Thermochromic Research Articles

Multi-objective optimization of thermochromic glazing based on daylight and energy performance evaluation

Many efforts have been detected to investigate thermochromic (TC) glazing for improving building energy saving, while only a few approaches for daylight performance analysis. In this study, the performance of TC glazing is investigated based on multi-objective optimization for minimizing energy demand while maximizing daylight availability. The effects of five parameters including transition temperature, solar transmittance in clear state, solar transmittance modulation ability, luminous transmittance in clear state, and luminous modulation ability on the building energy consumption and useful daylighting illuminance (UDI300–3000) are examined. Linear Programming Technique for Multi-dimensional Analysis of Preference (LINMAP) is used for the decision-making of Pareto frontier. This research aims to explore the ideal thermochromic glazing by considering the daylight and energy performance of a typical office room, taking the weather condition of Xiamen, China as an example. Although it is impossible to achieve both optimal values of energy consumption and UDI300–3000 simultaneously, the proposed multi-objective optimization method could still provide low energy consumption with sufficient daylight. The non-dominated sorting of Pareto optimal solution (POS) demonstrated that the optimum building energy consumption and UDI300–3000 for single glazed windows are 46.64 kWh/m2 and 70.92%, respectively, while the values for double glazed windows are 44.40 kWh/m2 and 71.88%, respectively. The selected hypothetical TC windows can improve the building energy and daylighting performance simultaneously when compared with traditional clear single and double glazed windows. The presented framework provides a multi-objective optimization method to determine the most suitable TC glazing technologies for designers and architects during the design and retrofit procedure.

Investigating the energy saving potential of thermochromic coatings on building envelopes

Thermochromic (TC) materials can switch solar absorptance (α) based on temperature stimuli. When coatings with TC properties are applied on building envelope surfaces, the amount of solar heat gains can be controlled to reduce the heating and cooling demand of buildings. To date, limited research has been conducted in investigating optimal TC coating properties for application on opaque building envelopes in various scenarios.In this research, a method to model TC coatings using building performance simulation (BPS) tools has been developed and coupled with python to optimize solar absorption states (α) and switching temperatures and reduce the annual heating and cooling demand. The simulation-based approach has been employed to perform early-stage exploration studies on multiple building types and climates to support material R&D in developing optimized coatings for target applications and assess the potential energy savings.The results indicate that the optimum TC properties are unique to climate and building types. TC coatings with high switching temperatures result in larger energy savings for scenarios with high heating demands, while TC coatings with low switching temperatures produce larger energy savings in scenarios with high cooling demands. Similarly, increasing the high solar absorption (αhigh) to 1 increases the heating savings, while reducing the low solar absorption (αlow) to 0 results in higher cooling savings. Furthermore, it was found that solar irradiance causes temperature spikes triggering the TC coatings to unnecessarily switch from high to low absorptance state in winters leading to heating penalties. Replacing optimal static with TC coatings on terraced houses in the Spanish climate with a 2:3 heating to cooling demand ratio results in 2 to 13% energy savings.

Preparation and luminescence performance of thermochromic luminescent fiber based on reversible thermochromic red pigment

SrAl2O4: Eu2+, Dy3+ (SAOED) and Y2O2S: Eu3+, Mg2+, Ti4+ (YOS), as two kinds of important rare earth luminescent materials, are widely used in fibers due to their excellent luminescent properties. However, the lack of sensing property limits the application areas of the fibers in intelligent materials. In this work, the thermochromic luminescent fiber (TLF) was prepared by wet spinning from the cellulose acetate (CA)/dimethyl formamide (DMF) spinning solution. The rare earth luminescent materials serviced as the luminescent sources and thermochromic pigments (TP) acted as the thermochromic agent in this color changing system. The absorptivity curves and fluorescence spectra were recorded at 25 and 45 °C to investigate the thermosensitive characteristics of the fiber. The scanning electron microscope (SEM) observation presents that the TLFs were cylindrical with the diameters of 300–400 µm and three kinds of particles were evenly distributed in the cellulose matrix. X-ray diffraction (XRD) results confirm that cellulose matrix and the wet spinning process did not destroy the phase of rare earth luminescent materials in the fiber. Thermal stability of TLF was illustrated by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). Absorptivity and emission spectra measurement indicates that the TLF had perspicuous thermochromic luminescence properties. Decay curves showed that the TLF glowed continuously. This work exploits a new type of intelligent luminescent fiber that can respond to ambient temperature, which broadens its application in sensors.

