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Highlights This study presents a novel variable thickness nested tube consisting of circular tube and origami tube (VTCO) designed to reduce the initial peak crushing force (PCF) under axial loading while maintaining high energy absorption. The core of this design is to achieve progressive and controlled energy absorption and to reduce peak forces as well as accelerations that can lead to passenger injuries. Nested tube structures were fabricated using short carbon fiber‐reinforced nylon composites through 3D printing technology, and quasi‐static axial compression tests were performed. The results show that equal‐thickness nested tubes consisting of circular tubes and origami tubes (ETCO) perform better in terms of energy absorption and deformation stability compared to circular and origami tubes individually. The further improved VTCO reduced the PCF by 53% and significantly improved the crash force efficiency (CFE) by 54%. The VTCO structure was parametrically investigated by means of a validated finite element model and optimized using the Non‐Symmetric Dominance Sorting Genetic Algorithm II (NSGA‐II). The optimization results provide a feasible way to adjust the structural crashworthiness to meet different engineering requirements. This study provides valuable insights into the energy‐absorbing properties of VTCO structures and is an important guide for the application and material development of novel VTCO structures. ETCO offers better energy absorption and stability than circular and origami tubes individually. VTCO is superior to ETCO in reducing PCF and increasing CFE. Multi‐objective optimization using NSGA‐II to balance conflicting crashworthiness indicators. [ABSTRACT FROM AUTHOR]

• This paper leveraged the distinctive properties of magnetorheological smart materials to devise and fabricate an integrated 3D-printed soft robot. • Such magnetorheological smart materials can function as both the supporting framework for hollow cavities and the propelling substance for the robot. • During the course of this process, we investigated material properties pertinent to 3D printing and refined the design of the robot's structure and driving mechanism. A core–shell structured, amoeba-like, magnetically controlled soft robot is proposed for 3D printing using magnetically controlled smart materials and silicone materials. The purpose of this robot is to overcome the limitations of existing soft robot kinematic mechanisms that rely on the elastic deformation of flexible materials. The printability of the magnetically controlled smart material was verified through rheological tests. The effect of different component ratios on the rheological properties of the material was investigated and a suitable material ratio for printing was selected by adjusting the amount of SiO 2 in the silicone and conducting rheological tests. Mechanical simulation was used to select and optimize the design of the amoeboid soft robotic shell structures. Printing was then used to verify the stability of the shell structures. The self-supporting capability of the magnetically controlled smart materials was investigated under different magnetic field strengths. To solve the problem of the phase of the magnetron smart material and the silicone material, the composite printing of the two materials was accomplished by adjusting the printing process. Soft robots mimicking amoebas were then printed and fabricated. The magnetron array-based driving method is proposed, and the magnetic field of the array used to drive the amoeba-like soft robot is constructed. The magnetic field of the array surface was then simulated under several different driving modes. Based on the simulation results, a suitable driving mode was selected. Using the material mechanism of the magnetron-only material sol–gel transformation, the pseudopod extension gait of the amoeba-like soft robot was designed, and the localized deformation of the amoeba-like soft robot was realized. This paper leveraged the distinctive properties of magnetorheological smart materials to devise and fabricate an integrated 3D-printed soft robot. Such magnetorheological smart materials can function as both the supporting framework for hollow cavities and the propelling substance for the robot. During the course of this process, we investigated material properties pertinent to 3D printing and refined the design of the robot's structure and driving mechanism. [ABSTRACT FROM AUTHOR]