Smart Materials Research Articles

Dynamics of a piezoelectric vibration energy harvester with a pseudoelastic SMA spring

The development of small-scale and low power consumption devices has been motivating the design of intelligent mechanisms, exhibiting a wide power density spectrum across various external sources. Smart materials come up as an attractive alternative due to their intrinsic multi-coupling between different physical domains. In this context, piezoelectric materials allow conversion of mechanical energy of movement into electrical power through the direct piezoelectric effect. This work investigates a piezoelectric energy harvester combined with a shape memory alloy (SMA) spring to explore the combination of both the smart materials for energy harvesting. The pseudoelastic hysteretic effect of SMA is explored in order to passively change the internal system properties such as stiffness and damping during the harvesting process. Numerical analyses are performed considering the normalized power converted by the harvester, focusing on the influence of the SMA martensite phase transformation under different scenarios. The results exhibit an increment in the harvester bandwidth when compared with a traditional linear piezoelectric energy harvester.

Aromatic-Carbonyl Interactions as an Emerging Type of Non-Covalent Interactions.

Aromatic-carbonyl (Ar···C═O) interactions, attractive interactions between the arene plane and the carbon atom of carbonyl, are in the infancy as one type of new supramolecular bonding forces. Here the study and functionalization of aromatic-carbonyl interactions in solution is reported. A combination of aromatic-carbonyl interactions and dynamic covalent chemistry provided a versatile avenue. The stabilizing role and mechanism of arene-aldehyde/imine interactions are elucidated through crystal structures, NMR studies, and computational evidence. The movement of imine exchange equilibria further allowed the quantification of the interplay between arene-aldehyde/imine interactions and dynamic imine chemistry, with solvent effects offering another handle and matching the electrostatic feature of the interactions. Moreover, arene-aldehyde/imine interactions enabled the reversal of kinetic and thermodynamic selectivity and sorting of dynamic covalent libraries. To show the functional utility diverse modulation of fluorescence signals is realized with arene-aldehyde/imine interactions. The results should find applications in many aspects, including molecular recognition, assemblies, catalysis, and intelligent materials.

Responsive organic room-temperature phosphorescence materials for spatial-time-resolved anti-counterfeiting

Stimulus-responsive room-temperature phosphorescence (RTP) materials have gained significant attention for their important optoelectronic application prospects. However, the fabrication strategy and underlying mechanism of stimulus-responsive RTP materials remain less explored. Herein, we present a reliable strategy for achieving pH-responsive RTP materials by integrating poly(vinyl alcohol) (PVA) with carboxylic acid or amino group functionalized terpyridine (Tpy) derivatives. The resulting Tpy derivatives-based RTP materials displayed reversible changes in emission color, intensity, and lifetime of both prompt and delayed emission. Notably, the RTP emission undergoes a significant diminish upon exposure to acid due to the protonation of Tpy units. Taking advantage of the decent RTP emission and pH-responsiveness of these RTP films, a spatial-time-resolved anti-counterfeiting application is demonstrated as a proof-of-concept for largely enhancing the security level. This study not only provides new prospects for developing smart RTP materials but also promotes the advancement of optical anti-counterfeiting applications.

An agent-based evolutionary system model of the transformation from building material industry (BMI) to green intelligent BMI under supply chain management

The building materials industry ranks first in terms of carbon emissions and energy consumption within the industrial sector. To achieve the goal of reducing carbon emissions, the development of the green intelligent building materials (GIBMs) industry has become a strategic priority and major demand for the country. Government support plays a vital role in promoting the growth of the GIBMs industry. This paper utilizes evolutionary game theory and Matlab software to analyze the impact of government regulations on the development of the GIBMs industry. The research findings indicate the following. i) Appropriate government control over building materials enterprises is beneficial for the advancement of the GIBMs industry. A balance is necessary, as both excessive control and weak control hinder the industry’s development. ii) Increased financial assistance from the government to enterprises producing GIBMs has a positive influence. This support enables building materials enterprises to overcome technical barriers, drive technological innovation, and encourage construction developers to actively purchase these materials. iii) Stronger government punishment for pollutant emissions by building materials enterprises serves as a catalyst for the production of GIBMs. Stricter penalties motivate these enterprises to adopt more environmentally friendly practices. iv) Moderate to strong government investment in infrastructure has a significant impact. It prompts construction developers to actively choose and purchase GIBMs. In response to government regulations and market demand, building materials enterprises are inclined to produce these environmentally friendly materials. This study emphasizes the importance of government regulations and support in promoting the growth of the GIBMs industry. By implementing appropriate control measures, providing financial assistance, imposing punishments for pollution, and investing in infrastructure, the government can effectively encourage the development of the GIBMs industry. These measures contribute to achieving the double carbon goals and fostering a more sustainable built environment.

