Laser etching of flattened copper mesh for fabricating continuous capillary channels in flexible heat pipe with high durability

Flexible heat pipes suffer from an intrinsic trade-off between heat transfer performance and bending durability. Although thinning the flexible section can effectively reduce bending stress and improve durability, it generally compromises capillary-driven liquid transport across the wick, thereby limiting heat transfer performance. To overcome this conflict, this study proposes laser etching of flattened copper mesh for constructing continuous capillary channels in ultrathin flexible heat pipes. Ultrafast laser processing was used to generate continuous capillary channels on the surface of flattened copper mesh, and a liquid transport model was established based on three-dimensional surface topography to clarify the relationship between laser-induced morphology and capillary behavior. The results show that flattening a 200-mesh copper mesh reduced its thickness by 50% and increased wire width by 56%, creating favorable conditions for continuous channel fabrication. By regulating laser parameters, continuous V-shaped capillary channels with a depth of 35 μm and a width of 30 μm were achieved, exhibiting strong capillary pumping capability with a maximum wicking coefficient of 17.94 mm/s 0.5 . When applied in a flexible heat pipe, the etched flattened copper mesh enabled an ultrathin flexible section of 261 μm and a low thermal resistance of 0.84 °C/W at 5 W. A bending test platform was further developed to quantitatively evaluate durability degradation during cyclic deformation.