Inspired by physically adaptive, agile, reconfigurable and multifunctional soft-bodied animals and human muscles, soft actuators have been developed for a variety of applications, including soft grippers, artificial muscles, wearables, haptic devices and medical devices. However, the complex performance of biological systems cannot yet be fully replicated in synthetic designs. In this Review, we discuss new materials and structural designs for the engineering of soft actuators with physical intelligence and advanced properties, such as adaptability, multimodal locomotion, self-healing and multi-responsiveness. We examine how performance can be improved and multifunctionality implemented by using programmable soft materials, and highlight important real-world applications of soft actuators. Finally, we discuss the challenges and opportunities for next-generation soft actuators, including physical intelligence, adaptability, manufacturing scalability and reproducibility, extended lifetime and end-of-life strategies.
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Madden, J. D. W. et al. Artificial muscle technology: physical principles and naval prospects. IEEE J. Ocean. Eng. 29, 706–728 (2004).
Mirvakili, S. M. & Hunter, I. W. Artificial muscles: mechanisms, applications, and challenges. Adv. Mater. 30, 1704407 (2018).
Rich, S. I., Wood, R. J. & Majidi, C. Untethered soft robotics. Nat. Electron. 1, 102–112 (2018).
Cianchetti, M., Laschi, C., Menciassi, A. & Dario, P. Biomedical applications of soft robotics. Nat. Rev. Mater. 3, 143–153 (2018).
Shintake, J., Rosset, S., Schubert, B., Floreano, D. & Shea, H. Versatile soft grippers with intrinsic electroadhesion based on multifunctional polymer actuators. Adv. Mater. 28, 231–238 (2016).
Sadeghi, A., Mondini, A. & Mazzolai, B. Toward self-growing soft robots inspired by plant roots and based on additive manufacturing technologies. Soft Robot. 4, 211–223 (2017).
Acome, E. et al. Hydraulically amplified self-healing electrostatic actuators with muscle-like performance. Science 359, 61–65 (2018).
Ilievski, F., Mazzeo, A. D., Shepherd, R. F., Chen, X. & Whitesides, G. M. Soft robotics for chemists. Angew. Chem. Int. Ed. 50, 1890–1895 (2011).
Awad, L. N. et al. A soft robotic exosuit improves walking in patients after stroke. Sci. Transl. Med. 9, eaai9084 (2017).
Sitti, M. Physical intelligence as a new paradigm. Extrem. Mech. Lett. 46, 101340 (2021).
Gorissen, B. et al. Hardware sequencing of inflatable nonlinear actuators for autonomous soft robots. Adv. Mater. 31, 1804598 (2019).
Vasios, N., Gross, A. J., Soifer, S., Overvelde, J. T. B. & Bertoldi, K. Harnessing viscous flow to simplify the actuation of fluidic soft robots. Soft Robot. 7, 1–9 (2019).
Gorissen, B., Melancon, D., Vasios, N., Torbati, M. & Bertoldi, K. Inflatable soft jumper inspired by shell snapping. Sci. Robot. 5, eabb1967 (2020).
Li, S., Vogt, D. M., Rus, D. & Wood, R. J. Fluid-driven origami-inspired artificial muscles. Proc. Natl Acad. Sci. USA 114, 201713450 (2017).
Siéfert, E., Reyssat, E., Bico, J. & Roman, B. Bio-inspired pneumatic shape-morphing elastomers. Nat. Mater. 18, 24–28 (2019).
Hajiesmaili, E. & Clarke, D. R. Reconfigurable shape-morphing dielectric elastomers using spatially varying electric fields. Nat. Commun. 10, 183 (2019).
Chortos, A., Hajiesmaili, E., Morales, J., Clarke, D. R. & Lewis, J. A. 3D printing of interdigitated dielectric elastomer actuators. Adv. Funct. Mater. 30, 1907375 (2020).
Pelrine, R., Kornbluh, R., Pei, Q. & Joseph, J. High-speed electrically actuated elastomers with strain greater than 100%. Science 287, 836–839 (2000).
Duduta, M., Hajiesmaili, E., Zhao, H., Wood, R. J. & Clarke, D. R. Realizing the potential of dielectric elastomer artificial muscles. Proc. Natl Acad. Sci. USA 116, 2476–2481 (2019).
Davidson, Z. S. et al. Monolithic shape-programmable dielectric liquid crystal elastomer actuators. Sci. Adv. 5, eaay0855 (2019).
Kellaris, N., Venkata, V. G., Smith, G. M., Mitchell, S. K. & Keplinger, C. Peano-HASEL actuators: muscle-mimetic, electrohydraulic transducers that linearly contract on activation. Sci. Robot. 3, eaar3276 (2018).
Rothemund, P., Kellaris, N., Mitchell, S. K., Acome, E. & Keplinger, C. HASEL artificial muscles for a new generation of lifelike robots — recent progress and future opportunities. Adv. Mater. 33, 2003375 (2020).
Cacucciolo, V. et al. Stretchable pumps for soft machines. Nature 572, 516–519 (2019).
