Application Of Smart Materials Research Articles

Wearable thermoelectric cooler encapsulated with low thermal conductivity filler and honeycomb structure for high cooling effect

Thermoelectric coolers (TEC) based on Peltier effect has been widely used in small scale cold storage because of its zero emission, and high efficiency, while wearable thermoelectric coolers (WTEC) for personal temperature management is garnered tremendous scientific attention. For out-of-plane structured WTEC using inorganic TE materials encapsuled in flexibility substrate, on the one hand, encapsulating materials are required to have low thermal conductivity, high reliability and high flexibility, and on the other hand, heat dissipation of devices is required to be lightweight, portable and efficient. For this reason, we propose a composite material synthesised from SiO2 aerogel, hollow glass beads (HGB) and polydimethylsiloxane (PDMS) as a filler, which takes advantage of the low thermal conductivity of (0.094 W/mK) to increase the temperature difference in the encapsulation layer of the device, and moreover performs the fabrication of honeycomb holes, which further reduces the thermal conductivity of the encapsulation layer and at the same time brings a certain degree of compression resistance to the device. Radiative cooling (RC) films synthesised using hexagonal boron nitride (HBN) and PDMS for lowering the temperature of the hot side in outdoor environments without additional energy consumption, providing heat dissipation at the hot side. Honeycomb wearable thermoelectric cooler (HWTEC) proposed in this work deliver high cooling temperature difference of 9.1 °C and 6.5 °C indoor and outdoor through human wear. Our work represents an important step in the development of flexible TE devices and is believed to have promising future applications in personal thermal management, e-skin and smart textiles.

Fabrication of pressure visual fiber based on liquid metal control thermochromic pigments

AbstractIn this study, pressure visual fibers (PVF) with a core‐shell structure were prepared using a coaxial wet spinning process. The fiber composite shell consists of a luminescent material (as a light source) and a thermochromic pigment (as a filter light source) mixed with a polyacrylonitrile (PAN) matrix. The fiber core layer, on the other hand, was made of gallium‐indium alloy liquid metal. In operation, the filter light source is activated by joule heat drive (resulting in the fading of the thermochromic pigment), and the PVF releases phosphorescence upon exposure to ultraviolet light. When a certain pressure is applied to the fiber shell, the liquid metal in the core layer is squeezed, resulting in a local cross‐sectional area reduction, an increase in local joule thermal power, and thus local discoloration. This localized compression, in combination with a small rated current and the presence of an ultraviolet light source, converts the mechanical force (strain and compression) into an optical response. The excellent electrical conductivity of the liquid metal, combined with its compatibility with the soft matrix, makes it a promising candidate for applications in smart textiles and flexible sensing.Highlights The technology of visual fiber controlled by current is presented. The bendability and controllability of visual composites are improved. The composite fiber can be visualized when stressed.

Smart materials for sustainable energy

In the new era of technologies, different smart or responsive materials are used which can respond to external stimuli, such as a specific amount of mechanical stress, pressure, temperature, pH, or sunlight radiations, by modifying their shape or dimensions or mechanical properties. As global temperatures rise and weather patterns become more erratic and severe. The risk to communities with energy-passive structures is growing, smart materials such as smart rooftops, thermoelectrics, photovoltaics, pyroelectrics, chromoactive, photoluminescent, as well as other innovations, help to conserve renewable energy smartly and sustainably. This review paper reflects on the applications of different smart materials as renewable smart resources. Intelligent quantum dot solar cells, Schottky solar cells, organic thin-film photovoltaic cells, dye-sensitized solar cells (DSSCs), and organic-inorganic heterojunction solar cells have high conversion efficiency, low cost, and possess wide absorption spectra that reach the near-infrared range. Biomechanical energy can be transformed into green energy using triboelectric and piezoelectric-based smart nanogenerators such as zinc oxide nanowires. Shape memory materials such as Nitinol (NiTi) have been embedded in the wind turbine blades to enhance aerodynamic efficiency. Piezoelectric nanogenerators can convert mechanical energy directly into electrical energy by using wireless sensors to harvest energy from moving water in hydroelectric power plants. Thermoelectric materials such as silver antimony telluride (AgSbTe2) offer a sustainable energy option, which employs industrial waste heat to produce power. Smart materials like graphene are more reliable and effective than carbon nanotubes for storing green hydrogen. Smart non-enzymatic biofuel cells are used in biomedical gadgets such as anesthesia machines and pacemakers, which are self-powered and have great sensitivity. Shape memory materials (SMM) are introduced in natural gas and oil reservoirs because they offer exceptional qualities such as the shape memory effect (SME), lightweight, corrosion resistance, and superelasticity, which enhance the performance and robustness of offshore industries. These new advancements, challenges, and applications of smart materials for renewable energy are covered in this review paper.

