A lightweight Color-changing melon ripeness detection algorithm based on model pruning and knowledge distillation: leveraging dilated residual and multi-screening path aggregation.

Color-changing melons are a kind of cucurbit plant that combines ornamental and food. With the aim of increasing the efficiency of harvesting Color-changing melon fruits while reducing the deployment cost of detection models on agricultural equipment, this study presents an improved YOLOv8s network approach that uses model pruning and knowledge distillation techniques. The method first merges Dilated Wise Residual (DWR) and Dilated Reparam Block (DRB) to reconstruct the C2f module in the Backbone for better feature fusion. Next, we designed a multilevel scale fusion feature pyramid network (HS-PAN) to enrich semantic information and strengthen localization information to enhance the detection of Color-changing melon fruits with different maturity levels. Finally, we used Layer-Adaptive Sparsity Pruning and Block-Correlation Knowledge Distillation to simplify the model and recover its accuracy. In the Color-changing melon images dataset, the mAP0.5 of the improved model reaches 96.1%, the detection speed is 9.1% faster than YOLOv8s, the number of Params is reduced from 6.47M to 1.14M, the number of computed FLOPs is reduced from 22.8GFLOPs to 7.5GFLOPs. The model's size has also decreased from 12.64MB to 2.47MB, and the performance of the improved YOLOv8 is significantly more outstanding than other lightweight networks. The experimental results verify the effectiveness of the proposed method in complex scenarios, which provides a reference basis and technical support for the subsequent automatic picking of Color-changing melons.

Time-Dependent Color-Changing Room-Temperature Phosphorescence Materials with Mutual Achievement between Guest and Host Molecules.

Host-guest doping strategy has gradually become the mainstream in constructing organic room-temperature phosphorescence (RTP) materials. The two-component doped system typically emits monochromatic phosphorescence dominated by the guest molecule, which also means that the intrinsic phosphorescence emission of the host molecule is not well utilized. In this work, a time-dependent color-changing RTP material is constructed based on host-guest doped system, in which the initial yellow phosphorescence stems from the isoquinoline-pyrazole guest and the final cyan phosphorescence originates from the intrinsic emission of the polymer host. The phenomenon of the strong interaction between host and guest molecules leading to their respective intrinsic phosphorescence provides new design inspiration for designing and developing two-component doped materials with RTP properties of color variation over time.

Encapsulation of thermochromic tetradecyl myristate/methyl red composite via full poplar-based cellulose/lignin/SiO2 framework for preparation of thermochromic wood with thermal response and storage.

Thermochromic wood (TW), a smart material that can respond to temperature changes and store thermal energy, holds broad potential for application in the construction industry. This study fabricated thermochromic poplar (TP) by encapsulating a thermochromic phase change material (TPCM), consisting of tetradecyl myristate and methyl red, within a full poplar-based cellulose/lignin/SiO2 framework. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that the poplar matrix and the incorporated SiO2 formed an integrated cellulose/lignin/SiO2 framework, which encapsulated the TPCM within the poplar ducts. The TP exhibits a color change from light purple to dark purple within the temperature range of 30-48 °C, with a pronounced shift at approximately 42 °C, correlating with the sensation of scalding. Thus, TP-based products can alert users to the risk of scalding through a noticeable color change. The full poplar-based framework mitigates the impact of ultraviolet (UV) radiation on the TP and prevents the loss of TPCM during thermal processing. The mechanical properties of TP are enhanced to a strength grade comparable to that of Manchurian ash wood, making it suitable for load-bearing components in wooden structures. Additionally, the average temperature of TP is around 10 °C higher than that of untreated poplar within 25 min after the same thermal treatment. Consequently, TP can serve as a building material with capabilities for temperature response, thermal energy storage, and structural load-bearing.

YOLOv8-CML: a lightweight target detection method for color-changing melon ripening in intelligent agriculture.