Tuning the lattice thermal conductivity of Janus SnSSe by interlayer twisting: a machine-learning-based study

Twisted two-dimensional materials have recently attracted tremendous interest owing to their unique structures and fantastic electronic properties. However, the effect of interlayer twisting on the phonon transport properties is less known, especially for the twist-angle-dependent lattice thermal conductivity ( κL ). Using the emerging Janus SnSSe bilayer as a prototypical example, we develop an accurate machine learning potential, which is adopted to efficiently predict the κL at a series of twist angles via iterative solution of the Boltzmann transport equation. It is found that the κL exhibits a distinct non-monotonous dependence on the twist angle, which can be traced back to the bonding heterogeneity between high-symmetry stacking regions inside the moiré unit cell. In contrast to the general belief, the optical phonons make a major contribution toward the κL of the twisted structures. Moreover, we demonstrate that four-phonon scattering can significantly reduce the κL of SnSSe bilayer at higher temperatures, which becomes more pronounced by interlayer twisting. Our work not only highlights the strong predictive power of machine learning potential, but also offers new insights into the design of thermal smart materials with tunable κL .

Special issue on organic intelligent materials and devices

Special issue on organic intelligent materials and devices

Flexible and Stretchable Printable Conductive Inks for Wearable Textile Applications

As wearable electronic devices become increasingly integrated into our daily routines, there is a growing demand for soft, flexible, and comfortable devices that can seamlessly deliver electronic functionalities. Electronic textiles (e-textiles) combine the electronic capabilities of devices such as sensors, actuators, energy storage, and communication tools with the comfort and flexibility inherent in traditional textiles. The rising interest in E-textile and sensor applications has thrust the field of printed electronics (PE) into the spotlight. Printed electronics is a rapidly expanding technology that allows the construction of electronic devices on affordable, flexible substrates, including paper and textiles. This is achieved through printing techniques, such as screen printing, 3D printing, gravure printing, offset printing, flexography, and inkjet printing, which are traditionally used in various industries like graphic arts, textiles, and polymers. This paper provides a comprehensive overview of printable conductive inks, with a focus on their role in designing textile-based wearable conductive devices for E-textile applications. Within this scope, it was examined the properties of conductive inks, presented the various printing methods used to fabricate wearable textile materials for potential use in wearable textile devices, and analyzed their performance characteristics. Lastly, it was addressed the key challenges faced in this field and identify future research directions. The aim of this paper is to contribute to the advancement of cost-effective functional conductive inks and formulations, promoting their integration into E-textile applications.

Trabecular bone-inspired tung oil-derived spongy cellular networks with intelligent pH-responsive wettability and superelasticity for efficient multitasking separation

Development of new biomass sponges with controllable wettability and excellent resilience is urgent while challenging for multitasking and effective oil–water separation because incorporating these performances into conventional biomass sponges is complicated and even contradictory. Herein, a hypersalinity-confined thermopolymerization strategy is presented for fabricating the tung oil-derived spongy cellular network (TSN), during which its interconnected porous skeleton with ionizable carboxyl groups is formed due to the self-initiated thermal polymerization and crosslinking of tung oil precursors enclosed in the stacking space of sodium chloride (NaCl) particles. By mimicking trabecular bone architecture with good energy transfer/dissipation, high porosity and strong capillary absorption, the resultant TSN with carboxylic acid groups exhibits reversible pH-responsive wettability (transition from hydrophobicity/lipophilicity to hydrophilicity/oleophobicity), superelasticity (nearly 100 % stress and height retention after 1000 cycles), good thermal/chemical stability and efficient oil–water separation performance (>99.4 % separation efficiency) in multitasking situations. This study provides an encouraging insight for the tailored fabrication of smart sponge materials derived from renewable vegetable oils for oil–water separation in multitasking and complex situations.

Fabrication of the Ag/silk fibers for electrically conductive textiles

As a good substrate, silk fibers are widely employed in the field of intelligent textiles. In this work, the surface of silk fibers were firstly roughened by formic acid and sensitized by tannic acid, and then the silver ammonia solution was reduced by glucose to synthesize nano-silver in situ on the silk surface to obtain composite conductive silk fibers with resistivity as low as 0.24 mΩ·cm. It was proved by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) tests that a uniformly deposited nano-silver layer was fabricated on the silk surface. The prepared silk fibers had stable mechanical, thermal, electrical, and antibacterial properties and can be used for human sensing.