Phase change materials in textiles: synthesis, properties, types and applications – a critical review

Phase change properties of clothing gain attention of the researcher now for their significant unique ability to absorb, release, store, and deposit temperature during phase transition. Phase change materials have been widely used and utilized now in various fields, as well as in textiles. In apparel products, phase change materials are used to introduce various special features, especially its make garments smart or have technical functions. Various researchers pay attention to this area for its large organic and inorganic resources. This review paper summarizes the road map of phase change materials in textiles, including the way of synthesis, the characteristics of phase change materials, and their applications in smart textiles. In addition, the diverse usage of phase change materials in different textiles is discussed. It also tries to cover the principles of phase change behavior, phase change material types, and their thermal properties. After that, the paper will try to mention the potential benefits and challenges associated with utilizing phase change materials in various applications that have been discussed here. Finally, this paper concludes with the mass acceptance of phase change materials in various technological advancements, along with a short note about future research opportunities.

Stimuli-responsive cyclodextrin-based materials for biomedical applications

Smart materials or intelligent or responsive materials are those materials with one or more properties that can be changed in a controlled fashion by surrounding stimuli. Cyclodextrin-based functional systems have grabbed considerable attention for their applications in the biomedical and therapeutic fields due to their unique bioactive properties, selective recognition ability, and excellent biocompatibility. The physicochemical properties of the cyclodextrin-based systems can be altered in the presence of stimuli such as pH, temperature, redox, glutathione and enzyme. This review discusses the current advances in the biomedical and therapeutic applications of stimuli-responsive cyclodextrin-based smart materials.

Deep eutectic supramolecular polymer functionalized MXene for enhancing mechanical properties, photothermal conversion, and bacterial inactivation of cellulose textiles

Two-dimensional (2D) transition metal carbides (Ti3C2Tx MXene) have gained significant attention for their potential in constructing diverse functional materials, However, MXene is easily oxidized and weakly bound to the cellulose matrix, which pose challenges in developing MXene-decorated non-woven fabric with strong bonding and stable thermal management properties. Herein, we successfully prepared deep eutectic supramolecular polymer (DESP) functionalized MXene to address these issues. MXene can be wrapped with DESP to be insulated from water and protected from being oxidized. Subsequently, we achieved an efficient in-situ deposition of DESP-functionalized MXene onto fibers through a combination of dip coating and photopolymerization technique. The resulting nonwoven fabric (CNs-DESP@M) exhibited excellent photothermal conversion properties along with rapid thermal response and functional stability. Interestingly, the interface bonding between MXene and the fiber surface was significantly enhanced due to the abundant pyrogallol groups in DESP, resulting in the composite textile exhibiting commendable mechanical properties (2.68 MPa). Moreover, the as-prepared textile demonstrates outstanding bactericidal efficacy against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The multifunctional textile, created through a facile and efficient approach, demonstrates remarkable potential for applications in smart textiles, catering to the diverse needs of individuals in the future.

