Fluorescent Elastomer Research Articles

Mechanically Ultra-Robust Fluorescent Elastomer for Elaborating Auxetic Composite.

Fluorescent elastomers are predominantly fabricated through doping fluorescent components or conjugating chromophores into polymer networks, which often involves detrimental effects on mechanical performance and also makes large-scale production difficult. Inspired by the heteroatom-rich microphase separation structures assisted by intensive hydrogen bonds in natural organisms, an ultra-robust fluorescent polyurethane elastomer is reported, which features a remarkable fracture strength of 87.2MPa with an elongation of 1797%, exceptional toughness of 678.4MJm-3 and intrinsic cyan fluorescence at 445nm. Moreover, the reversible fluorescence variation with temperature could in situ reveal the microphase separation of the elastomer in real time. By taking advantage of mechanical properties, intrinsic fluorescence and hydrogen bonds-promoted interfacial bonding ability, this fluorescent elastomer can be utilized as an auxetic skeleton for the elaboration of an integrated auxetic composite. Compared with the auxetic skeleton alone, the integrated composite shows an improved mechanical performance while maintaining auxetic deformation in a large strain below 185%, and its auxetic process can be visually detected under ultraviolet light by the fluorescence of the auxetic skeleton. The concept of introducing hydrogen-bonded heteroatom-rich microphase separation structures into polymer networks in this work provides a promising approach to developing fluorescent elastomers with exceptional mechanical properties.

Multi-functional fluorescent silicon elastomer cross-linked with AIE polymer by dynamic imine bond and its application in anti-counterfeiting

Fluorescent elastomer materials have received extensive attention due to their excellent optical performance, flexibility, and chemical stability in recent years, and demonstrate great application potentials in intelligent sensors, optoelectronic devices, medical equipment and other fields. Although the traditional method for constructing fluorescent elastomers by doping fluorescent small molecules is facile and universal, it also has limitations such as low luminous efficiency, uneven dispersion, poor stability and single function. In this work, an aggregation-induced emission (AIE) fluorescent polymer with aldehyde groups in side chain was synthesized and crosslinked with aminopropyl double capped polydimethylsiloxane (NH2-PDMS-NH2) through mild Schiff base reaction to construct a fluorescent elastomer. Compared with fluorescent small molecules, AIE polymers have superior fluorescence performance and can be flexibly designed according to demands. The dynamic imine bonds endow the as-obtained elastomers with self-healing and recycling properties, enabling rapid repair and remodeling at room temperature. Besides, the tensile and swelling properties of PDMS enable them to adjust the concentration of fluorescent units in the matrix under corresponding stimulus, thereby achieving tunable fluorescence emission. Taking advantage of the fluorescent elastomers, we prepared fluorescent anti-counterfeiting patterns that were hidden in daylight and visible under UV light, demonstrating the potential applications of the fluorescent elastomers in the fields of anti-counterfeiting and information encryption. This study also provides an alternative strategy for developing multifunctional fluorescent elastomers.

A compact system for accurate measurement of true stress-strain curves in transparent materials subject to extensive deformation

Accurate quantification of the true stress-strain curve over an extensive strain range is pivotal for elucidating material mechanical properties and simulating non-linear plastic deformation. A novel experimental approach was developed to directly measure true stress-strain behavior in transparent materials. Our setup featured a single 3CCD camera and mirrors, capturing images of both specimen surfaces with bicolored fluorescent speckle patterns. Initially, we determined and corrected the specimen’s refractive index using a point-by-point least squares method. Subsequently, we used multispectral dual 3D digital image correlation (DIC) to reconstruct surface profiles and correct refractive distortions. This allowed precise computation of the deformed cross-sectional area over an expansive strain range. True stress was calculated from the measured engineering stress and computed deformed area. Validity was confirmed by deforming a fluorescent elastomer, and results aligned with the theoretical predictions. This compact experimental setup effectively evaluates true stress-strain relationships in transparent materials under extensive deformation.

Strong, Healable, Stimulus-Responsive Fluorescent Elastomers Based on Assembled Borate Dynamic Nanostructures.