Carbon fiber reinforced liquid crystalline elastomer composites: a dual exploration in strength augmentation and transformation flexibility through 4D printing

ABSTRACT Liquid Crystal Elastomers (LCEs) are renowned for their reversible deformation capabilities. Yet, enhancing their mechanical strength while retaining such flexibility has posed a considerable challenge. To overcome this, we utilized 4D printing to develop an innovative composite of LCE with carbon fiber fabric (LCEC). This approach has notably increased the tensile strength of LCE by eightfold, all the while maintaining its exceptional capacity for reversible deformation. By adjusting the alignment angle between carbon fiber and the LCE printing direction from 0° to 90°, the LCEC demonstrates an array of new deformation patterns, including bending, twisting, wrapping, and S-shaped transformations, which are distinct from pure LCE materials. Our study unveils that LCE composites exhibit deformation processes markedly different from their pure material counterparts, with the ability of pure LCE to sustain tensile strains exceeding 1900%. These findings, previously undocumented and unexplored, represent a substantial contribution to the field of smart materials. Employing finite element analysis, we explored the carbon fiber and LCE matrix dynamics, revealing bending mechanics in LCECs. This combined experimental and simulation approach yields crucial insights for crafting durable, high-strength LCECs with diverse deformational properties, advancing smart material technology.

Identification of Mineral Zircon (ZrSiO4) Rare Earth Metal (REM) As Smart Material For Electric Tactical Motor Bike Battery

Rare earth metals are associated minerals that are magnetic used as the main component in providing power to most electronic devices. Rare earth metal (REM) as a smart material that has 14 chemical elements. These elements are grouped according to their molecular weight, namely light rare earth metals (Ce, Pr, Nd, Pm, Sm, Eu) and heavy rare earth metals (Gd, Tb, Dy, Ho, Tr, Tm, Yb, Lu) . The use of this REM includes electric cars, health identification devices, LCDs and computer hardware. From some of the benefits and contents of REM, its development is not only in the industrial world but also in the world of defense, one of which is as a battery for motorized vehicles developed by the ministry of defense (Electric Tactical Motor Bike) that uses lithium batteries as a source of electrical energy. However, the use of lithium batteries which have shortcomings in terms of charging makes them look for other alternatives so that they can be charged optimally, one of which is using REM. The strategic position of rare earth minerals in the future must be developed so that they can be used sustainably, considering that Indonesia has potential resources that can be utilized.

Viscosity Analysis of Copper Aluminium Manganese (CuAlMn) Shape Memory Alloy Mixed with Polyethylene Glycol (Peg), Polymethyl Methacrylate Acrylic (Pmma) and Stearic Acid (Sa) Based Binder

Shape memory alloys (SMAs) are a class of smart materials that have the unusual feature of remembering the initial shape after plastic deformation. SMAs differ from traditional elastic/plastic materials in because of reversible hysteretic thermos mechanical behavior. Copper (Cu) based shape memory alloys are the most promising in terms of practical application due to their inexpensive cost and high recovery force. Powder injection molding (PIM) is well known for the creation of complex components (micro parts) and Copper Aluminium Manganese (CuAlMn) materials are studied through this process. The rheological behavior of the feedstock needs to be determined to avoid any nonhomogeneous mixture between powder and binder that may result in powder and binder separation during the injection molding process. This work focused on the rheological properties of CuAlMn with a binder system of polyethylene glycol (Peg), polymethyl methacrylate acrylic (Pmma) and stearic acid (Sa). The critical powder volume percentage of composite was at 85wt% Cu, 12wt% Al and 3wt% Mn was obtained. Based on such value, the powder loadings used in this work was 58wt% mixed with 73wt% Peg, 12wt% Pmma and 5wt% Sa. A capillary rheometer was employed for the rheological studies where the relationship between shear rate and viscosity was investigated. There were 3 variant temperatures (115℃, 125℃ and 135℃) and 4 loads (40N, 50N, 60N and 70N) applied for the rheology test. The obtained result shows that the overall shear rate and viscosity are within the PIM process recommended range and flow index is below 1. This shows pseudoplastic behavior of the feedstock.

