Improved thermal stability of antireflective moth-eye topography imprinted on PMMA/TiO2surface nanocomposites.

The thermal stability of antireflective moth-eye topographical features fabricated by nanoimprint lithography on poly (methyl methacrylate) (PMMA) incorporating TiO2nanoparticles is explored. The effect of nanoparticle load on the relaxation dynamics of the moth-eye nanostructure is evaluated via grazing incidence small angle x-ray scattering measurements byin situmonitoring the structural decay of the nanopatterns upon thermal annealing. It is demonstrated that the incorporation of TiO2nanoparticles to the imprinted surface nanocomposite films delays greatly the pattern relaxation which, in turn, enhances the stability of the patterned topography even at temperatures well above the polymer glass transition (Tg). The improved thermal behavior of the antireflective films will significantly enhance their functionality and performance in light-trapping applications where temperatures typically rise, such as solar devices or solar glass panels.

Bioinspired antireflective flexible films with optimized mechanical resistance fabricated by roll to roll thermal nanoimprint.

This work describes the fabrication process of moth eye antireflective poly (methyl methacrylate) transparent films via roll to roll thermal nanoimprint lithography. The process parameters are investigated and adjusted in order to obtain from a single moth-eye structured mold, a range of antireflective topographies that gradually vary their geometry from protruding to intruding nanocones. A correlation between the process parameters with the optical and mechanical properties of the films is established to illustrate the influence of the processing parameters and serve as guideline to produce antireflective flexible films with balanced properties and optimized performance adequate to the application environment. A finite element model is described predicting the mechanical behavior of the moth-eye PMMA imprinted nanostructures.

Moth-eye mimetic cytocompatible bactericidal nanotopography: a convergent design.

The rapid emergence of antibiotic resistant bacteria has prompted the need for radically different approaches to combat bacterial infections. Among these, bioinspired surface topographies have emerged as an effective sustainable strategy to deter bacterial infection. This study demonstrates the bactericidal activity and cytocompatibility of the moth-eye mimetic topography produced by thermal polymer nanoimprinting. The moth-eye topography was found to have bactericidal capabilities against Gram negative and Gram positive bacteria. Electron microscopy imaging revealed the bactericidal effect caused by mechanical rupture of the bacteria wall inflicted by the topography on the adhered cells. The cytocompatibility of the surfaces was evidenced by assessing the proliferation and morphology of keratinocytes cultured on the nanotopography. The technology meets important needs in medical implant technology for materials that not only have good biocompatibility but also antibacterial properties for reducing the risk of infections and related health complications.

Nano-engineering safer-by-design nanoparticle based moth-eye mimetic bactericidal and cytocompatible polymer surfaces.

Nanotechnology provides a new design paradigm for alternative antibacterial strategies in the fight against drug-resistant bacteria. In this paper, the enhanced bactericidal action of moth-eye nanocomposite surfaces with a collaborative nanoparticle functional and topography structural mode of action is reported. The moth-eye nanocomposite surfaces are fabricated in combined processing steps of nanoparticle coating and surface nanoimprinting enabling the production of safer-by-design nanoparticle based antibacterial materials whereby the nanoparticle load is minimized whilst bactericidal efficiency is improved. The broad antibacterial activity of the nanocomposite moth-eye topographies is demonstrated against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Pseudomonas aeruginosa as model bacteria. The antibacterial performance of the moth-eye nanocomposite topographies is notably improved over that of the neat moth-eye surfaces with bacteria inhibition efficiencies up to 90%. Concurrently, the moth-eye nanocomposite topographies show a non-cytotoxic behaviour allowing for the normal attachment and proliferation of human keratinocytes.

Single-imprint moth-eye anti-reflective and self-cleaning film with enhanced resistance.

Antireflective transparent materials are essential for a myriad of applications to allow for clear vision and efficient light transmission. Despite the advances, efficient and low cost solutions to clean antireflective surfaces have remained elusive. Here, we present a practical approach that enables the production of antireflective polymer surfaces based on moth-eye inspired features incorporating photoinduced self-cleaning properties and enhanced mechanical resistance. The methodology involves the fabrication of sub-wavelength moth-eye nanofeatures onto transparent surface composite films in a combined processing step of nanoparticle coating and surface nanoimprinting. The resulting surfaces reduced the optical reflection losses from values of 9% of typical PMMA plastic films to an optimum value of 0.6% in the case of double-sided moth-eye nanoimprinted films. The composite moth-eye topography also showed an improved stiffness and scratch resistance. This technology represents a significant advancement not limited by scale, for the development of antireflective films for low cost application products.

Multifunctional Nano-engineered Polymer Surfaces with Enhanced Mechanical Resistance and Superhydrophobicity.

This paper presents a multifunctional polymer surface that provides superhydrophobicity and self-cleaning functions together with an enhancement in mechanical and electrical performance. These functionalities are produced by nanoimprinting high aspect ratio pillar arrays on polymeric matrix incorporating functional reinforcing elements. Two distinct matrix-filler systems are investigated specifically, Carbon Nanotube reinforced Polystyrene (CNT-PS) and Reduced Graphene Oxide reinforced Polyvinylidene Difluoride (RGO-PVDF). Mechanical characterization of the topographies by quantitative nanoindentation and nanoscratch tests are performed to evidence a considerable increase in stiffness, Young's modulus and critical failure load with respect to the pristine polymers. The improvement on the mechanical properties is rationalized in terms of effective dispersion and penetration of the fillers into the imprinted structures as determined by confocal Raman and SEM studies. In addition, an increase in the degree of crystallization for the PVDF-RGO imprinted nanocomposite possibly accounts for the larger enhancement observed. Improvement of the mechanical ruggedness of functional textured surfaces with appropriate fillers will enable the implementation of multifunctional nanotextured materials in real applications.