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. 2025 Dec 19;11(1):2084–2096. doi: 10.1021/acsomega.5c10728

Mechanically and Magnetically Property-Tunable Magnetorheological Silicone Elastomers Prepared by UV Curing for Smart Transport Packaging Sensors

Yishan Li 1, Jiaxin Cai 1, Shuang Tian 1, Jianming Lin 1, Yuluo Zheng 1, Miaolei Feng 1, Yao Sheng 1, Zehao Huang 1, Yingying Yang 1, Chongxing Huang 1, Qingshan Duan 1, Lijie Huang 1,*
PMCID: PMC12809290  PMID: 41552465

Abstract

Silicone elastomers containing magnetic materials are both magnetically responsive and flexible, providing sensors with high sensitivity, excellent elasticity, and good durability and wearability. Nonetheless, challenges persist in controlling the density of the cross-linked network and optimizing their mechanical properties, which limits their sustainable application in emerging fields. In this work, magnetorheological elastomers (MREs) with tunable mechanical and magnetic properties are developed by filling modified magnetic nanoparticles into silicone elastomers using UV light to initiate the thiol–ene click reaction. The gel content and cross-link density of the silicone elastomer could be accurately controlled by UV curing to optimize its mechanical properties. The monomer conversion of the material reached up to 91%, and polymerization took only 15 s. The gel content and cross-link density of the material reached up to 92.23% and 4.145 × 10–4 mol/cm3, respectively. Additionally, magnetic nanoparticles with improved dispersion by capped silica and grafted sulfhydryl groups were prepared, and the mechanical and magnetic properties of the magnetorheological elastomers were tuned by adjusting the parameters of the preparation process, the ratio of the MRE raw materials, and the alignment direction. The developed 60° anisotropic MREs are integrated into a PVDF piezoelectric substrate to prepare a piezoelectric sensor with excellent magnetically responsive piezoelectric sensing characteristics, which has stable reliability and cyclic durability, with its voltage increasing with the increase of the magnetic field strength. Its signal remains stable in 400 magnetic field sensing cycling tests and can be used in smart packaging, which not only provides physical protection but also responds to changes in the external magnetic field. Our findings significantly advance the theoretical and experimental understanding of silicone elastomer materials and offer new technological avenues for the manufacturing of flexible, magnetically responsive sensors.

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1. Introduction

Magnetorheological elastomers (MREs) combine an inorganic magnetic component with an organic polymer matrix, − breaking through the limitations of the performance of purely inorganic or organic materials, − and combining both magnetism and flexibility, which makes them suitable for sensors in situations where flexibility, wearable properties, and magnetic sensitivity are required. Most of the current magnetorheological elastomer preparation methods involve curing magnetic particles uniformly dispersed into an elastomer matrix, but the unstable properties and the difficulty in optimizing the mechanical and magnetic properties have resulted in magnetorheological elastomers that exhibit a considerable gap between laboratory research and practical engineering applications. At present, research on performance optimization has focused on the content and particle size adjustment of magnetic particles, as well as the use of additives such as plasticizers and the improvement of structural processes. However, the addition method of magnetic particles and the overall preparation process have not yet been systematic study, which limits further improvement of magnetic silicone elastomer performance and expansion of the application scope to a certain extent. The instability of the material properties and the contradiction between improving the mechanical properties and magnetic properties mainly originate from the poor dispersion of magnetic particles in silicon-based elastomers, which are prone to agglomeration; therefore, improving the homogeneous dispersion of magnetic particles in the elastomeric matrix and optimizing the comprehensive properties of the materials and the material preparation process are key to promoting the engineering applications of magnetic elastomers.

Silicone elastomers are widely used across various sectors, including medicine, materials science, and the electronics industry, due to their distinct mechanical properties, chemical stability, and excellent biocompatibility. These attributes make them highly valued for a broad range of applications in these fields. − Efficient and precise photocuring molding produces high-performance silicone elastomer materials tailored for specific functions and structures. − In recent years, silicone elastomers based on the thiol-alkene click reaction combined with UV curing have attracted researchers’ attention due to their good mechanical strength and elasticity. Wallin et al. have shown that the molar fraction of thiol groups and the molecular weight of vinyl PDMS affect the mechanical properties of elastomers. Rodriguez et al. prepared silicone elastomers with tunable mechanical properties by UV curing of mercapto-alkene cross-links. Liu et al. prepared materials with high gel content, conversion, and polymerization rate by the photoinitiated thiol–ene click reaction of mercapto-modified polysiloxane (PDMS-SH) and vinyl-capped silicone oils, and the improvement of physical properties could be promoted by heating. The formation of ionic cross-linked network and the improvement of the physical properties could be promoted by further heating. The core advantage of this preparation method lies in its high efficiency and flexibility of functionalization, which enables precise control of material properties by regulating reaction conditions during the preparation process, such as the ratio of thiols to vinyl, the light time, and the light intensity.

Magnetic filler particles serve as the basis for the magnetic response of elastomers, and their properties are directly related to the functional properties of magnetic elastomers. These magnetic particles are commonly found in ferric iron tetraoxide (Fe3O4), carbonyl iron (CIPs), cobalt ferrite (CoFe2O4), and neodymium–iron-boron (NdFeB), among others. Fe3O4 magnetic nanoparticles exhibit superparamagnetic properties, biocompatibility, and low toxicity, finding extensive applications across multiple fields including medicine, electronics, and environmental science. However, as the magnetic particles are directly dispersed in the polymer substrate, resulting in poor dispersion, they are prone to agglomeration, which affects the overall performance and functionality of the material, and their motion under the magnetic field is limited, leading to a weak magnetorheological (MR) effect. Careful modulation of the dispersion and content of the magnetic particles, the cross-linking density of the polymer, and the magnetic properties of the final material can effectively solve this problem. Magnetic nanoparticles can be obtained by different synthesis methods, such as chemical coprecipitation, thermal decomposition, and microemulsion, to obtain specific sizes, shapes, and magnetic properties. The dispersibility can also be improved by modification methods such as surface modification, coating, and adsorption of functional molecules. In addition, isotropic and anisotropic magnetorheological elastomers , prepared with or without an applied magnetic field have internal magnetic nanoparticles either randomly distributed or in a chain-like columnar structure, and such differences in the internal structure will affect the magnetic response properties of MREs, which provide more possibilities for the research, development, and application of magnetic elastomers, allowing MREs to be used in sensor devices, , actuators and soft robots , among others, with great potential for development.

Herein, we report a new type of mechanically and magnetically property-tunable MREs prepared by the UV-initiated thiol–ene click reaction. First, a thiol-modified polysiloxane was prepared by hydrolysis polycondensation, and then the thiol-modified polysiloxane reacted with vinyl-terminated dimethylpolysiloxane in a thiol–ene click reaction under ultraviolet light to successfully prepare the silicone elastomer. By adjusting the raw material ratios and process conditions, the elastomer exhibits adjustable mechanical properties. In addition, Fe3O4 magnetic nanoparticles were successfully synthesized by the coprecipitation method, and MRE was successfully prepared by modifying magnetic nanoparticles through coating silica and grafting sulfhydryl groups, optimizing their dispersion, and then adding them into organosilicon elastomers as magnetic filler powders. The magnetic properties could be tuned by varying the amount of the additive and the arrangement of the magnetic nanoparticles. Finally, the piezoelectric sensing properties of these composites and their responsiveness to magnetic fields were tested and verified by using an in-house-built testing device. The results show that these elastomers exhibit superior magnetic response properties and piezoelectric sensing performance and have great potential for the development of magnetically responsive piezoelectric sensors.

