Irreversible Color Change Research Articles

Fundamental Aspects of Stretchable Mechanochromic Materials: Fabrication and Characterization.

Mechanochromic materials provide optical changes in response to mechanical stress and are of interest in a wide range of potential applications such as strain sensing, structural health monitoring, and encryption. Advanced manufacturing such as 3D printing enables the fabrication of complex patterns and geometries. In this work, classes of stretchable mechanochromic materials that provide visual color changes when tension is applied, namely, dyes, polymer dispersed liquid crystals, liquid crystal elastomers, cellulose nanocrystals, photonic nanostructures, hydrogels, and hybrid systems (combinations of other classes) are reviewed. For each class, synthesis and processing, as well as the mechanism of color change are discussed. To enable materials selection across the classes, the mechanochromic sensitivity of the different classes of materials are compared. Photonic systems demonstrate high mechanochromic sensitivity (Δnm/% strain), large dynamic color range, and rapid reversibility. Further, the mechanochromic behavior can be predicted using a simple mechanical model. Photonic systems with a wide range of mechanical properties (elastic modulus) have been achieved. The addition of dyes to photonic systems has broadened the dynamic range, i.e., the strain over which there is an optical change. For applications in which irreversible color change is desired, dye-based systems or liquid crystal elastomer systems can be formulated. While many promising applications have been demonstrated, manufacturing uniform color on a large scale remains a challenge. Standardized characterization methods are needed to translate materials to practical applications. The sustainability of mechanochromic materials is also an important consideration.

Recording thermal history of pork meat by self-coloration gel

For real-time dynamic quality evaluation of pork meat, the thermal accumulation monitoring for the entire period is essential. The research aims to develop a novel covalent organic framework (COF) gel capable of recording such information. The COF with self-responsive irreversible color change property was synthesized using benzene-1,3,5-tricarboxaldehyde, 2,5-diamino-1,4-benzenedithiol dihydrochloride and p-phthalaldehyde as monomers. The thermal accumulation was monitored based on the COF over a broad temperature range (−22 °C–55 °C), which covered the storage temperatures of the pork meat. The results were easily readable by series visible color variations (yellow, green, blue and dark blue) displayed by COF during the thermal accumulation monitoring in the temperature range (25 °C–55 °C) of study. At the lower temperature (−22 °C–4 °C), small variation of the thermal information can be effectively represented by quantitative analysis. The color change rates were in the order of k-22 °C < k4°C < k25 °C < k35 °C < k55 °C. The activation energy of reaction was 65.31 kJ mol−1. The indicator gel was prepared by the COF combining with carrageenan in pure aqueous medium. The potential application of the COF gel for real-time monitoring the dynamic quality change of pork samples was investigated. The response signals of the COF gel were well matched with the growth rate of microbe in pork meat. The proposed COF gel based thermal history indicator is promising for real-time monitoring dynamic quality changes of pork meat during the cold supply chain.

Irreversible temperature indicator based cellulose membranes conjugated with leuco‐dye pigment

AbstractThis research focuses on the development of thermochromic membranes made of cellulose acetate (CA) for temperature monitoring of sensitive food products. Two dual TC membranes developed for the control of different temperature ranges were formulated using a three‐component system: a leuco‐dye membrane (crystal violet lactone, CVL) integrated with an acidic membrane containing the color developer (salicylic acid) and the acidic solvent with different melting points (decanoic acid, DA, or methacrylic acid, MA). The CVL membrane, together with the DA membrane, showed an irreversible color change when exposed to 35°C, which was facilitated by the melting of DA. The CVL membrane also underwent an irreversible color change when exposed to 15°C together with the MA membrane. The membranes were characterized in detail using scanning electron microscopy. The evaluation of color changes, reproducibility, specificity, and stability ensured the practical suitability of these membranes. Overall, this innovative approach has proven to be a reproducible, sustainable, cost‐effective method to produce irreversible colorimetric temperature sensors. These sensors have significant potential for applications in the food and pharmaceutical industries and offer a promising way to improve product safety and quality.