Soft alchemy: a comprehensive guide to chemical reactions for pneumatic soft actuation

Soft robotics has emerged as a transformative field, leveraging bio-inspired novel actuation mechanisms to enable more adaptable, compliant, and sophisticated robotic systems. However, the portability of soft pneumatic actuators is typically constrained by the tethering to bulky power sources. This review offers a thorough analysis of autonomous power alternatives facilitated by chemical reactions for gas generation and absorption, a concept analogous to biological energy conversion processes. These bio-inspired strategies propel soft pneumatic actuators towards new horizons of autonomy and portability, essential for real-world applications. This comprehensive review explores the critical intersection of gas evolution reactions (GERs) and gas consumption reactions (GCRs) as a power source for pneumatic actuation in soft robotics. We here emphasize the importance and impact of bio-inspired design, control, efficiency, safety, and sustainability within soft robotics to not only mimic biological motions but to enhance them. This review explores the fundamentals of both pneumatic and chemically powered actuation, highlighting the need for careful consideration of reaction kinetics. Additionally, this work highlights key aspects of smart materials that draw from biological structures and response mechanisms, along with state-of-the-art techniques for precise pressure modulation. Finally, we chart prospective development pathways and provide a future outlook for bio-inspired soft robotics, emphasizing the transformative impact of integrating chemical actuation methods. This exploration underlines the quest for further autonomy in soft robotic systems and points towards the future opportunities in this exciting and fast-developing field.

Tumor microenvironment responsive multifunctional smart living materials based on engineered bacteria for inducing macrophage polarization to enhance tumor immunotherapy

The utilization of bacteria as a drug delivery system represents a promising strategy for tumor therapy, owing to their inherent ability to selectively colonize and induce apoptosis of tumor cells at the solid tumor. However, the occurrence of dose-dependent toxicity has led to the failure of clinical trials. Unfortunately, the implementation of a singular bacterial treatment strategy for tumor therapy is inherently limited. In this study, we developed a living drug delivery material named DOX@TA@ECN (D@T@E) by utilizing Fe3+ and tannin acid (TA) as a cross-linking network to encapsulate doxorubicin (DOX) and form a protective coating on the surface of Escherichia coli Nissle 1917 (ECN). In an acidic tumor microenvironment, D@T@E disintegrated the coating to release DOX through the highly expressed H2O2. To enhance biosafety, the D@T@E was equipped with a hypoxic lytic circuit (Pvhb-Lysis) to regulate the number of ECN in vivo (D@T@E-PL). The hypoxic promotor of Vitreoscilla hemoglobin protein (Pvhb) were activied to induce expression of lysis protein (PhiX174E) in the tumor hypoxic microenvironment (3 %), resulting in ECN lysis and subsequent elimination by the immune system. Additionally, D@T@E-PL pass lysis to release relevant antigens (DNA and flagellin). This antigen promotes the polarization of M2-type tumor-promoting macrophages towards M1-type anti-tumor macrophages at the tumor microenvironment by activating Toll-like receptor 4 (TLR4), eliciting immune-mediated anti-tumor responses. The in vivo findings demonstrated that D@T@E-PL intelligent material demonstrated enhanced biosecurity through the lytic circuit and effectively suppressed tumor growth, thereby achieving a dual therapeutic approach combining chemotherapy and immunotherapy for tumor inhibition.

Insights into dual-emitting Eu-doped Mn–organic framework with 1D helical chain SBUs as a ratiometric thermometer for temperature sensing

The development and construction of smart luminescent MOF materials are highly desired. For the construction of luminescent MOF with new network and smart responsiveness, the introduction of Ln3+ into porous materials by the post-synthetic modification approach is one of the most effective strategies. Herein, a new anionic Mn–organic framework with 1D helical chain SBUs, [(CH3)2NH2][Mn3(OH)(TATB)2] (SQNU-24, H3TATB = 4,4′,4″-s-triazine-2,4,6-triyltribenzoic acid, SQNU = Shangqiu Normal University), was successfully prepared under a DMF/CH3CN solvent system. Benefitting from the anionic skeleton, high porosity, double-walled structure and 1D helical chain SBUs within SQNU-24, the dual-emitting Eu@SQNU-24 was successfully constructed by a post-synthetic modification approach. This work demonstrates the TATB3− ligand as an “antenna” can effectively sensitize Eu3+ ions. Interestingly, the dual-emitting Eu@SQNU-24 as a ratiometric thermometer exhibits a good temperature-responsive property.

Fabricating a photochromic Schiff base into a wearable cellulose sensor and a smart textile for ultraviolet radiation monitoring outdoors

A dual-channel photochromic Schiff base HBA is reported herein, which undergoes a reversible tautomerism in response to UV exposure, showing visible changes in both color and fluorescence. The spectral behavior, fatigue resistance, sensitivity are studied. The quantification of photochromic fluorescence/color change is solved by applying color spaces and chromatic aberration. HBA is further fabricated into low-cost wearable sensor and smart textile, enabling visual feedback under UV radiation. It demonstrates a low-costing platform for naked-eye-based dosimetry of outdoor UV radiations, providing an early warning for excessive UV exposure.