2. Materials and Methods

2.1. Materials

3-Mercaptopropyl (dimethoxy) silane (≥96%), dimethoxydimethylsilane (97%), vinyl-capped polydimethylsiloxane (Mw = 28,000), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) (97%), and poly­(ethylene glycol) (PEG) (Mn = 20,000) were purchased from Shanghai McLean Biochemistry and Technology Co. Concentrated hydrochloric acid (AR) was purchased from Nanjing Zhongtai Chemical Co. Anhydrous ethanol (AR) was purchased from Tianjin Zhiyuan Chemical Reagent Co. FeCl2·4H2O (AR) was purchased from Xi’an Tianmao Chemical Co. FeCl3 (AR) and tetraethyl orthosilicate (AR) were supplied by the Sinopharm Group, and hydrogen peroxide (H2O2), sodium hydroxide (AR), and glacial acetic acid (AR) were supplied by Tianjin Damao Chemical Reagent Factory. Ammonia (AR) was provided by Guangdong Guanghua Technology Co. All materials were used as received without further purification.

2.2. Preparation of Silicone Elastomers

Vinyl-capped polydimethylsiloxanes and thiol-modified silicone fluids (see Supporting Information for detailed step-by-step synthesis methods) were mixed in 0.5:1, 1:1, 1.5:1, and 2:1 thiol–ene molar ratios, referred to as thiol–ene0.5, thiol–ene1, thiol–ene1.5, and thiol–ene2, respectively. TPO was added at (0.5, 1, 1.5, 2) wt % of the total mass of the mixture. The mixture was homogeneously stirred under light-avoiding conditions to form a liquid silicone resin. This resin was then poured into PTFE molds, defoamed, and cured with a UV curing machine before being heat-treated in an oven at 110 °C for 6, 9, 12, and 15 h to enhance the cross-linked network and obtain solid silicone elastomers. These samples were stored and subsequently tested for cross-link density and gel content using the equilibrium swelling test, with details provided in the Supporting Information.

2.3. Preparation of Magnetorheological Elastomers

First, Fe3O4 magnetic nanoparticles were prepared according to the coprecipitation method described in the Supporting Information, and then Fe3O4@SiO2 magnetic nanoparticles were prepared by the Stöber method. Then, 0.5 g of Fe3O4@SiO2 was taken and dispersed by ultrasonic waves for 20 min to make it completely dispersed in ethanol. The time parameter settings are configured as 1.5 s of ultrasonication followed by a 1.0-s interval. Once fully dispersed, 5 mL of PDMS-SH3 was added gradually, and the mixture was subjected to ultrasonic stirring for 5 h. The ultrasonic frequency is 100 kHz. Upon completion of the reaction, the colloid was separated by using centrifugation. The resultant colloid was then washed alternately with water and ethanol until the wash solution appeared clear. Subsequently, a magnet was used to isolate the products magnetically. The isolated black powder, termed Fe3O4@SiO2–SH, was obtained through freeze-drying for 48 h and stored at low temperatures for future use. (1, 3, 5, and 8) wt % of Fe3O4@SiO2–SH were added to the silicone resin prepared by the optimal process. Stirring in the dark until a homogeneous dispersion was achieved, the mixture was then placed into a polytetrafluoroethylene mold and subjected to 365 nm UV curing and molding. The molded samples were subsequently subjected to a thermal baking treatment at 120 °C for 12 h to produce Fe3O4@SiO2-SH/PDMS MREs. According to Figure a, isotropic MREs without an applied magnetic field and anisotropic MREs with an applied magnetic field at 30°, 60°, and 90°, respectively, were prepared, and the directional modulation of the MREs was achieved.

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(a) Preparation process of isotropic and anisotropic MREs, (b) Schematic diagram of magnetically responsive piezoelectric sensors, and (c) Schematic diagram of the testing device.

2.4. Preparation of Magnetically Responsive Piezoelectric Sensors

The prepared Fe3O4@SiO2-SH/PDMS MREs were attached to a PVDF piezoelectric substrate to prepare magnetic-responsive composite piezoelectric sensors, as shown in Figure b. Attaching the nonsmooth side of the MREs to the piezoelectric substrate increases its interlayer friction and thus prevents sliding.

2.5. Characterization and Measurements

2.5.1. Structural Characterization

Fourier transform infrared spectroscopy (FTIR, TENSOR II, Bruker, USA) was employed to analyze the infrared spectra of the sulfhydryl-modified silicone oil, its raw materials, and the magnetic nanoparticles. Before the IR tests, potassium bromide was dried, and the samples were scanned 32 times using the KBr press method across a wavenumber range from 4000 to 400 cm–1. The size, morphology, and dispersion of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2–SH magnetic nanoparticles were analyzed by using transmission electron microscopy (Talos F200X G2, Thermo Fisher). The zeta potential of these nanoparticles was measured with a nanoparticle sizer (NANO ZS90, Malvern Instruments, UK) to evaluate their stability and dispersion within the system. The crystal shapes of the three magnetic nanoparticles were tested with an X-ray powder diffractometer (MINFLEX600, Rigaku Corporation) using a Cu target and Kα radiation, scanned at 40 kV and 30 mA settings over a 10–80° range. The mechanical strength of the silicone elastomers was evaluated using a universal material testing machine (INSTRON-3367, Instron, USA). The tensile and compressive properties of the MREs were evaluated using a universal material testing machine and a mass tester (TMS-Pro FTC, USA), as described in the Supporting Information. Specific steps for the remaining test methods can be found in the Supporting Information.

2.5.2. Magnetic Response Piezoelectric Sensor Performance Test

The performance of the magnetic response sensor was tested using the CHI760E electrochemical station and a self-assembled test setup. The leads on both sides of the fabricated magnetic response piezoelectric sensor were connected to the reference and working electrodes of the electrochemical workstation. An electromagnet was positioned beneath the sample and was activated via a switch to apply a magnetic field. The magnetic field strength was measured by a digital magnetic field strength meter (GS-25). Under a uniform magnetic field, the sample underwent compressive or tensile bending deformation, causing voltage fluctuations detected by the electrochemical workstation (CHI760E). These fluctuations were recorded as the induction voltages of the magnetic response sensor. The overall test schematic is shown in Figure c. The magnetic field strength applied to the sample was controlled by uniformly adjusting the distance between the magnet and the sample at a rate of 0.25 m/s. The magnetic field was repeatedly applied to the sensor for a total of 400 tests, with the induced voltage magnitude recorded in real time. This evaluated the repeatability of the magnetic response piezoelectric sensor with 60° anisotropy. Without an applied magnetic field, one end of the sensor is fixed, while the other end undergoes periodic angular displacement. Each bending cycle is defined as follows: bending from the initial position (0°) to +30°, then reversing to −30°, and finally returning to the initial position (0°). This test was conducted for a total of 400 cycles, with the sensor’s output voltage recorded in real time. The test evaluated the performance retention of the anisotropic 60° magnetoresponsive piezoelectric sensor under repeated mechanical stress.

3. Results and Discussion

3.1. Synthesis of Silicone Elastomers and Kinetic Analysis of Photothermal Polymerization Reaction

The peaks at 2960 cm–1, 2560 cm–1, and 1100 cm–1 in the FTIR spectrum of Figure b correspond to the methoxy (−OCH3), sulfur–hydrogen (−SH), and silica-oxygen (Si–O–Si) bonds, respectively, on the PDMS-SH3. The presence of these groups suggests that sulfhydryl groups have been successfully introduced and that the sulfhydryl-modified silicone oil PDMS-SH3 has been prepared. We determined the concentration and sulfhydryl content (Table S1) in different samples using a standard solution curve of sulfhydrylacetic acid (Figure S1) and found that PDMS-SH3 had the highest sulfhydryl concentration and content of 0.5481 mmol/L and 1.8272 mmol/g, respectively, and was therefore selected for further experiments.

