Metasurface-based nanoprinting: principle, design and advances

Metasurface-based nanoprinting(meta-nanoprinting)has fully demonstrated its advantages in ultrahigh-density gray-scale/color image recording and display.A typical meta-nanoprinting device usually has image resolutions reaching 80 k dots per inch(dpi),far exceeding conventional technology such as gravure printing(typ.5 k dpi).Besides,by fully exploit-ing the design degrees of freedom of nanostructured metasurfaces,meta-nanoprinting has been developed from previ-ous single-channel to multiple-channels,to current multifunctional integration or even dynamic display.In this review,we overview the development of meta-nanoprinting,including the physics of nanoprinting to manipulate optical amplitude and spectrum,single-functional meta-nanoprinting,multichannel meta-nanoprinting,dynamic meta-nanoprinting and mul-tifunctional metasurface integrating nanoprinting with holography or metalens,etc.Applications of meta-nanoprinting such as image display,vortex beam generation,information decoding and hiding,information encryption,high-density optical storage and optical anti-counterfeiting have also been discussed.Finally,we conclude the opportunities and chal-lenges/perspectives in this rapidly developing research field of meta-nanoprinting.

Scaling behavior of nanoimprint and nanoprinting lithography for producing nanostructures of molybdenum disulfide

Top-down lithography techniques are needed for manufacturing uniform device structures based on emerging 2D-layered materials.Mechanical exfoliation approaches based on nanoimprint and nanoprint principles are capable of producing ordered arrays of multilayer transition metal dichalcogenide microstructures with a high uniformity of feature dimensions.In this study,we present a study on the applicability of nanoimprint-assisted shear exfoliation for generating ultrathin monolayer and few-layer MoS_(2) structures as well as the critical limits of feature dimensions produced via such nanoimprint and nanoprint-based processes.In particular,this work shows that give a lateral feature size of MoS_(2) structures that are pre-patterned on a bulk stamp,there exists a critical thickness or aspect ratio value,below which the exfoliated layered structures exhibit major defects.To exfoliate a highquality,uniform monolayer or few-layer structures,the characteristic lateral feature sizes of such structures need to be in the sub-100 nm regimes.In addition,the exfoliated MoS_(2) flakes of critical thicknesses exhibit prominent interlayer twisting features on their cleaved surfaces.Field-effect transistors made from these MoS_(2) flakes exhibit multiple(or quasi-analog-tunable)charge memory states.This work advances the knowledge regarding the limitations and application scope of nanoimprint and nanoprint processes in manufacturing nano/microstructures based on layered materials and provides a method for producing multi-bit charge memory devices.

Cascaded metasurface for separated information encryption[Invited]

For a conventional cascaded metasurface,the combination channel and each single channel are mutually dependent because the phase modulation of a cascaded metasurface is the sum of each single one.Here we propose a cascaded metasurface that can independently encode information into multiple channels.Based on the orientation degeneracy of anisotropic metasurfaces,each single metasurface can produce a quick-response(QR)image in the near field,governed by the Malus law,while the combined channel can produce a holographic image in the far field,governed by geometric phase.The independent and physically separated trichannel design makes information encryption safer.

Four-channel metasurface for multiplexing images under two nonorthogonal polarization states

By its unparalleled capacity to manipulate optical parameters,metasurfaces demonstrate the ability to simultaneously manipulate the amplitude and phase of incident light.Exhibiting both near-field nanoprinting images and far-field holography images is a quintessential illustration of this capability.In preceding investigations,image multiplexing commonly transpires within the single polarization state or orthogonal polarization states,thereby exhibiting a deficiency in terms of information security when contrasted with the nonorthogonal polarization states.In this research,a multifunctional metasurface with the capability of exhibiting four-channel images has been proposed by using a nanobrick as a quarter-wave plate.Through the adjustment of the orientation angles of each nanobrick,nanoprinting can be displayed under both linearly and circularly polarized light.Building on this,the propagation phase is combined with the geometric phase to generate diverse phase delays,enabling the metasurface to be multiplexed under two nonorthogonal polarization states to achieve four-channel image displays.Intriguingly,bidirectional nanoprinting and bidirectional holography can be achieved by altering the direction of incidence polarization states.The proposed metasurface platform can open new possibilities for creating compact multifunctional optical devices,while also enhancing applications in multichannel image displays,information anticounterfeiting,and encryption.

Controlled Molecular Assembly of Tetrazine Derivatives on Surfaces

While self-assembly is relatively well-known and widely used to form hierarchical structures and thin film coatings,controlled assembly is less known and utilized.Our prior work has demonstrated the concept of controlled assembly of macromolecules such as star polymers[molecular weight(M_(w))∼383 kDa,hydrodynamic radius R∼13.8 nm]in droplets.This work extends this concept to smaller molecules,in this case,poly(ethylene glycol)bis-tetrazine(PEGbisTz,M_(w) 8.1 kDa,R∼1.5 nm).The key to controlled molecular assembly is to first deliver ultrasmall volumes(sub-fL)of solution containing PEG-bisTz to a substrate.The solvent evaporates rapidly due to the minute volume,thus forcing the assembly of solute,whose overall size and dimension are dictated by the initial liquid geometry and size.Using prepatterned surfaces,this work revealed that the initial liquid shape can be further tuned,and we could control the final assembly of solute such as PEGbisTz molecules.The degree of control was demonstrated by varying the micropatterns and delivery conditions.This work demonstrated the validity of controlled assembly for PEG-bisTz and enables three-dimensional(3D)nanoprinting of functional materials.The technology has promising applications in nanophotonics,nanoelectronics,nanocomposite materials,and tissue engineering.