Color-changing melon is an ornamental and edible fruit. Aiming at the problems of slow detection speed and high deployment cost for Color-changing melon in intelligent agriculture equipment, this study proposes a lightweight detection model YOLOv8-CML.Firstly, a lightweight Faster-Block is introduced to reduce the number of memory accesses while reducing redundant computation, and a lighter C2f structure is obtained. Then, the lightweight C2f module fusing EMA module is constructed in Backbone to collect multi-scale spatial information more efficiently and reduce the interference of complex background on the recognition effect. Next, the idea of shared parameters is utilized to redesign the detection head to simplify the model further. Finally, the α-IoU loss function is adopted better to measure the overlap between the predicted and real frames using the α hyperparameter, improving the recognition accuracy. The experimental results show that compared to the YOLOv8n model, the parametric and computational ratios of the improved YOLOv8-CML model decreased by 42.9% and 51.8%, respectively. In addition, the model size is only 3.7 MB, and the inference speed is improved by 6.9%, while mAP@0.5, accuracy, and FPS are also improved. Our proposed model provides a vital reference for deploying Color-changing melon picking robots.

Research Progress of Bioinspired Structural Color in Camouflage.

Bioinspired structural color represents a burgeoning field that draws upon principles, strategies, and concepts derived from biological systems to inspire the design of novel technologies or products featuring reversible color changing mechanisms, with significant potential applications for camouflage, sensors, anticounterfeiting, etc. This mini-review focuses specifically on the research progress of bioinspired structural color in the realm of camouflage. Firstly, it discusses fundamental mechanisms of coloration in biological systems, encompassing pigmentation, structural coloration, fluorescence, and bioluminescence. Subsequently, it delineates three modulation strategies-namely, photonic crystals, film interference, and plasmonic modulation-that contribute to the development of bioinspired structural color materials or devices. Moreover, the review critically assesses the integration of bioinspired structural color materials with environmental contexts, with a particular emphasis on their application in camouflage. Finally, the paper outlines persisting challenges and suggests future development trends in the camouflage field via bioinspired structural color.

Design of an Optical Device Based on Kirigami Approach.

The aim of this work was to design a kirigami-based metamaterial with optical properties. This idea came from the necessity of a study that can improve common camouflage techniques to yield a product that is cheap, light, and easy to manufacture and assemble. The author investigated the possibility of exploiting a rotation to achieve transparency and color changing. One of the most important examples of a kirigami structure is a geometry based on rotating squares, which is a one-degree-of-freedom mechanism. In this study, light polarization and birefringence were exploited to obtain transparency and color-changing properties using two polarizers and common cellophane tape. These elements were assembled with a rotating-square structure that allowed the rotation of a polarizer placed on the structure with respect to a fixed polarizer equipped with cellophane layers.

Ultrasensitive Nanofiber Biosensor: Rapid In Situ Chromatic Detection of Bacteria for Healthcare Innovation.

Rapid detection of bacterial presence in skin wounds is crucial to prevent the transition from acute to chronic wounds and the onset of systemic infections. Current methods for detecting infections, particularly at low concentrations (<1.0 × 105 CFU/cm2), often require complex technologies and direct sampling, which can be invasive and time-consuming. Addressing this gap, we introduce a colorimetric nanofibrous biosensor enabling real-time in situ monitoring of bacterial concentrations in wounds. This biosensor employs a colorimetric hemicyanine dye (HCy) probe, which changes color in response to bacterial lipase, a common secretion in infected wounds. To enhance the biosensor's sensitivity, we incorporated two key materials science strategies: aligning the nanofibers to promote efficient bacterial attachment and localization and integrating Tween 80, a surfactant, within the nanofiber matrix. This combination of physical and chemical cues results in a notable increase in lipase activity. The cross-aligned core-shell nanofibers, embedded with Tween 80 and HCy, demonstrate an immediate and distinct color change when exposed to as low as 3.0 × 104 CFU/cm2 of common pathogens such as Pseudomonas aeruginosa and MRSA. Significantly, the presence of Tween 80 amplifies the colorimetric response, making visual detection more straightforward and four times more pronounced. Our nanobiosensor design facilitates the detection of low-concentration bacterial infections in situ without the need to remove wound dressings. This advancement marks a significant step forward in real-time wound monitoring, offering a practical tool for the early detection of clinical bacterial infections.