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(a) Cross-linking mechanism of PDMS elastomers based on UV photocatalysis. (b) FTIR spectra of 3-mercaptopropyl­(dimethoxy) methyl silane, dimethyl dimethoxy silicane, and PDMS-SH3. (c) Conversion of monomers over time under UV irradiation. (d) Curves of G' and G'' versus irradiation time. (e) Curves of G′ versus vibrational frequency for silicone elastomers with different thermal curing times.

As shown in Figure a, the TPO absorbs UV light energy in the preparation process, decomposes to generate free radicals, and attacks the polysiloxanes containing thiol groups, generating new free radicals. The newly formed free radicals react with the carbon–carbon double bonds in the dimethylsiloxane oligomers containing vinyl-terminal groups to form a sulfide ether bond (−S−) that connects polymer chains. This reaction continues, with each new radical potentially triggering the ring-opening of subsequent carbon–carbon double bonds, thus forming a stable, continuous cross-linked network. At the same time, the silicone groups on the molecular chain of the silicone elastomer break when heated and form a cross-linking structure with the silicone groups on other molecular chains, thus forming a more compact network structure between the molecular chains. The formation of this three-dimensional network cross-linking structure can effectively improve the strength and wear resistance of silicone elastomers. In situ infrared tests were conducted on the samples to assess the impact of UV irradiation time on the cross-linking conversion rate. As illustrated in Figure c, the monomer conversion stabilized at 91% after a UV exposure time of 20 s, indicating that the majority of the vinyl and thiol groups participated in the reaction, forming a stable cross-linked network. This observation confirms the rapid reactivity and high conversion of the UV-initiated thiol–ene click reaction.

As shown in Figure d, the preparation of silicone elastomers involves two primary stages: light-curing cross-linking and thermal cross-linking. Initially, in the absence of UV irradiation for the first 30 s, the loss modulus (G″) exceeds the storage modulus (G'), indicating the material’s liquid state. Upon UV exposure, both moduli exhibit a rapid increase, with G’ rising more swiftly, signaling the onset of transition to a gel-like solid state. The crossover point of G' and G″approximately 3 s after UV exposuremarks the gelation threshold, where the material transitions from a rheological liquid to a gel. After 15 s of UV exposure, the rates of increase in G' and G″ slow down and plateau, stabilizing after 20 s, suggesting the completion of the photo-cross-linking reaction. In the thermal cross-linking stage, as shown in Figure e, G' continues to rise with increasing thermal curing times (6 h, 9 h, and 12 h), indicating ongoing thermal cross-linking and gradual network strengthening, which enhances the mechanical properties of the materials. However, a thermal curing time of 15 h results in a decrease in G', possibly due to overcuring, which could damage the cross-linked structure and reduce the material’s overall elasticity.

3.2. Preparation and Analysis of Magnetic Nanoparticles Modified by Sulfhydryl Groups

As shown in Figure a, we introduced sulfhydryl groups for better dispersion of the prepared Fe3O4 magnetic nanoparticles in our silicone elastomers. The Fe3O4@SiO2–SH magnetic nanoparticles exhibit a core–shell structure (Figure d) similar to Fe3O4@SiO2 (Figure c), and Figure c shows that they are better dispersed, with the particle spacing becoming larger and the agglomeration phenomenon becoming less compared to Fe3O4 (Figure b). As shown in Figure e, the introduction of sulfhydryl groups increases the particle size of the Fe3O4@SiO2–SH magnetic nanoparticles by a small amount. The absolute value of the zeta potential of Fe3O4@SiO2–SH is relatively high compared to Fe3O4 and slightly decreased compared to Fe3O4@SiO2, but still relatively high, which indicates that the introduction of the capping layer of SiO2 and the functionalized layer of −SH improves the dispersion and stability of magnetic nanoparticles, allowing the magnetic nanoparticles in aqueous solution to maintain good dispersion and be used as magnetic fillers for the preparation of MRE.

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(a) Schematic diagram of the magnetic nanoparticle preparation and thiolation mechanism. TEM images of (b) Fe3O4, (c) Fe3O4@SiO2, and (d) Fe3O4@SiO2–SH magnetic nanoparticles. (e) Particle size distribution of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2–SH magnetic nanoparticles. (f) FTIR spectra of Fe3O4@SiO2–SH magnetic nanoparticles. (g) XRD patterns of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2–SH magnetic nanoparticles. (h) Hysteresis lines of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2–SH magnetic nanoparticles.

The appearance of each characteristic peak in the infrared spectrogram (Figure f) of Fe3O4@SiO2–SH magnetic nanoparticles indicates that Fe3O4@SiO2 has been successfully prepared, and the stretching vibration peak of the −SH bond at 2560 cm–1 indicates that the sulfhydryl group (−SH) has also been successfully modified on the Fe3O4@SiO2 surface.

The diffraction pattern of X-rays allows the identification of the crystalline phases present in the magnetic nanoparticles and further analysis of the information on the crystal structure. From the diffraction peaks in Figure g, it can be determined that the fabricated Fe3O4 magnetic nanoparticles have an antispinel structure. Furthermore, it can be seen in the XRD patterns of Fe3O4@SiO2 and Fe3O4@SiO2–SH that, in addition to having the corresponding diffraction peaks similar to those of the Fe3O4 magnetic nanoparticles, a diffraction peak at 18.3°, which is attributed to amorphous SiO2, is observed, indicating that the Fe3O4 magnetic nanoparticle surface modification was successful in modifying the silica layer.

As shown in Figure h, the hysteresis curves for both Fe3O4 and Fe3O4@SiO2 magnetic nanoparticles show minimal hysteresis, indicating their efficient magnetic properties. The hysteresis observed in the sulfhydryl-modified magnetic nanoparticles is remarkably small, demonstrating that these nanoparticles can be quickly magnetized under an applied magnetic field. As the magnetic field strength increases, the magnetization intensity approaches saturation. At a field strength of 10 kOe, the saturated magnetization intensity was recorded at 34.72 emu/g, showing a slight decrease from the value before sulfhydryl grafting. This reduction is likely due to the influence of organic functional groups introduced by sulfhydryl modification on the surface of the nanoparticles. Despite this slight decrease in magnetization, the Fe3O4@SiO2–SH nanoparticles maintain excellent magnetic response capabilities. Their properties make them suitable for use as magnetic functional fillers in the fabrication of MREs, where they contribute to the overall performance and functionality of the composites.

3.3. Analysis of Tunable Mechanical Properties of MREs

From Figure a, it can be seen that the molar ratio of thiol-alkenes has a significant effect on the mechanical properties of silicone elastomers. As the thiol–ene molar ratio increased from 1:1 to 2:1, we observed a decrease in tensile strength from 70.43 to 27.88 kPa, in modulus of elasticity from 124.00 to 48.12 kPa, and in elongation at break from 124.38% to 93.55%. This reduction is attributed to an excess of −SH groups, which accelerates surface curing under UV light, hindering UV penetration and free radical migration within the resin, resulting in incomplete curing of the internal layers and diminished mechanical strength.