Seok, S. et al. Meshworm: a peristaltic soft robot with antagonistic nickel titanium coil actuators. IEEE/ASME Trans. Mechatron. 18, 1485–1497 (2013).
Aksoy, B. & Shea, H. Reconfigurable and latchable shape-morphing dielectric elastomers based on local stiffness modulation. Adv. Funct. Mater. 30, 2001597 (2020).
Lima, M. D. et al. Electrically, chemically, and photonically powered torsional and tensile actuation of hybrid carbon nanotube yarn muscles. Science 338, 928–932 (2012).
Mu, J. et al. Sheath-run artificial muscles. Science 365, 150–155 (2019).
Kanik, M. et al. Strain-programmable fiber-based artificial muscle. Science 365, 145–150 (2019).
Yuan, J. et al. Shape memory nanocomposite fibers for untethered high-energy microengines. Science 365, 155–158 (2019).
Haines, C. S. et al. Artificial muscles from fishing line and sewing thread. Science 343, 868–872 (2014).
Kang, B. B., Choi, H., Lee, H. & Cho, K.-J. Exo-Glove Poly II: a polymer-based soft wearable robot for the hand with a tendon-driven actuation system. Soft Robot. 6, 214–227 (2018).
Goswami, D., Liu, S., Pal, A., Silva, L. G. & Martinez, R. V. 3D-architected soft machines with topologically encoded motion. Adv. Funct. Mater. 29, 1808713 (2019).
Schlagenhauf, C. et al. Control of tendon-driven soft foam robot hands. In 2018 IEEE-RAS 18th Intl Conf. on Humanoid Robots (Humanoids) 1–7 (IEEE, 2018).
Mishra, A. K., Del Dottore, E., Sadeghi, A., Mondini, A. & Mazzolai, B. SIMBA: tendon-driven modular continuum arm with soft reconfigurable gripper. Front. Robot. AI 4, 4 (2017).
Kim, Y. & Cha, Y. Soft pneumatic gripper with a tendon-driven soft origami pump. Front. Bioeng. Biotechnol. 8, 461 (2020).
Ren, T. et al. A novel tendon-driven soft actuator with self-pumping property. Soft Robot. 7, 130–139 (2020).
Wehner, M. et al. An integrated design and fabrication strategy for entirely soft, autonomous robots. Nature 536, 451–455 (2016).
Aubin, C. A. et al. Electrolytic vascular systems for energy-dense robots. Nature 571, 51–57 (2019).
Li, G. et al. Self-powered soft robot in the Mariana Trench. Nature 591, 66–71 (2021).
Ji, X. et al. An autonomous untethered fast soft robotic insect driven by low-voltage dielectric elastomer actuators. Sci. Robot. 4, eaaz6451 (2019).
He, Q. & Cai, S. Soft pumps for soft robots. Sci. Robot. 6, eabg6640 (2021).
Hu, W., Lum, G. Z., Mastrangeli, M. & Sitti, M. Small-scale soft-bodied robot with multimodal locomotion. Nature 554, 81–85 (2018).
Lu, H. et al. A bioinspired multilegged soft millirobot that functions in both dry and wet conditions. Nat. Commun. 9, 3944 (2018).
Ren, Z., Hu, W., Dong, X. & Sitti, M. Multi-functional soft-bodied jellyfish-like swimming. Nat. Commun. 10, 2703 (2019).
Dong, X. et al. Bioinspired cilia arrays with programmable nonreciprocal motion and metachronal coordination. Sci. Adv. 6, eabc9323 (2020).
Lum, G. Z. et al. Shape-programmable magnetic soft matter. Proc. Natl Acad. Sci. USA 113, E6007–E6015 (2016).
Gu, H. et al. Magnetic cilia carpets with programmable metachronal waves. Nat. Commun. 11, 2637 (2020).
Huang, H.-W. et al. Adaptive locomotion of artificial microswimmers. Sci. Adv. 5, eaau1532 (2019).
Lee, H. et al. 3D-printed programmable tensegrity for soft robotics. Sci. Robot. 5, eaay9024 (2020).
Cao, L. et al. Ferromagnetic liquid metal putty-like material with transformed shape and reconfigurable polarity. Adv. Mater. 32, 2000827 (2020).
Kim, Y., Yuk, H., Zhao, R., Chester, S. A. & Zhao, X. Printing ferromagnetic domains for untethered fast-transforming soft materials. Nature 558, 274 (2018).
Cui, J. et al. Nanomagnetic encoding of shape-morphing micromachines. Nature 575, 164–168 (2019).
Zhang, J. et al. Voxelated three-dimensional miniature magnetic soft machines via multimaterial heterogeneous assembly. Sci. Robot. 6, eabf0112 (2021).
Alapan, Y., Karacakol, A. C., Guzelhan, S. N., Isik, I. & Sitti, M. Reprogrammable shape morphing of magnetic soft machines. Sci. Adv. 6, eabc6414 (2020).
Deng, H. et al. Laser reprogramming magnetic anisotropy in soft composites for reconfigurable 3D shaping. Nat. Commun. 11, 6325 (2020).