An investigation into the electromechanical performance of textile fabrics with conductive yarn elements for data transfer capabilities

This paper investigates the electromechanical performance of textile fabric with conductive yarn elements for data transmission capabilities. Electromechanical experiments were conducted to evaluate the electrical response of copper yarn elements stitched axially to the textile fabric, while assessing the mechanical response of the system during tensile tests under axial loading. The results indicated that the yarn element exhibited low electricomechanical coupling below 1.5% strain, making it suitable for consistent electrical performance during low mechanical strain conditions. Computational models were also developed and correlated with the experimental results of the conductive yarn. The computational model was then expanded to investigate the effect of the braiding angle in the braiding system, providing insights into how these parameters influence the system’s performance. Overall, this research contributes valuable insights into the electromechanical behavior of textile fabric with conductive yarn elements, and presents a framework for optimizing data transfer capabilities in e-textiles and smart textile applications. The findings open opportunities for further advancements in the design and engineering of functional textiles for a wide range of applications.

Investigating the Application of Smart Materials for Enhanced Maintenance of Rubber Expansion Joints in Bridge Expansion Joint Systems

In South Korea, the public infrastructure encompasses 172,111 facilities, with bridges accounting for a significant segment (totaling 34,199). These bridges undergo expansion due to traffic, vehicular loads, and temperature fluctuations. Expansion joint devices are installed to maintain vehicle stability and driving performance across expansion gaps. While these devices effectively ensure vehicular stability and performance, they do not address issues such as leakage and debris fall; therefore, rubber expansion joints should be installed. However, these rubber joints are prone to damage from various factors, resulting in secondary issues such as girder corrosion and accidents under bridges. Because of these inherent vulnerabilities, these joints require frequent replacements, making continuous bridge maintenance challenging. Therefore, this study explores the development of novel expansion joints using superelastic shape memory alloys to overcome the limitations of traditional rubber expansion joints. A comparative finite element analysis was conducted on the developed superelastic shape memory alloy and traditional rubber expansion joints. This study also assessed the long-term usability of these novel joints, particularly their ability to revert to their original shape post load removal. This research presents a promising alternative to conventional expansion joints and holds potential implications for enhancing the durability and safety of bridge infrastructure.

Highly reliable and stretchable OLEDs based on facile patterning method: toward stretchable organic optoelectronic devices

Stretchable displays attract significant attention because of their potential applications in wearable electronics, smart textiles, and human-conformable devices. This paper introduces an electrically stable, mechanically ultra-robust, and water-resistant stretchable OLED display (SOLED) mounted on a stress-relief pillar platform. The SOLED is fabricated on a thin, transparent polyethylene terephthalate (PET) film using conventional vacuum evaporation, organic-inorganic hybrid thin film encapsulation (TFE), and a nonselective laser patterning process. This simple and efficient process yields an OLED display with exceptional stretchability, reaching up to 95% strain and outstanding durability, enduring 100,000 stretch-release cycles at 50% strain. Operational lifetime and water-resistant storage lifetime measurements confirm that the TFE provides effective protection even after the nonselective laser patterning process. A 3 × 3 array SOLED display module mounted on a stress-relief pillar platform is successfully implemented, marking the first case of water-resistant display array operation in the field of SOLEDs. This work aims to develop practical stretchable displays by offering a reliable fabrication method and device design for creating mechanically robust and adaptable displays, potentially paving the way for future advances in human-conformable electronics and other innovative applications.