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(a) Mechanical properties of silicone elastomers with different thiol–ene molar ratios. (b) Mechanical properties of silicone elastomers with different TPO contents. (c) Mechanical properties of silicone elastomers with different heat-curing times. (d) Mechanical properties of silicone elastomers with different UV-light wavelengths. (e) Tensile and (f) compressive stress–strain curves of magnetorheological elastomers with different Fe3O4@SiO2–SH contents. (g) Tensile and (h) compressive stress–strain curves of isotropic and anisotropic MREs. (i) Textural curves of isotropic and anisotropic MREs.

From Figure b, it can be seen that the elongation at break significantly improves from 48.37% to 124.38%, and the tensile strength increases from 49.67 to 70.43 kPa when the TPO content is increased from 0.5% to 1%. However, excessive TPO can generate too many free radicals, leading to premature termination of polymerization through the caging effect, which compromises the elastomer’s curing and mechanical integrity. Consequently, the optimal TPO concentration in the silicone resin is determined to be 1 wt %. Figure c demonstrates that thermal curing time also impacts the degree of curing, with tensile strength and modulus increasing from 49.03 and 90.88 kPa to 70.43 and 124.00 kPa, respectively, as curing time extends from 6 to 12 h. However, overly prolonged thermal curing can cause excessive cross-linking, rendering the elastomers brittle. Additionally, the effect of UV lamp wavelength on the mechanical properties was investigated, revealing that a wavelength of 365 nm optimizes the tensile strength, elasticity, and elongation at break (Figure d). Therefore, the silicone elastomers prepared at a thiol-alkene molar ratio of 1:1, a TPO content of 1 wt %, heat curing for 12 h, and UV light at a wavelength of 365 nm exhibited excellent mechanical properties, including high tensile strength, moderate elastic modulus, and good elongation at break, which were identified as the most effective process parameters for preparing silicone elastomers. This optimal process was further validated through response surface methodology experiments (Tables S2–S5 and Figures S2–S4Tables S2–S5 and Figures S2–S4 in the Supporting Information). Moreover, it can be seen from Table that elastomers produced using this method exhibited the lowest swelling rates and the highest gel content and cross-link density, at 92.23% and 4.145 × 10–4 mol/cm³, respectively.

1. Gel Content, Swelling, and Crosslinking Density of Silicone Elastomers from Different Preparation Processes.

Ratio Heat time UV wavelength Gel content Swelling Cross-link density
  h nm % % mol/cm3
Thiol–ene0.5/1 12 365 83.26 638.50 1.876 × 10–05
Thiol–ene1/1 12 365 92.23 524.67 4.145 × 10–05
Thiol–ene1.5/1 12 365 85.01 683.64 3.894 × 10–05
Thiol–ene2/1 12 365 83.16 676.65 3.272 × 10–05
Thiol–ene1/0.5 12 365 88.03 527.17 3.722 × 10–05
Thiol–ene1/1.5 12 365 83.71 545.40 3.081 × 10–05
Thiol–ene1/2 12 365 82.65 799.36 2.569 × 10–05
Thiol–ene1/1 6 365 82.78 562.99 2.400 × 10–05
Thiol–ene1/1 9 365 80.19 677.91 3.749 × 10–05
Thiol–ene1/1 15 365 78.25 750.61 4.291 × 10–05
Thiol–ene1/1 12 395 74.23 657.33 3.464 × 10–05
Thiol–ene1/1 12 405 74.57 725.05 3.095 × 10–05
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Adjusting the content and method of adding Fe3O4@SiO2–SH to the silicone matrix allows for tailored mechanical properties of the elastomers. From Figure e, it is observed that a 3% content of Fe3O4@SiO2–SH results in a tensile stress of 68.86 kPa and a higher elongation at break of 99.81%, which is similar to the tensile properties of magnetorheological elastomers with 1 wt % content. In contrast, increasing the Fe3O4@SiO2–SH content to 8% raises the tensile stress to 75.45 kPa while reducing the elongation at break to 89.33%. As shown in Figure f, the compression stresses at a fixed strain of 40% for MREs with 1%, 3%, 5%, and 8% Fe3O4@SiO2–SH content are 162.27, 171.41, 198.15, and 237.78 kPa, respectively. These results indicate that the compressive properties of MREs with 1 and 3 wt % content are similar. Taken together, Figure e,f show that lower Fe3O4@SiO2–SH content enhances the flexibility of MREs. However, the 3% Fe3O4@SiO2–SH MREs not only maintain higher tensile and compressive stresses and elongation at break but also exhibit a relatively lower modulus of elasticity, thereby offering better flexibility. Furthermore, these MREs possess superior magnetic properties and optimal thermal stability compared with those with 1% Fe3O4@SiO2–SH content, as demonstrated in Figure S5. Consequently, MREs with a 3% Fe3O4@SiO2–SH content are deemed most suitable for flexible sensor applications due to their balanced mechanical and magnetic properties. Based on these findings, isotropic and anisotropic MREs are prepared using the 3% Fe3O4@SiO2–SH concentration, targeting specific application requirements in sensor technology.

Overall, modified magnetic nanoparticles Fe3O4@SiO2–SH are crucial for fabricating uniform and fully formed magnetorheological elastomers at magnetic nanoparticle loadings exceeding 5 wt % when used with the optimal silicone elastomer formulation. Pristine Fe3O4 magnetic nanoparticles are prone to magnetic agglomeration, while the hydrophilic surface of Fe3O4@SiO2 results in poor compatibility with the hydrophobic silicone matrix. They exhibit poor dispersibility in hydrophobic silicone elastomers. Higher particle loading leads to severe particle aggregation and may destroy the continuity of the elastomer matrix. The higher the loading of magnetic nanoparticles, the darker the elastomer becomes, making it more difficult for ultraviolet light to penetrate completely. Therefore, magnetorheological elastomers prepared with these two types of magnetic nanoparticles at loadings reaching 5 wt % cannot be fully cured and exhibit nonuniformity (Figure S6) that is unsuitable for reliable performance evaluation. Uniform dispersion of fillers in the polymer matrix is a crucial step to obtain optimal performance in the composite. Therefore, the Fe3O4@SiO2–SH magnetic nanoparticles prepared by modifying silica through encapsulation and thiol grafting exhibit significantly enhanced dispersion properties, which markedly improve the overall performance of magnetorheological elastomers.

The magnetorheological effect of MREs refers to the phenomenon in which the mechanical properties of the material change under an applied magnetic field, and the arrangement and distribution of magnetic nanoparticles affect the macroscopic mechanical properties of the material. The orientation of the magnetic particles within the elastomer has a significant effect on the tensile properties of MREs (Figure g), with a minimum tensile stress of 60.29 kPa when the magnetic nanoparticles in the MREs are aligned at 90°, a maximum tensile stress of 76.13 kPa when the alignment direction is 45°, and a maximum elongation at break of 179.13% when the alignment direction is 60°. In addition, the elastic moduli of the MREs with isotropic and anisotropic orientations of 45°, 60°, and 90° were 125.47, 70.21, 46.99, and 78.74 kPa, respectively, and the difference in the orientation of the particle arrangement resulted in the difference in the stiffness of the MREs. The MREs with isotropic and anisotropic orientations of 45°, 60°, and 90° exhibit widely varying compressive strengths of 171.41, 131.21, 97.12, and 118.86 kPa, respectively, at a fixed compressive strain of 40% (Figure h). When the direction of the magnetic field is aligned with the alignment of the magnetic particles, as in the case of anisotropic MREs, higher elongation at break than isotropic MREs can be achieved, suggesting that the chains of particles may be more ordered in the tensile direction, allowing the material to stretch more before fracture.