Self-healing materials integrated with robust mechanical property and fascinating functions synchronously hold great prospects in many applications, but it still remains a grand challenge. Here, a bottom-up assembly method of preparing borate dynamic nanostructures (BDN) with controllable morphologies and interfacial crosslinks is proposed, from which a robust self-healing elastomer is fabricated. The BDN is optimized to construct dense and strong interfacial boronic easter crosslinks, endowing the elastomer with outstanding stretchability (2050%), high strength (17.9MPa) as well as healing efficiency (77.1%). Moreover, the elastomer also exhibits pH stimulus-responsive fluorescence property and excellent functional repairability, enabling its potential application in intelligent material fields such as information encoding and encryption. This study demonstrates a general approach to produce self-healable functional materials with robust mechanical properties, and defines a rich platform for exploring various functional nanostructured materials.

Getting old: an endangered seahorse (Hippocampus whitei) lives for up to 7 years in the wild

A long-term monitoring programme from 2005 to 2021 has allowed the assessment of age and longevity in an endangered seahorse Hippocampus whitei in the wild. Seahorses were marked using visible implant fluorescent elastomer (VIFE) which allows for individual identification. The longest period from marking to last sighting was 6 years 8 months and 17 days for a female. Using a von Bertalanffy growth function model for the species, this individual would have been approximately 7 years 7 months old on last sighting. These observations suggest that seahorses in the wild can live for over 7 years and demonstrate the benefits of using VIFE in long-term movement, population abundance and life-history studies of seahorses.

Ecological and growth patterns of the longsnout seahorse Hippocampus reidi inferred by mark-recapture techniques in a tropical estuary

Abstract: The population structure of the longsnout seahorse Hippocampus reidi (Ginsburg 1933) was evaluated in an estuarine system in northeastern Brazil. A total of 425 captures were performed in the Vaza-Barris estuary and 232 individuals were marked with Visible Implant Fluorescent Elastomers. The population was estimated to be composed of 428 fish. The von Bertalanffy growth curve shows a steeper growth during the first months of life, up to about 17 months, and stabilization after 16 cm and 27 months of age. The hereby study indicates that the Vaza-Barris estuary is home to resident populations of longsnout seahorses. Moreover, these populations use mangrove roots as the main substrate for attachment and present well-defined ecological characteristics, such as habitat fidelity and highly structured social organization.

Life history and population dynamics of an endangered seahorse (Hippocampus capensis) within an artificial habitat.

Species-specific life-history information is critical for successful conservation, particularly in establishing an accurate baseline status. Obtaining such information is challenging for most species, but in particular for rare and threatened marine species. To facilitate future conservation of the endangered Knysna seahorse (Hippocampus capensis) this study aimed to determine important life-history information for this species. Visible implant fluorescent elastomer (VIFE) tags were used to mark 78 seahorses within a residential marina estate in the Knysna estuary, South Africa, in February 2018. Using a mark-resight approach, the size and movement patterns of the population and growth rate of seahorses were determined over a 14-month period. The closed population estimate for H. capensis, within Thesen Islands Marina, was estimated to be 134 (118-152 95% C.I.) in February 2018 compared to only 72 (48-108 95% C.I.) in February 2019. The species showed rapid initial growth with males and females having similar rates of growth based on the specialised von Bertalanffy growth function model. The importance of Reno mattresses as a habitat for H. capensis was confirmed based on the high abundance and site fidelity of the population, which emphasises the conservation potential of heavily modified environments for threatened seahorse species. The use of VIFE tags was deemed effective in studying this endangered seahorse and allowed the collection of important information for this species which can be used in future Red List assessments and conservation actions.

Structural Features Guiding the Design of Liquid-Crystalline Elastomeric Fluorescent Force Sensors

Liquid single crystal elastomers (LSCEs) containing carbazole fluorogenic components alter their luminescence when they are stretched along the director direction. The differential luminescent behavior arises from the distinct interaction between the carbazole fluorophores and their local environment before and after the application of the mechanical input. Indeed, the uniaxial deformation of the material, along its anisotropic direction, forces a closer mesogen–fluorophore interaction, which leads to the quenching of the carbazole luminescence. Importantly, this intermolecular interaction is intimately related to the intrinsic order present in the LSCE. As a result, the amount of light emitted by the material in the form of fluorescence diminishes upon deformation. Thus, the application of mechanical stimuli to liquid-crystalline elastomers furnishes to two interconvertible states for the system with distinct optical properties (with either different emission color or fluorescence intensity). The initial state of the material is completely restored once the applied force is removed. In this way, this kind of macromolecular system can transduce mechanical events into detectable and processable optical signals, thus, having great potential as optical force sensors. In this context, the realization of the distinct structural factors that govern the interactions established between the mesogenic and fluorogenic units at the supramolecular level upon deformation is essential for the development of efficient LSCE-based force sensors. In fact, not only the density of carbazole units and their connection to the main polymer backbone, but also the presence of long range molecular order in the system and the type of mesophase exhibited by the LSCE are key factors for the conception of efficient force sensors based on these self-organized polymer networks. In this review, we present a comprehensive and systematic description of the different features that control the mechanoluminescent behavior of fluorescent liquid-crystalline elastomers and will guide the future design of LSCE-based force sensors with improved performances.