Nonlinear dynamic analysis of opto-electro-thermo-elastic perovskite plates

AbstractPhotostrictive materials have attracted tremendous interest as the new generation of smart materials that can achieve a direct conversion from optical energy to mechanical energy. Understanding their nonlinear mechanical properties under light illumination is of paramount significance for their realistic optomechanical applications. This article proposes a novel opto-electro-thermo-elastic constitutive model that can consider the effects of photostriction, photothermal temperature, and electrostriction for metal halide perovskite crystals and investigates the nonlinear static and dynamic responses of the perovskite plates. The nonlinear governing equations are established based on the first-order shear deformation theory and von Kármán nonlinearity and are numerically solved by the differential quadrature method. A detailed parametric investigation is performed to analyze the effects of light and electricity on the nonlinear mechanical behaviors of perovskite plates. It is concluded that light illumination leads to the presence of optical stress and thermal stress in the perovskite plates, giving rise to increased static and dynamic deformations and stresses, as well as reduced postbuckling and free vibration characteristics. The research findings pave the way for the optomechanical applications of perovskite-based smart materials and structures.

A green large-scale fabrication of cellulose-based multifunctional fluorescent fibers for versatile applications

Luminescent fibers, particularly deriving from sustainable polymers, exhibit considerable potential for application in flexible smart materials. However, the large-scale preparation of fluorescent fibers has been hindered by the instability of physically doped fluorescent substrates or the complexity and cost of chemical modification. Herein, a scalable and green strategy for the fabrication of cellulose-based multifunctional fluorescent fibers is presented. Specifically, based on the clustering-triggered emission (CTE) mechanism, cellulose acetoacetate (CAA) fluorescent fibers are continuously synthesized for the first time through a lab-scale pilot wet-spinning machine. Subsequent derivatization processes are implemented to further improve the fluorescent properties of CAA fibers by promoting the radiation transition while suppressing nonradiative transition processes and impart additional functionalities to CAA fibers. The resulting fibers exhibit integrated performances with bright cyan-blue fluorescence emission (quantum yield of 36.07%), excellent UV-blocking (UPF being up to 72.04), hydrophobic (contact angle of 141.9°), and effective antibacterial properties. Benefiting from their flexible and superior fluorescent performances, the resulting fibers have demonstrated potential applications in the fields of wearable fluorescent displays, information encryption, and fluorescent handicrafts. More interestingly, the multifunctional fluorescent fibers can be processed into clothes, showing promising application in multiple fields, such as multifunctional textiles, antibacterial dressing etc. This strategy not only provides a rational approach for the scalable production of one-dimensional (1D) multifunctional fluorescent material but also inspires the development of non-traditional sustainable fluorescent polymers.

Synergistic Self-Healing Enhancement in Multifunctional Silicone Elastomers and Their Application in Smart Materials.

Organosilicon polymers (silicones) are of enduring interest both as an established branch of polymer chemistry and as a segment of commercial products. Their unique properties were exploited in a wide range of everyday applications. However, current silicone trends in chemistry and materials engineering are focused on new smart applications, including stretchable electronics, wearable stress sensors, protective coatings, and soft robotics. Such applications require a fresh approach to methods for increasing the durability and mechanical strength of polysiloxanes, including crosslinked systems. The introduction of self-healing options to silicones has been recognized as a promising alternative in this field, but only carefully designed multifunctional systems operating with several different self-healing mechanisms can truly address the demands placed on such valuable materials. In this review, we summarized the progress of research efforts dedicated to the synthesis and applications of self-healing hybrid materials through multi-component systems that enable the design of functional silicon-based polymers for smart applications.

Design and integration of textile-based temperature sensors for smart textile applications

Wearable technology is now frequently utilized to check people’s health. Body temperature measurements needed for telemedicine and real-time health monitoring applications can be taken with wearable temperature sensors. The goal of this work was to create thermocouples made of textiles for use in smart textile applications, particularly temperature monitoring in outfield uniforms. The thermocouples were created using metal wire and conductive yarns; however, metal-based thermocouples were only created for reference. In these studies, three junction levels and three distinct materials were used, and the Seebeck coefficient for these samples was examined. A four-probe heating system coupled with a multimeter was used to calculate the Seebeck coef-ficient. Results show that the cotton-based conductive yarn thermo-couple with stainless steel yarn (C + SS2) junction performed well with the best Seebeck coefficient value. The thermocouple values with one, five, and ten junctions were sequentially 167.56 µv °C−1, 227.30 µv °C−1, and 267.54 µv °C−1. After the integration, ten junction thermocouples of C + SS2 showed the best Seebeck coefficient values.