Figure i presents the textural property curves of isotropic and anisotropic MREs after undergoing two extrusions. The isotropic MREs demonstrate the highest hardness value at 56.13 N, indicating robust resistance to deformation under compression testing. In contrast, the anisotropic MREs exhibit lower hardness values compared with their isotropic counterparts and show some variation. The anisotropic samples oriented at 60° show the lowest hardness (31.91 N), marking them as the softest and most prone to deformation. Furthermore, the elasticity of the materials, indicative of their ability to recover after pressure is removed and return to their original shape, is relatively consistent across all samples, as detailed in Table S6. However, the anisotropic 60° sample stands out with the highest elasticity value of 2.57 and a resilience of 0.94. These characteristics suggest that it quickly regains its shape after deformation. This property is particularly advantageous for applications such as flexible sensors, where rapid recovery to an original shape is crucial after the removal of stress or strain.

3.4. Tunable Magnetic Properties Analysis of MREs and Magnetic Response Performance of Sensors

The quantity of magnetic nanoparticles added also plays a crucial role in determining the magnetic properties of the elastomer. Saturation magnetization strengths of Fe3O4@SiO2–SH/PDMS MREs with varying contents of magnetic nanoparticles were measured at a magnetic field strength of 10 kOe, as shown in Figure a.

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(a) Hysteresis loops of MREs with different Fe3O4@SiO2–SH contents. (b) Hysteresis loops of isotropic and anisotropic MREs. Curves of (c) G′ and (d) G″ versus vibrational frequency for isotropic and anisotropic MREs. (e) Variation of induced voltage with magnetic field for anisotropic and isotropic magnetorheological piezoelectric sensors. (f) Variation of induced voltage of sensor under different magnetic field strengths. (g) Variation of induced voltage under magnetic field on–off cycleS. (h) Induced voltage at 30° bend. (i) Variation of induced voltage of free-release shocks with different masses of weights.

The results indicated that MREs with 1%, 3%, 5%, and 8% nanoparticle contents exhibited saturation magnetization strengths of 11.83, 16.12, and 13.66 emu/g, respectively. Notably, samples with 3% and 5% nanoparticle additions demonstrated a higher structural density, which supports maintaining a higher magnetization intensity. In contrast, a higher nanoparticle content of 8% can negatively impact the thiol–ene clicking reaction and the formation of a dense elastomer structure, thus hindering the overall magnetization effect. In addition, lower concentrations, such as 3% of magnetic nanoparticles, lead to a more uniform distribution within the samples, minimizing interactions among the particles. This concentration ensures effective magnetization while minimizing the negative effects of nanoparticle aggregation, making it an ideal choice for the development of high-performance magnetically responsive materials.

The magnetic properties of MREs prepared under different magnetic field orientations vary, − and are strongly influenced by the arrangement and distribution of magnetic nanoparticles. The saturation magnetization strengths of MREs, measured under a magnetic field strength of 10 kOe, varies depending on the orientation of the field during the material’s formation, as detailed in Figure b. The isotropic MREs exhibit a saturation magnetization of 16.12 emu/g. In contrast, anisotropic MREs aligned at 45°, 60°, and 90° orientations have magnetization strengths of 11.84, 18.61, and 8.69 emu/g, respectively. The saturation magnetization strength is highest in the 60° direction. This enhancement is attributed to the magnetic nanoparticles aligning along the magnetic field lines during preparation, creating a more ordered structure. The alignment fosters stronger magnetic coupling between the particles, enhancing their collective magnetization effect. This orderly arrangement results in a more uniform and concentrated magnetization throughout the material when subjected to a magnetic field. By manipulating the orientation of the magnetic field during the material’s synthesis, the magnetic properties of the elastomers can be tailored to suit specific application requirements. This adjustability allows for the optimization of MREs to achieve desired performance characteristics in various applications, ranging from sensors to actuators and beyond, demonstrating the material’s versatility and adaptability in response to external magnetic influences.

The arrangement of magnetic nanoparticles within MREs significantly influences both their magnetic properties and rheological behavior, which in turn affects the material’s magnetorheological effects. As demonstrated in Figure c, the energy storage modulus for all samples increases with frequency, showcasing typical elastomeric behavior. This behavior indicates that the material’s stiffness intensifies under vibrational forces. Among the samples, anisotropic MREs, particularly those oriented at 60°, exhibit a higher energy storage modulus across the entire frequency range compared with isotropic MREs.

As shown in Figure d, the rate of change in the loss modulus serves as an indicator of material stability, with isotropic MREs showing the fastest decrease, implying a higher susceptibility to damage and failure at elevated frequencies. The decrease in the loss modulus for anisotropic MREs, especially those at 60°, is more gradual. The chain-like structure formed by the magnetic particles under the influence of the magnetic field contributes to the enhanced stability of these anisotropic MREs (especially at 60°) more stable. Additionally, the high energy storage modulus highlights the superior mechanical properties and elastic recovery ability of the material, reflecting its structural stability.

According to the induced voltage results depicted in Figure e, the induced voltage signals from all samples were contingent upon both the strength of the applied magnetic field and the alignment orientation of the magnetic nanoparticles within the MREs. As the magnetic field strength incrementally increased, a corresponding rise in the piezoelectric peak was observed across all samples. Notably, under the influence of the maximum magnetic field, samples with magnetic nanoparticles aligned at 60° demonstrated the highest voltage peak, reaching up to 420 mV. Therefore, the subsequent Figure f–i were tested using a magnetically responsive sensor prepared by a 60° oriented MRE.

Figure f shows the continuous and stable voltage response of the magnetically responsive sensor with the magnetic field strength ranging from 53 to 216 mT. This enhancement in piezoelectric performance as the external magnetic field strength increases can be attributed to greater deformation experienced by the MREs, leading to higher dynamically induced voltages. As shown in Figure g, during 400 magnetic field induction cycles, the induced voltage exhibited minimal fluctuation, remaining largely within the 0–0.42 V range. Figure h demonstrates that the induced voltage of the sensor fluctuated within the range ± 0.4 to ± 0.5 V during 400 bending cycles, exhibiting a stable overall trend in voltage signal variation. The experimental results confirm that the magnetoresponsive piezoelectric sensor can accurately convert magnetic field changes into electrical signals while maintaining consistent sensing performance during repeated operations, indicating high stability and reliable repeatability.

Items are susceptible to physical damage such as shock and vibration during transportation, so the magnetic response sensor was subjected to a shock experiment of free release from a height of 1 cm above the substrate to record its induced voltage change. As can be seen in Figure i, under eight free-release shocks of the same weight mass, the voltage change value of the sensor remained almost constant and almost linear with the increase of the weight mass, and the voltage change of the weight mass in the range from small grams to large grams can be recorded; this experimental result fully demonstrates the potential application of magnetic response sensors in smart packaging to record logistic information in the transportation process.

3.5. Response Mechanism and Applications of Magnetically Responsive Piezoelectric Sensors

As shown in Figure a, in these sensors, MREs do not convert magnetic signals directly to electrical signals. Instead, an electromagnet modulates the strength of the external magnetic field applied to the sensor. This varying magnetic field induces deformation in the MREs (Video S1), which then transmits mechanical stress to the attached piezoelectric material, typically (PVDF). When subjected to mechanical stress, the internal arrangement of electric dipoles within the piezoelectric material shifts, creating a potential difference across its ends. This shift generates a voltage that effectively converts mechanical stress into an electrical signal. Once the external magnetic field is withdrawn, the MREs promptly revert to their original mechanical state before magnetic field application, causing the electrical signal generated by the piezoelectric material to diminish or cease entirely.