Flexible electrochromic and thermochromic hybrid smart window based on a highly durable ITO/graphene transparent electrode

Abstract A flexible smart window with electrochromic (EC) and thermochromic (TC) properties is fabricated on a highly durable transparent indium-tin oxide (ITO)/graphene/polyethylene terephthalate (PET) electrode. An amorphous WO3 film and crystalline VO2 film are used as the EC and TC material, respectively, in the device. The ITO film deposited via atomic layer deposition acts as a protective layer and suppresses the plasma-induced damage of graphene, which typically occurs during the sputtering process. In this device, the amorphous WO3 film undergoes cathodic electrochromic reactions with high coloration efficiency, while the crystalline VO2 film shows characteristic thermochromic behavior. Thus, the flexible EC–TC hybrid smart window shows the controlled transmission of optical and solar energies according to the surrounding temperature and the applied voltage, allowing selective modulation of the visible and near-infrared light. The flexible EC–TC hybrid device is also very stable under mechanical bending, owing to the robust adhesion of the ITO film on the graphene support and the reduced plasma-induced damage of graphene. The fabricated high-performance, durable ITO/graphene/PET transparent electrode can pave the way for next-generation flexible optoelectronic devices as well as multifunctional flexible smart windows.

Microencapsulation of Thermochromic Material by Silicon Oxide Nanoparticles

This study is mainly focused on the fabrication of SiO2 as an inorganic shell material encapsulated an organic thermochromic (TC) core material comprises of either the (i) three-component as-synthesized blue dyes [BDTCM@SiO2] or (ii) off-the-shelf (commercial) black dyes [CDTCM@SiO2]. Both the SiO2 encapsulated thermochromic systems have successfully demonstrated the color transition at around 31 °C. For the three-component thermochromic microcapsules, we have used the crystal violet lactone (CVL) as a leuco dye, bisphenol-A (BPA) as a color developer, and 1-tetradecanol (TD) as a solvent. Different ratios of the thermochromic dye and the metal oxide were prepared to examine the effect of the core@shell ratio on the microstructural and thermal properties of the encapsulated microcapsules. The mean particles sizes of the BDTCM@SiO2 are below 100 nm, whereas, the CDTCM@SiO2 samples exhibited the mean particle sizes varied in a range of 100-1000 nm. The endothermic phase transition due to melting and in general, the thermal stabilities of these SiO2 encapsulated TCMs have been explored for the purpose of deploying these systems for thermal energy savings or storage applications.

Esthetic performance of thermochromic pigments in cataphoretic and sprayed coatings for outdoor applications

AbstractThis study aims to assess the aesthetical performances of thermochromic coatings for outdoor applications. In details, this work focuses on the efficiency of thermochromic pigments inside cataphoretic and sprayed primers, evaluating the possible synergic effect of a protective transparent topcoat. The structure of thermochromic pigments is examined by optical microscope, and their color‐changing behavior is evaluated by colourimetric measurements. Colourimetric analyses are also carried out to monitor the thermochromic performances of the coatings during exposure to an aggressive NaCl solution and UV‐B radiations, and to assess the protective role of the top‐coat. In addition to that, wet‐ and dry‐abrasion tests are carried out to define the suitability of these coatings for outdoor applications where good resistance to mechanical damage is required. Thus, this work evidences the better aesthetical features of the cataphoretic primer, which, however, particularly suffers from chemical–physical degradation processes. Nevertheless, the application of the transparent topcoat allows to maintain the integrity of the cataphoretic primer. The double‐layer coating exhibits a remarkable color‐changing behavior even when subjected to degradation phenomena due to exposure to aggressive environments.

