The rock-climbing fish is a benthic organism that can move rapidly and flexibly on rock surfaces in complex underwater environments. Studies have shown that this unique adhesion-sliding movement mechanism of the rock-climbing fish relies on the anisotropic friction exhibited by its sucker structure, which helps to reduce friction in the forward direction and defend against the impact of the flow field. In this work, inspired by the anisotropic friction phenomenon of the sucker of the rock-climbing fish, we designed the absorption module and pectoral and pelvic fin flapping module of the robotic fish to realize the contact switching from low friction to high friction. Meanwhile the propulsion module adopts a novel design of wire-driven caudal fin that can oscillate at high frequency (exceeding ~5 Hz). Resulting robotic fish can realize different motion modes such as adhesion-sliding movement (~0.5 BL/s) and wall-stabilized adsorption. This work will provide a new solution for the design pattern of underwater wall robots.

Engineered skeletal muscle tissue (SMT) is the ideal driving units for achieving fine movements in biosyncretic robots due to their excellent controllability and potentially large driving force. However, the selective stimulation of SMTs continues to pose a significant technical challenge. In this study, we propose a method for the selective stimulation of 3D SMT using thin-film interdigitated electrodes (IDEs). By optimizing the IDEs geometry through finite element simulations, electrical field intensity of fingertip is effectively reduced. The thin-film IDEs are fabricated on a Polyester (PET) substrate using screen printing technology and successfully enable selective activation and controlled contraction of the SMTs. Compared to conventional parallel-plate electrodes (PPEs) and rod-shaped electrodes (RSEs), the IDEs significantly improve the electrical field distribution and enhance spatial resolution. This advancement provides a promising new approach for achieving high-precision motion control in biosyncretic robots (or biohybrid robots).

Fish can adaptively adjust their body kinematics and swimming modes by sensing to realize optimal propulsion. However, most soft robotic fish have an unchangeable swimming mode through simple structure design, making them difficult to adapt to dynamic and complex fluid environments. Here, inspired by the multiple muscle synergy and lateral line sensing function of fish, we developed a soft robotic fish with multiple actuating units and embedded sensing elements. By collaboratively controlling the amplitude and phase of excitation from the multiple flexible actuating units, the soft robotic fish can successfully realize various swimming modes very similar to those of natural fish. Additionally, the embedded flexible sensing elements enable the robotic fish to sense the swimming state and the surrounding fluid environment in real time. The multiple actuation and embedded sensing allow the soft robotic fish to adaptively switch to an optimal swimming mode in a certain fluid environment. The multimode swimming and perception capabilities proposed in this work not only make soft robotic fish more intelligent and adaptable to complex fluid environments, but also contribute to the future implementation of autonomous control capabilities for robotic fish.

In recent years, bio-syncretic robots actuated by living materials have received widespread attention. Among the common living materials, engineered skeletal muscle tissue (eSKT) has been the focus of researchers due to its high contraction force and good controllability. However, the current performance of eSKT is far from that of natural skeletal muscle tissue. In this paper, an optimized design method for eSKTs has been proposed. By combining simulation analysis with experiments, the eSKTs with multiple strips have been developed. The results show that under a specific volume (250 μL), the optimized strip structures can enhance the stability of eSKT and facilitate the penetration of nutrients and oxygen, leading to improved fusion of myoblasts and the directional arrangement of myotubes, thus improving the performance of eSKT. The eSKT with multiple strips exhibits a significant contraction force and has been successfully utilized in a bio-syncretic robot to demonstrate its actuation capability. This work may provide insights into the development of the field of bio-syncretic robots and even tissue engineering.