Microchannelled Biomorphous Al ₂ O ₃ Wick Structures for Capillary‐Driven Two‐Phase Heat Transfer Devices

This work reports the synthesis and fluid‐dynamic characterization of rattan‐derived microchannelled biomorphous Al 2 O 3 wick structures ( µ BWS) integrated into a capillary pumped loop (CPL) for passive heat transfer. Rattan templates are converted into Al 2 O 3 via a biotemplating route involving a two‐step gas infiltration–reaction process, yielding ceramic structures that preserve the hierarchical capillary microarchitecture of the vegetal precursor. The µ BWS are characterized by scanning electron microscopy, Archimedes‐based porosimetry, gas permeametry, and capillary extrusion for capillary head determination. Fluid flow modeling is used to evaluate pressure drop, flow regime, and viscous and inertial contributions as a function of applied heat load. Laminar flow is observed throughout the CPL, with non‐negligible inertial effects within the wick at elevated heat loads. The experimentally measured capillary head is combined with modeled pressure‐drop data to estimate the capillary limit of the µ BWS. A CPL assembled with the µ BWS demonstrates stable operation for 3 h at a heat load of 40 W, yielding an evaporator thermal resistance of 0.657°C/W ± 0.022. The results demonstrate the feasibility of biomorphous ceramic wicks as planar, hierarchically structured capillary media for two‐phase heat transfer devices.