameters of the pores of each of the wick layers gradually decrease from the inner wall to center of the casing.

Abstract: A heat pipe includes a longitudinal casing, a main wick structure, at least one auxiliary wick structure and a working fluid contained in the casing and saturating the main wick structure and the at least one auxiliary wick structure. The main wick structure is received in the casing and attached to an inner surface of the casing. The at least one auxiliary wick structure is received in the main wick structure. An inner peripheral surface of the main wick structure and an outer peripheral surface of the at least one auxiliary wick structure cooperatively define a vapor channel therebetween. At least one end of the at least one auxiliary wick structure is fixed on a corresponding end of the casing.