3D interfacial visualization of ice on solid substrates: unveiling microinterlocking ice

Hypothesis: Mechanical interlocking (anchoring) of ice within surface roughness features is a primary contributor to ice adhesion, yet the interfacial region in which it occurs remains concealed between the bulk ice and the solid surface. Previous efforts to explore this hidden region have relied on 2D side-view or top-view optical and electron microscopy, or on destructive, indirect 3D replica imaging, leaving the mechanical anchoring of ice largely hypothetical and inadequately understood. We hypothesize that in situ freezing X-ray computed tomography (XCT) can non-destructively resolve the ice-solid interfacial region in three dimensions, yielding valuable information about ice mechanical interlocking at the interface. Experiments: This study presents a multi-step approach using in situ freezing XCT for non-destructive 3D visualization and analysis of interlocked ice at the interface between ice droplets and hydrophilic, fully wetted (Wenzel state) femtosecond-laser-textured aluminum substrates (voxel size: 1.6 mu m). Freezing XCT is coupled with wetting, ice adhesion, and confocal profilometry measurements to link interfacial morphology to icing behavior. Findings: Freezing XCT resolved the hidden ice infiltrated and anchored within the microgrooves at two-phase (ice + substrate) interfaces, a region previously obscured or merely speculated about. Interlocked-ice volume followed the trend of functional (volume) roughness parameters of surfaces, whereas conventional height-based parameters (e.g., Sa, Ra, Sq, Rq) remained insensitive to it, exposing the shortcomings of prevailing roughness-ice adhesion correlations.