Mirvakili, S. M., Sim, D., Hunter, I. W. & Langer, R. Actuation of untethered pneumatic artificial muscles and soft robots using magnetically induced liquid-to-gas phase transitions. Sci. Robot. 5, eaaz4239 (2020).
Sitti, M. & Wiersma, D. S. Pros and cons: magnetic versus optical microrobots. Adv. Mater. 32, 1906766 (2020).
Liu, Y. et al. Humidity- and photo-induced mechanical actuation of cross-linked liquid crystal polymers. Adv. Mater. 29, 1604792 (2017).
Lu, X. et al. Liquid-crystalline dynamic networks doped with gold nanorods showing enhanced photocontrol of actuation. Adv. Mater. 30, 1706597 (2018).
Lancia, F., Ryabchun, A., Nguindjel, A.-D., Kwangmettatam, S. & Katsonis, N. Mechanical adaptability of artificial muscles from nanoscale molecular action. Nat. Commun. 10, 4819 (2019).
Shahsavan, H. et al. Bioinspired underwater locomotion of light-driven liquid crystal gels. Proc. Natl Acad. Sci. USA 117, 5125–5133 (2020).
Kuenstler, A. S., Kim, H. & Hayward, R. C. Liquid crystal elastomer waveguide actuators. Adv. Mater. 31, e1901216 (2019).
Yang, H. et al. 3D printed photoresponsive devices based on shape memory composites. Adv. Mater. 29, 1701627 (2017).
Liu, J. A.-C., Gillen, J. H., Mishra, S. R., Evans, B. A. & Tracy, J. B. Photothermally and magnetically controlled reconfiguration of polymer composites for soft robotics. Sci. Adv. 5, eaaw2897 (2019).
Wang, S. et al. Asymmetric elastoplasticity of stacked graphene assembly actualizes programmable untethered soft robotics. Nat. Commun. 11, 4359 (2020).
Wang, Y. et al. Light-activated shape morphing and light-tracking materials using biopolymer-based programmable photonic nanostructures. Nat. Commun. 12, 1651 (2021).
Cai, G., Ciou, J.-H., Liu, Y., Jiang, Y. & Lee, P. S. Leaf-inspired multiresponsive MXene-based actuator for programmable smart devices. Sci. Adv. 5, eaaw7956 (2019).
Li, J. et al. Photothermal bimorph actuators with in-built cooler for light mills, frequency switches, and soft robots. Adv. Funct. Mater. 340, 1808995 (2019).
Li, C. et al. Fast and programmable locomotion of hydrogel-metal hybrids under light and magnetic fields. Sci. Robot. 5, eabb9822 (2020).
Li, C. et al. Supramolecular–covalent hybrid polymers for light-activated mechanical actuation. Nat. Mater. 19, 900–909 (2020).
Wang, W. et al. Direct laser writing of superhydrophobic PDMS elastomers for controllable manipulation via Marangoni effect. Adv. Funct. Mater. 27, 1702946 (2017).
Li, M., Wang, X., Dong, B. & Sitti, M. In-air fast response and high speed jumping and rolling of a light-driven hydrogel actuator. Nat. Commun. 11, 3988 (2020).
Zhu, Q. L. et al. Light-steered locomotion of muscle-like hydrogel by self-coordinated shape change and friction modulation. Nat. Commun. 11, 5166 (2020).
Zhao, Y. et al. Soft phototactic swimmer based on self-sustained hydrogel oscillator. Sci. Robot. 4, eaax7112 (2019).
Li, M. et al. Flexible magnetic composites for light-controlled actuation and interfaces. Proc. Natl Acad. Sci USA 115, 8119–8124 (2018).
Li, M., Kim, T., Guidetti, G., Wang, Y. & Omenetto, F. G. Optomechanically actuated microcilia for locally reconfigurable surfaces. Adv. Mater. 32, 2004147 (2020).
Aghakhani, A., Yasa, O., Wrede, P. & Sitti, M. Acoustically powered surface-slipping mobile microrobots. Proc. Natl Acad. Sci. USA 117, 3469–3477 (2020).
Ren, L. et al. 3D steerable, acoustically powered microswimmers for single-particle manipulation. Sci. Adv. 5, eaax3084 (2019).
Ahmed, D. et al. Artificial swimmers propelled by acoustically activated flagella. Nano Lett. 16, 4968–4974 (2016).
Kaynak, M., Dirix, P. & Sakar, M. S. Addressable acoustic actuation of 3D printed soft robotic microsystems. Adv. Sci. 7, 2001120 (2020).
Chen, T., Bilal, O. R., Shea, K. & Daraio, C. Harnessing bistability for directional propulsion of soft, untethered robots. Proc. Natl Acad. Sci. USA 115, 5698–5702 (2018).
Kotikian, A., Truby, R. L., Boley, J. W., White, T. J. & Lewis, J. A. 3D Printing of liquid crystal elastomeric actuators with spatially programed nematic order. Adv. Mater. 30, 1706164 (2018).
