Direct 4D printing of functionally graded hydrogel networks for biodegradable,untethered,and multimorphic soft robots

Recent advances in functionally graded additive manufacturing(FGAM)technology have enabled the seamless hybridization of multiple functionalities in a single structure.Soft robotics can become one of the largest beneficiaries of these advances,through the design of a facile four-dimensional(4D)FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed objects.Herein,we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials(FGMM)by introducing rationally designed graded multiphase feeder beds.Compositionally graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles,enabling programmable hygroscopic deformation without complex mechanical designs.Furthermore,a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus selectivity.The biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach,with immediate degradation rates of 96.6%within 72 h.The proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.

Deformation and Locomotion of Untethered Small-Scale Magnetic Soft Robotic Turtle with Programmable Magnetization

Inspired by the way sea turtles rely on the Earth’s magnetic field for navigation and locomotion,a novel magnetic soft robotic turtle with programmable magnetization has been developed and investigated to achieve biomimetic locomotion patterns such as straight-line swimming and turning swimming.The soft robotic turtle(12.50 mm in length and 0.24 g in weight)is integrated with an Ecoflex-based torso and four magnetically programmed acrylic elastomer VHB-based limbs containing samarium-iron–nitrogen particles,and was able to carry a load more than twice its own weight.Similar to the limb locomotion characteristics of sea turtles,the magnetic torque causes the four limbs to mimic sinusoidal bending deformation under the influence of an external magnetic field,so that the turtle swims continuously forward.Significantly,when the bending deformation magnitudes of its left and right limbs differ,the soft robotic turtle switches from straight-line to turning swimming at 6.334 rad/s.Furthermore,the tracking swimming activities of the soft robotic turtle along specific planned paths,such as square-shaped,S-shaped,and double U-shaped maze,is anticipated to be utilized for special detection and targeted drug delivery,among other applications owing to its superior remote directional control ability.

Bioinspired Centimeter-scale Sensor Free Obstacle-passing Robots with a Wireless Control System

Obstacle avoidance is of great importance for mobile robots since it provides protection for the robots’safety and ensures their routine operations.Sensors are proven to play an important role in robots obstacle avoidance,and they are useful as well.However,more sensors indicating additional space,larger weight load and more energy consumption.Reducing unnecessary sensors is conducive to the development of mobile robots and remains promising.Here we demonstrate Sensor Free Obstacle-Passing Robots(SFOPRs)inspired by flies using the Obstacle-passing strategy instead of Obstacle avoidance.The ability to autonomously adjust its direction after hitting obstacles and the ability to continuously hit obstacles are 2 key problems that need to be solved to build this robot.Owing to arc-shaped head design and undulating motion behaviors,the robots can autonomously adjust their direction to the outline of obstacles,such as a 90°corner,dispersive irregular obstacles,and even an"S"type channel without the assistance of any sensor.Besides,the caterpillar-like movement enables robots to continuously hit obstacles.Furthermore,collaborative awareness and mutual aid can be realized among two or more prototype robots,indicating simple yet functional units for future swarm robots.This study could provide a new strategy to pursue sensor-free obstacle-passing robots for future swarm robot applications.