Collapse-Engineered Inverse-Opal Photonic Microarchitectures Fabricated by Two-Photon Lithography for Optical Information Encoding

Two-photon lithography (TPL) offers unparalleled geometric freedom for fabricating three-dimensional micro/nanostructures. However, directly encoding multiple information with vivid structural colors into freeform architectures remains experimentally challenging. Here, we present a hybrid strategy that integrates colloidal self-assembly with TPL to realize inverse-opal-based three-dimensional microstructures that are simultaneously shape-programmable, structurally colored, and information-rich. The key process innovation is a one-step development protocol in which propylene glycol monomethyl ether acetate concurrently removes both the unpolymerized photoresist and the polystyrene colloidal template, thereby markedly simplifying conventional, time-intensive workflows. Building on this approach, we fabricate intricate inverse-opal microarchitectures with vivid coloration governed by the ordered (111) planes of the colloidal crystal. We further exploit freeform three-dimensional design, focal-plane selectivity, color multiplexing, and fabrication-induced stochastic defects to construct microstructures capable of storing multiple layers of information and exhibiting physically unique optical signatures. In addition, we demonstrate that intentionally tilt-printed structures undergo a reproducible collapse during development and drying that can be deliberately harnessed rather than mitigated. This collapse reorients the crystal lattice with respect to the incident illumination, thereby enabling angle-selective color readout. This work establishes TPL-printed 3D inverse opal as a versatile platform for miniaturized structural color devices, anti-counterfeiting labels, and high-density optical information carriers.