Soft materials and actuators enable applications that are not possible using traditional rigid robots and actuators. Owing to their flexibility and compliance, soft actuators can adapt to complex and dynamic environments, which makes them exceptionally advantageous for physical interaction with fragile objects or living organisms. However, despite great advances in the field of soft robotics, both replicating the performance of biological actuators and the implementation of soft robots in industrial applications remain a challenge owing to the high-level complexity of biological actuators. Biological muscle and animal limbs have long served as inspiration for the design of soft actuators featuring a range of complex actuations (such as reversible contraction, expansion and rotation) and motions (such as bending and twisting), as well as specific strain, force, energy and power performance metrics 1-3 (Box 1). However, biological muscles have evolved to operate robustly in dynamic environments with high performance (efficiency, speed and power) and complex actions (including sensing, tunable stiffness or repair mechanisms), all of which are challenging to replicate in synthetic systems.Individual performance metrics can be particularly useful for specific tasks and are thus usually designed for specific applications. However, combining the performance and physical intelligence of biological systems (such as self-healing and self-adaptive behaviours) would greatly advance the integration of soft actuator and robot technology in multiple fields (for example, health care 4 , agriculture 5,6 , industry 7,8 and mobility 9 ).In this Review, we discuss materials and soft actuation methods that can enable advanced physical intelligence 10 , function and performance in soft actuator technology. We first examine promising soft actuation methods, including tethered, untethered and biohybrid actuation, and then discuss actuation strategies based on programmable soft materials that improve the performance and multifunctionality of soft actuators. We highlight state-of-the-art demonstrations of soft actuators towards real-world applications, including soft grippers, artificial muscles, sensor-integrated soft robots, haptic displays and biomedical applications. Lastly, we discuss challenges and opportunities for next-generation soft actuators, including integrating physical intelligence, encoding adaptability, manufacturing scalability and reproducibility, and improving the durability of soft robots. Promising soft actuation methodsMaterial selection, structural design and fabrication techniques are key factors in designing soft actuators that can convert multiple energy inputs into mechanical energy outputs using tethered, untethered or biohybrid approaches. Tethered synthetic soft actuationTethered soft actuators are usually actuated through a change of fluidic pressure in hollow channels of the soft actuator body, by electrically driven shape change or through passive deformation produced by motion

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Storage of elastic energy is key to increasing the efficiency, speed, and power output of many biological systems. This paper describes a simple design strategy for the rapid fabrication of prestressed soft actuators (PSAs), exploiting elastic energy storage to enhance the capabilities of soft robots. The elastic energy that PSAs store in their prestressed elastomeric layer enables the fabrication of grippers capable of zero-power holding up to 100 times their weight and perching upside down from angles of up to 116°. The direction and magnitude of the force used to prestress the elastomeric layer can be controlled not only to define the final shape of the PSA but also to program its actuation sequence. Additionally, the release of the elastic energy stored by PSAs causes their high-speed recovery (≈50 ms), which significantly improves the actuation rates of soft pneumatic actuators, especially after motions requiring large deformations. Moreover, judicious prestressing of PSAs can also create bistable soft robotic systems, which use their stored elastic energy as a source of power amplification for rapid movements. These strategies serve as a basis for a new class of entirely soft robots capable of recreating bioinspired high-powered and high-speed motions using stored elastic energy.

He received his B.Eng. degree from the Department of Production Engineering, Jadavpur University in 2014. He then joined the lab of Prof. Ramses Martinez in the School of Industrial Engineering, Purdue University, working on soft robotics and flexible biosensors, and in 2020, he obtained his Ph.D. His current research interests focus on modeling and development of soft robots, mechanical metamaterials, and flexible electronics.