Novel thermochromic (TC) and electrochromic (EC) characteristics of the V4O7 liquid crystal for LCDs and versatile optoelectronic applications

To form an electrochromic cell, the chemical reaction procedures were obeyed to prepare the V4O7 crystal suspended in a strong electrolytic HCl solution. Some of these suspended V4O7 crystals were injected between two sealed parallel ITOs/glass' slabs to construct an optoelectronic cell. A spray system technique was used to deposit the residue of the V4O7 solution as thin-film over glass' slabs. X-ray diffraction pattern (XRD), Field Emission Scanning electron microscopy (FESEM) with Energy Dispersive Analysis X-Ray (EDAX), and optical characterizations were used to inspect the obtained crystals. The structural investigations confirmed the hexagonal crystalline nature of the V4O7 crystal. The thermochromic (TC) and the electrochromic (EC) measurements showed that the studied V4O7 liquidus crystals have high sensitivity for the external either heat or the applied electric field. The applied thermal and electrical influences caused the direct optical band gap to change from 3.8 eV to 3.98 and 4.03 eV under EC and TC tests, respectively. The third-order nonlinear optical susceptibilities reached their maxima about 4.4 × 10−11 esu and 5.9 × 10−11 esu under TC and EC effects. The nonlinear refractive index was varied till reached 5.26 × 10−10 and 6.91 × 10−10 under TC and EC, respectively. Such properties plus optoelectronic response time about 1.5 mSec and high stability all qualifies this inorganic cell to be nominate for light modulation applications, i.e., optical filters, inorganic liquid crystals display (LCD), smart windows, optical switching, and optical fibers.

Luminescent polyurethane composite with real-time thermal response via visible signal

Visible signals are vital to human communication. Thermal signals are often difficult to observe unless they are in physical contact with the subject or an infrared thermal imaging system is used. In this study, we prepared a luminescent polyurethane composite (LPC), which can intelligently alter its colour and luminescence based on temperature. The LPC is fabricated from rare-earth luminescent materials (Sr2ZnSi2O7: Eu2+, Dy3+ and Y2O2S: Eu3+, Mg2+, Ti4+), a heat-sensitive rose-red TF-R1 thermochromic pigment (TP), polyurethane (PU), and polyester fabric. Microstructure and crystal structure analyses were carried out to determine the basic material properties of the LPC. The reflectivity and K S−1 value under different temperatures indicate that blue and green light were absorbed by LPC at 25 °C and the absorption decreased at 45 °C. This results in the LPC turning white. The emission spectra demonstrate that the quinoid structure of TP blocked the light of Sr2ZnSi2O7: Eu2+, Dy3+. Meanwhile, the lactone structure of TP allowed the light emission of Sr2ZnSi2O7: Eu2+, Dy3+ and Y2O2S: Eu3+, Mg2+, Ti4+. As a result, LPC emits red light at low temperatures and blue light at high temperatures. The advantage of the fabricated LPC is that the output can be easily manipulated into patterns. The uncured PU could form various graphics to cooperate with visible signals. Therefore, the LPC has significant potential as a functional material in smart clothing, flexible electronics, and wearable devices.

Optimization of the thermochromic glazing design for curtain wall buildings based on experimental measurements and dynamic simulation

Thermochromic (TC) glazing could provide a significant reduction of energy consumption in curtain wall buildings. However, each application requires a design tailored to building’s specifications. This paper proposes a complete approach for designing TC glaze based on building energy simulation starting from the production of thin thermochromic layers and the measurements of their optical properties by means of a customized spectrophotometer. The main focus of this work is to identify the optimal TC optical response that minimises the building energy consumption. Energy simulations have been performed for a virtual mock-up set at two locations with different climates, Italy and Poland. A set of profiles, each one determining thermochromic properties in terms of switching temperature, range of solar transmittance and transition speed, have been created with a fine step of temperature (2 °C) and used to simulate different scenarios. The outcome of the optimization provided the optimal properties to achieve the right balance between cooling energy reduction and heating energy increase due to the application of the thermochromic layer, in comparison to a standard clear glass. The fine step in switching temperature allowed to accurately estimate the subtle differences for the two different climates (25 °C Italy, 24–26 °C Poland). The highest impact has been found for the Italian location with a maximum reduction of total energy consumption of 22.8%. This was achieved with a thermochromic switching at 25 °C, with fast transition and range of transmittance between 0.1 (switched state) and 0.5 (normal state), which is a not extreme behaviour.

