Polymersome Crack Lithography with PEI-Rich Interfacial Layers for Robust Transparent Conductive Metal Meshes

Herein, we demonstrate that self-cracking films derived from polyethyleneimine-block-poly(2-phenyl-2-oxazoline) (PEI-b-PPOZ) polymersomes can serve as colloidal templates for transparent conductive metal meshes while retaining a polymer-derived interfacial structure at the crack–substrate interface. Drop casting an aqueous polymersome dispersion onto glass spontaneously produced a two-dimensional crack network through vesicle packing, deformation, and rupture. Subsequent vacuum deposition of copper or gold followed by methanol-assisted lift-off generated continuous metal meshes that faithfully replicated the crack network. The resulting copper mesh exhibited an optical transmittance of 82.9% in the measured 400–500 nm range and a sheet resistance of 17.7 Ω/sq, while the gold mesh exhibited an optical transmittance exceeding 85% in the measured 400–700 nm range and a sheet resistance of 18.9 Ω/sq. Both metal meshes remained intact after Scotch tape-peeling tests. Structural observations further revealed that the crack channels were not simply empty geometrical voids but were associated with a thin, polymer-derived interfacial layer exhibiting a PEI-rich lamellar morphology, which is consistent with deformation and rupture of polymersomes near the substrate during drying. The presence of this interfacial layer, together with the known affinity of PEI for silica surfaces and metal species, is consistent with its contribution to the mechanical retention of the deposited metal networks. These findings highlight the crack-bottom interface as an important structural element in crack lithography and suggest that crack channels can function not only as geometrical templates but also as interfacial regions that influence the properties of crack-derived metal networks.