Thermodynamically unusual surfaces that possess two contradictory wetting properties, i.e., underoil superhydrophobicity and underwater superoleophobicity, are prepared by the combination of re-entrant topography and delicately matched surface chemistry. The preparation of such extraordinary surfaces relies on two key design criteria and employs a metastable state effect in solid-oil-water systems.

PbTe has been leading the advancements in the field of thermoelectricity due to its capability for demonstrating and integrating various new concepts. However, the toxicity of Pb is always a concern for terrestrial applications, which inspired great advancement to be achieved very recently in its alternative analogue SnTe. Challenges making p-type SnTe as thermoelectrically efficient as PbTe rely on a reduction of its carrier concentration, valence band offset, and lattice thermal conductivity. Utilization of newly developed concepts including both band and defect engineering amazingly increases the thermoelectric figure of merit, zT, from 0.4 up to 1.6 while remaining a nontoxic composition. The corresponding conceptual route diagram is surveyed, and future considerations on composition, crystal structure, and microstructure for further advancements are discussed in this Perspective. Concepts discussed here not only have promoted SnTe as a highly efficient environment-friendly thermoelectric material but also guided advancements in many other thermoelectrics.

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