A carrot-inspired solar thermal evaporator exhibits a water evaporation rate of 2.04 kg m⁻² h⁻¹ and an outstanding durability and stability.

Solar steam generation is an emerging technique that harvests intermittent sustainable solar energy for large-scale wastewater purification and desalination. However, the application of solar steam generators is currently restricted by their high cost and low solar-thermal conversion efficiency. Herein, we demonstrate a highly efficient, portable, low cost and reusable interfacial solar evaporator fabricated using three-dimensional (3D) printing technology. Using cues from nature, the 3D-printed honeycomb lightweight evaporators are designed to have microporous capillary channels, which facilitate water transportation for continuous solar steam generation. The graphene coating on the surface enables efficient solar-to-vapor energy transfer, and a thermally insulating photopolymer suppresses heat loss. The optimized 3D-printed solar evaporator thus has a rapid evaporation rate of 2.67 kg m⁻² h⁻¹ (normalized to the projection area) and a high apparent solar-to-heat efficiency of 178.5% under 1 sun irradiation. The device shows outstanding antifouling properties and hence has wide application prospects for long-term domestic wastewater reduction and desalination of high-salinity brine.

A theory for treating terahertz (THz) surface wave propagation and focusing on conical metal wire waveguides is presented. According to the theory, the surface wave propagation and focusing on the conical copper wire waveguide is investigated by the numerical calculation, and the results show the theory agrees with experimental measurement result obtained by Ji et al. The theory presented provides a basis for describing surface wave propagation and focusing on conical metal wire waveguides and, importantly, the theory suggests that a simple conical metal wire can be used for subwavelength energy concentration and superfocusing.

We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices.