Flying insects capable of navigating in highly cluttered natural environments can withstand inflight collisions because of the combination of their low inertia 1 and the resilience of their wings 2 , exoskeletons 1 , and muscles. Current insect-scale (<10 cm, <5 g) aerial robots 3-6 use rigid microscale actuators, which are typically fragile under external impact. Biomimetic artificial muscles 7-10 capable of large deformation offer a promising alternative for actuation because they can endure the stresses caused by such impacts. However, existing soft actuators 11-13 have not yet demonstrated sufficient power density for liftoff, and their actuation nonlinearity and limited bandwidth further create challenges for achieving closed-loop flight control. Here we develop the first heavier-than-air aerial robots powered by soft artificial muscles that demonstrate open-loop, passively stable ascending flight as well as closed-loop, hovering flight. The robots are driven by 100 mg, multilayered dielectric elastomer actuators (DEA) that have a resonant frequency and power density of 500 Hz and 600 W/kg, respectively. To increase actuator output mechanical power and to demonstrate flight control, we present strategies to overcome challenges unique to soft actuators, such as nonlinear transduction and dynamic buckling. These robots can sense, and withstand, collisions with surrounding obstacles, and can recover from in-flight collisions by exploiting material robustness and vehicle passive stability. We further perform a simultaneous flight with two micro-aerial-vehicles (MAV) in cluttered environments. These robots rely on offboard amplifiers and an external motion capture system to provide power to the DEAs and control flights. Our work demonstrates how soft actuators can achieve sufficient power density and bandwidth to enable controlled flight, illustrating the vast potential of developing next-generation agile soft robots. Soft robotics 14-16 is an emerging field aiming to develop versatile systems that can safely interact with humans and manipulate delicate objects in unstructured environments. A major challenge in building softactuated mobile robots involves developing muscle-like actuators that have high energy density, bandwidth, robustness, and lifetime. Previous studies have described soft actuators that can be actuated chemically 17 , pneumatically 18,19 , hydraulically 20 , thermally 21,22 , or electrically 7,23. Among these soft transducers, DEAs have shown a combination of muscle-like energy density and bandwidth 8 , enabling the development of biomimetic robots capable of terrestrial 11,24,25 and aquatic locomotion 26,27. However, while there is growing interest in developing heavier-than-air, soft-actuated aerial robots, existing soft robots 11-13 have been unable to achieve liftoff due to limited actuator power density (<200 W/kg), bandwidth (<20 Hz), and difficulties of integration with rigid robotic structures such as transmission and wings. To enable controlled hovering flight of a soft-actuated robot,...

Efficient and effective generation of high-acceleration movement in biology requires a process to control energy flow and amplify mechanical power from power density–limited muscle. Until recently, this ability was exclusive to ultrafast, small organisms, and this process was largely ascribed to the high mechanical power density of small elastic recoil mechanisms. In several ultrafast organisms, linkages suddenly initiate rotation when they overcenter and reverse torque; this process mediates the release of stored elastic energy and enhances the mechanical power output of extremely fast, spring-actuated systems. Here we report the discovery of linkage dynamics and geometric latching that reveals how organisms and synthetic systems generate extremely high-acceleration, short-duration movements. Through synergistic analyses of mantis shrimp strikes, a synthetic mantis shrimp robot, and a dynamic mathematical model, we discover that linkages can exhibit distinct dynamic phases that control energy transfer from stored elastic energy to ultrafast movement. These design principles are embodied in a 1.5-g mantis shrimp scale mechanism capable of striking velocities over 26 m s−1 in air and 5 m s−1 in water. The physical, mathematical, and biological datasets establish latching mechanics with four temporal phases and identify a nondimensional performance metric to analyze potential energy transfer. These temporal phases enable control of an extreme cascade of mechanical power amplification. Linkage dynamics and temporal phase characteristics are easily adjusted through linkage design in robotic and mathematical systems and provide a framework to understand the function of linkages and latches in biological systems.

Significance Soft actuators have advantages over traditional rigid robots in various applications due to their robustness, low mechanical stiffness, and low weight. Thus far, conventional rigid valves are the most common approach to control hydraulic soft actuators. Although soft valves have been designed in various forms, they have not achieved the pressure or flow rate conditions as required by many existing hydraulic actuators. In this paper, we introduce an electrically driven soft valve using dynamic dielectric elastomer actuators (DEAs). These soft valves have a fast response time and are able to control fluidic pressure and flow rates that match the needs of hydraulic actuators with mesoscale channels. The DEA valves enable possibilities for soft onboard controls for future fluidic soft robots.

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