Modulus-Adjustable Smart Insole with Magneto-tunable Flexibility, High Impact-Responsive Energy Absorption and Low-Voltage Thermal Management

Abstract

Foot-mounted wearable equipment is rapidly being applied in healthcare and sports protection. However, it still faces limitations such as un-tunable mechanical properties, insufficient impact cushioning, and single functionality, failing to meet the personalized dynamic requirements. Herein, a magnetorheological-shear stiffening synergistic conductive composite fabric (named MRG/MFC) is proposed for smart insoles, integrating magneto-tunable flexibility, efficient impact cushioning, and electrothermal therapy. Under applying the magnetic field, the modulus of MRG/MFC can be adjusted and the magnetorheological effect of the magnetorheological shear stiffening gel (MRG) reaches up to 3161% (600 mT). Meanwhile, the shear stiffening gel endows the MRG/MFC with the typical rate-dependent energy dissipation, in which the peak impact force can be critically reduced (>45%) and the buffer time can be particularly prolonged (>80%). In addition, MRG/MFC can quickly absorb sweat; thus, it also enhances the wearing comfort. Furthermore, owing to the good electric conductivity, the MRG/MFC shows wonderful electrothermal properties (30–115 °C) under low voltage, and this offers the possibility for foot health care. Finally, a smart insole integrated with MRG/MFC is constructed and its plantar stress distribution can be regulated via attaching a magnetic sticker. As a result, this design concept provides a multifunctional composite for personalized foot protection which possesses wide application potential for athletes and diabetic patients.

Graphical Abstract

Keywords

Magnetorheological / Shear stiffening / Electrothermal / Fabric / Smart insoles

References

[1] Heng WZ, Yin SK, Min JH, Wang CR, Han H, Shirzaei SE, Li JJ, Song Y, Rossiter HB, Gao W. A smart mask for exhaled breath condensate harvesting and analysis. Science. 2024, 385954.

[2] Wang ZY, Zhao XQ, Yan K, Zhang PL, Zhang S, Fan HJ. Smart textiles for chronic disease management: advancements, applications, and future prospects. Mater Sci Eng R Rep. 2025, 164100987.

[3] Yang XD, Chen Y, Chen TY, Li JW, Wang YF. Active fabrics with controllable stiffness for robotic assistive interfaces. Adv Mater. 2024, 362404502.

[4] Ates HC, Nguyen PQ, Gonzalez-Macia L, Morales-Narváez E, Güder F, Collins JJ, Dincer C. End-to-end design of wearable sensors. Nat Rev Mater. 2022, 7887.

[5] Pu JH, Li HQ, Liu J, Li K, Tao XM. Vector-stimuli-responsive magnetorheological fibrous materials. Nature. 2025, 647375.

[6] Li F, Pan TS, Li WH, Peng ZJ, Guo DJ, Jia X, Hu TQ, Wang LX, Wang W, Gao M, Yao G, Zuo L, Bi M, Weng XL, Tang WX, Lin Y. Flexible intelligent microwave metasurface with shape-guided adaptive programming. Nat Commun. 2025, 163161.

[7] Huang H, Fan YL, Chen ZL, Hu HH, Lyu YD, Xu J, Xu JH, Wu D, Liang YL, Mao QJ, Wang J, Zhang HY, Fu HR, Guan YX, Chen J, Xu KC, Chung HU, Yu XG, Nan KW. A gastric retentive robotic capsule enables emergency-prepared and responsive oral drug delivery in canine models. Sci Adv. 2025, 11eady6745.

[8] du Pasquier C, Tessmer L, Scholl I, Tilton L, Chen T, Tibbits S, Okamura A. Haptiknit: distributed stiffness knitting for wearable haptics. Sci Robot. 2024, 9eado3887.

[9] Abbott CA, Chatwin KE, Foden P, Hasan AN, Sange C, Rajbhandari SM, Reddy PN, Vileikyte L, Bowling FL, Boulton AJM, Reeves ND. Innovative intelligent insole system reduces diabetic foot ulcer recurrence at plantar sites: a prospective, randomised, proof-of-concept study. Lancet Digit Health. 2019, 1e308.

[10] Mohammadi MM, Nourani A. Testing the effects of footwear on biomechanics of human body: a review. Heliyon. 2025, 11e42870.

[11] Lippa NM, Collins PK, Bonacci J, Piland SG, Rawlins JW, Gould TE. Mechanical ageing performance of minimalist and traditional footwear foams. Footwear Sci. 2017, 99.

