The substitution of p-block heteroatoms into polyaromatic hydrocarbons offers the potential for introducing enhanced molecular properties and advancing material development for electro-optical applications. Using density functional theory, we characterize the substitution of boron and nitrogen atoms into a 2,3,6,7,10,11-hexakis(hexathiol)triphenylene (TTP) core, a precursor for a material with a discotic liquid crystal phase, to determine the strength of exciton dissociation and the influence doping has on the formation of a heterojunction with graphene. The substitution of nitrogen and boron into the TTP motif enables tunability of both electron and hole coupling between hetero- and homodyads. The coupling is found to far exceed that of TTP and varied transport behavior with different combinations of doped cores of nitrogen-TTP and boron-TTP is reported. Heterodyads of nitrogen-TTP with boron-TTP appear to be ambipolar in electron/hole coupling, whereas heterodyads of boron- or nitrogen-TTP with TTP form strong electron coupling dyads and homodyads of nitrogen-TTP and boron-TTP form strong hole coupling. Finally, we describe the heterojunction of nitrogen- or boron-TTP with monolayer graphene and observe Ohmic contacts with large hole transport barriers. The presence of induced dipoles occurs at the interface in all heterojunctions, suggesting the possibility of tuning the junction with external potentials and improving exciton dissociation.

Acorn barnacles are efficient colonizers on a wide variety of marine surfaces. As they proliferate on critical infrastructure, their settlement and growth have deleterious effects on performance. To address acorn barnacle biofouling, research has focused on the settlement and adhesion processes with the goal of informing the development of novel coatings. This effort has resulted in the discovery and characterization of several proteins found at the adhesive substrate interface, i.e. cement proteins, and a deepened understanding of the function and composition of the biomaterials within this region. While the adhesive properties at the interface are affected by the interaction between the proteins, substrate and mechanics of the calcified base plate, little attention has been given to the interaction between the proteins and the cuticular material present at the substrate interface. Here, the proteome of the organic matrix isolated from the base plate of the acorn barnacle Amphibalanus amphitrite is compared with the chitinous and proteinaceous matrix embedded within A. amphitrite parietal plates. The objective was to gain an understanding of how the basal organic matrix may be specialized for adhesion via an in-depth comparative proteome analysis. In general, the majority of proteins identified in the parietal matrix were also found in the basal organic matrix, including nearly all those grouped in classes of cement proteins, enzymes and pheromones. However, the parietal organic matrix was enriched with cuticle-associated proteins, of which ca 30% of those identified were unique to the parietal region. In contrast, ca 30-40% of the protease inhibitors, enzymes and pheromones identified in the basal organic matrix were unique to this region. Not unexpectedly, nearly 50% of the cement proteins identified in the basal region were significantly distinct from those found in the parietal region. The wider variety of identified proteins in the basal organic matrix indicates a greater diversity of biological function in the vicinity of the substrate interface where several processes related to adhesion, cuticle formation and expansion of the base synchronize to play a key role in organism survival.

Interfacial interactions between liquid crystal (LC) and two-dimensional (2D) materials provide a platform to facilitate novel optical and electronic material properties. These interactions are uniquely sensitive to the local energy landscape of the atomically thick 2D surface, which can be strongly influenced by defects that are introduced, either by design or as a byproduct of fabrication processes. Herein, we present density functional theory (DFT) calculations of the LC mesogen 4-cyan-4′-pentylbiphenyl (5CB) on graphene in the presence of a monovacancy (MV-G). We find that the monovacancy strengthens the binding of 5CB in the planar alignment and that the structure is lower in energy than the corresponding homeotropic structure. However, if the molecule is able to approach the monovacancy homeotropically, 5CB undergoes a chemical reaction, releasing 4.5 eV in the process. This reaction follows a step-by-step process gradually adding bonds, inserting the 5CB cyano group into MV-G. We conclude that this irreversible insertion reaction is likely spontaneous, potentially providing a new avenue for controlling both LC behavior and graphene properties.