A New Non-Invasive Technique for Temporarily Tagging Coral Reef Fishes

The ability to identify individuals is important for the success of many behavioral and ecological studies. In fishes, there is a lot of variation in body size, shape, skin thickness, behavior, and ecology, which means that any given marking/ tagging method may not work well for all species. For the Humbug Damselfish Dascyllus aruanus, a widely used model species of coral-reef fish, we found that standard tagging methodologies (e.g., phenotypic variation, beads and PVC tags, fluorescent elastomer injections) were ineffective as they could not be applied to the fish or easily detected by observers or from videos. In response, we developed a new method to temporarily tag D. aruanus using colored plastic films and topical surgical glue. These films were easily detectable both directly by human observers and indirectly by video/photo-cameras. We tested the efficacy of this new method by examining the survival time of the tags at various positions on the body. Our results showed that the optimal tag locations were dorsal anterior (with a median attachment time of 53 hours) and dorsal middle (with a median attachment time of 49 hours). Total length of fish was not a significant predictor of tag life. In sum, we demonstrate an effective new method for temporarily tagging a widely studied coral reef fish. This method could be applied to other fishes and aquatic organisms (e.g., amphibians) in both marine and freshwater ecosystems.

A cephalopod-inspired mechanoluminescence material with skin-like self-healing and sensing properties

A cephalopod-inspired mechanoluminescence material with skin-like self-healing and sensing properties was developed by the construction of a unique strain-dependent microcrack-structured conductive UV-shielding layer upon a self-healable supramolecular fluorescent elastomer with synergistic dynamic crosslinking network design.

Rewritable, light-driven recordings in a full-colour fluorescent polydimethylsiloxane elastomer

A new approach for rewritable, light-driven recordings in PDMS was presented by manipulating the light-induced photobleaching phenomenon.

Polysiloxane-based two-photon fluorescent elastomers with superior mechanical and self-healing properties and their application in bioimaging

The first report of the synthesis of novel self-healing elastomers possessing a dynamic dual cross-linked network and exhibiting a unique two-photon fluorescence, which show potential for application in bioimaging.

Evaluation of visible fluorescent elastomer tags implanted in marine medaka, Oryzias dancena

The aim of this study was to assess visible implant fluorescent elastomer (VIE) tagging and stress response in marine medaka, Oryzias dancena. The experimental fish were anesthetized individually and marked with red, yellow, or green elastomer at each of the following three body locations: (1) the abdomen, (2) the back, and (3) the caudal vasculature. During 12 months, the accumulated survival rates of fish in the experimental treatments were not different among red, yellow, and green elastomers. The experimental fish retained > 85% of the tags injected in the back, > 70% of the tags injected in the caudal vasculature, and > 60% of the tags injected in the abdomen (P < 0.05). An important observation was that the abdomen site was associated with poor tag retention. For all injected sites, the red and green tags were able to be detected more easily than the yellow tags when observed under both visible and UV lights. Tag readability was lower for the abdomen site than for the other sites (back and caudal vasculature). Thus, VIE tags were easy to apply to marine medaka (< 1 min per fish) and were readily visible when viewed under UV light.