A Color-Changing Biomimetic Material Closely Resembling the Spectral Characteristics of Vegetation Foliage.

Multispectral/hyperspectral technologies can easily detect man-made objects in vegetation by subtle spectral differences between the object and vegetation, and powerful reconnaissance increases the demand for camouflage materials closely resembling vegetation spectra. However, previous biomimetic materials have only presented static colors that cannot change color, and camouflage in multiple bands is difficult to achieve. To address this challenge, inspiration is drawn from the color change of foliage, and a color-change model is proposed with active and static pigments embedded in a matrix medium. The color of a composite material is dominated by the colored active pigment, which conceals the color of the static pigments and the color is revealed when the active pigment fades. A color-changing biomimetic material (CCBM) is developed with a solution casting method by adopting microcapsuled thermochromic pigments and chrome titanate yellow pigments as fillers in a base film with polyvinyl alcohol and lithium chloride. A Kubelka-Munk four-flux model is constructed to optimize the component proportions of the CCBM. The material has a reversible color change, closely resembles the foliage spectrum in UV-vis-NIR ranges, and imitates the thermal behavior of natural foliage in the mid-infrared regime. These results provide a novel approach to multispectral and hyperspectral camouflage.

Authenticity identification of high - Temperature Daqu Baijiu through multi-channel visual array sensor of organic dyes combined with smart phone App.

High - temperature Daqu Baijiu faces a challenge from illegal adulteration of high-grade Baijiu bottles with low-grade Baijiu, affecting its quality and value. This study developed a rapid identification method for high temperature Daqu Baijiu with the same aroma type using a four-channel visual array sensor and detection of color changes caused by competition coordination with Zn2+ and color-changing organic dyes. The array sensor demonstrated high stability and repeatability in targeting flavor components and achieved 97.78 % or more accuracy combined with DD-SIMCA model in detecting adulteration across the Baijiu with same aroma type. The results of GC-MS and Quantum Chemical Calculation showed that esters, acids, and pyrazines played a crucial role. The smart phone App could quickly identify the authenticity of Baijiu with accuracy achieved 93 %. This research provides a foundation for rapid and reliable assessment of Baijiu quality and authenticity, enabling the industry to combat fraudulent practices effectively.

Characterization and Application of Guar Gum/Polyvinyl Alcohol-Based Food Packaging Films Containing Betacyanins from Pokeweed (Phytolacca acinosa Roxb.) Berries and Silver Nanoparticles.

Food packaging films were prepared by using guar gum/polyvinyl alcohol (GP) as the film matrix, 2% Ag nanoparticles (AgNPs) as reinforcing filler and antimicrobial agent, and 1%, 2% and 3% pokeweed betacyanins (PB) as the colorant and antioxidant agent. The structures and color-changing, barrier, mechanical, thermal and antioxidant/antibacterial properties of different films were measured. The results show that the PB were pH-sensitive pigments with pink, purple and yellow colors at pH 3-8, pH 9-11 and pH 12, respectively. PB improved the compatibility of guar gum and polyvinyl alcohol through hydrogen bonds. The films with PB showed a color-changing capacity under ammonia vapor and good color stability in chilled storage. AgNPs and PB elevated the barrier capacity of GP film to light, water vapor and oxygen gas. Meanwhile, AgNPs and PB improved the stiffness, thermal stability and antioxidant/antibacterial activity of GP film. The film with AgNPs and 3% PB showed the highest barrier capacity, stiffness, thermal stability and antioxidant/antimicrobial activity. In shrimp spoilage test, the films with AgNPs and 2% and 3% PB indicated shrimp freshness through film color changes. The results reveal the potential use of the prepared films in active and smart packaging.

Study on the color-changing mechanism and law of visual formaldehyde sensing system based on hyperbranched polyamines.

