A soft robotic fish can quickly swim and turn with a fully integrated onboard system for power and remote control.

The deep ocean, Earth’s untouched expanse, presents immense challenges for exploration due to its extreme pressure, temperature, and darkness. Unlike traditional marine robots that require specialized metallic vessels for protection, deep-sea species thrive without such cumbersome pressure-resistant designs. Their pressure-adaptive forms, unique propulsion methods, and advanced senses have inspired innovation in designing lightweight, compact soft machines. This perspective addresses challenges, recent strides, and design strategies for bioinspired deep-sea soft robots. Drawing from abyssal life, it explores the actuation, sensing, power, and pressure resilience of multifunctional deep-sea soft robots, offering game-changing solutions for profound exploration and operation in harsh conditions.

Hydrogels consist of cross-linked polymers that are highly swollen with water. Water evaporation or freezing during temperature changes may lead to stiff and brittle hydrogels. We introduce a strategy called “hydro-locking,” which involves immobilizing the water molecules within the polymer network of the hydrogel. This is accomplished by establishing robust connections between water molecules and the polymer by using sulfuric acid. A sacrificial network is introduced to shield the prime polymer network from collapsing. Under the hydro-locking mode, an alginate-polyacrylamide double-network hydrogel remains soft and stretchable within a temperature range that spans from –115° to 143°C. The strategy works with a range of hydrogels and solutions and may enable the preservation and observation of materials or even living organisms at extreme temperatures.

Typical hydrogels undergo slow and continuous shape change. Inspired by the Venus Flytrap, the current work presents a hydrogel assembly that can reversibly undergo a non-continuous rapid snapping shape change due to a bi-stable structure of the assembly. In particular, the reversible snapping change goes beyond the Venus Flytrap and is not known in the literature.

Inspired by natural creatures, soft robots possess the unique advantages of large actuation and excellent adaptability. Untethered designs of soft robots are drawing more attention to researchers, but current research is limited. Also, there is an increasing need to improve the performance of bio-mimetic robots. This work describes an untethered soft robotic jellyfish with high mobility that can mimic a natural jellyfish’s performance. The electrode of the robotic jellyfish is made by sandwiching carbon grease between two layers of dielectric elastomer film. The frame of the material, where six plastic paddles are attached, is made from a silicone elastomer. The robotic jellyfish has a maximum recorded swim speed of up to 1 cm s ⁻¹ , with a peak thrust force of 0.000 12 N. A finite element simulation is developed to study the performance of the robotic jellyfish in a theoretical manner. By embedding a compact remote-controlled power source, the robotic jellyfish is made autonomous. In this case, the max peak speed is around 0.5 cm s ⁻¹ . Ultimately, the working principles of the bio-mimetic robotic jellyfish can be useful in field studies and to guide the design of soft robots and flexible devices.