Electrospun microfibers with embedded leuco dye-based thermochromic material for textile applications

Electrospinning is an inexpensive and versatile technique for fabricating micro- and nano- scaled fibers. There have been limited attempts to employ it for the fabrication of thermochromic (TC) fibers, and the fabrication of a three-component (dye, developer, and solvent) TC material has required the use of a more complicated coaxial electrospinning technique. Herein, a simple and novel method for creating thermochromic fibers by electrospinning single strands of poly (methyl methacrylate) (PMMA) with embedded thermochromic powder of a polymer encapsulated three-component system was employed. Unlike past leuco dye-based thermochromic fibers, an unmodified syringe tip can be used for the spinning process and only one flow rate needs to be determined. A solution of solvent (either N-dimethylformamide or chloroform), PMMA, and a commercially available black thermochromic powder was prepared and spun using a custom-made electrospinning apparatus. The spun fibers exhibited a clear color transition from grey to white and had average diameters of 2.53 µm and 1.96 µm for chloroform and N-dimethylformamide based fibers, respectively. The fibers were characterized by scanning electron and optical microscopy to determine their morphology, Fourier transform infrared spectroscopy to determine their chemical composition, and differential scanning calorimetry and thermogravimetric analysis to characterize their thermal properties.

Effect of SiO2 coated leuco-dye based thermochromic pigment on the properties of Portland cement pastes

This study investigates the influence of silica-coated leuco dye-based thermochromic pigment (STC) on the properties of white Portland cement pastes. The surficial-SiO2 coating around thermochromic pigment was generated using the Stober method, followed by assessing the properties of cement pastes prepared using coated thermochromic pigment. The properties such as standard consistency, setting time, temperature change due to hydration reaction, compressive strength, and color stability of cement pastes were assessed. Besides, analytical characterizations such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope (SEM), and Energy dispersive X-ray (EDX) analyses were also performed to evaluate the degree of hydration in cement pastes. Analytical characterizations indicate that STC pigment promotes the degree of hydration of cement pastes and accelerates the setting process, which in turn leads to higher compressive strength. SEM analysis revealed the presence of well-intact STC pigment microcapsules, indicating the protective effect of SiO2 coating against a harsh cementitious environment. The colorimetric study results indicate that STC pigment retains its thermochromic response; it can withstand the alkaline cementitious environment, thereby protecting the leuco-dye mixtures from unwanted reactions when exposed to water and high temperature.

Description of Thermochromic Offset Prints Morphologies Depending on Printing Substrate

In this study, the influence of physio-chemical properties of four printing substrates, fibrous papers (filter, bulky, recycled), and polymer film (synthetic paper) on the size of the thermochromic (TC) prints microcapsules was investigated. Results indicate that interaction between thermochromic ink and printing substrate determine the print morphology, i.e., porosity and roughness of printing substrate affect dimensions of TC microcapsules of resulting prints, while ink adhesion affects dimensional changes during heating–cooling cycle. Atomic force microscopy (AFM) analysis showed that microcapsules of the prints, on the surface of the smoothest synthetic paper, possess the smallest diameter and height, while, on the most porous and the most roughened surface of F paper, the microcapsules of the prints possess the highest diameter and height. By increasing the temperature to 40 °C, the biggest changes in the shape of the microcapsules (increase in height and decrease in diameter) were obtained using the surface of the hydrophilic filter paper. While using the recycled paper surface, the situation is opposite; the height and diameter of the microcapsules are reduced, and the microcapsules penetrate deeper into the paper structure (due to optimum adhesion). On the bulky paper surfaces, which are more hydrophobic than recycled paper (higher interfacial tension), the increase of temperature does not cause any significant changes in the shape and position of the microcapsules. The same behavior is observed using hydrophobic non-porous synthetic paper.

Reversible thermochromic polydiacetylene/zinc-aluminium layered double hydroxides nanocomposites for smart paints and colorimetric sensors: The crucial role of zinc ions

This work presents our continuing effort to develop PDA-based nanocomposites for reversible thermochromic sensors and smart paints. Here, we demonstrate that an incorporation of zinc-aluminium layered double hydroxides (ZnAl-LDH) into PDA assemblies via a simple mixing process promotes local interactions, yielding reversible thermochromism. The Zn2+ ions, released from ZnAl-LDH particles, play an essential role on achieving this phenomenon. X-ray diffraction and infrared spectroscopy reveal that the Zn2+ ions intercalate with PDA bilayer and strongly interact with carboxylate headgroup. Color-transition temperature of the nanocomposites can be tuned from 50 to 90 °C by varying the alkyl side chain of PDA. Furthermore, the reversible thermochromism persists in various organic solvents, allowing the utilization in smart paints and coating technologies. Compared to the previous studies of other PDA/LDH nanocomposites, our new materials exhibit more distinct color transition. The synthetic method is also much simpler. The new nanocomposites are more stable at low or high pH regions compared to the system of PDA/Zn2+/ZnO nanocomposite, expanding new routes for fabrication and applications in harsh conditions.