This study focuses on addressing the limitations associated with most chemical derivatization methods commonly used for formaldehyde detection. These methods often suffer from prolonged derivative times (≥30 min) and complex procedures, which hinder their ability to meet the requirements of real-time and accurate sensing. In this research, a novel formaldehyde indicator system based on hyperbranched polyamine molecule was developed, and its mechanism and principles of color change were investigated. The findings revealed that hyperbranched polyamine molecule effectively reacts with formaldehyde, leading to a reduction in electron cloud density in the amine group N and subsequently causing a decrease in pH value. This reaction enables the visualization of formaldehyde detection through changes in the indicator spectrum. Moreover, the spectral variation pattern exhibits a strong linear correlation with the formaldehyde concentration when the PAMAM concentration is optimized. The detection limit of this method was determined to be 1.8 ppm. Notably, the reaction between PAMAM and formaldehyde is almost instantaneous, the color change is insensitive to temperature, and the method demonstrates high selectivity. Overall, this research contributes to the advancement of real-time formaldehyde monitoring technology and provides insights for future developments in this field.

Enhanced fresh-keeping capacity of printed surimi by Ca2+-nano starch-lutein and its nondestructive freshness monitoring based on 4D printed anthocyanin.

To solve undiscernible freshness changes of printed functional surimi while maintaining printed shape, 4D printable color-changing material were prepared. Firstly, based on results of printing properties and fresh-keeping of Ca2+-NS-L-surimi, it showed better printing effects (enhanced mechanical strength) and good preservation (inhibition of amino acids decomposition, bacterial growth). However, freshness changes of printed Ca2+-NS-L-surimi were not distinguished directly. To avoid that, 4D printable color-changing material-anthocyanin-hydroxypropyl methyl cellulose-xanthan gum-carrageenan (AHXK) was prepared for indicating freshness through discoloration. Printing results showed AHX with 5 % K had the most suitable mechanical strength (appropriate gel strength, texture, rheology) for printing. Based on that, AHXK had stable color (ΔE fluctuation <5) and was sensitive to pH and ammonia (obvious discoloration; ΔE > 10). Actual freshness monitoring results (co-printing of AHXK-surimi) exhibited significant discolorations, especially for HXK with 0.75 % A. It became green during refrigeration of 3-5 d (keeping fresh, ΔE < 4), brighter green at 7 d (decreased freshness, ΔE > 6), turned yellow at 9 d (spoilage, ΔE > 16), which were distinguished significantly with naked eyes rather than traditional freshness determining. In conclusion, printed AHXK-functional surimi exhibited good printing, preservation and nondestructive freshness monitoring, facilitating application of 3D printed functional surimi.

Multi-Stimuli Dually-Responsive Intelligent Woven Structures with Local Programmability for Biomimetic Applications.

This work focuses on multi-stimuli-responsive materials with distinctive abilities, that is, color-changing and shape-memory. Using metallic composite yarns and polymeric/thermochromic microcapsule composite fibers, processed via a melt-spinning technique, an electrothermally multi-responsive fabric is woven. The resulting smart-fabric transfers from a predefined structure to an original shape while changing color upon heating or applying an electric field, making it appealing for advanced applications. The shape-memory and color-changing features of the fabric can be controlled by rationally controlling the micro-scale design of the individual fibers in the structure. Thus, the fibers' microstructural features are optimized to achieve excellent color-changing behavior along with shape fixity and recovery ratios of 99.95% and 79.2%, respectively. More importantly, the fabric's dual-response by electric field can be achieved by a low voltage of 5 V, which is smaller than the previously reported values. Above and beyond, the fabric is able to be meticulously activated by selectively applying a controlled voltage to any part of the fabric. The precise local responsiveness can be bestowed upon the fabric by readily controlling its macro-scale design. A biomimetic dragonfly with the shape-memory and color-changing dual-response ability is successfully fabricated, broadening the design and fabrication horizon of groundbreaking smart materials with multiple functions.

Proteomics study of mitochondrial proteins in tilapia red meat and their effect on color change during storage.