Long-Distance Movements of Six Darters (Teleostei: Percidae) in the Red River, Kentucky

We compared the long-distance movements of the Frecklebelly Darter, Percina stictogaster, a pelagic fish species, to those of five other sympatric benthic or semipelagic darters. In four reaches of the Red River, Kentucky we tagged 942 individuals of six darter species using subcutaneous injections of visible implant fluorescent elastomer (VIE) from May 2012 to May 2013. These reaches, plus an additional four reaches, were surveyed by snorkeling or seining to detect previously tagged fishes. Over seven sampling sessions spanning June 2012 to November 2013 a total of 58 tagged darters were detected, including 20 P. stictogaster. Most darters were detected in the same reach in which they were tagged; inter-reach movements occurred more in pelagic (3 of 20) and semipelagic species (2 of 4) (both Percina) than in benthic species (2 of 34, all Etheostoma). Most (6 of 7) inter-reach movements were upstream. The relatively high dispersal tendencies of Percina darters suggest these darters are particularly vulnerable to in-stream barriers and that maintaining connectivity among populations should be a critical management goal.

Fidelidad al sitio y rango de hogar del caballito de mar narizón &lt;i&gt;Hippocampus reidi&lt;/i&gt; (Teleostei: Syngnathidae) en la dársena de Varadero, noroeste de Cuba

En las últimas décadas se ha constatado un importante declive mundial en las poblaciones de peces de la familia Syngnathidae, entre las que se encuentran los carismáticos caballitos de mar. Hasta el momento en Cuba han sido escasas las investigaciones realizadas a las poblaciones de estos peces en su medio natural. El objetivo de este trabajo fue determinar la fidelidad al sitio y el rango de hogar del caballito de mar narizón (Hippocampus reidi Ginsburg, 1933), especie pobremente estudiada y clasificada en la categoría de Datos Deficientes (DD) por la UICN. Los muestreos se realizaron entre abril de 2009 y agosto de 2010 en dos estaciones localizadas en la dársena de Varadero, que es un canal artificial localizado al noroeste de Cuba. Se llevaron a cabo censos visuales en 17 transectos (20 x 1 m) en cada estación. Un total de 68 individuos fueron identificados y marcados con elastómeros fluorescentes. H. reidi mostró fidelidad al sitio, recapturándose el 48.5% de los ejemplares marcados muy cerca o en el mismo transecto donde fueron localizados y censados por primera vez. El rango de hogar fue de 70.6 ± 60.1 m (media ± desviación estándar) y no se encontraron diferencias significativas en esta variable entre ambas estaciones o entre las hembras y los machos. Estos resultados incrementan el conocimiento actual que se tiene acerca de esta especie de caballito de mar y demuestran la vulnerabilidad de sus poblaciones a las posibles perturbaciones de su restringido hábitat.

Color-Transformable Silicone Elastomers Prepared by Thiol-Ene Reaction with Potential Application in UV-LEDs.

A series of high-efficiency, full-color fluorescent elastomers based on polysiloxane matrix prepared by an easy thiol-ene "click" reaction is reported here. It is found for the first time that the same elastomer can emit transformable colors by conveniently altering the excitation wavelength because of the effect of energy transfer and the "fluorescence switch" of lanthanide ions. A fluent change in emission colors can also be feasible and conveniently reproducible by varying the stoichiometric ratio of lanthanide ions and rhodamine-B in solution and in polymer elastomers. The obtained elastomers are further coated onto commercially available UV-LED cells from the solution medium followed by an in situ cross-linking step.

A novel stimuli-responsive fluorescent elastomer based on an AIE mechanism

In this paper, a facile approach for the synthesis of stimuli-responsive fluorescent elastomer was developed. The photoluminescence should partly be attributed to the hampered intramolecular rotation of the aryl rotors of the dye molecules by wrapping and coiling of the flexible polymer chains. In addition, the reversibility of this responsiveness was also confirmed.

Ontogenetic and sex-based differences in habitat preferences and site fidelity of White's seahorse Hippocampus whitei.