Barnacles interest the scientific community for multiple reasons: their unique evolutionary trajectory, vast diversity and economic impact—as a harvested food source and also as one of the most prolific macroscopic hard biofouling organisms. A common, yet novel, trait among barnacles is adhesion, which has enabled a sessile adult existence and global colonization of the oceans. Barnacle adhesive is primarily composed of proteins, but knowledge of how the adhesive proteome varies across the tree of life is unknown due to a lack of genomic information. Here, we supplement previous mass spectrometry analyses of barnacle adhesive with recently sequenced genomes to compare the adhesive proteomes of Pollicipes pollicipes (Pedunculata) and Amphibalanus amphitrite (Sessilia). Although both species contain the same broad protein categories, we detail differences that exist between these species. The barnacle-unique cement proteins show the greatest difference between species, although these differences are diminished when amino acid composition and glycosylation potential are considered. By performing an in-depth comparison of the adhesive proteomes of these distantly related barnacle species, we show their similarities and provide a roadmap for future studies examining sequence-specific differences to identify the proteins responsible for functional differences across the barnacle tree of life.

Proteomics results for P. pollicipes adhesive samples analyzed on the Thermo Orbitrap with the Ppol_2 predicted proteome.

The ability to control the alignment of liquid crystals (LCs) is a challenge that is near-universal in LC research and applications. While several practical solutions exist for controlling the azimuthal (in-plane) alignment of LCs at an interface, control over the polar, or pretilt angle of the LC often requires a combination of materials or expensive and intricate processing. Here, we introduce a method for exerting control over large pretilt angles utilizing a two-step exposure method applied to Brilliant Yellow (BY) photoalignment films. We demonstrate that BY photoalignment films have the unique ability to enforce a large range of pretilt angles spanning homeotropic (90°) and planar (0°) anchoring conditions at the LC-substrate interface. The alignment is stable over time, rewritable, and patternable. Ultimately the control established here provides a powerful and low-cost means to align and take full advantage of the anisotropic and electro-optic properties of LCs for a wide range of applications.

DNA scaffolds provide a means to precisely organize chromophores into large biomimetic exciton networks and direct energy transport for nanoscale sensing and light‐harvesting applications. Here, a functional building block of minimal complexity that maximizes the Förster resonance energy transfer (FRET) efficiency is sought. Using a model system consisting of three FRET steps in a 4‐dye cascade: Cy3→Cy3.5→Cy5→Cy5.5, we evaluate how this building block employs multiple interacting versus redundant FRET pathways. Variants of a dual rail design, where one or two copies of each dye are aligned in rigid linear parallel rows, are compared to a split rail format, where varying degrees of spacing are introduced between the rows. The FRET processes are assessed via steady‐state, time‐resolved, and single‐molecule spectroscopy. Experiments and simulation reveal the dual rail design as more efficient than the split rail and suggest the design principle that efficient FRET networks must balance the increase in FRET rate from multiple interacting pathways with undesirable fluorescence quenching between dyes in close proximity. Hybrid fluorophore combinations are identified as a strategy to mitigate this quenching, leading to optimized dual rails capable of 50% end‐to‐end efficiency. These insights can help guide the design of functional photonic wires based on DNA scaffolds.

In a planar dielectric waveguide, weak confinement of a propagating mode in a high index core leads to a measurable evanescent interaction with the cladding. In this work, we study the effect of a reorientable anisotropic cladding on the behaviour of Transverse Electric (TE) and Transverse Magnetic (TM) mode polarisations using a liquid crystal (LC)-clad waveguide architecture. The polarised evanescent field of a guided mode interacts with a voltage-tunable birefringent LC cladding to deflect an out-coupled beam. Experimental measurements are coupled with a theoretical framework and show good consistency with simulation results. We isolate the effect of mode confinement by changing the thickness of the high index core. Interactions between the LC index ellipsoid and the mode polarisation are probed by changing the initial alignment of the LC. Finally, we examine the difference in deflection between TE and TM modes, which incorporates both a change in mode confinement and a difference in LC index components.