The underlying mechanism of the role of mitochondria in color changing of tilapia fillet during 0-4 d storage is not completely clear. A total of 209 differentially significant expressed proteins (DSEPs) were identified by using label-free mitochondrial proteomics, with 56 proteins up-regulated in T2 and 61 proteins (up-regulated) in T3. Protein-Protein interaction reveled proteins which participate in TCA cycles (Citrate synthase (cs)), Oxidoreductase (Malate dehydrogenase (mdh1, mdh2), Succinyl-CoA (Oxct1), Hydroxyacyl-coenzyme a dehydrogenase (hadh), Dehydrogenase/reductase (SDR family) member 1 (dhrs1)) interacted strongly with each other. In turn, they can increase the level of mitochondrial respiration and mitochondrial function, leading to color changing of tilapia fillet. The heat shock 60kD protein 1 (chaperonin, hspd1) interacted with metabolic enzymes (cs and mdh2) and had important effects on color. These results could help researchers better understand the color changing mechanism on the surface of tilapia fillet during the storage.

Preparation of Wide-Domain pH Color-Changing Nanocapsules and Application in Hydrogel Fibers.

In recent years, there has been an increase in demand for pH color-changing materials. These materials can visually communicate signals to people by connecting pH changes with color information. Embedding pH indicators into fibers to create flexible color-changing materials is an effective way to develop daily wearable products. For the stability of the indicator and the indirect contact of the indicator with the human body, it is usually necessary to encapsulate it in capsules. In this study, different pH indicators (Thymol Blue-TB, Bromocresol Green-BCG, and Bromocresol Purple-BCP) were mixed into a wide-domain pH color-changing indicator and encapsulated with ethyl cellulose (EC) by the flash nanoprecipitation (FNP) method using a new-type droplet-shaped confined impinging jet mixer. The effects of flow rate, core-to-wall ratio, and mixed solution concentration on the formation of the nanocapsules were investigated. In addition, the morphology, particle size, size distribution, dispersion stability, and encapsulation efficiency were systematically studied. At a core-to-wall ratio of 1:2, a mixed solution with a concentration of 6 mg/mL and a feed flow rate of 40 mL/min produced nanocapsules with an average particle size of 141.83 ± 0.98 nm and a PDI of 0.125 ± 0.01. Furthermore, a zeta potential with a range of -31.83 ± 0.23 mV and an encapsulation efficiency of 75.20 ± 1.72% were observed at 1:2 core-to-wall ratios. It was concluded that the color of the nanocapsules continuously changed from yellow to green and green to blue when the pH range was increased from 3 to 10. The color-changing nanocapsules were then embedded into sodium alginate hydrogel fibers, resulting in the same color-changing trend (pH 3-10) as that obtained for the nanocapsules. This study can be useful for the pH monitoring of various body fluids, such as wound exudate, urine, and sweat.

An "Instantaneous" Response of a Human Visual System to Hue: An EEG-Based Study.

(1) The article presents a new technique to interpret biomedical data (EEG) to assess cortical responses to continuous color/hue variations. We propose an alternative approach to analyze EEG activity evoked by visual stimulation. This approach may augment the traditional VEP analysis. (2) Considering ensembles of EEG epochs as multidimensional spatial vectors evolving over time (rather than collections of time-domain signals) and evaluating the similarity between such vectors across different EEG epochs may result in a more accurate detection of colors that evoke greater responses of the visual system. To demonstrate its suitability, the developed analysis technique was applied to the EEG data that we previously collected from 19 participants with normal color vision, while exposing them to stimuli of continuously varying hue. (3) Orange/yellow and dark blue/violet colors generally aroused better-pronounced cortical responses. The selection of EEG channels allowed for assessing the activity that predominantly originates from specific cortical regions. With such channel selection, the strongest response to the hue was observed from Parieto-Temporal region of the right hemisphere. The statistical test-Kruskal-Wallis one-way analysis of variance-indicates that the distance evaluated for spatial EEG vectors at different post-stimulus latencies generally originate from different statistical distributions with a probability exceeding 99.9% (α = 0.001).

Stretchable Soft Composites with Strain-Induced Architectured Color.