6.

6

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(a) Magnetic response mechanism of magnetically responsive composite MREs sensor. (b) Schematic diagram of MREs used for transportation packaging of precision instruments. (c) Schematic diagram of MREs packaging for intelligent anticounterfeiting packaging.

During this dynamic process, the sensor produces a dynamic voltage that is captured and recorded by the electrochemical workstation. The deformation of MREs under a magnetic field is efficiently converted to electrical signals through the piezoelectric effect. The magnitude of these signals varies with changes in the magnetic field strength, enabling the detection of magnetic field changes by monitoring the electrical signals. By accurately controlling the properties of the external magnetic field and the piezoelectric material, sensors can be developed for a wide variety of different application scenarios, such as vibration monitoring, actuators, etc., which are capable of responding in real-time to changes in the external environment and providing accurate sensing feedback.

Magnetically responsive piezoelectric sensors crafted from MREs can be innovatively integrated into smart packaging materials. These sensors are capable of monitoring and responding to external mechanical and magnetic field changes, thereby offering vital feedback and monitoring capabilities during the transportation and storage of packaged goods. The adjustable mechanical and magnetic properties of MREs make them particularly suitable for packaging sensitive device products that can be affected by magnetic fields. Figure b illustrates how personal measurement radiometers, susceptible to magnetic fields, shocks, and vibrations during transport, can be safeguarded. Magnetically responsive piezoelectric sensors in such settings not only provide customized vibration protection but also react to changes in magnetic fields, producing electrical signals that reflect any undue impacts or vibrations. This feature allows real-time monitoring of the product’s condition within the package, signaling any excessive stress and helping to enhance the product’s quality and reliability throughout the logistics process. Additionally, as shown in Figure c, the unique properties of MREs can be employed to develop magnetically responsive security labels for anticounterfeiting purposes. When exposed to a magnetic field, parts of the label containing magnetic particles will deform, resulting in raised lettering that provides a tangible anticounterfeiting measure.

Since the behavior of MREs is dependent on the interaction between their internal magnetic nanoparticles and the substrate, it becomes challenging to replicate or imitate, thus bolstering the anticounterfeiting efficacy. In summary, magnetically responsive piezoelectric sensors developed using magnetorheological elastomers for smart packaging not only ensure customized protection for products but also enhance anticounterfeiting measures and enable smart sensing capabilities, significantly boosting product safety and integrity during transport and storage.

4. Conclusion

In this research, we introduced homemade modified Fe3O4 magnetic nanoparticles into silicone elastomers and successfully synthesized magnetorheological elastomers with tunable mechanical and magnetic properties utilizing UV light-initiated thiol–ene click chemistry. By adjusting the thiol–ene molar ratio, initiator content, thermal curing time, and UV irradiation wavelength, we were able to regulate the mechanical properties of the silicone elastomers in a highly efficient and rapid process, with the monomer conversion of the material was up to 91%, and the polymerization taking only 15 s. The optimal process conditions were a 1:1 thiol–ene molar ratio, 1 wt % initiator content, 12 h thermal curing time, and 365 nm UV irradiation wavelength, determined through one-way experiments and response surface optimization. Under these conditions, the silicone elastomers exhibited the highest gel content, and the cross-link density of the material reached up to 92.23% and 4.145 × 10–4 mol/cm3, respectively. Furthermore, after coating the self-synthesized magnetic nanoparticles with SiO2 and grafting sulfhydryl groups, their absolute zeta potential increased from 1.51 to 33.15 mV, with a magnetization of 34.72 emu/g. A higher absolute zeta potential indicates a reduced agglomeration tendency in magnetic nanoparticles. Consequently, Fe3O4@SiO2–SH exhibits excellent stability, dispersibility, and superparamagnetism. These modified nanoparticles were incorporated into the elastomer matrix to serve as magnetically responsive functional fillers, thereby improving both the thermal stability and magnetically responsive properties of the elastomers. We also investigated the effects of the concentration of magnetic nanoparticles and the arrangement of anisotropic and isotropic nanoparticles on the magnetic and mechanical properties of the MREs. Through extensive performance testing, it was confirmed that the organosilicon elastomers prepared exhibited excellent physicochemical properties. The MREs demonstrated a significant magnetorheological effect, and when applied to magnetically responsive piezoelectric sensors, they showed a robust piezoelectric effect. The highly stable and reliably repeatable sensing performance of the sensors is demonstrated by cycling and shock experiments. This study achieves active control over the magnetorheological elasticity mechanics and magnetic properties, providing an effective strategy for addressing the dispersion of magnetic nanoparticles within elastomers. Future systematic research into MRE performance under various environmental conditionssuch as high temperatures, humidity, or chemical corrosionalong with its stable sensing and durability under long-term cyclic loading, will be crucial for advancing its use in smart transport packaging.

Supplementary Material

Download video file (34.8MB, mp4)
ao5c10728_si_002.pdf (687.9KB, pdf)

Acknowledgments

This work was supported by the Guangxi Natural Science Foundation (Task No. 2025GXNSFAA069614) and the National Natural Science Foundation of China (Project Grant No. 22468007).

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.5c10728.

  • Video of magnetorheological effects in anisotropic 60° 3% magnetic nanoparticle magnetorheological elastomers (MP4)

  • Detailed information about the materials and methods, including the preparation of sulfhydryl-modified silicone oil, and the preparation and modification of Fe3O4 magnetic nanoparticles; detailed information about the characterization and measurements, including in situ infrared tests, dynamic rheological tests, thermogravimetric analysis, mechanical property tests, magnetic properties determination, gel content, and cross-link density; detailed information about the determination and analysis of sulfhydryl content in sulfhydryl-modified polysiloxane. Response surface experiment results and analysis of silicone elastomers. Analysis of thermal stability; 5 wt % Fe3O4 magnetorheological elastomer and 5 wt % Fe3O4@SiO2 magnetorheological elastomer; and table of texture characteristics of anisotropic MREs and isotropic MREs (PDF)

#.

Y.L. and J.C. contributed equally to this work

The authors declare no competing financial interest.