Influence of a polymeric gel on the in situ electropolymerization of 3,4-ethylenedioxythiophene and application in irreversible electrochemical indicators

Electropolymerization triggered inside of a pre-assembled device can produce a high-contrast, visually irreversible color change. This format of electrochemical indicator has potential applications in a broad range of commercial sectors, including authenticity labeling, healthcare, food packaging, and logistics. However, there is limited work exploring how polymer gel electrolytes, which are commonly employed in flexible electrochemical devices, influence the electropolymerization process. Here, we study the electrochemical polymerization of 3–4-ethylenedioxythiphene (EDOT) in a UV-curable ethylene oxide-propylene oxide-allyl glycidyl ether (EO-PO-AGE) polymer gel electrolyte. Using potential step methods and cyclic voltammetry, we find that the addition of the polymer gel matrix lowers the overpotential required for film formation by 0.1 V compared to the liquid electrolyte. Furthermore, indicators with the polymer gel electrolyte show an increase in coloration efficiency, and greater visual homogeneity compared to indicators with the liquid electrolyte.Graphical

Chromic textiles: Colour fastness properties and irreversible colour change behaviour of textiles screen printed with thermochromic, photochromic and hydrochromic colourants

AbstractThe objective of this work was to study how ultraviolet (UV) light exposure, washing and rubbing can influence colour and dynamic qualities of chromic textiles, and to explore how the results attained can be applied by designers for the development of colour changing palettes. The experimental work was conducted with 74% polyamide and 26% elastane elastics screen printed with thermochromic, photochromic and hydrochromic pigments in diverse colours. Initially, colourfastness properties of each pigment type versus colour were assessed. Although washing and rubbing can interfere in samples' colours by becoming lighter at different degrees, the results attained highlight the poor stability to lighting of thermochromic and photochromic pigments, which also present changes between hues along exposure time. For conventional textile applications, poor colour fastness commonly represents a limitation. This work proposes that the way textile colours and behaviour are permanently affected by the studied conditions can be interpreted as a creative variable in the design process. Research samples with a combination of pigments were developed and tested with a combination of cycles of different fastness tests, namely one washing cycle for every 4 h of UV light exposure, totalling 48 h and 12 washing cycles. Results demonstrate the possibility of creating interactive surfaces capable of displaying a wide range of colours that evolve to static within different hues, over stimuli conditions.

Stimuli‐Responsive Sponge for Imaging and Measuring Weak Compression Stresses

Imaging and measuring compression stresses secure a safe and healthy life. Compression stresses in kPa range are not easily detected by conventional mechanoresponsive materials because microscopic molecular motion of the chromophores is not induced by such weak stresses. Moreover, imaging of the stress distribution is not achieved so far. The present study shows a sponge device combining two stimuli-responsive materials, a capsule releasing interior liquid and color-changing polymer in responses to compression stress and chemical stimulus, respectively. The stimuli-responsive capsule is dispersed on a melamine sponge comprised of the fibers with coating the layered polydiacetylene (PDA). The application of weak compression stresses induces collapse of the capsules, outflow of the interior liquid, and subsequent irreversible color change of PDA. The cascading response in the sponge device colorimetrically enables imaging of the distribution and measuring the strength of the compression stresses in kPa range. Furthermore, the device demonstrates imaging and measuring unknown weak compression stresses applied by the irregular-shaped objects. A couple of clinical issues in surgical operation of intestine are studied using the stress-imaging sponge device. The device and its design strategy can be applied to stress imaging in a variety of fields.

Dual bacterial strains TTI for monitoring fish quality in food cold chain.

Most microbial time-temperature indicators (TTIs) considered only one spoilage strain. This research compared single and dual spoilage strains-based microbial TTI for quality changes of chilled grouper fish (Epinephelus fuscoguttatus x E. lanceolatus) fillet products during distribution. The next-generation sequencing (NGS) and traditional plate count approach showed that Pseudomonas fragi and Vibrio parahaemolyticus were specific spoilage bacteria at 7 and 15°C. A dual-strain TTI response provides more accurate results than a single-strain TTI and provides an irreversible color change from yellow to reddish-brown, showing levels of fish freshness. The microbial TTI comprises fish spoilage bacteria strains with 3 log CFU/ml, a nutrient broth supplemented with 2% NaCl as a medium, and phenol red with 0.25 mg/ml as a pH indicator. Overall, this study points to the applicability of a dual-strain microbial TTI as a valuable tool for monitoring fish quality changes during cold chain break condition.

Transient Structural Colors with Magnesium‐Based Reflective Filters (Advanced Optical Materials 13/2022)

Marina S. Leite and co-workers (article number 2200159) demonstrate thin-film-based color filters using Mg and MgO, both biodegradable materials. The devices exhibit vivid hues spanning a broad gamut, besides angle-insensitive chromaticity up to 40 degrees. A transient color response is attained by etching the Mg-containing layers with water, which reveals the hue of a bottom Fabry–Pérot cavity structure. This approach enables pixels with irreversible color change as well as zero-power consumption and low cost, while making use of non-toxic materials.

