Ultra-thin vapor chambers with composite wick fabricated by ultrafast laser for enhancing thermal performance

•A 1-mm-thick UTVC with hierarchical wick is fabricated by ultrafast laser combined with chemical etching.•The UTVC could effectively withstand is 90 W, the minimum thermal resistance is 0.175 ℃/W, and the maximum thermal conductivity is 1422.8 W/m·K, which is 3.56 times higher than the copper plate.•The thermal performance of the UTVC is enhanced by the hierarchical wick with double-layer liquid circulation, which effectively reduces liquid return resistance. With the increasing heat flux required in portable electronic devices, the miniaturization of wicks and the continual reduction in vapor channel size have emerged as key challenges for high-performance ultra-thin vapor chambers (UTVCs). In this study, a 1-mm-thick UTVC with the composite wick composed of copper mesh and microgrooves was fabricated by ultrafast laser combined with chemical etching. The heat transfer performance of UTVCs was investigated under varying conditions including depth-to-width ratio of microgrooves, size of copper mesh, liquid-filling ratios, and tilt angles. The results demonstrated that the optimal liquid-filling ratio for the proposed UTVC is 100 % and its maximum heat transfer power is 90 W with a thermal resistance of 0.175 ℃/W in the horizontal state. Compared to the copper plate, the UTVC exhibited a relatively higher heat transfer performance, which reached the maximum thermal conductivity of 1422.8 W/m*K, and reduced the thermal resistance by up to 53.8 %. Moreover, both decreasing liquid-filling ratio and increasing the microgrooves depth-to-width ratio could enhance the thermal performance of UTVC. When employing the different copper mesh in the anti-gravity state, the prepared UTVC demonstrates excellent thermal performance of the UTVC under the low capillary force exerted by the wick. The reason for this discrepancy is the hierarchical wick with double-layer liquid circulation, which reduces the liquid return resistance and may be used for enhancing the thermal performance of the UTVC.