Jin, B. et al. Programming a crystalline shape memory polymer network with thermo-and photo-reversible bonds toward a single-component soft robot. Sci. Adv. 4, eaao3865 (2018).
Kotikian, A. et al. Untethered soft robotic matter with passive control of shape morphing and propulsion. Sci. Robot. 4, eaax7044 (2019).
Wang, Y. et al. Stimuli-responsive composite biopolymer actuators with selective spatial deformation behavior. Proc. Natl Acad. Sci. USA 117, 14602–14608 (2020).
Shin, B. et al. Hygrobot: a self-locomotive ratcheted actuator powered by environmental humidity. Sci. Robot. 3, eaar2629 (2018).
Sydney Gladman, A., Matsumoto, E. A., Nuzzo, R. G., Mahadevan, L. & Lewis, J. A. Biomimetic 4D printing. Nat. Mater. 15, 413–418 (2016).
Cao, J. et al. Arbitrarily 3D configurable hygroscopic robots with a covalent-noncovalent interpenetrating network and self-healing ability. Adv. Mater. 31, e1900042 (2019).
Li, H., Go, G., Ko, S. Y., Park, J.-O. & Park, S. Magnetic actuated pH-responsive hydrogel-based soft micro-robot for targeted drug delivery. Smart Mater. Struct. 25, 027001 (2016).
Qin, H., Zhang, T., Li, N., Cong, H.-P. & Yu, S.-H. Anisotropic and self-healing hydrogels with multi-responsive actuating capability. Nat. Commun. 10, 2202 (2019).
Jiang, Y., Korpas, L. M. & Raney, J. R. Bifurcation-based embodied logic and autonomous actuation. Nat. Commun. 10, 1–10 (2019).
Mu, J. et al. Molecular-channel driven actuator with considerations for multiple configurations and color switching. Nat. Commun. 9, 590 (2018).
Bartlett, N. W. et al. A 3D-printed, functionally graded soft robot powered by combustion. Science 349, 161–165 (2015).
Yang, X., Chang, L. & Pérez-Arancibia, N. O. An 88-milligram insect-scale autonomous crawling robot driven by a catalytic artificial muscle. Sci. Robot. 5, eaba0015 (2020).
Pena-Francesch, A., Giltinan, J. & Sitti, M. Multifunctional and biodegradable self-propelled protein motors. Nat. Commun. 10, 3188 (2019).
Kong, L., Ambrosi, A., Nasir, M. Z. M., Guan, J. & Pumera, M. Self-propelled 3D-printed “aircraft carrier” of light-powered smart micromachines for large-volume nitroaromatic explosives removal. Adv. Funct. Mater. 29, 1903872 (2019).
Cangialosi, A. et al. DNA sequence–directed shape change of photopatterned hydrogels via high-degree swelling. Science 357, 1126–1130 (2017).
Ricotti, L. et al. Biohybrid actuators for robotics: a review of devices actuated by living cells. Sci. Robot. 2, eaaq0495 (2017).
Alapan, Y. et al. Microrobotics and microorganisms. Annu. Rev. Control. Robot. Auton. Syst. 2, 205–230 (2019).
Park, S.-J. et al. Phototactic guidance of a tissue-engineered soft-robotic ray. Science 353, 158–162 (2016).
Raman, R. et al. Optogenetic skeletal muscle-powered adaptive biological machines. Proc. Natl Acad. Sci. USA 113, 3497–3502 (2016).
Aydin, O. et al. Neuromuscular actuation of biohybrid motile bots. Proc. Natl Acad. Sci. USA 116, 19841–19847 (2019).
Raman, R., Cvetkovic, C. & Bashir, R. A modular approach to the design, fabrication, and characterization of muscle-powered biological machines. Nat. Protoc. 12, 519–533 (2017).
Morimoto, Y., Onoe, H. & Takeuchi, S. Biohybrid robot powered by an antagonistic pair of skeletal muscle tissues. Sci. Robot. 3, eaat4440 (2018).
Li, Z. et al. Biohybrid valveless pump-bot powered by engineered skeletal muscle. Proc. Natl Acad. Sci. USA 116, 1543–1548 (2019).
Fu, F., Shang, L., Chen, Z., Yu, Y. & Zhao, Y. Bioinspired living structural color hydrogels. Sci. Robot. 3, eaar8580 (2018).
Xu, B. et al. A remotely controlled transformable soft robot based on engineered cardiac tissue construct. Small 15, e1900006 (2019).
Guix, M. et al. Biohybrid soft robots with self-stimulating skeletons. Sci. Robot. 6, eabe7577 (2021).
Park, B.-W., Zhuang, J., Yasa, O. & Sitti, M. Multifunctional bacteria-driven microswimmers for targeted active drug delivery. ACS Nano 11, 8910–8923 (2017).
Singh, A. V., Hosseinidoust, Z., Park, B.-W., Yasa, O. & Sitti, M. Microemulsion-based soft bacteria-driven microswimmers for active cargo delivery. ACS Nano 11, 9759–9769 (2017).
