Mechanism suppressing depletion attraction at corrugated colloidal surfaces

Determine the precise surface-architectural mechanism by which corrugated lateral surfaces produced by two-photon polymerization suppress depletion-induced interactions, despite their characteristic spacing being larger than the depletant size and their potentially complementary geometry being capable of generating strong excluded-volume overlap.

Background

The paper observes that flat colloidal faces engage in strong, selective depletion-mediated attraction, whereas corrugated faces remain largely non-interacting. A simplified geometric model based on the nominal voxel radius, hatch spacing, and vertical offset predicts that idealized opposing corrugated surfaces could instead produce a large excluded-area overlap and therefore strong attraction, creating a discrepancy between the idealized model and the experiments.

The authors suggest that small fabrication-induced deviations in the corrugated surface parameters may reduce geometric complementarity and weaken depletion attraction. However, the precise surface-architectural origin of this suppression is not established, making it an unresolved mechanistic problem relevant to the rational design of selective colloidal interactions.

References

The absence of such interactions suggests that the suppression of depletion attraction cannot be attributed solely to the roughness length scale. We hypothesize that the suppression of depletion induced interactions at the corrugated sides arises from the precise surface architecture, which may limit the geometric complementarity between approaching corrugated surfaces.

— Designing corrugated surfaces to guide colloidal self-assembly  (2609.04001 - Sahu et al., 3 Sep 2026) in Section Discussion