References

  1. Li S., Zhang J., He J., Liu W., Wang Y., Huang Z., Pang H., Chen Y.. Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication. Adv. Sci. 2023;10(34):2304506. doi: 10.1002/advs.202304506. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Díez A. G., Tubio C. R., Etxebarria J. G., Lanceros-Mendez S.. Magnetorheological Elastomer-Based Materials and Devices: State of the Art and Future Perspectives. Adv. Eng. Mater. 2021;23:2170023. doi: 10.1002/adem.202100240. [DOI] [Google Scholar]
  3. Bastola A. K., Paudel M., Li L., Li W.. Recent progress of magnetorheological elastomers: a review. Smart Mater. Struct. 2020;29:123002. doi: 10.1088/1361-665X/abbc77. [DOI] [Google Scholar]
  4. Akhtarian S., Veladi H., Mohammadi Aref S.. Fabrication and characterization of conductive poly­(dimethylsiloxane)-carbon nanotube nanocomposites for potential microsensor applications. Sens. Rev. 2019;39:1–9. doi: 10.1108/SR-04-2017-0055. [DOI] [Google Scholar]
  5. Palacios-Pineda L. M., Perales-Martinez I. A., Lozano-Sanchez L. M., Martínez-Romero O., Puente-Córdova J., Segura-Cárdenas E., Elías-Zúñiga A.. Experimental investigation of the magnetorheological behavior of PDMS elastomer reinforced with iron micro/nanoparticles. Polymers. 2017;9:696. doi: 10.3390/polym9120696. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Kumar V., Park S. -J., Lee D. -J., Park S.. Mechanical and magnetic response of magneto-rheological elastomers with different types of fillers and their hybrids. J. Appl. Polym. Sci. 2021;138:50957. doi: 10.1002/app.50957. [DOI] [Google Scholar]
  7. Kumar V., Alam N., Park S. S.. Robust magneto-rheological elastomers performance for composites based on iron oxide and carbon black in silicone rubber. J. Polym. Res. 2022;29:251. doi: 10.1007/s10965-022-03084-5. [DOI] [Google Scholar]
  8. Zeng Y., Zhou N., Xiong C., Huang Z., Du G., Fan Z., Chen N.. Highly stretchable silicone rubber nanocomposites incorporated with oleic acid-modified Fe3O4 nanoparticles. J. Appl. Polym. Sci. 2022;139:51476. doi: 10.1002/app.51476. [DOI] [Google Scholar]
  9. Xu Z., Wu H., Wang Q., Yi L., Wang J.. Simulation Study on the Motion of Magnetic Particles in Silicone Rubber-Based Magnetorheological Elastomers. Math. Probl. Eng. 2019;2019(1):8182651. doi: 10.1155/2019/8182651. [DOI] [Google Scholar]
  10. Krpovic S., Dam-Johansen K., Skov A. L.. Importance of Mullins effect in commercial silicone elastomer formulations for soft robotics. J. Appl. Polym. Sci. 2021;138:50380. doi: 10.1002/app.50380. [DOI] [Google Scholar]
  11. Bai L., Yan X., Feng B., Zheng J.. Mechanically strong, healable, and reprocessable conductive carbon black/silicone elastomer nanocomposites based on dynamic imine bonds and sacrificial coordination bonds. Compos Part B: Eng. 2021;223:109123. doi: 10.1016/j.compositesb.2021.109123. [DOI] [Google Scholar]
  12. Chen J., Song L., Wu Y., Zhao B., Deng J.. Aggregation-Induced Emissive Silicone Elastomer with Multiple Stimuli Responsiveness. ACS Appl. Polym. Mater. 2022;4:4264–4273. doi: 10.1021/acsapm.2c00231. [DOI] [Google Scholar]
  13. Kleger N., Fehlmann S., Lee S. S., Dénéréaz C., Cihova M., Paunović N., Bao Y., Leroux J. -C., Ferguson S. J., Masania K.. et al. Light-based printing of leachable salt molds for facile shaping of complex structures. Adv. Mater. 2022;34:2203878. doi: 10.1002/adma.202203878. [DOI] [PubMed] [Google Scholar]
  14. Mogi K., Hashimoto Y., Tsukahara T., Terano M., Yoshino M., Yamamoto T.. Nanometer-level high-accuracy molding using a photo-curable silicone elastomer by suppressing thermal shrinkage. RSC Adv. 2015;5:10172–10177. doi: 10.1039/C4RA12062K. [DOI] [Google Scholar]
  15. Yu D., Hensel R., Beckelmann D., Opsölder M., Schäfer B., Moh K., de Oliveira P. W., Arzt E.. Tailored polyurethane acrylate blend for large-scale and high-performance micropatterned dry adhesives. J.Mater.Sci. 2019;54:12925–12937. doi: 10.1007/s10853-019-03735-x. [DOI] [Google Scholar]
  16. Wallin T., Pikul J., Bodkhe S., Peele B., Mac Murray B., Therriault D., McEnerney B., Dillon R., Giannelis E., Shepherd R.. Click chemistry stereolithography for soft robots that self-heal. J. Mater. Chem. B. 2017;5:6249–6255. doi: 10.1039/C7TB01605K. [DOI] [PubMed] [Google Scholar]
  17. Rodriguez N., Ruelas S., Forien J.-B., Dudukovic N., DeOtte J., Rodriguez J., Moran B., Lewicki J. P., Duoss E. B., Oakdale J. S.. 3D printing of high viscosity reinforced silicone elastomers. Polymers. 2021;13:2239. doi: 10.3390/polym13142239. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Liu Z., Hong P., Xiang H., Huang Z., Luo Q., Yang X., Liu X.. Preparation and self-healability of silicone elastomer with dual-crosslinked network. Acta Polym. Sin. 2020;51:656–669. [Google Scholar]
  19. Li Q., Wang Z., Wang Y., Liu X., Song X., Liu J., Zhang M., Zhang L.. Design of magnetic elastomer composites with tunable magnetic responses from soft to hard magnetization. Mater. Res. Bull. 2024;179:112949. doi: 10.1016/j.materresbull.2024.112949. [DOI] [Google Scholar]
  20. Liu S., Yu B., Wang S., Shen Y., Cong H.. Preparation, surface functionalization and application of Fe3O4 magnetic nanoparticles. Adv. Colloid Interface Sci. 2020;281:102165. doi: 10.1016/j.cis.2020.102165. [DOI] [PubMed] [Google Scholar]
  21. Pang H., Xu Z., Shen L., Li J., Zhang J., Li Z., Xuan S., Gong X.. The dynamic compressive properties of magnetorheological plastomers: enhanced magnetic-induced stresses by non-magnetic particles. J. Mater. Sci. Technol. 2022;102:195–203. doi: 10.1016/j.jmst.2021.05.075. [DOI] [Google Scholar]
  22. Gharibshahi E., Young B. D., Bhalla A. S., Guo R.. Theory, simulation and experiment of optical properties of cobalt ferrite (CoFe2O4) nanoparticles. J. Mater. Sci. Technol. 2020;57:180–187. doi: 10.1016/j.jmst.2020.02.056. [DOI] [Google Scholar]
  23. Sorokin V. V., Stepanov G. V., Shamonin M., Monkman G. J., Kramarenko E. Y.. Magnetorheological behavior of magnetoactive elastomers filled with bimodal iron and magnetite particles. Smart Mater. Struct. 2017;26(3):035019. doi: 10.1088/1361-665X/26/3/035019. [DOI] [Google Scholar]
  24. Fatmawati T., Shiddiq M., Armynah B., Tahir D.. Synthesis Methods of Fe3O4 Nanoparticles for Biomedical Applications. Chem. Eng. Technol. 2023;46(11):2356–2366. doi: 10.1002/ceat.202200384. [DOI] [Google Scholar]
  25. Tang S. C. N., Lo I. M. C.. Magnetic nanoparticles: Essential factors for sustainable environmental applications. Water Res. 2013;47(8):2613–2632. doi: 10.1016/j.watres.2013.02.039. [DOI] [PubMed] [Google Scholar]