Cao, F., Zhang, C., Choo, H. Y. & Sato, H. Insect–computer hybrid legged robot with user-adjustable speed, step length and walking gait. J. R. Soc. Interface 13, 20160060 (2016).
Magdanz, V. et al. IRONSperm: sperm-templated soft magnetic microrobots. Sci. Adv. 6, eaba5855 (2020).
Xu, N. W. & Dabiri, J. O. Low-power microelectronics embedded in live jellyfish enhance propulsion. Sci. Adv. 6, eaaz3194 (2020).
Alapan, Y. et al. Soft erythrocyte-based bacterial microswimmers for cargo delivery. Sci. Robot. 3, eaar4423 (2018).
Wu, M. et al. Photosensitizer-bacteria biohybrids promote photodynamic cancer cell ablation and intracellular protein delivery. Chem. Mater. 31, 7212–7220 (2019).
Shintake, J., Cacucciolo, V., Floreano, D. & Shea, H. Soft robotic grippers. Adv. Mater. 30, 1707035 (2018).
Zhang, Y.-F. et al. Miniature pneumatic actuators for soft robots by high-resolution multimaterial 3D printing. Adv. Mater. Technol. 4, 1900427 (2019).
Paek, J., Cho, I. & Kim, J. Microrobotic tentacles with spiral bending capability based on shape-engineered elastomeric microtubes. Sci. Rep. 5, 10768 (2015).
Yap, H. K., Ng, H. Y. & Yeow, C.-H. High-force soft printable pneumatics for soft robotic applications. Soft Robot. 3, 144–158 (2016).
Li, X., Cai, X., Gao, Y. & Serpe, M. J. Reversible bidirectional bending of hydrogel-based bilayer actuators. J. Mater. Chem. B 5, 2804–2812 (2017).
Taccola, S. et al. Toward a new generation of electrically controllable hygromorphic soft actuators. Adv. Mater. 27, 1668–1675 (2015).
Leeladhar & Singh, J. P. Photomechanical and chemomechanical actuation behavior of graphene–poly(dimethylsiloxane)/gold bilayer tube for multimode soft grippers and volatile organic compounds detection applications. ACS Appl. Mater. Interfaces 10, 33956–33965 (2018).
Hubbard, A. M., Mailen, R. W., Zikry, M. A., Dickey, M. D. & Genzer, J. Controllable curvature from planar polymer sheets in response to light. Soft Matter 13, 2299–2308 (2017).
Diller, E. & Sitti, M. Three-dimensional programmable assembly by untethered magnetic robotic micro-grippers. Adv. Funct. Mater. 24, 4397–4404 (2014).
Abbott, J. J., Diller, E. & Petruska, A. J. Magnetic methods in robotics. Annu. Rev. Control 3, 57–90 (2020).
Fusco, S. et al. An integrated microrobotic platform for on-demand, targeted therapeutic interventions. Adv. Mater. 26, 952–957 (2014).
Jin, Q., Yang, Y., Jackson, J. A., Yoon, C. & Gracias, D. H. Untethered single cell grippers for active biopsy. Nano Lett. 20, 5383–5390 (2020).
Malachowski, K. et al. Stimuli-responsive theragrippers for chemomechanical controlled release. Angew. Chem. Int. Ed. 53, 8045–8049 (2014).
Breger, J. C. et al. Self-folding thermo-magnetically responsive soft microgrippers. ACS Appl. Mater. Interfaces 7, 3398–3405 (2015).
Shintake, J., Schubert, B., Rosset, S., Shea, H. & Floreano, D. Variable stiffness actuator for soft robotics using dielectric elastomer and low-melting-point alloy. In 2015 IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS) 1097–1102 (IEEE, 2015).
Amend, J., Cheng, N., Fakhouri, S. & Culley, B. Soft robotics commercialization: jamming grippers from research to product. Soft Robot. 3, 213–222 (2016).
Hawkes, E. W., Christensen, D. L., Kyungwon Han, A., Jiang, H. & Cutkosky, M. R. Grasping without squeezing: shear adhesion gripper with fibrillar thin film. In 2015 IEEE Int. Conf. on Robotics and Automation (ICRA) 2305–2312 (IEEE, 2015).
Song, S., Drotlef, D.-M., Majidi, C. & Sitti, M. Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces. Proc. Natl Acad. Sci. USA 114, E4344–E4353 (2017).
Wang, L., Ha, K.-H., Rodin, G. J., Liechti, K. M. & Lu, N. Mechanics of crater-enabled soft dry adhesives: a review. Front. Mech. Eng. 6, 98 (2020).
Josephson, R. K. Contraction dynamics and power output of skeletal muscle. Annu. Rev. Physiol. 55, 527–546 (1993).
Mirfakhrai, T., Madden, J. D. W. & Baughman, R. H. Polymer artificial muscles. Mater. Today 10, 30–38 (2007).
Christianson, C., Goldberg, N. N., Deheyn, D. D., Cai, S. & Tolley, M. T. Translucent soft robots driven by frameless fluid electrode dielectric elastomer actuators. Sci. Robot. 3, eaat1893 (2018).