Experimental evaluation of thermal stress on the surface of butterfly specimen through irreversible colour change of thermal paint

Gas Turbines have been used effectively and extensively in jet propulsion and the sectors of electricity production. The flame produced due to combustion of air & fuel propagates through the gas turbine’s parts. As the hot combustible gases flow through these components, high thermal stresses are imposed on these components. The material life of the individual elements of the gas turbine system depends on its operating temperature and thermal stress. To achieve higher efficiency, the operating temperature may be increased to a certain level. Temperature (or) thermal profiling of the engine components is mandatory to make the engine design reliable. Thermal paint used for temperature profiling of hot surfaces is estimated to be the structured method even after removing the heat source. The present research concentrates on the investigations on the evaluation of thermal stress induced on a hot specimen through the application of thermal paint. A butterfly specimen made of Mild Steel has been fabricated and used for the present experimental investigations. The current work also concentrates on the variation in the surface temperature of the specimen based on the heat input using the butterfly specimen. The colour change on the surface of the specimen has been related to temperature using the RGB values of colour through MATLAB’s fuzzy logic. The results of the experimental investigation prove that the usage of thermal paint reveals the exact deal of stress developed thermally on the surface of the specimen based on the colour change.

Design and synthesis of polydiacetylenes, and their low temperature irreversible thermochromic properties

A thermochromic material that show irreversible color change at or below freezing temperatures has potential utility as a temperature indicator for frozen food and meat products, therefore, the goods transporters and customers would easily recognize when the goods exposed to high temperatures during their storage and delivery. In this study, we have successfully synthesized and used polydiacetylenes functionalized with glycol ester groups as a thermochromic dye, which show irreversible thermochromic behavior at below freezing temperatures. The photochromic and thermochromic properties of diacetylenes were investigated in the solid state, and color-transition temperatures for poly(DCDA-EGME), poly(DCDA-DGME) and poly(DCDA-TGME) were found to be 2, −10 and −16 °C, respectively. Moreover, we prepared a paper test strip and used as a warning indicator for deep freeze products.

Indicator Dyes and Catalytic Nanoparticles for Irreversible Visual Hydrogen Sensing

Using ultraviolet-visible (UV-vis) absorption spectroscopy, we have tested the reactivity of various indicator molecules combined with catalytic bimetallic gold-palladium nanoparticles (Au-Pd NPs) in solution for an irreversible and visual response to H2. Our aim was to identify the most suitable indicator/Au-Pd NP system for the future development of a thin, wearable, and visual H2 sensor for noninvasive monitoring of in vivo Mg-implant biodegradation in research and clinical settings with fast response time. The indicators studied were bromothymol blue, methyl red, and resazurin, and the reactions of each system with H2 in the presence of Au-Pd NPs caused visual and irreversible color changes that were concluded to proceed via redox processes. The resazurin/Au-Pd NP system was deemed best-suited for our research objectives because (1) this system had the fastest color change response to H2 at levels relevant to in vivo Mg-implant biodegradation compared to the other indicator/Au-Pd NP systems tested, (2) the observed redox chemistry with H2 followed well-understood reaction pathways reported in the literature, and (3) the redox products were nontoxic and appropriate for medical applications. Studying the effects of the concentrations of H2, Au-Pd NPs, and resazurin on the color change response time within the resazurin/Au-Pd NP system revealed that the H2-sensing elements can be optimized to achieve a faster or slower color change with H2 by varying the relative amounts of resazurin and Au-Pd NPs in solution. The results from this study are significant for future optical H2 sensor design.

Thermal history analysis on a hot surface using temperature indicating paints

Temperature-sensitive paint (or) Temperature indicating paint (or) Thermal paint is a kind of coating to measure the temperature distribution (or) profile through its colour change. Thermal paint is considered to be one of the most efficient ways for temperature measurement. The analysis of these paints can be done through the observation of irreversible colour change with temperature. This paper describes the investigations done on the chemistry and behaviour of thermal paints with respect to temperature and time. The study also focuses on the calibration of thermal paints in both experimental and computational methods. In the experimental methods, the results hold in good agreement with K-type thermocouples as well as the computational results of ANSYS also provide similar results. The experimental thermal map of a butterfly specimen has been observed through the continuous exposure of thermal paint MC 350-8 to the continuous flame.