Acorn barnacles are major marine fouling organisms. Their success is largely due to an ability to adhere to diverse substrates via a sub-micron thick proteinaceous adhesive layer that develops as the organism molts and expands its base. Recent work has expanded the set of proteins identified within the adhesive interface, but one outstanding question concerns their spatial distribution throughout the organism. Here, we employ immunological analysis of Amphibalanus amphitrite tissue sections and identify the presence of two cement proteins, AaCP19-1 and AaCP43-1, in areas far removed from the adhesive interface. Confocal imaging reveals specific staining along different tissue linings of the organism as well as other non-cementing regions. Additionally, we employ a modified, pressure cycling technology approach to recover protein from histological tissue sections to perform proteomics analysis. Mass spectrometry analysis of proteins recovered from transverse histological sections of the upper portion of barnacles indicates the presence of these same proteins, complementing the immunostaining observations. The proteomics analysis also revealed the presence of other proteins first identified in the adhesive layer. While some proteins are clearly enriched at the surface interface, our findings challenge the concept that cement proteins are exclusive to the substrate interface and suggest they may have an expanded physiological role beyond substrate adhesion-related processes of A. amphitrite.

In-plane, or azimuthal, photo-reorientation of azodye films using polarized exposure makes them promising alignment layers for a host of liquid crystal (LC) applications beyond displays including beam steering, q-plates, liquid crystal elastomer origami, and control of active matter. Out-of-plane, or polar, reorientation of azodye films, which dictates the liquid crystal pretilt, has received far less attention. Spatial control over the full polar and azimuthal orientation enables the generation of complex patterns that have broad interests and applications. In this paper, we describe an enhanced out-of-plane reorientation in Brilliant Yellow films utilizing a two-step exposure and demonstrate a liquid crystal pretilt angle that is tunable over a range of 0-33° with the associated anchoring strength of the alignment layer being unaffected by the inclusion of a pretilt. We report an order of magnitude increase in both amplitude and tunability of the pretilt angle in terms of previous results for single photoalignment films. This is a significant result for liquid crystal applications because it offers a simple, scalable, single-component solution with the potential to provide three-dimensional (3-D) patternability of the LC director at the surface.

Successful proteomic characterization of biological material depends on the development of robust sample processing methods. The acorn barnacle Amphibalanus amphitrite is a biofouling model for adhesive processes, but the identification of causative proteins involved has been hindered by their insoluble nature. Although effective, existing sample processing methods are labor and time intensive, slowing progress in this field. Here, a more efficient sample processing method is described which exploits pressure cycling technology (PCT) in combination with protein solvents. PCT aids in protein extraction and digestion for proteomics analysis. Barnacle adhesive proteins can be extracted and digested in the same tube using PCT, minimizing sample loss, increasing throughput to 16 concurrently processed samples, and decreasing sample processing time to under 8 hours. PCT methods produced similar proteomes in comparison to previous methods. Two solvents which were ineffective at extracting proteins from the adhesive at ambient pressure (urea and methanol) produced more protein identifications under pressure than highly polar hexafluoroisopropanol, leading to the identification and description of >40 novel proteins at the interface. Some of these have homology to proteins with elastomeric properties or domains involved with protein-protein interactions, while many have no sequence similarity to proteins in publicly available databases, highlighting the unique adherent processes evolved by barnacles. The methods described here can not only be used to further characterize barnacle adhesive to combat fouling, but may also be applied to other recalcitrant biological samples, including aggregative or fibrillar protein matrices produced during disease, where a lack of efficient sample processing methods has impeded advancement. Data are available via ProteomeXchange with identifier PXD012730.

