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Recently, there have been notable advances in nanophotonic structural color generation which enabled various applications in display, anti-counterfeiting, sensors and detectors. However, most advances in this domain have been achieved through the use of high-index materials which require expensive and complex fabrication. In this work, we enable low-index polymer nanostructures to generate structural colors using the multipolar decomposition technique which allows a better understanding and design of the scattering process by identifying the dominant multipole modes from the scattered fields. We set a polymeric (n~1.56) cuboid as the structural color generation platform, examined the contributions of various multipoles from the wave scattered by it, and synthesized the desired color spectrum by adjusting only the height of the cuboid. To validate our findings, we fabricated the designed structural color pixels via light-controlled, low-pressure nanoimprinting and measured the color and spectrum from them. Our experimental results agreed well with the simulation results, providing insights for bringing further advances to structural coloring. 

Understanding the dynamic behavior of photopolymers in nanoscale environment is essential to improving MEMS/NEMS device fabrication technologies. Here, we unveil the highly nonlinear behaviors of photopolymers exhibited during the process of light-controlled, low-pressure nanoimprinting. Such peculiarities can complicate the relation between the UV-dose and the height of the nanoimprinted feature, degrading the accuracy of the height control. To address the issue, we establish a theoretical process model and used the control of the nanoimprinting height for structural coloring applications. Our findings will broadly benefit nanotechnology and nanoscience. 

Nanopatterned tribocharge can be generated on the surface of elastomers through their replica molding with nanotextured molds. Despite its vast application potential, the physical conditions enabling the phenomenon have not been clarified in the framework of analytical mechanics. Here, we explain the final tribocharge pattern by separately applying two models, namely cohesive zone failure and cumulative fracture energy, as a function of the mold nanotexture’s aspect ratio. These models deepen our understanding of the triboelectrification phenomenon. 

The multipole interference (MPI) effect plays pivotal roles in the formation of electromagnetic responses in various settings. In the optics regime, it has been realized typically through the Mie resonance that necessitates high‐index, deep‐subwavelength‐scale dielectric resonators that are challenging to fabricate. Herein, a new, diffraction‐based MPI scheme that can be realized with low‐index, mesoscale dielectric structures is demonstrated. It is verified that this “diffractive MPI” concept by realizing various MPI states using micrometric polymeric cuboids fabricated by soft‐lithography. Subsequent analyses reveal that the MPI states with a distinct near‐zero forward scattering (NZFS) characteristic played crucial roles in shaping the cuboid's transmission spectrum. A hitherto unreported NZFS state, which exhibits a unique, “trifolium” radiation pattern, is also identified. The spectral position of such NZFS states turns out to be strongly dependent on the cuboid's geometry. By combining these results, the diffractive NZFS formation is related to the important phenomena of induced transparency and structural color generation. 

Abstract Nature finds a way to leverage nanotextures to achieve desired functions. Recent advances in nanotechnologies endow fascinating multi-functionalities to nanotextures by modulating the nanopixel’s height. But nanoscale height control is a daunting task involving chemical and/or physical processes. As a facile, cost-effective, and potentially scalable remedy, the nanoscale capillary force lithography (CFL) receives notable attention. The key enabler is optical pre-modification of photopolymer’s characteristics via ultraviolet (UV) exposure. Still, the underlying physics of the nanoscale CFL is not well understood, and unexplained phenomena such as the “forbidden gap” in the nano capillary rise (unreachable height) abound. Due to the lack of large data, small length scales, and the absence of first principles, direct adoptions of machine learning or analytical approaches have been difficult. This paper proposes a hybrid intelligence approach in which both artificial and human intelligence coherently work together to unravel the hidden rules with small data. Our results show promising performance in identifying transparent, physics-retained rules of air diffusivity, dynamic viscosity, and surface tension, which collectively appear to explain the forbidden gap in the nanoscale CFL. This paper promotes synergistic collaborations of humans and AI for advancing nanotechnology and beyond. 

Diffraction gratings are ubiquitous in many optical applications such as sensors, filters, and optical security devices. Capillary force lithography, which utilizes the capillary rise of photopolymer into nanoscale cavities, is a simple and rapid method to construct diffraction gratings without necessitating expensive instruments or complex steps. With the help of spatial light modulators, such as the digital micromirror device, the height of the grating can also be spatially modulated, printing spatially height-modulated gratings. When white light normally impinges on the grating, the light propagates into the grating interferes with light that propagates into air. By varying the height of the grating, the optical path lengths of two lights can be varied, leading to different interference effects and structural coloring. Judicious design of the grating’s parameters and patterning process will even allow encoding of multiple images. In this work, by tuning the height of the grating through the light-controlled capillary force lithography, we demonstrate grating-based structural color printing. This technique is promising for producing the custom patterns for anti-counterfeiting, authentication, and cryptography. 

Nanolenses are gaining importance in nanotechnology, but their challenging fabrication is thwarting their wider adoption. Of particular challenge is facile control of the lens’ curvature. In this work, we demonstrate a new nanoimprinting technique capable of realizing polymeric nanolenses in which the nanolens’ curvature is optically controlled by the ultraviolet (UV) dose at the pre-curing step. Our results reveal a regime in which the nanolens’ height changes linearly with the UV dose. Computational modeling further uncovers that the polymer undergoes highly nonlinear dynamics during the UV-controlled nanoimprinting process. Both the technique and the process model will greatly advance nanoscale science and manufacturing technology. 

The behavior of liquid-phase polymer in nanoscale cavities are essential and important to many technological processes. The level of our understanding on them, however, is still limited. This paper reports a new photofluidic technique to capture, or “freeze-frame”, the capillary rise of polymer into elastomeric nanocavities with nanoscopic resolutions and reveals nonlinear and unstable natures of the polymeric capillary effect. Based on the results, a nanofluidic model is also proposed to explain the anomalies. Both the freeze-framing technique and the established model will open new pathways to analyze and utilize nanofluidics. 

Replica molding-based triboelectrification has emerged as a new and facile technique to generate nanopatterned tribocharge on elastomer surfaces. The “mechano-triboelectric charging model” has been developed to explain the mechanism of the charge formation and patterning process. However, this model has not been validated to cover the full variety of nanotexture shapes. Moreover, the experimental estimation of the tribocharge’s surface density is still challenging due to the thick and insulating nature of the elastomeric substrate. In this work, we perform experiments in combination with numerical analysis to complete the mechano-triboelectrification charging model. By utilizing Kelvin probe force microscopy (KPFM) and finite element analysis, we reveal that the mechano-triboelectric charging model works for replica molding of both recessed and protruding nanotextures. In addition, by combining KPFM with numerical electrostatic modeling, we improve the accuracy of the surface charge density estimation and cross-calibrate the result against that of electrostatic force microscopy. Overall, the regions which underwent strong interfacial friction during the replica molding exhibited high surface potential and charge density, while those suffering from weak interfacial friction exhibited low values on both. These multi-physical approaches provide useful and important tools for comprehensive analysis of triboelectrification and generation of nanopatterned tribocharge. The results will widen our fundamental understanding of nanoscale triboelectricity and advance the nanopatterned charge generation process for future applications.