Surface temperature measurement of gas turbine combustor using temperature-indicating paint

ABSTRACT Surface temperature measurement of a hot surface is necessary in order to determine its thermal life. The combustors used in gas turbine systems may be subject to high thermal load due to continuous combustion. In order to analyse the surface temperature distribution of combustor, temperature-sensing instruments are necessary. Temperature-indicating paint is a kind of coating to measure the temperature distribution through its colour change. Temperature-indicating paint is considered to be one of the most efficient ways for temperature measurement. The analysis of this paint can be done through the observation of irreversible colour change with temperature. This work deals with the fabrication of gas turbine combustor, investigates the thermal distribution and finds the hot spots of the combustor using temperature-indicating paint.

High Temperature Sensing and Detection for Cementitious Materials Using Manganese Violet Pigment

In recent years, advanced materials have attracted considerable interest in the field of temperature detection and sensing. This study examined the thermochromic properties of inorganic manganese violet (MV) with increasing temperature. According to the thermochromic test, the material was found to have reversible and irreversible color change properties. The MV pigment was then applied to cementitious material at ratios of 1%, 3%, and 5%. The mixed cement samples with MV pigment were heated in a furnace, and digital images were captured at each temperature interval to evaluate the changes in the color information on the surface of the specimen. The mixed samples exhibited an irreversible thermochromic change from dark violet to grayish green above 400 °C. At the critical temperature of 440 °C, the RGB values increased by approximately 22%–55%, 28%–68%, and 7%–25%, depending on the content of MV pigment. In Lab space, the L value increased by approximately 23%–60% at 440 °C. The a value completely changed from positive to negative, and the b value changed from negative to positive. All the values differed according to the content of MV pigment at room temperature but approached similar ranges at the critical temperature, irrespective of the amount of MV pigment. To assess the changes in their microstructure and composition, scanning electron microscopy and energy dispersive X-ray spectroscopy were performed on the samples exposed to temperatures ranging from room temperature to 450 °C.

Anthocyanin immobilization in carboxymethylcellulose/starch films: A sustainable sensor for the detection of Al(III) ions in aqueous matrices

A robust and sustainable sensor for the detection of Al(III) ions in water was developed by immobilization of anthocyanin (AN) from black rice in a film formed by carboxymethylcellulose (CMC) and starch. Characterization of the films was performed using solubility, thickness, FTIR, and mechanical analysis. The film exhibited an irreversible color change from red to purple in response to the presence of Al(III). The best colorimetric response of the sensor was observed at pH 4.5 and a time of 60 min, achieving the detection of 3 mg L−1 of Al(III). For concentrations higher than 5 mg L−1, the sensor response time decreased to 20 min. The minimum Al(III) concentration detected with the naked eye was lower than the maximum permissible concentrations in aqueous effluents according to different legislations, indicating the potential of this study to develop sensors for the detection of Al(III).

Reversible and Irreversible Color Change during Photo and Thermal Degradation of PolyphenyleneSulfide Composite.

The effect of the light spectral composition and temperature on the change of color characteristics and reflection spectra during the irradiation of polyphenylene sulfide reinforced by short glass fibers in the SUNTEST apparatus was analyzed. The scales of reversible color change upon successive exposure to total radiation corresponding to the sunlight spectrum and to visible light wereevaluated and the possible mechanisms for the observed effects are discussed. The features of the color change upon visible light irradiation of previously thermally aged samples wereconsidered. Possible causes for deviation from the Arrhenius law during thermal aging of the composite are discussed. It wasdemonstrated that even with a significant change in color, the physicomechanical and electrotechnical characteristics of the composite only changedslightly or remained virtually at the same high level.

Pressure-Induced Emission Enhancement and Multicolor Emission for 1,2,3,4-Tetraphenyl-1,3-cyclopentadiene: Controlled Structure Evolution.

Mechanoresponsive luminescent (MRL) materials have attracted considerable attention because of their potential applications in mechanical sensors, memory chips, and security inks; MRL materials possessing high efficiency and multicolor emission qualities are especially interesting. In this Letter, we found 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPC) crystal exhibited both pressure-induced emission enhancement (PIEE) and multicolor behavior. In addition, infrared spectroscopy analysis indicated that the ring-opening reaction of the phenyl ring occurred when pressure was beyond 24.7 GPa. The reaction was promoted from 24.7 to 35.9 GPa, which resulted in the redder irreversible color change for the sample released from 35.9 GPa than from 24.7 GPa. The results regarding the mechanoresponsive behavior of TPC offered a deep insight into PIEE and multicolor properties from the structural point of view and inspired the idea of capturing different colors by hydrostatic pressure, which will facilitate the design of and search for high-performance MRL materials.

