Inverse Opal Torus-Shaped Photonic Microobjects with Superior Stimulus-Responsive Properties to Their Spherical Equivalents.

Because of their many uses and simplicity of manufacture, colloidal photonic microobjects made from droplet templates have been the subject of extensive research. Owing to the low interfacial energy, the majority are spherical, however nonspherical forms, such as torus-shaped photonic microobjects (TSPMs) have also been seen. Although there have been reports of TSPMs based on various colloidal building blocks, their usual lack of stimulus-responsive qualities restricts their potential uses. In this work, hydrogel-based inverse opal TSPMs (IO-TSPMs) that are sensitive to alcohol and pH are created. IO-TSPMs that react more quickly than spherical ones are produced by first creating opal-structured TSPMs, then infiltrating monomers, polymerizing under UV light, and etching, to visibly illustrate the difference. Unlike spherical structures, which only provide unidirectional stimulus propagation, torus structures allow stimulation to bidirectionally propagate from both the inner and outer borders. Potential applications for these IO-TSPMs include biomimetic materials, quick diagnostic and inspection tools, and building blocks for innovative patterns.