Synergic behavior of graphene-based filler and thermochromic pigments in cataphoretic coatings

This study aims to assess the synergic effect of graphene-based filler and thermochromic pigments on the protective and aesthetical performances of cataphoretic acrylic coatings. The nature of the thermochromic pigments was investigated by electron microscopy observations and infrared spectroscopy analysis. The aesthetical features of the coatings were evaluated by colorimetric measurements, estimating the colour change with temperature due to the filler addition. The corrosion protection properties were assessed by means of salt spray chamber exposure and electrochemical impedance spectroscopy measurements, which evidenced a negative contribution of the combined presence of functionalized graphene oxide flakes and thermochromic pigments. Otherwise, the incorporation of both the two fillers improved the abrasion resistance of the cataphoretic coating, as observed thanks to scrub test, as well as its aesthetical performances after chemical degradation due to UV-B exposure. Thus, this work highlighted both the positive and the negative effects caused by the synergy of reinforcing graphene-based fillers and functional pigments on the properties of cataphoretic coatings.

Improvement of an Experiment for Collecting Sunlight with a Convex Lens Using Thermochromic Sticker

Improvement of an Experiment for Collecting Sunlight with a Convex Lens Using Thermochromic Sticker

Preparation and assessment of the potential energy savings of thermochromic and cool coatings considering inter-building effects

Cool coatings show high solar reflectance and have been proposed to decrease the building energy demand by reducing solar heat gains. However, cool coatings may have a negative effect during cold seasons when solar gains would be beneficial. Thermochromic coatings, thanks to their ability to change their solar reflectance at different temperatures, have been proposed to reduce the heating penalties during colder seasons of traditional cool coatings. In this work, four different thermochromic pigments have been used to create façade paints. The solar reflectance and thermal emissivity of these paints have been evaluated experimentally. A significant change of 0.37 in the reflectance of the four paints was registered in the visible range. These products are hence compared with common cool coatings available on the market. In order to evaluate the potential energy savings of thermochromic paints, an office building in downtown Toronto (Ontario, Canada) and the surrounding area have been modeled in Energy Plus. Different scenarios have been simulated and compared among conventional, cool, and thermochromic coatings applied on the roof or on the building facades. The study also evaluates the different new coatings under several climate change scenarios. Overall results show that for the context of analysis, thermochromic paints can provide an 8.9% decrease in the cooling demand, while limiting the winter penalties to 1.7%, compared to the heating penalties of 2.6% resulted using A cool coating. Despite the limited heating penalties, the annual energy demand for all the simulated scenarios is comparable. Similar results were also obtained when the inter-building effects were taken into account in the analyzed context. Finally, thermochromic paints proved to be more beneficial considering future climate conditions as Canada is projected to show significantly higher cooling energy demands.

Adaptive building roof by coupling thermochromic material and phase change material: Energy performance under different climate conditions

Energy transfer in and out through the building envelope plays a prominent role in determining the energy consumption of a building. This study proposes a new paradigm to enhance the energy efficiency of buildings by designing adaptive building roofs that embrace dynamic responses to the fluctuating climatic conditions. Adaptive building roof is designed by integrating with thermochromic (TC) coating and/or phase change material (PCM) layer, namely TC roof, PCM roof, and TC/PCM roof, which could intelligently control both solar energy absorption/reflection and thermal energy transfer in the building. EnergyPlus simulation is implemented to investigate the potential use of adaptive roofs for the building energy saving under five different climatic conditions. The simulation results show that compared to traditional asphalt roof, the TC roof, PCM roof, TC/PCM roof reach total energy saving of up to 13%, 15%, and 17%, respectively. It is also found that TC/PCM roof shows seasonal control of building energy consumption. The sensitivity analysis reveals that when using TC/PCM roof, placing the PCM layer outside the roof insulation has more energy load reduction potential whereas the increase in thickness of PCM layer and TC coating contributes to limited improvement of energy efficiency in the building. Furthermore, adaptive roof is found to perform the best for the building located in the mild climate region. The methodology presented in this study will guide the design of adaptive roof for energy efficient buildings in different climate zones.