Nonlinear electromechanical responses in multi-layered fiber-reinforced dielectric elastomer composites

The capabilities of dielectric elastomer actuators (DEAs) across various applications of soft smart materials constantly expands. However, the electromechanical behavior of multi-layer anisotropic dielectric elastomer composites (DECs), has not been studied accurately despite of its great potentials. Hence, this paper proposes a comprehensive coupled electromechanical model to address this issue and effectively capture various attributes of such an actuator including the number of layers and layers’ configuration. Using a coupled nonlinear model enables it to analyze multi-layer DECs with an unlimited number of layers, and reinforcing fiber families. A new user defined material subroutine is developed to explore the actuation performance of different multi-layer DECs such as binder, diaphragm, and tubular actuators. It provides a unique insight into effects of the number and arrangement of layers on the electromechanical performance of these actuators. Experimental results have been used for validation of developed model and numerical implementation. The results propose a practical tool for designing and optimizing fiber-reinforced multi-layer DECs based on objective purposes, contributing to developing more efficient and reliable electromechanical models for these materials.

Host-guest assembly triggered lower critical solution temperature behavior with reversible photo-regulation

The less frequent lower critical solution temperature (LCST) phenomenon has attracted extensive attention due to the foresighted application in smart materials. Nevertheless, the existing LCST-type materials are mainly dominated by a few polymers with specific moieties due to the damped hydration at a higher temperature and the lack of reversible regulations of the corresponding temperature sensitivity. Herein, an unanticipated and reversibly photo-responsive LCST behavior was uncovered in the BSC4/Azo-4 assembly solution. Such behavior arose from the host-guest binding between BSC4 and Azo-4 in an aqueous solution since neither the guest nor host alone exhibited an LCST property. Ascribing to the distinct π-π stacking between the trans- and cis-isomers of Azo-4, a reversible regulation of LCST behavior was achieved by irradiating UV and blue light alternately. Our study demonstrated the complexity and possibility of supramolecular self-assembly, opening a new avenue in the fabrication and adjustment of LCST-type materials in the future.

Advanced hydrophobic cotton threads enhanced with graphene/SWCNT nanocomposites for exceptionally high electrical conductivity

This study investigates the fabrication and characterization of conductive threads using graphene and single-walled carbon nanotubes (SWCNTs), focusing on their application in wearable electronics and smart textiles. We employed the drop casting method to coat cotton threads with a polar solvent-based dispersion of graphene and SWCNTs, aiming to enhance their electrical conductivity and hydrophobic properties. Our results demonstrate that the electrical conductivity of these conductive threads significantly increases with the concentration of graphene and SWCNTs, reaching a peak conductivity of 68.75 S. cm−1 in threads coated with a SWCNT layer followed by a graphene layer. These threads exhibit metallic behavior across a broad temperature range (room temperature to 130 °C) and maintain electrical stability over an extended period. Additionally, varying degrees of hydrophobicity were observed among the different thread compositions. A washability study revealed that threads with a bilayer of SWCNT and graphene maintained higher electrical conductivity after multiple wash cycles compared to those fabricated with a mixed layer of these materials. This research not only highlights the potential of graphene and SWCNTs in developing advanced conductive threads but also addresses the challenges in scalability and reproducibility, paving the way for future innovations in smart textile applications.