Hines, L., Petersen, K., Lum, G. Z. & Sitti, M. Soft actuators for small-scale robotics. Adv. Mater. 29, 1603483 (2017).
Yirmibesoglu, O. D. & Menguc, Y. Hybrid soft sensor with embedded IMUs to measure motion. In 2016 IEEE Int. Conf. on Automation Science and Engineering (CASE) 798–804 (IEEE, 2016).
Farrow, N., McIntire, L. & Correll, N. Functionalized textiles for interactive soft robotics. In 2017 IEEE Int. Conf. on Robotics and Automation (ICRA) 5525–5531 (IEEE, 2017).
Koivikko, A., Raei, E. S., Mosallaei, M., Mäntysalo, M. & Sariola, V. Screen-printed curvature sensors for soft robots. IEEE Sens. J. 18, 223–230 (2018).
Meerbeek, I. M. V., Sa, C. M. D. & Shepherd, R. F. Soft optoelectronic sensory foams with proprioception. Sci. Robot. 3, eaau2489 (2018).
Thuruthel, T. G., Abidi, S. H., Cianchetti, M., Laschi, C. & Falotico, E. A bistable soft gripper with mechanically embedded sensing and actuation for fast closed-loop grasping. Preprint at https://arxiv.org/abs/1902.04896 (2019).
Bai, H. et al. Stretchable distributed fiber-optic sensors. Science 370, 848–852 (2020).
Tapia, J., Knoop, E., Mutnỳ, M., Otaduy, M. A. & Bächer, M. Makesense: automated sensor design for proprioceptive soft robots. Soft Robot. 7, 332–345 (2020).
Truby, R. L. et al. Soft somatosensitive actuators via embedded 3D printing. Adv. Mater. 30, 1706383 (2018).
Zhao, H., O’Brien, K., Li, S. & Shepherd, R. F. Optoelectronically innervated soft prosthetic hand via stretchable optical waveguides. Sci. Robot. 1, eaai7529 (2016).
Justus, K. B. et al. A biosensing soft robot: Autonomous parsing of chemical signals through integrated organic and inorganic interfaces. Sci. Robot. 4, eaax0765 (2019).
Chu, C.-Y. & Patterson, R. M. Soft robotic devices for hand rehabilitation and assistance: a narrative review. J. Neuroeng. Rehabil. 15, 9 (2018).
Kim, D. et al. Eyes are faster than hands: a soft wearable robot learns user intention from the egocentric view. Sci. Robot. 4, eaav2949 (2019).
Dang, W., Vinciguerra, V., Lorenzelli, L. & Dahiya, R. Printable stretchable interconnects. Flex. Print. Electron. 2, 013003 (2017).
Wang, H., Totaro, M. & Beccai, L. Toward perceptive soft robots: progress and challenges. Adv. Sci. 5, 1800541 (2018).
Biswas, S. & Visell, Y. Emerging material technologies for haptics. Adv. Mater. Technol. 4, 1900042 (2019).
Miriyev, A., Stack, K. & Lipson, H. Soft material for soft actuators. Nat. Commun. 8, 596 (2017).
Kanjanapas, S., Nunez, C. M., Williams, S. R., Okamura, A. M. & Luo, M. Design and analysis of pneumatic 2-DoF soft haptic devices for shear display. IEEE Robot. Autom. Lett. 4, 1365–1371 (2019).
Thai, M. T., Hoang, T. T., Phan, P. T., Lovell, N. H. & Nho Do, T. Soft microtubule muscle-driven 3-axis skin-stretch haptic devices. IEEE Access. 8, 157878–157891 (2020).
Leroy, E., Hinchet, R. & Shea, H. Multimode hydraulically amplified electrostatic actuators for wearable haptics. Adv. Mater. 32, 2002564 (2020).
Phung, H., Nguyen, C. T., Jung, H., Nguyen, T. D. & Choi, H. R. Bidirectional tactile display driven by electrostatic dielectric elastomer actuator. Smart Mater. Struct. 29, 035007 (2020).
Kim, J. et al. Braille display for portable device using flip-latch structured electromagnetic actuator. IEEE Trans. Haptics 13, 59–65 (2020).
Kim, S.-W. et al. Thermal display glove for interacting with virtual reality. Sci. Rep. 10, 11403 (2020).
Torras, N. et al. Tactile device based on opto-mechanical actuation of liquid crystal elastomers. Sens. Actuators A 208, 104–112 (2014).
Lipomi, D. J., Dhong, C., Carpenter, C. W., Root, N. B. & Ramachandran, V. S. Organic haptics: intersection of materials chemistry and tactile perception. Adv. Funct. Mater. 30, 1906850 (2020).
Dhong, C. et al. Role of indentation depth and contact area on human perception of softness for haptic interfaces. Sci. Adv. 5, eaaw8845 (2019).
Skylar-Scott, M. A., Mueller, J., Visser, C. W. & Lewis, J. A. Voxelated soft matter via multimaterial multinozzle 3D printing. Nature 575, 330–335 (2019).
