Coherent Cancellation in Oscillatory Structural Forces Enables Surface Recognition in Colloidal Assembly

While oscillatory structural forces (solvation/depletion) are ubiquitous in colloidal systems, the mechanism by which they guide the precise self-assembly of complex particles remains elusive. Here, we reveal that the extreme sensitivity of these damped oscillatory forces to surface orientation stems from their coherent cancellation. We find that minute inclination angles or curvature mismatch trigger coherent cancellation, causing a precipitous drop in attraction. Maximum attraction is achieved only under conformal contact between surfaces with complementary curvature, which avoids cancellation. This universal mechanism successfully governs the two-dimensional self-assembly of nanodumbbells, yielding a series of superlattices, including parallel, Kagome, and chevron structures.