  26. Lu A.-H., Salabas E. L., Schüth F.. Magnetic Nanoparticles: Synthesis, Protection, Functionalization, and Application. Angew. Chem., Int. Ed. 2007;46(8):1222–1244. doi: 10.1002/anie.200602866. [DOI] [PubMed] [Google Scholar]
  27. Wang G., Geng J., Qi X., Du T., Zeng Y., Yu R., Yuan M., Peng H., Li H., Chen C.. Rheological performances and enhanced sedimentation stability of mesoporous Fe3O4 nanospheres in magnetorheological fluid. J. Mol. Liq. 2021;336:116389. doi: 10.1016/j.molliq.2021.116389. [DOI] [Google Scholar]
  28. Amara D., Felner I., Nowik I., Margel S.. Synthesis and characterization of Fe and Fe3O4 nanoparticles by thermal decomposition of triiron dodecacarbonyl. Colloids Surfaces A. 2009;339(1):106–110. doi: 10.1016/j.colsurfa.2009.02.003. [DOI] [Google Scholar]
  29. Moumen N., Pileni M. P.. Control of the size of cobalt ferrite magnetic fluid. J. Phys. Chem. 1996;100(5):1867–1873. doi: 10.1021/jp9524136. [DOI] [Google Scholar]
  30. Ausanio G., Iannotti V., Guarino V., Ambrosio L., Lanotte L.. Magneto-piezoresistive elastomers optimization and sensitivity in prospect of MEMS using magnetization direction reading. Sens. Actuat A Phys. 2017;265:253–260. doi: 10.1016/j.sna.2017.09.008. [DOI] [Google Scholar]
  31. Díez A. G., Tubio C. R., Gómez A., Berastegi J., Insausti M., Garitaonandia J. S., Bou-Ali M. M., Gutiérrez Etxebarria J., Lanceros-Mendez S.. Anisotropic nanoparticle-based magnetorheological elastomers: Effect of shape and orientation on the magnetorheological performance. Polymer. 2024;295:126776. doi: 10.1016/j.polymer.2024.126776. [DOI] [Google Scholar]
  32. Nam T. H., Petríková I., Marvalová B.. Experimental characterization and viscoelastic modeling of isotropic and anisotropic magnetorheological elastomers. Polym. Test. 2020;81:106272. doi: 10.1016/j.polymertesting.2019.106272. [DOI] [Google Scholar]
  33. Khalid M. A., Saleem M. M., Bukhari S. A. R., Tiwana M. I., Shakoor R. I., Cheung R.. Design and Characterization of Three-Axis High-Range Inductive Tactile Force Sensor Utilizing Magnetorheological Elastomer for Robotic Surgical Applications. IEEE Sens. J. 2023;23(1):247–255. doi: 10.1109/JSEN.2022.3222930. [DOI] [Google Scholar]
  34. Hu H., Zhang C., Pan C., Dai H., Sun H., Pan Y., Lai X., Lyu C., Tang D., Fu J.. et al. Wireless flexible magnetic tactile sensor with super-resolution in large-areas. ACS Nano. 2022;16(11):19271–19280. doi: 10.1021/acsnano.2c08664. [DOI] [PubMed] [Google Scholar]
  35. Do T. N., Phan H., Nguyen T. -Q., Visell Y.. Miniature soft electromagnetic actuators for robotic applications. Adv. Funct. Mater. 2018;28(18):1800244. doi: 10.1002/adfm.201800244. [DOI] [Google Scholar]
  36. Hellebrekers T., Kroemer O., Majidi C.. Soft magnetic skin for continuous deformation sensing. Adv. Intell. Syst. 2019;1(4):1900025. doi: 10.1002/aisy.201900025. [DOI] [Google Scholar]
  37. Zhou Y., Zhao X., Xu J., Fang Y., Chen G., Song Y., Li S., Chen J.. Giant magnetoelastic effect in soft systems for bioelectronics. Nat. Mater. 2021;20(12):1670–1676. doi: 10.1038/s41563-021-01093-1. [DOI] [PubMed] [Google Scholar]
  38. Xiang H., Yin J., Lin G., Liu X., Rong M., Zhang M.. Photo-crosslinkable, self-healable and reprocessable rubbers. Chem. Eng. J. 2019;358:878–890. doi: 10.1016/j.cej.2018.10.103. [DOI] [Google Scholar]
  39. Stöber W., Fink A., Bohn E.. Controlled growth of monodisperse silica spheres in the micron size range. J. Colloid Interface Sci. 1968;26(1):62–69. doi: 10.1016/0021-9797(68)90272-5. [DOI] [Google Scholar]
  40. Makarova L., Alekhina Y. A., Isaev D., Khairullin M., Perov N.. Tunable layered composites based on magnetoactive elastomers and piezopolymer for sensors and energy harvesting devices. J. Phy D App Phys. 2021;54(1):015003. doi: 10.1088/1361-6463/abb7b7. [DOI] [Google Scholar]
  41. Nikje M. M. A., Vakili M., Farajollah R., Akbar R., Haghshenas M.. Dipodal Silane-modified Nano Fe3O4/Polyurethane Magnetic Nanocomposites: Preparation and Characterization. Ulu̅m Va Tiknuluzhi̅-I Puli̅mir. 2016;28(6):453–443. doi: 10.22063/jipst.2016.1324. [DOI] [Google Scholar]
  42. Liu Y., Wang Z., Zhao Y., Hou G., Jiang R., Bockstaller M. R., Qin X., Zhang L., Matyjaszewski K.. SiO2-g-Polyisoprene Particle Brush Reinforced Advanced Elastomer Nanocomposites Prepared via ARGET ATRP. Adv. Funct. Mater. 2024;34(26):2315741. doi: 10.1002/adfm.202315741. [DOI] [Google Scholar]
  43. Mordina B., Tiwari R. K., Setua D. K., Sharma A.. Magnetorheology of Polydimethylsiloxane Elastomer/FeCo3 Nanocomposite. Phys. Chem. C. 2014;118(44):25684–25703. doi: 10.1021/jp507005s. [DOI] [Google Scholar]
  44. Zeng Y., Zhou N., Xiong C., Huang Z., Du G., Fan Z., Chen N.. Highly stretchable silicone rubber nanocomposites incorporated with oleic acid-modified Fe3O4 nanoparticles. Appl. Polym. Sci. 2022;139(2):51476. doi: 10.1002/app.51476. [DOI] [Google Scholar]
  45. Khanouki M. A., Sedaghati R., Hemmatian M.. Experimental characterization and microscale modeling of isotropic and anisotropic magnetorheological elastomers. Compos. Part B Eng. 2019;176:107311. doi: 10.1016/j.compositesb.2019.107311. [DOI] [Google Scholar]
  46. Wang B., Li Y., Gao Y., Zhang J., Xu Z., Li J., Li J., Kari L., Wang Y., Gong X.. The influence of particle chain-magnetic field spatial location, frequency, dynamic strain amplitude and the prestrain on the mechanical performance of anisotropic magneto-rheological elastomer. Polym. Test. 2021;104:107411. doi: 10.1016/j.polymertesting.2021.107411. [DOI] [Google Scholar]
  47. Sapouna K., Xiong Y., Shenoi R.. Dynamic mechanical properties of isotropic/anisotropic silicon magnetorheological elastomer composites. Smart Mater. Struct. 2017;26(11):115010. doi: 10.1088/1361-665X/aa8b26. [DOI] [Google Scholar]
  48. Yao J., Yang W., Gao Y., Scarpa F., Li Y.. Magnetorheological elastomers with particle chain orientation: modelling and experiments. Smart Mater. Struct. 2019;28(9):095008. doi: 10.1088/1361-665X/ab2e21. [DOI] [Google Scholar]
  49. Bian Y., Liang X., Gao Z.. Vibration reduction for a flexible arm using magnetorheological elastomer vibration absorber. Shock Vib. 2018;2018(1):9723538. doi: 10.1155/2018/9723538. [DOI] [Google Scholar]
  50. Martins P., Nunes J., Oliveira J., Peřinka N., Lanceros-Mendez S.. Spray-printed magnetoelectric multifunctional composites. Compos Part B Eng. 2020;187:107829. doi: 10.1016/j.compositesb.2020.107829. [DOI] [Google Scholar]

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