Zhai, Y. et al. Printing multi-material organic haptic actuators. Adv. Mater. 33, 2002541 (2021).
Kayser, L. V. & Lipomi, D. J. Stretchable conductive polymers and composites based on PEDOT and PEDOT:PSS. Adv. Mater. 31, 1806133 (2019).
Carpenter, C. W. et al. Electropneumotactile stimulation: multimodal haptic actuators enabled by a stretchable conductive polymer on inflatable pockets. Adv. Mater. Technol. 5, 1901119 (2020).
Jeon, S. et al. A magnetically controlled soft microrobot steering a guidewire in a three-dimensional phantom vascular network. Soft Robot. 6, 54–68 (2018).
Kim, Y., Parada, G. A., Liu, S. & Zhao, X. Ferromagnetic soft continuum robots. Sci. Robot. 4, eaax7329 (2019).
Pancaldi, L. et al. Flow driven robotic navigation of microengineered endovascular probes. Nat. Commun. 11, 6356 (2020).
Kashyap, V. et al. Multilayer fabrication of durable catheter-deployable soft robotic sensor arrays for efficient left atrial mapping. Sci. Adv. 6, eabc6800 (2020).
Han, M. et al. Catheter-integrated soft multilayer electronic arrays for multiplexed sensing and actuation during cardiac surgery. Nat. Biomed. Eng. 4, 997–1009 (2020).
Son, D., Gilbert, H. & Sitti, M. Magnetically actuated soft capsule endoscope for fine-needle biopsy. Soft Robot. 7, 10–21 (2019).
Payne, C. J. et al. Soft robotic ventricular assist device with septal bracing for therapy of heart failure. Sci. Robot. 2, eaan6736 (2017).
Wang, C. & Park, J. Magnetic micropump embedded in contact lens for on-demand drug delivery. Micro Nano Syst. Lett. 8, 1 (2020).
Cabanach, P. et al. Zwitterionic 3D-printed non-immunogenic stealth microrobots. Adv. Mater. 32, 2003013 (2020).
Ceylan, H. et al. 3D-printed biodegradable microswimmer for theranostic cargo delivery and release. ACS Nano 13, 3353–3362 (2019).
Park, J., Kim, J., Pané, S., Nelson, B. J. & Choi, H. Acoustically mediated controlled drug release and targeted therapy with degradable 3D porous magnetic microrobots. Adv. Healthc. Mater. 5, 2001096 (2020).
Yang, X. et al. An agglutinate magnetic spray transforms inanimate objects into millirobots for biomedical applications. Sci. Robot. 5, eabc8191 (2020).
Pal, A., Restrepo, V., Goswami, D. & Martinez, R. V. Exploiting mechanical instabilities in soft robotics: control, sensing, and actuation. Adv. Mater. 33, 2006939 (2021).
Rothemund, P. et al. A soft, bistable valve for autonomous control of soft actuators. Sci. Robot. 3, eaar7986 (2018).
Preston, D. J. et al. Digital logic for soft devices. Proc. Natl Acad. Sci. USA 116, 7750–7759 (2019).
Preston, D. J. et al. A soft ring oscillator. Sci. Robot. 4, eaaw5496 (2019).
Pal, A., Goswami, D. & Martinez, R. V. Elastic energy storage enables rapid and programmable actuation in soft machines. Adv. Funct. Mater. 30, 1906603 (2020).
Tang, Y. et al. Leveraging elastic instabilities for amplified performance: spine-inspired high-speed and high-force soft robots. Sci. Adv. 6, eaaz6912 (2020).
Wang, T., Ren, Z., Hu, W., Li, M. & Sitti, M. Effect of body stiffness distribution on larval fish–like efficient undulatory swimming. Sci. Adv. 7, eabf7364 (2021).
Rafsanjani, A., Zhang, Y., Liu, B., Rubinstein, S. M. & Bertoldi, K. Kirigami skins make a simple soft actuator crawl. Sci. Robot. 3, eaar7555 (2018).
Jin, L., Forte, A. E., Deng, B., Rafsanjani, A. & Bertoldi, K. Kirigami-inspired inflatables with programmable shapes. Adv. Mater. 32, 2001863 (2020).
Li, S. et al. A vacuum-driven origami “magic-ball” soft gripper. In 2019 Int. Conf. on Robotics and Automation (ICRA) 7401–7408 (IEEE, 2019).
Cafferty, B. J. et al. Fabricating 3D Structures by combining 2D printing and relaxation of strain. Adv. Mater. Technol. 4, 1800299 (2018).
Coyle, S., Majidi, C., LeDuc, P. & Hsia, K. J. Bio-inspired soft robotics: material selection, actuation, and design. Extrem. Mech. Lett. 22, 51–59 (2018).
Laschi, C. et al. Soft robot arm inspired by the octopus. Adv. Robot. 26, 709–727 (2012).
Laschi, C. & Cianchetti, M. Soft robotics: new perspectives for robot bodyware and control. Front. Bioeng. Biotechnol. 2, 1–5 (2014).