The aim of this study was to determine and compare habitat preferences for male and female adult and juvenile White's seahorse Hippocampus whitei and assess their movements and site fidelity over 4 years. Data were collected from three sites along 1.5 km of estuarine shoreline in Port Stephens, New South Wales, Australia, from 2006 to 2009 using H. whitei that had been tagged with visible implant fluorescent elastomer. Relative availability of 12 habitats and habitat preferences of H. whitei was determined, based on the habitat that H. whitei used as a holdfast. Hippocampus whitei occurred in nine different habitats; adults preferred sponge and soft coral Dendronephthya australis habitats with no difference between male and female habitat preferences whilst juveniles preferred gorgonian Euplexaura sp. habitat. There was a significant preference by adults for D. australis colonies with height >40 cm and avoidance of colonies <20 cm. Neither adults nor juveniles used sand or the seagrasses Zostera muelleri subsp. capricorni and Halophila ovalis. Hippocampus whitei showed cryptic behaviour with c. 50% of adult sightings cryptic and c. 75% for juveniles with crypsis occurring predominantly in Sargassum sp. for adults and Euplexaura sp. habitat for juveniles. Within sites, females moved significantly longer distances (maximum of 70 m) than males (maximum of 38 m) over 20 months. Strong site fidelity was displayed by H. whitei with males persisting at the same site for up to 56 months and females for 49 months and no H. whitei moved between sites. The longest period that an H. whitei was recorded on the same holdfast was 17 months for a male and 10 months for a female. As this species displays strong site fidelity, specific habitat preferences and has a limited distribution, future management needs to minimize the risk of habitat disturbance as loss of key habitats could have a negative effect on species abundance and distribution.

Evaluation of a Visible Implant Fluorescent Elastomer Tag in the Greenling Hexagrammos otakii

The aim of this study was to assess visible implant fluorescent elastomer (VIE) tagging in greenling Hexagrammos otakii. The experiental fish were anesthetized individually and marked with orange, yellow, red, and green elastomer at the following five body locations, respectively: the adipose eyelid, the surface of the dorsal fin base, the inside surface of the pectoral fin base, the inside surface of the pelvic fin base, and the surface of the anal fin base. Control fish were anesthetized but not marked. During the 20-month trial, fish growth and retention, underwater visibility, and readability of the tags were determined. After 20 months, body length of marked greenling (<TEX>$43.2{\pm}3.5cm$</TEX>, mean <TEX>${\pm}$</TEX> standard deviation [SD]) did not differ from that of the control (<TEX>$41.4{\pm}3.7cm$</TEX>). Additionally, the body weight of marked greenling (<TEX>$527.4{\pm}39.8g$</TEX>, mean <TEX>${\pm}$</TEX> SD) did not differ from that of the controls (<TEX>$505.9{\pm}31.7g$</TEX>). Greenling retained >90% of the tags at the surface of the dorsal fin base. The anal fin base showed a higher tag retention rate than the inside surfaces of the pectoral fin and the pelvic fin bases (P < 0.05). Red and orange tags were identified more easily underwater than green and yellow tags. Green and yellow tags emitted fluorescence in response to a narrower range of light wavelengths. Thus, the VIE mark was easy to apply to greenling (< 1 min per fish) and was readily visible when viewed under an ultraviolet lamp.

Population dynamics and life history of a geographically restricted seahorse, Hippocampus whitei

The aim of this study was to collect data on population dynamics and life history for White's seahorse Hippocampus whitei, a geographically restricted species that is listed as data deficient under the IUCN Red List. Data from H. whitei populations were collected from two regions, Port Stephens (north) and Sydney Harbour (south) in New South Wales, Australia, covering most of the known range of H. whitei, from 2005 to 2010. Over 1000 individuals were tagged using fluorescent elastomer and on subsequent recaptures were re-measured for growth data that were used in a forced Gulland-Holt plot to develop growth parameters for use in a specialized von Bertalanffy growth-function model. Growth parameters for Port Stephens were: females L(∞) = 149·2 mm and K = 2·034 per year and males L(∞) = 147·9 mm and K = 2·520 per year compared with estimates from Sydney Harbour: females L(∞) = 139·8 mm and K = 1·285 per year and males L(∞) = 141·6 mm and K = 1·223 per year. Whilst there was no significant difference in growth between sexes for each region, H. whitei in Port Stephens grew significantly quicker and larger and matured and reproduced at a younger age than those from Sydney Harbour. The life span of H. whitei is at least 5 years in the wild with six individuals recorded reaching this age. Data collected on breeding pairs found that H. whitei displays life-long monogamy with three pairs observed remaining pair bonded over three consecutive breeding years. Baseline population densities were derived for two Port Stephens' sites (0·035 and 0·110 m(-2)) and for Manly in Sydney Harbour (1·050 m(-2)). Even though the life-history parameters of H. whitei suggest it may be reasonably resilient, precaution should be taken in its future management as a result of its limited geographical distribution and increasing pressures from anthropogenic sources on its habitats.