Azimuthal rotation-controlled nanoinscribing for continuous patterning of period-and shapetunable asymmetric nanogratings

We present an azimuthal-rotation-controlled dynamic nanoinscribing(ARC-DNI)process for continuous and scalable fabrication of asymmetric nanograting structures with tunable periods and shape profiles.A sliced edge of a nanograting mold,which typically has a rectangular grating profile,slides over a polymeric substrate to induce its burrfree plastic deformation into a linear nanopattern.During this continuous nanoinscribing process,the“azimuthal angle,”that is,the angle between the moving direction of the polymeric substrate and the mold’s grating line orientation,can be controlled to tailor the period,geometrical shape,and profile of the inscribed nanopatterns.By modulating the azimuthal angle,along with other important ARC-DNI parameters such as temperature,force,and inscribing speed,we demonstrate that the mold-opening profile and temperature-and time-dependent viscoelastic polymer reflow can be controlled to fabricate asymmetric,blazed,and slanted nanogratings that have diverse geometrical profiles such as trapezoidal,triangular,and parallelogrammatic.Finally,period-and profile-tunable ARC-DNI can be utilized for the practical fabrication of diverse optical devices,as is exemplified by asymmetric diffractive optical elements in this study.

Nanoimprint lithography for high-throughput fabrication of metasurfaces

Metasurfaces are composed of periodic subwavelength nanostructures and exhibit optical properties that are not found in nature.They have been widely investigated for optical applications such as holograms,wavefront shaping,and structural color printing,however,electron-beam lithography is not suitable to produce large-area metasurfaces because of the high fabrication cost and low productivity.Although alternative optical technologies,such as holographic lithography and plasmonic lithography,can overcome these drawbacks,such methods are still constrained by the optical diffraction limit.To break through this fundamental problem,mechanical nanopatteming processes have been actively studied in many fields,with nanoimprint lithography(NIL)coming to the forefront.Since NIL replicates the nanopattem of the mold regardless of the diffraction limit,NIL can achieve sufficiently high productivity and patterning resolution,giving rise to an explosive development in the fabrication of metasurfaces.In this review,we focus on various NIL technologies for the manufacturing of metasurfaces.First,we briefly describe conventional NIL and then present various NIL methods for the scalable fabrication of metasurfaces.We also discuss recent applications of NIL in the realization of metasurfaces.Finally,we conclude with an outlook on each method and suggest perspectives for future research on the high-throughput fabrication of active metasurfaces.

Solution-processable electrode-material embedding in dynamically inscribed nanopatterns(SPEEDIN)for continuous fabrication of durable flexible devices

A facile and scalable lithography-free fabrication technique,named solution-processable electrode-material embedding in dynamically inscribed nanopatterns(SPEEDIN),is developed to produce highly durable electronics.SPEEDIN uniquely utilizes a single continuous flow-line manufacturing process comprised of dynamic nanoinscribing and metal nanoparticle solution coating with selective embedding.Nano-and/or micro-trenches are inscribed into arbitrary polymers,and then an Ag nanoparticle solution is dispersed,soft-baked,doctor-bladed,and hard-baked to embed Ag micro-and nanowire structures into the trenches.Compared to lithographically embossed metal structures,the embedded SPEEDIN architectures can achieve higher durability with comparable optical and electrical properties and are robust and power-efficient even under extreme stresses such as scratching and bending.As one tangible application of SPEEDIN,we demonstrate a flexible metal electrode that can operate at 5 V at temperatures up to 300℃even under the influence of harsh external stimuli.SPEEDIN can be applied to the scalable fabrication of diverse flexible devices that are reliable for heavy-duty operation in harsh environments involving high temperatures,mechanical deformations,and chemical hazards.