[12] Leung MSH, Yick KL, Sun Y, Chow L, Ng SP. 3D printed auxetic heel pads for patients with diabetic mellitus. Comput Biol Med. 2022, 146105582.

[13] Addison BJ, Lieberman DE. Tradeoffs between impact loading rate, vertical impulse and effective mass for walkers and heel strike runners wearing footwear of varying stiffness. J Biomech. 2015, 481318.

[14] Holowka NB, Wynands B, Drechsel TJ, Yegian AK, Tobolsky VA, Okutoyi P, Mang’eni Ojiambo R, Haile DW, Sigei TK, Zippenfennig C, Milani TL, Lieberman DE. Foot callus thickness does not trade off protection for tactile sensitivity during walking. Nature. 2019, 571261.

[15] Jia R, Wang F, Jiang J, Zhang H, Li J. The biomechanical effects of insoles with different cushioning on the knee joints of people with different body mass index grades. Front Bioeng Biotechnol. 2023, 111241171.

[16] Fan ZY, Lu L, Sang M, Wu JP, Wang XY, Xu F, Gong XL, Luo TZ, Leung KCF, Xuan SH. Wearable safeguarding leather composite with excellent sensing, thermal management, and electromagnetic interference shielding. Adv Sci. 2023, 102302412.

[17] Fan ZY, Wang Y, Yao XY, Yao Y, Gong XL, Yang W, Ma HH, Xuan SH. Enhancement of impact resistance and shock wave protection in strain rate-reinforced leather composite. Macromol Rapid Commun. 2025, 462401135.

[18] Yang JJ, Zhao CY, Lai SY, Wang DP, Gong XL. Hybrid additive manufacturing of shear-stiffening elastomer composites for enhanced mechanical properties and intelligent wearable applications. Adv Mater. 2025, 372419096.

[19] Zhang X, Zhou JY, Wu KJ, Zhang SS, Xie LL, Gong XL, He LH, Ni Y. Simultaneous enhancement of thermal insulation and impact resistance in transparent bulk composites. Adv Mater. 2024, 362311817.

[20] Fan ZY, Sang M, Wang Y, Wu JP, Wang XY, Gong XL, Ma HH, Xuan SH. Synchronous enhancement of safety protection and impact perception in intelligent leather. Adv Compos Hybrid Mater. 2025, 8146.

[21] Fan ZY, Zhao CY, Wu JP, Cai Y, Zhou JJ, Zhang JS, Gong XL, Xuan SH. Intelligent safeguarding leather with excellent energy absorption via the toughness-flexibility coupling designation. Compos Part A Appl Sci Manuf. 2022, 161107078.

[22] Zhang SS, Lu L, Wang S, Yuan F, Xuan SH, Gong XL. Coaxial direct ink writing of shear stiffening gel/Ecoflex composite for customized insoles. Compos Part B Eng. 2021, 225109268.

[23] Sterman Y, Solav D, Rosen N, Saffuri E, Zaritsky LS. Custom orthotic insoles with gradual variable stiffness using 3D printed spacer technique. Virtual Phys Prototyp. 2024, 19e2336151.

[24] Wang DP, Zhao CY, Yang JJ, Lai SY, Wang XY, Gong XL. Enhanced mechanical-magnetic coupling and bioinspired structural design of magnetorheological elastomers. Adv Funct Mater. 2025, 352419111.

[25] Bastola AK, Hossain M. A review on magneto-mechanical characterizations of magnetorheological elastomers. Compos Part B Eng. 2020, 200108348.

[26] Lee G, Bae GY, Son JH, Lee S, Kim SW, Kim D, Lee SG, Cho K. User-interactive thermotherapeutic electronic skin based on stretchable thermochromic strain sensor. Adv Sci. 2020, 72001184.

[27] Jeong WJ, Shin HS, Nam HN, Cho HD, Heo JB, Seo JS, Han TH. Nature-inspired design of twisted MXene heating wires for robust wearable heating textiles. Adv Funct Mater. 2024, 352418824.

[28] Zhao CY, Wang Y, Ni MY, He XK, Xuan SH, Gong XL. Dynamic behavior of impact hardening elastomer: a flexible projectile material with unique rate-dependent performance. Compos Part A Appl Sci Manuf. 2021, 143106285.

[29] Li Y, Wang BC, Gong XL. Modelling the Mullins effect and the magnetic-dependent nonlinear viscoelasticity of isotropic soft magnetorheological elastomers. Int J Solids Struct. 2023, 283112475.