Behavior of chromogenic pigments and influence of binder in organic smart coatings

Chromogenic commercial pigments belonging to different classes of smart materials (photochromic and thermochromic) were selected from commercially available examples: a photochromic pigment, able to change from colorless to purple when radiated with UV light; a thermochromic pigment, changing from red to colorless above 31 °C, and a thermochromic changing from orange to yellow above 28 °C. All the pigments were produced by SFXC. They were chemically analyzed using SEM, EDXS and FTIR in order to understand their composition and the mechanisms responsible for their chromogenic behavior. Their behavior was studied by triggering the color transitions. The pigments were introduced in an epoxy binder to produce smart paints.The optical properties of the so produced coatings were analyzed using a spectrophotometer, with an emphasis on their reflectance, absorption and emission spectra. Their color was studied in different working conditions, inducing the transitions responsible for their smart behavior.The samples were subjected to different degrees of degradation using a UV-B chamber, in order to simulate with an accelerated test, the exposure to several days of sunlight and heat. The data collected in the various conditions were compared and discussed, with particular focus on their performances after prolonged usage and their eligibility for practical everyday use.The smart coatings that were produced are still able to display their chameleonic behavior at the end of the UV-B degradation time, which lasted for 500 h. The pigments partially degrade, as the color transition becomes attenuated. The epoxy binder also degrades and its yellowing partially compromises the chromatic behavior. However, it is able to protect the pigments from further degradation and concurs to guarantee the functionality of the system.

Gaining thermochromic property of quartz lamel surface and functionalization

The aim of this study was to obtain functional features by coating the quartz lamella with a sol-gel technique. Smart functional material was developed by including microencapsulated thermochromic pigments in coatings. Using anatase powder titanium (IV) oxide with additions in different ratios, the coatings were applied to the quartz lamel surfaces by dip-coating technique. The sol formulation was made using the initial precursors Tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES). Tetraethoxysilane was added to the structure of the coatings to increase the adhesion of the coatings to the substrate. Thermochromic coatings were synthesized by reacting polyvinylpyrrolidone in aqueous solution with tetraethoxysilane. The structural and thermochromic performance of coatings prepared with the sol-gel dip-coating method was systematically characterized and its functionality was determined. In this study, the effects of the addition of titanium (IV) oxide on the phase composition, transition temperature, and surface morphology of the coatings were investigated. The result obtained showed that the formed anatase phase increased as the titanium (IV) oxide content increased. Exothermic and endothermic transition temperatures for the undoped sample ranged from 34.6 °C to 26.5 °C, while 3 g titanium (IV) oxide doped sample these temperatures varied from 34.6 °C to 26.7 °C. Smooth surface coatings were prepared using polyethylene glycol. The results demonstrated that the colors of the obtained thermochromic coatings could be reversibly changed between green and white.

Shutter luminous fibres based on rare-earth materials for real-time thermal response

Rare earth luminescent materials (RELMs) are commonly used in optics and products intended for safety and decoration. However, there is still a great challenge to alternate the emission performance after the RELMs are activated. In this work, a novel shutter luminous fibre (SLF) was developed using a water-spin method with polyacrylonitrile (PAN) as the filament material. The emission performance of the RELMs SLFs could be alternated at near-ambient temperatures. A heat-sensitive thermochromic pigment composed mainly of 7-Anilino-3-diethylamino-6-methyl fluoran (TF-BL1) served as the shutter material. The emitting properties, shielding effect, and the temperature response behaviour of RELMs SLFs with primary colour-emitting properties (Sr2ZnSi2O7: Eu2+, Dy3+; SrAl2O4: Eu2+, Dy3+; and Y2O2S: Eu3+, Mg2+, Ti4+) were investigated. The quinoid structure of TF-BL1 blocked the light of primary colours at low temperatures. At high temperatures, the lactone structure of TF-BL1 allowed the light of the RELMs to emit. SLFs with real-time responding behaviour have great potential as electronic skin in soft robotics, flexible electronics, and camouflage applications.