Gu, G., Zou, J., Zhao, R., Zhao, X. & Zhu, X. Soft wall-climbing robots. Sci. Robot. 3, eaat2874 (2018).
Hawkes, E. W., Blumenschein, L. H., Greer, J. D. & Okamura, A. M. A soft robot that navigates its environment through growth. Sci. Robot. 2, eaan3028 (2017).
Zhang, J. et al. Liquid crystal elastomer-based magnetic composite films for reconfigurable shape-morphing soft miniature machines. Adv. Mater. 33, 2006191 (2021).
Zhang, L., Naumov, P., Du, X., Hu, Z. & Wang, J. Vapomechanically responsive motion of microchannel-programmed actuators. Adv. Mater. 29, 1702231 (2017).
Sanchez, V., Walsh, C. J. & Wood, R. J. Textile technology for soft robotic and autonomous garments. Adv. Funct. Mater. 31, 2008278 (2021).
Baldé, C. P. et al. The Global e-Waste Monitor 2017: Quantities, Flows, and Resources (United Nations Univ., 2017).
Wang, Z., Zhang, B. & Guan, D. Take responsibility for electronic-waste disposal. Nature 536, 23–25 (2016).
Blaiszik, B. J. et al. Self-healing polymers and composites. Annu. Rev. Mater. Res. 40, 179–211 (2010).
Markvicka, E. J., Bartlett, M. D., Huang, X. & Majidi, C. An autonomously electrically self-healing liquid metal–elastomer composite for robust soft-matter robotics and electronics. Nat. Mater. 17, 618–624 (2018).
Wang, S. & Urban, M. W. Self-healing polymers. Nat. Rev. Mater. 5, 562–583 (2020).
Pena-Francesch, A., Jung, H., Demirel, M. C. & Sitti, M. Biosynthetic self-healing materials for soft machines. Nat. Mater. 19, 1230–1235 (2020).
Terryn, S., Brancart, J., Lefeber, D., Assche, G. V. & Vanderborght, B. Self-healing soft pneumatic robots. Sci. Robot. 2, eaan4268 (2017).
Yu, K., Xin, A., Du, H., Li, Y. & Wang, Q. Additive manufacturing of self-healing elastomers. npg Asia Mater. 11, 7 (2019).
Tee, B. C.-K., Wang, C., Allen, R. & Bao, Z. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications. Nat. Nanotech 7, 825–832 (2012).
Tan, Y. J. et al. A transparent, self-healing and high-κ dielectric for low-field-emission stretchable optoelectronics. Nat. Mater. 19, 182–188 (2020).
Tan, Y. J., Susanto, G. J., Anwar Ali, H. P. & Tee, B. C. K. Progress and roadmap for intelligent self-healing materials in autonomous robotics. Adv. Mater. 33, 2002800 (2020).
Yang, H. et al. Graphene oxide-enabled synthesis of metal oxide origamis for soft robotics. ACS Nano 13, 5410–5420 (2019).
Pena-Francesch, A. et al. Programmable proton conduction in stretchable and self-healing proteins. Chem. Mater. 30, 898–905 (2018).
Tomko, J. A. et al. Tunable thermal transport and reversible thermal conductivity switching in topologically networked bio-inspired materials. Nat. Nanotech 13, 959–964 (2018).
Hartmann, F., Baumgartner, M. & Kaltenbrunner, M. Becoming sustainable, the new frontier in soft robotics. Adv. Mater. 33, 2004413 (2020).
Raman, R. et al. Light-degradable hydrogels as dynamic triggers for gastrointestinal applications. Sci. Adv. 6, eaay0065 (2020).
Bellinger, A. M. et al. Oral, ultra–long-lasting drug delivery: application toward malaria elimination goals. Sci. Transl. Med. 8, 365ra157 (2016).
Feig, V. R., Tran, H. & Bao, Z. Biodegradable polymeric materials in degradable electronic devices. ACS Cent. Sci. 4, 337–348 (2018).
Walker, S. et al. Using an environmentally benign and degradable elastomer in soft robotics. Int. J. Intell. Robot. Appl. 1, 124–142 (2017).
Baumgartner, M. et al. Resilient yet entirely degradable gelatin-based biogels for soft robots and electronics. Nat. Mater. 19, 1102–1109 (2020).
Goudu, S. R. et al. Biodegradable untethered magnetic hydrogel milli-grippers. Adv. Funct. Mater. 30, 2004975 (2020).
This work is funded by the Max Planck Society, the European Research Council (ERC) Advanced Grant SoMMoR project (grant number 834531) and the German Research Foundation (DFG) Soft Material Robotic Systems (SPP 2100) Program (grant number 2197/3-1). M.L., A.P. and A.P.-F. received the Humboldt Postdoctoral Research Fellowship and thank the Alexander von Humboldt Foundation for their financial support.
The authors declare no competing interests.
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Li, M., Pal, A., Aghakhani, A. et al. Soft actuators for real-world applications. Nat Rev Mater 7, 235–249 (2022). https://doi.org/10.1038/s41578-021-00389-7
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