Colors enable interaction and communication between living species in a myriad of biological and artificial environments. While living organisms feature low-power mechanisms to dynamically control color in soft tissues, man-made color-changing devices remain predominantly rigid and energy intensive. Here, architectured composites that display striking color changes when stretched in selective directions under ambient light with minimum power input are reported. The orientation-dependent color change results from the rotation of reflective coated platelets that are embedded in a soft polymer matrix and pre-aligned in a well-defined architecture. The light reflected by the platelets generates structural color defined by the oxide coating on the platelet surface. By magnetically programming the initial orientation and spatial distribution of selected platelets within the soft matrix, composites with strain-modulated color-changing effects that cannot be achieved using state-of-the-art technologies are created. The proposed concept of strain-induced architectured color can be harnessed to develop low-power smart stretchable displays, tactile synthetic skins, and autonomous soft robotic devices that undergo fast and reversible color changes through the mechano-optic coupling programmed within their soft composite architecture.

Covalent immobilization of bromocresol purple on cellulose nanocrystals for use in pH-responsive indicator films.

This study developed pH-indicator films by combining esterified cellulose nanocrystals (e-CNCs) with activated bromocresol purple (a-BCP) via covalent bonding for pH-sensitive color-changing applications. The e-CNC/a-BCP particles were incorporated into cellulose acetate polymer to prepare pH-sensitive color changing films. Binding of a-BCP to e-CNCs was proven by attenuated total reflection infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Colorimetric analysis showed that films containing 10% or 15% e-CNC/a-BCP particles had critical color changes either at pH 4-5, or pH 7-8. The films with 10% e-CNC/a-BCP particles also revealed excellent leaching resistance under acidic conditions. Color changes were reversible between pH 2 and 10. These pH-indicator films had visible color changes in response to pH variations, color reversibility, leaching resistance, and sufficient rigidity even though mechanical properties decreased as the e-CNC/a-BCP content increased from 0% to 15%.

Bioinspired Multi-Stimuli Responsive Actuators with Synergistic Color- and Morphing-Change Abilities.

The combination of complex perception, defense, and camouflage mechanisms is a pivotal instinctive ability that equips organisms with survival advantages. The simulations of such fascinating multi-stimuli responsiveness, including thigmotropism, bioluminescence, color-changing ability, and so on, are of great significance for scientists to develop novel biomimetic smart materials. However, most biomimetic color-changing or luminescence materials can only realize a single stimulus-response, hence the design and fabrication of multi-stimuli responsive materials with synergistic color-changing are still on the way. Here, a bioinspired multi-stimuli responsive actuator with color- and morphing-change abilities is developed by taking advantage of the assembled cellulose nanocrystals-based cholesteric liquid crystal structure and its water/temperature response behaviors. The actuator exhibits superfast, reversible bi-directional humidity and near-infrared (NIR) light actuating ability (humidity: 9 s; NIR light: 16 s), accompanying with synergistic iridescent appearance which provides a visual cue for the movement of actuators. This work paves the way for biomimetic multi-stimuli responsive materials and will have a wide range of applications such as optical anti-counterfeiting devices, information storage materials, and smart soft robots.

Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material.

Chitosan and pectin films were enriched with blackcurrant pomace powder (10 and 20% (w/w)), as bio-based material, to minimize food production losses and to increase the functional properties of produced films aimed at food coatings and wrappers. Water vapor permeability of active films increased up to 25%, moisture content for 27% in pectin-based ones, but water solubility was not significantly modified. Mechanical properties (tensile strength, elongation at break and Young's modulus) were mainly decreased due to the residual insoluble particles present in blackcurrant waste. FTIR analysis showed no significant changes between the film samples. The degradation temperatures, determined by DSC, were reduced by 18 °C for chitosan-based samples and of 32 °C lower for the pectin-based samples with blackcurrant powder, indicating a disturbance in polymer stability. The antioxidant activity of active films was increased up to 30-fold. Lightness and redness of dry films significantly changed depending on the polymer type. Significant color changes, especially in chitosan film formulations, were observed after exposure to different pH buffers. This effect is further explored in formulations that were used as color change indicators for intelligent biopackaging.