Compact multi-foci metalens spectrometer

A lightweight and portable spectrometer is desirable for miniaturization and integration.The unprecedented capability of optical metasurfaces has shown much promise to perform such a task.We propose and experimentally demonstrate a compact high-resolution spectrometer with a multi-foci metalens.The novel metalens is designed based on wavelength and phase multiplexing,which can accurately map the wavelength information into its focal points located on the same plane.The measured wavelengths in the light spectra agree with simulation results upon the illumination of various incident light spectra.The uniqueness of this technique lies in the novel metalens that can simultaneously realize wavelength splitting and light focusing.The compactness and ultrathin nature of the metalens spectrometer render this technology have potential applications in on-chip integrated photonics where spectral analysis and information processing can be performed in a compact platform.

Self-healing ability of Prussian blue analogs for aqueous potassium-ion batteries

The slow reaction kinetics,combined with the relatively large radius of K-ion,makes it challenging to develop acceptable electrode materials for reversible insertion/deinsertion of potassium ions,thus reducing the cycle stability and reversible capacity of aqueous potassium-ion batteries(PIBs)[1].Given this,there is still a long way to go in developing high-performance electrode materials for PIBs with a stable cycle life and high energy density.According to a literature study on PIB electrode materials,the electrochemical performance of cathode materials can be easily achieved through various structural modifications[2–4].Nevertheless,the study of cathode material optimization and operating mechanisms is insufficient,hindering the energy density of PIBs from reaching a satisfactory level.In this context,the performance of cathode material becomes the decisive factor for the performance of PIBs.

Color-selective three-dimensional polarization structures

Polarization as an important degree of freedom for light plays a key role in optics.Structured beams with controlled polarization profles have diverse applications,such as information encoding,display,medical and biological imaging,and manipulation of microparticles.However,conventional polarization optics can only realize two-dimensional polarization structures in a transverse plane.The emergent ultrathin optical devices consisting of planar nanostructures,so-called metasurfaces,have shown much promise for polarization manipulation.Here we propose and experimentally demonstrate color-selective three-dimensional(3D)polarization structures with a single metasurface.The geometric metasurfaces are designed based on color and phase multiplexing and polarization rotation,creating various 3D polarization knots.Remarkably,different 3D polarization knots in the same observation region can be achieved by controlling the incident wavelengths,providing unprecedented polarization control with color information in 3D space.Our research findings may be of interest to many practical applications such as vector beam generation,virtual reality,volumetric displays,security,and anti-counterfeiting.

Chitosan biopolymer-derived self-powered triboelectric sensor with optimized performance through molecular surface engineering and data-driven learning

The state-of-the-art triboelectric nanogenerators(TENGs)are constructed with synthetic polymers,curtailing their application prospects and relevance in sustainable technologies.The economically viable transformation and engineering of naturally abundant materials into efficient TENGs for mechanical energy harvesting is meaningful not only for fundamental scientific exploration,but also for addressing societal needs.Being an abundant natural biopolymer,chitosan enables exciting opportunity for low-cost,biodegradable TENG applications.However,the electrical outputs of chitosan-based TENGs are low compared with the devices built with synthetic polymers.Here,we explore the facile molecular surface engineering in chitosan to significantly boost the performance of chitosan-based TENG for enabling the practical applications,for example,self-powered car speed sensor.The molecular surface engineering offers a potentially promising scheme for designing and implementing high-performance biopolymer-based TENGs for selfpowered nanosystems in sustainable technologies.We further explore for the first time the feasibility of data mining approaches to analyze and learn the acquired triboelectric signals from the car speed sensors and predict the relationship between the triboelectric signals and car speed values.