Concerns about the bioaccumulation of toxic antifouling compounds have necessitated the search for alternative strategies to combat marine biofouling. Because many biologically essential minerals have deleterious effects on organisms at high concentration, one approach to preventing the settlement of marine foulers is increasing the local concentration of ions that are naturally present in seawater. Here, we used surface-active borate glasses as a platform to directly deliver ions (Na + , Mg 2+ and BO 4 3− ) to the adhesive interface under acorn barnacles ( Amphibalanus ( =Balanus ) amphitrite ). Additionally, surface-active glasses formed reaction layers at the glass–water interface, presenting another challenge to fouling organisms. Proteomics analysis showed that cement deposited on the gelatinous reaction layers is more soluble than cement deposited on insoluble glasses, indicating the reaction layer and/or released ions disrupted adhesion processes. Laboratory experiments showed that the majority (greater than 79%) of adult barnacles re-attached to silica-free borate glasses for 14 days could be released and, more importantly, barnacle larvae did not settle on the glasses. The formation of microbial biofilms in field tests diminished the performance of the materials. While periodic water jetting (120 psi) did not prevent the formation of biofilms, weekly cleaning did dramatically reduce macrofouling on magnesium aluminoborate glass to levels below a commercial foul-release coating. This article is part of the theme issue ‘Transdisciplinary approaches to the study of adhesion and adhesives in biological systems’.

We present ground-state electronic properties of the liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) on the two-dimensional materials monolayer graphene, hexagonal boron nitride, and phosphorene. Our density functional theory results show that the physisorption is robust on all surfaces with the strongest binding of 5CB on phosphorene. All surfaces exhibit flexural distortion, especially monolayer graphene and hexagonal boron nitride. While we find type-I alignment for all three substrates, meaning the Fermi level of the system is in the HOMO-LUMO gap of 5CB, the band structures are qualitatively different. Unlike for graphene and phosphorene, the HOMO-LUMO of 5CB appear as localized states within the band gap of boron nitride. In addition, we find that the valence band for boron nitride is sensitive to the orientation of 5CB relative to the surface. The qualitatively different band structures demonstrate the importance of substrate selection for tailoring the electronic and optoelectronic properties of nematic liquid crystals on two-dimensional materials.

Next generation sequencing (NGS) technologies can provide an understanding of the molecular processes involved in marine fouling by Amphibalanus spp. barnacles. Here, seven methods for extracting DNA from A. amphitrite prosomata were assessed with respect to recovery, purity and size distribution. Methods incorporating organic extractions generally resulted in low recovery of fragmented DNA. The most promising method was the commercial E.Z.N.A. Blood DNA Mini kit, which provided tens of micrograms of DNA of sufficient molecular weight for use in long-read NGS library preparation. Other kits resulted in DNA preps suitable for short read length NGS platforms.

The heightened demand for non-mechanical approaches to beam redirection and steering has led to several electro-optical approaches. One with great potential integrates liquid crystal (LC) as a cladding layer to a planar waveguide for continuous two dimensional steering. The birefringence of LC is leveraged to tune the waveguide effective leading to refractive steering, while efficient coupling with a freespace beam is accomplished with a “tapered gap” prism coupler. The out-coupled beam can be steered by refraction in a continuous manner to follow a path or address random points with sub millisecond response times. This device architecture presents a challenge for modeling and simulation with a large parameter space. Experimental successes have motivated a custom MATLAB model that couples LC and waveguide physics. The model simulates the distortion of the nematic LC and uses the graded index profile at the cell boundary to solve the waveguide equation as a function of applied voltage. Raytracing methods are used to track the refraction of an input beam through regions of tunable waveguide index and predict the angular field of regard (FOR). Numerical simulations of the coupling region predict the coupling efficiency given the conditions of the input beam including arbitrary bandwidth. Comparison of coupling conditions and FOR measurements with empirical results allows us to rapidly prototype a device by optimizing parameters with fast algorithms that maximize the field of regard and throughput efficiency.

