Drawing inspiration from the ability of fish to maintain efficient swimming over a wide range of speeds by tuning the stiffness of their tails, researchers have explored stiffness adjustment mechanisms in fish-like robots. Typically, existing mechanisms require extra actuators or power sources only for tuning stiffness, resulting in additional energy consumption and more complex structures. To address this, our study introduces an innovative fishtail featuring an online stiffness modulation mechanism that does not require additional actuators or power sources solely for stiffness adjustment. Through model-based simulations and experimental testing, we evaluated the effectiveness of the proposed method. The results demonstrate that the designed mechanism enables efficient swimming across a broader frequency range (0–4 Hz) compared to most servo-actuated platforms with adjustable stiffness reported in existing studies. The robot achieves a maximum average speed of 1.4 BL/s and a minimum cost of transport of 9.5 J/(m•kg).

In nature, fish are excellent swimmers due to their flexible and precise control of tail, which allows them to freely transform between the smooth flapping and the motion of rapid response so that they can move with dexterity. Here, inspired by the versatile motion abilities of fish, a novel robotic fish has been developed, featuring the capability of adaptable bistability. Through tuning the bistability, the robot can acquire two locomotion modes, namely monostable and bistable modes, and it can also swim at different energy barrier that needs to be overcome to realize the bistable motion. The theoretical models are derived to facilitate the control of the robot and the understanding of its nonlinear behavior. The impact of the tunable bistability on the swimming and turning performance is investigated through extensive experiments. The study effectively demonstrates the robotic fish’s capability to swiftly and efficiently navigate through mode switches, enabled by its tunable bistability. This feature is essential for underwater robots to perform tasks in intricate environments.

In recent years, AI-driven drug development has emerged as a prominent research topic in computer chemistry. A key focus is the application of generative models for molecule synthesis, which create extensive virtual libraries of chemical molecules based on latent spaces. However, locating molecules with desirable properties within the vast latent spaces remains a significant challenge. Large regions of invalid samples in the latent space, called “dead zones”, can impede the exploration efficiency. The process is always time-consuming and repetitive. Therefore, we aim to propose a visualization system to help experts identify potential molecules with desirable properties as they wander in the latent space. Specifically, we conducted a literature survey about the application of generative networks in drug synthesis to summarize the tasks and followed this with expert interviews to determine their requirements. Based on the above requirements, we introduce ChemNav, an interactive visual tool for navigating latent space for desirable molecules search. ChemNav incorporates a heuristic latent space interpolation path search algorithm to enhance the efficiency of valid molecule generation, and a similar sample search algorithm to accelerate the discovery of similar molecules. Evaluations of ChemNav through two case studies, a user study, and experiments demonstrated its effectiveness in inspiring researchers to explore the latent space for chemical molecule discovery.

Developing a good control strategy for biomimetic robots is challenging. Robust control methods require an accurate model of the robot. Nowadays, model-free methods are being extensively explored for the control and navigation of terrestrial robots. In this paper, we consider a novel deep reinforcement learning-based model-free swimming control for our bio-inspired robotic tadpole. To realize this, we utilize dynamic motion primitives, which can represent a large range of motion behaviors, and combine them with a decoupled reinforcement learning framework. The proposed architecture optimizes the motion primitives first to develop a travelling wave undulation pattern in the tail and then to navigate the robot along different predefined paths. Through this framework, effective swimming gait emerges, and the robot is able to navigate well on the surface of water. This framework combines the optimization potential of deep reinforcement learning with stability and generalization properties of dynamic motion primitives. We train and test our method on a simulated model of the robot to demonstrate the effectiveness of the method and also conduct experimental testing on the real robot to verify the results.