Liesegang Phenomenon of Liquid Metals on Au Film

Abstract

Room temperature liquid metals (LM) such as gallium (Ga) own the potential to react with specific materials which would incubate new application categories. Here, diverse self‐organized ring patterns due to nonequilibrium reaction‐diffusion and spreading‐limitation of Ga‐based LM clusters on gold (Au) film are reported, among which diffusion is the controlling step and the self‐limiting oxide layer plays the role of kinetic barrier. Such phenomena, classically known as the Liesegang rings, mainly occur in electrolyte media. Unlike existing systems, the present periodic crystallization mechanism enables highly symmetric spatiotemporal periodic Liesegang rings on a smaller scale under ambient conditions. Typically, the Ga‐Au and eutectic gallium‐indium alloy (EGaIn)‐Au reaction‐diffusion‐spreading systems are constructed, obtaining the revert type and hybrid type concentric Liesegang patterns, respectively. The competitive patterning behavior of the intermediate phase products AuGa2 and AuIn2 in hybrid Liesegang patterns is further analyzed by altering the initial Ga/In mass ratio, first‐principles calculations, and molecular dynamic simulations. When the mass ratio of In in GaIn alloy exceeds 15%, it will preferentially react with Au. The discovery of LM Liesegang phenomenon is expected to be a flashpoint for self‐organized reaction‐diffusion systems and offers promising rules for diverse areas such as materials synthesis and the jewelry design industry.

Non‐equilibrium‐Growing Aesthetic Ionic Skin for Fingertip‐Like Strain‐Undisturbed Tactile Sensation and Texture Recognition

“…Liesegang patterning generally occurs when a precipitation reaction is coupled with the mass transport of reagents in porous gel media, leading to periodic bands of precipitates. [35][36][37][38][39] Experimentally, the Liesegang patterning process involves layering an aqueous solution of the outer electrolyte onto a gel substrate containing its complementary inner electrolyte (the concentration of the outer electrolyte is at least one order of magnitude larger than that of the inner electrolyte). The diffusion of the outer electrolyte into the gel reaction medium causes an increase in local ion concentrations, and consequently, microcrystals start to nucleate and grow when the local concentrations exceed the threshold supersaturation value.…”

Patterning Complex Line Motifs in Thin Films Using Immersion‐Controlled Reaction‐Diffusion

“…[8] Moreover, reaction-diffusion processes such as Liesegang pattern formation induce rhythmic precipitation of line or band patterns of many different chemical compositions, and combinations with top-down fabrication techniques such as wet-stamping can yield more complex patterns. [30][31][32][33][34][35] Unfortunately, because of the diffusive nature of these processes, lines or bands form at increasing spacing, resulting in non-uniform patterning over larger distances, hence limiting scalability. [36] To overcome such drawbacks, we recently have shown highly uniform banding patterns in bulk gels by employing a mechanochemical feedback loop that transports reagents non-diffusively through opening channels.…”

Turing Instability of Liquid–Solid Metal Systems

“…Diverse spatiotemporal patterns can form in the systems driven away from equilibrium. [10b] Hybrid surface patterns during the LM solidification process, [21] Liesegang patterns in LM-Au spreading-limitation systems, [22] and spider's web patterns in LM-Al penetration systems [23] are all artistic examples. So far there exist tremendous unknown mysteries and spaces for exploration.…”