Thin films of arsenic triselenide (As2Se3) glass degrade significantly under ambient conditions in the presence of light. We investigate the mechanism of this degradation by maintaining thin film As2Se3 samples in a variety of environmental conditions for approximately one year and show that exposure to below-band gap light in the presence of oxygen and moisture lead to the formation of crystallites of arsenic oxide and selenium. Spectroscopic measurements, X-ray diffraction (XRD), and microscopy reveal that deposition of a thin (~10 nm) passivation layer together with preventing exposure to below-band gap light inhibits degradation. These results indicate that As2Se3 is a practical material for use in applications such as integrated optic waveguides or dielectric metasurfaces operating in wavelengths from the short-wave infrared through the long-wave infrared.

Beam steering is a crucial technology for a number of applications, including chemical sensing/mapping and light detection and ranging (LIDAR). Traditional beam steering approaches rely on mechanical movement, such as the realignment of mirrors in gimbal mounts. The mechanical approach to steering has several drawbacks, including large size, weight and power usage (SWAP), and frequent mechanical failures. Recently, alternative non-mechanical approaches have been proposed and developed, but these technologies do not meet the demanding requirements for many beam steering applications. Here, we highlight the development efforts into a particular non-mechanical beam steering (NMBS) approach, refractive waveguides, for application in the MWIR. These waveguides are based on an Ulrich-coupled slab waveguide with a liquid crystal (LC) top cladding; by selectively applying an electric field across the liquid crystal through a prismatic electrode, steering is achieved by creating refraction at prismatic interfaces as light propagates through the device. For applications in the MWIR, we describe a versatile waveguide architecture based on chalcogenide glasses that have a wide range of refractive indices, transmission windows, and dispersion properties. We have further developed robust shadow-masking methods to taper the subcladding layers in the coupling region. We have demonstrated devices with >10 degrees of steering in the MWIR and a number of advantageous properties for beam steering applications, including low-power operation, compact size, and fast point-to-point steering.

We use density functional theory to explore the stable adsorption geometries of the liquid crystal molecule 5CB on a graphene sheet. First, we calculate the dependence of the polarizability of 5CB on its geometry. Our results break down the contributions of the cyano, biphenyl, and alkyl groups to the optical properties of 5CB, confirming the biphenyl group as the most influential. Second, we quantify possible adsorption structures of 5CB on graphene. We find that 5CB can stably adsorb with its biphenyl group oriented intermediate to the armchair and zigzag crystallographic directions, in addition to adsorbing with the biphenyl oriented along those directions.

The response time of liquid crystal proximal to an aligning interface, where surface anchoring energy dominates, is quantified as a function of voltage utilizing the evanescent field of the guided mode in a planar waveguide.

Midwave infrared (MWIR) light is critically important for a variety of applications, such as chemical sensing and LIDAR. Directional control over MWIR light is required for these applications and is typically accomplished using mechanical devices such as gimbal-mounted mirrors. Mechanical steerers, however, are subject to a host of problems, and replacing them has been a long-standing goal. In this paper, we describe the first nonmechanical beam steerer capable of continuous angular tuning in the MWIR. These devices are chip-based and provide steering in two dimensions without relying on moving parts. Previous work has demonstrated nonmechanical beam steering (NMBS) in the short-wave infrared and near infrared using a waveguide in which a portion of the propagating light is evanescently coupled to a liquid crystal (LC) layer in which the refractive index is voltage-tuned. We have extended this NMBS technology into the MWIR by utilizing a unique combination of materials, specifically chalcogenide glass waveguides and LC materials that exhibit high MWIR transparency. We explain the working principles behind these steerers, discuss material considerations for transparency in the MWIR, describe steerer fabrication, and present experimental results showing up to 14 degrees in-plane and 0.6 degrees out-of-plane steering. (C) 2018 Optical Society of America