Research progress of packaging indicating materials for real-time monitoring of food quality

The rapid development of cold-chain transportation necessitates consumers to present high requirements on safety and freshness of fresh food in recent years. The quality and taste of fresh food can be monitored and controlled through the intelligent packaging technologies and new food packaging materials such as time-temperature indicators (TTIs), Radio Frequency Identification (RFID), biological composites and polymer nanocomposites. Based on different packaging materials, indicators and sensors are employed in food packaging for real-time detection of information about freshness, temperature, microbiological, and shelf life of products in the supply chain. Wide varieties of packaging materials are suitable for providing intelligent and smart properties for food packaging, such as oxygen scavenging capability, antimicrobial activity, and recording the thermal history. Due to the special properties of prepared materials, TTIs are used to point out the remaining shelf life of perishable products throughout the supply chain. Compared with others, they have the advantages of low cost, small size and convenient indication. Additionally, the TTIs can effectively solve food quality and safety problems caused by temperature fluctuation in supply chain. Since the irreversible color change of TTIs, the food safety situation would be shown intuitively. Currently, the TTIs were widely used in application of food packaging by providing safety information. However, the application is also accompanied with some deficiencies such as the accuracy of monitoring, migration of toxic substances, stability and expensive cost etc. This review will deeply discuss the preparation of various types of TTIs based on different package indicating materials with a particular emphasis on how to improve their accuracy and stability, control the migration of toxic substances and to develop new TTIs.

Amylase based enzymatic time temperature indicator (TTI) as thermal abuse marker for frozen chicken meat

Amylase based enzymatic time temperature indicator (TTI) was prepared using starch as substrate and enzyme amylase to monitor thermal abuse history of frozen (−18±2°C) chicken meat during supply chain. TTI showed an irreversible distinct colour change from initial bluish black colour to intermediate light yellow colour to final irreversible white yellow during temperature abuse conditions at 15±1, 25±1 and 35±1°C except 5±1°C. At different temperature abuse conditions viz., 15±1°C, 25±1°C and 35±1°C, quantitative changes in various parameters of chicken meat were evaluated and correlated with distinct colour alterations of TTI. The values for FAA, TVBN and instrumental colour analysis were beyond the meat safety limit at 35±1°C but within the limit at 15±1°C and 25±1°C at final colour changes of TTI. However, pH and microbiological parameters values were within the meat safety limit at 15±1, 25±1 and 35±1°Cat final colour changes of TTI. The results showed significant correlation of meat quality parameters with colour changes in TTI at 35±1°C and non-significant correlation of meat quality parameters with colour changes in TTI at 15±1 and 25±1°C. So, changes in quality characteristics of frozen chicken meat are not adequately indicated by TTI after exposure to different temperature abuse conditions. Therefore, amylase based enzymatic TTI has lesser applicability for utilization of quality marking of frozen chicken meat at different temperature abuse conditions.

Synthesis and Irreversible Thermochromic Sensor Applications of Manganese Violet.

An irreversible thermochromic material based on manganese violet (MnNH4P2O7) is synthesized. The crystal phase, chemical composition, and morphology of the synthesized material are analyzed using X-ray diffraction, scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, and Fourier-transform infrared spectroscopy. The absorption spectra of the synthesized material are obtained using a UV-Vis spectrometer, and the thermochromism exhibited by the powdered samples at high temperatures is also investigated. The as-synthesized manganese violet pigment consists of pure α-MnNH4P2O7 phase. In addition, the synthesized pigment largely consists of hexagonal crystals with a diameter of hundreds of nanometers. On heating, the pigment simultaneously loses H2O and NH3 in two successive steps at approximately 330–434.4 °C and 434.4–527 °C, which correspond to the formation of an intermediate phase and of Mn2P4O12, respectively. An overall mass loss of 14.22% is observed, which is consistent with the expected 13.79%. An irreversible color change from violet to white is observed after exposure of the synthesized manganese violet pigment at 400 °C for 30 min. This is attributed to the oxidation of ammonia to hydroxylamine, which then decomposes to nitrogen and water, or alternatively to the direct oxidation of ammonia to nitrogen. Furthermore, we demonstrate the potential application of synthesized manganese violet in the production of irreversible thermochromic paint by mixing with potassium silicate solution as a binder and deionized water as a solvent at a specific ratio. The thermochromic paint is then applied in fabrication of irreversible thermochromic sensors by coating it onto a steel plate surface. Finally, we show that manganese violet-based irreversible thermochromic sensors are able to detect temperatures around 400 °C by changing color from violet to white/milky.