[30] Wang YP, Wang S, Xu CH, Xuan SH, Jiang WQ, Gong XL. Dynamic behavior of magnetically responsive shear-stiffening gel under high strain rate. Compos Sci Technol. 2016, 127169.

[31] Song JX, Zheng SN, Jiao S, Wu N, Sui ZY, Zhang Y, Pan F, Liu JR, Zeng ZH. Recent progress on MXene-based aerogels for electromagnetic interference shielding. Rare Met. 2025, 448356.

[32] Wu N, Yang YF, Wang CX, Wu QL, Pan F, Zhang RN, Liu JR, Zeng ZH. Ultrathin cellulose nanofiber assisted ambient-pressure-dried, ultralight, mechanically robust, multifunctional mxene aerogels. Adv Mater. 2023, 352207969.

[33] Deng YL, Zeng ZH, Lin JP, Wei M, Wang YD, Pan F, Liu JR, Wu N. A sustainable ultrawide-spectrum-selective paper-based heating window against microwave radiation. Adv Funct Mater. 2025.

[34] Zheng SN, Xu WL, Liu JR, Pan F, Zhao SY, Wang YD, Zeng ZH, Wu N. One-hour ambient-pressure-dried, scalable, stretchable MXene/polyurea aerogel enables synergistic defense against high-frequency mechanical shock and electromagnetic waves. Adv Funct Mater. 2024, 342402889.

[35] Xiao W, Chen YT, Pan GX, Yan J, Zhang J, Gao JF. Hydrophobic, hemostatic and durable nanofiber composites with a screw-like surface architecture for multifunctional sensing electronics. Adv Fiber Mater. 2023, 52040.

[36] Lai SY, Zhao CY, Gong LP, Liu S, Yang JJ, Wang DP, Mei GL, Li WH, Gong XL. Beetle elytra-inspired shear-stiffening warp-knitted spacer fabric composites with enhanced impact resistance. Compos Struct. 2025, 370119443.

[37] Zheng SJ, Li WZ, Ren YY, Liu ZY, Zou XY, Hu Y, Guo JN, Sun Z, Yan F. Moisture-wicking, breathable, and intrinsically antibacterial electronic skin based on dual-gradient poly (Ionic Liquid) nanofiber membranes. Adv Mater. 2022, 342106570.

[38] Zhang YC, Fang R, Xue HY, Ye YS, Jian L, Lin Q, Xia JR. Study on rheological behaviors and rheokinetics of urushiol/MDI resin system during curing process. Thermochim Acta. 2023, 721179451.

[39] Salem AMH, Ali A, Ramli RB, Muthalif AGA, Julai S. Effect of carbonyl iron particle types on the structure and performance of magnetorheological elastomers: a frequency and strain dependent study. Polymers. 2022, 144193.

[40] Zhang YF, Fang FZ, Huang W, Chen YC, Qi S, Yu M. Dynamic mechanical hysteresis of magnetorheological elastomers subjected to the cyclic loading and periodic magnetic field. Front Mater. 2019, 6292.

[41] Cura’ F, Sesana R, Zhang XC, Scarpa F, Lu WJ, Peng HX. Stiffness, energy dissipation, and hyperelasticity in hierarchical multilayer composite nanocoated open-cell polyurethane foams. Adv Eng Mater. 2019, 211900459.

[42] Petrofsky JS, Lawson D, Berk L, Suh H. Enhanced healing of diabetic foot ulcers using local heat and electrical stimulation for 30 min three times per week. J Diabetes. 2010, 241.

[43] Lin RB, Tao X, Wang GH, Liu JQ, Zhao Z, Liu W, Li WC. Biomechanical effects of insole material stiffness on the human foot: a finite element analysis. Sci Rep. 2025, 1544786.

[44] Wang XY, Tao Y, Pan SS, Fang X, Lou CC, Xu YQ, Wu JP, Sang M, Lu L, Gong XL, Luo TZ, Xuan SH. Biocompatible and breathable healthcare electronics with sensing performances and photothermal antibacterial effect for motion-detecting. npj Flex Electron. 2022, 695.

Funding

the National Natural Science Foundation of China(12572217)

Key Project of Anhui Provincial Natural Science Foundation(2508085ZD004)

the Key Project of Anhui Province Science and Technology Innovation Platform(S202305a12020030)

RIGHTS & PERMISSIONS

Donghua University, Shanghai, China