Improving the mechanical performance of low graphene content epoxy nanocomposites: investigation of hybrid and chemically modified nanofillers

Graphene is a promising nanofiller for producing polymer nanocomposites with enhanced mechanical, electrical, thermal, electromechanical, and flame retardancy properties, leading to applications in aerospace, automotive, ballistics, medicine, electronics, and smart materials. Solvent-assisted top-down methods, including mechanical exfoliation of graphite, show great potential for scale-up and mass production of graphene dispersions for use in the fabrication of nanocomposites. However, these approaches can suffer from poor efficiency, which limits the concentrations of graphene/polymer dispersions that can be produced using in situ methods. As such, it is important to find new ways of making more effective use of these low concentrations of graphene nanofillers. Possible approaches include chemical modification of the graphene or finding synergies with other nanofillers to form hybrid nanocomposites. In this work, we demonstrate results that make use of each approach. Specifically, we demonstrate a low-cost and simple method for producing carbon nanotube dispersions and creating hybrid nanocomposites with substantial enhancements to mechanical properties. We also extend the scope of our previously reported semi-in situ exfoliation method by demonstrating its application in the production of a nanocomposite that incorporates chemically modified graphene. The superior mechanical properties exhibited by the nanocomposite are attributed to increased interaction strength between the polymer and nanofiller.

Revolutionary applications of smart textiles: from shoe #choose to medical optical fibers: a case study of BLUEGRioT’s innovations

This article explores the innovative use of smart textiles in various industries, focusing on the contributions of BLUEGRioT and Brochier Technologies. It highlights key products like the #choose connected shoe, medical applications of optical fiber textiles, and the Fusio Watch, demonstrating the versatility and impact of smart textiles.

Hierarchical Mechanical Transduction of Precision-Engineered DNA Hydrogels with Sacrificial Bonds.

Engineering the response to external signals in mechanically switchable hydrogels is important to promote smart materials applications. However, comparably little attention has focused on embedded precision mechanisms for autonomous nonlinear response in mechanical profiles in hydrogels, and we lack understanding of how the behavior from the molecular scale transduces to the macroscale. Here, we design a nonlinear stress-strain response into hydrogels by engineering sacrificial DNA hairpin loops into model network hydrogels formed from star-shaped building blocks. We characterize the force-extension response of single DNA hairpins and are able to describe how the specific topology influences the nonlinear mechanical behavior at different length scales. For this purpose, we utilize force spectroscopy as well as microscopic and macroscopic deformation tests. This study contributes to a better understanding of designing nonlinear strain-adaptive features into hydrogel materials.

Real-time monitoring of self-sensing cementitious composite incorporating hybrid silicon carbide and graphite for enhanced structural health monitoring

This manuscript presents a comprehensive exploration of Silicon Carbide-Graphite Cement Composites (SCGCCs) by investigating their mechanical, electrical, and self-sensing properties. The study systematically varies SiC and graphite content, leading to remarkable insights. In terms of mechanical strength, specimens S50G1 and S50 stand out, exhibiting impressive enhancements of 15.6 % and 9.8 % in compressive strength, respectively, showcasing the pivotal role of particle content in bolstering structural integrity. Electrical resistivity analysis uncovers a percolation threshold at 25 % SiC and 2 % graphite, resulting in a substantial 97 % reduction in resistivity. This critical finding underscores the delicate balance required for optimal conductive networks within the composite material. The self-sensing capabilities of SCGCCs under flexural stress reveal a synergistic effect between SiC and graphite, with specimen S25G2 displaying the lowest voltage drop. The compressive stress analysis unveils a distinctive conductive path reconstruction behavior, offering valuable insights into the material's response to varying stress levels. Advanced CT scan porosity analysis further refines our understanding, indicating a significant reduction in porosity from 4.2 % to 3.1 % in specimen S25. Furthermore, specimens with lower graphite and SiC proportions exhibit efficient void compaction, resulting in a well-integrated microstructure with porosity as low as 2.5 %. These findings not only contribute to the fundamental understanding of SCGCCs but also offer practical applications in smart materials and structural health monitoring. Moreover, the inherent advantage of real-time monitoring within the context of smart mortar extends to the prognostication of an advanced warning signal for impeding the complete failure of the smart concrete matrix.