0D bio-based carbon dots and 2D MXene hybridization toward fabricating flame-retardant, conductive and sensing cellulose fabrics

With the rapid development of the smart era, there is an urgent need to replace traditional cellulosic textiles with flame retardant multifunctional cellulosic textiles. Herein, two novel multifunctional textiles (MXene@CDG-C/L and MXene@CDM-C/L) were obtained by constructing coatings consisting of MXene and bio-based carbon dot mixtures (CDG and CDM) on cellulose fabrics using a one-pot impregnation method. MXene@CDG-C/L and MXene@CDM-C/L exhibited desirable flame retardancy, electrical conductivity and sensing properties due to the synergistic effect of MXene and carbon dot mixtures. In the vertical burning test, MXene@CDG-C/L and MXene@CDM-C/L showed self-extinguishing when the external ignition source was removed, with limiting oxygen index values increasing from 18.1 % of untreated fabric to 34.4 % and 36.0 %, respectively. Meanwhile, the conductivities of MXene@CDG-C/L and MXene@CDM-C/L were as high as 31.8 S m−1 and 21.4 S m−1, respectively. Notably, benefiting from the inherent flexibility of cellulose fabrics, MXene@CDG-C/L and MXene@CDM-C/L were able to monitor human movement in a stable and continuous manner. In addition, MXene@CDG-C/L and MXene@CDM-C/L retained good integration properties including flame retardancy, electrical conductivity and sensing property after 20 washing cycles. In conclusion, the strategy reported in this work provided a new idea for the development of environment-friendly and economical multifunctional smart textiles.

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.

Orientation of graphene nanosheets in suspension under an electric field: theoretical model and molecular dynamic simulations

Orientation regulation of nanoparticles in a suspension by an electric field is a powerful tool to tune its mechanical, thermal, optical, electrical properties etc. However, how molecular modification can affect the orientation of two-dimensional nanoparticles is still unclear. In this paper, the influence of molecular modification on the orientation of graphene nanosheets (GNS) in water was investigated through theoretical analyses and molecular dynamics (MD) simulations. Firstly, a new orientation angle model was proposed, which considers hydration effects, dipole moments and resistance torque. Then, MD simulations were conducted to investigate the effects of position, direction, type, and number of functional groups on the orientation of GNS. The trend observed in MD simulations is consistent with the proposed theoretical model. The results reveal that, under the combined influence of the dipole moment and hydration effects, the modification with hydrophilic functional groups can reduce the orientation angle from 21.31° to 8.34°, while the modification with hydrophobic functional groups increases it to 26.43°. Among the hydrophilic functional groups, orientation of hydroxylated GNS is the best. With an increase in the number of hydroxyl groups, orientation angle is decreased from 12.61° to 8.34°. This work can provide valuable guidance for the design of high-performance suspensions and composites, such as thermal smart materials with adjustable thermal conductivity and intelligent devices with tailored capabilities.

Multifunctional flame-retardant cotton fabric with hydrophobicity and electrical conductivity for wearable smart textile and self-powered fire-alarm system

The domain of smart textiles represents a widely researched area, showcasing promising prospects. Herein, a multifunctional smart textile (CF@PM-AA) has been designed and fabricated, amalgamating flame retardancy, electrical conductivity, and hydrophobicity into a unified entity. The flame retardant, synthesized through the reaction between amino trimethylene phosphonic acid and allantoin, was impregnated into cotton fabric through a facile impregnation method. Through surface modification with polydimethylsiloxane and multi-walled carbon nanotubes, the obtained CF@PM-AA acquires exceptional hydrophobic and acid-base environment durability. Significantly, the electrical conductivity of CF@PM-AA is greatly enhanced, with a reduced resistance down from 15.9 GΩ to 13 MΩ. Based on their electrical characteristics, the copper sheet and CF@PM-AA function as the electrode and friction layers, respectively, in the construction of the triboelectric nanogenerator. This configuration produces a voltage output of up to 125.6 V at a frequency of 4 Hz. Given its outstanding flame retardancy, hydrophobicity, and electrical performance, CF@PM-AA can be integrated into firefighting suits to establish a fire-alarm system with remote signal transmission function, enhancing personnel safety. Simultaneously, the CF@PM-AA holds promise for diverse applications in wearable flame-retardant and fire-alarm systems, opening new avenues for smart textile utilization in the Internet of Things domain.