Stenus-inspired, swift, and agile untethered insect-scale soft propulsors.

Mimicking living creatures, soft robots exhibit incomparable adaptability and various attractive new features. However, untethered insect-scale soft robots are often plagued with inferior controllability and low kinetic performance. Systematically inspired by the swift swingable abdomen, conducting canals for secretion transport, and body setae of Stenus comma, together with magnetic-induced fast-transformed postures, herein, we present a swift, agile untethered millimetre-scale soft propulsor propelling on water. The demonstrated propulsor, with a body length (BL) of 3.6 mm, achieved a recorded specific speed of ~201 BL/s and acceleration of ~8,372 BL/s2. The comprehensive kinetic performance of this propulsor surpasses those of previous ones at similar scales by several orders. Notably, we discovered momentum-transfer-induced over-biological on-demand braking (deceleration ~-5,010 BL/s2) and elucidated the underlying hydrodynamics. This work offers new insights into systematically bio-inspired artificial insect-scale soft robots, enabling them to push boundaries in performance, and potentially revolutionizing robot design, optimization, and control paradigms.

Synergistical Mechanical Design and Function Integration for Insect-Scale On-Demand Configurable Multifunctional Soft Magnetic Robots.

Meso- or micro-scale(or insect-scale) robots that are capable of realizing flexible locomotion and/or carrying on complex tasks in a remotely controllable manner hold great promise in diverse fields, such as biomedical applications, unknown environment exploration, in situ operation in confined spaces, and so on. However, the existing design and implementation approaches for such multifunctional, on-demand configurable insect-scale robots are often focusing on their actuation or locomotion, while matched design and implementation with synergistic actuation and function modules under large deformation targeting varying task/target demands are rarely investigated. In this study, through systematical investigations on synergistical mechanical design and function integration, we developed a matched design and implementation method for constructing multifunctional, on-demand configurable insect-scale soft magnetic robots. Based on such a method, we report a simple approach to construct soft magnetic robots by assembling various modules from the standard part library together. Moreover, diverse soft magnetic robots with desirable motion and function can be (re)configured. Finally, we demonstrated (re)configurable soft magnetic robots shifting into different modes to adapt and respond to varying scenarios. The customizable physical realization of complex soft robots with desirable actuation and diverse functions can pave a new way for constructing more sophisticated insect-scale soft machines that can be applied to practical applications soon.

A Soft Reconfigurable Circulator Enabled by Magnetic Liquid Metal Droplet for Multifunctional Control of Soft Robots.

Integrated control circuits with multiple computation functions are essential for soft robots to achieve diverse complex real tasks. However, designing compliant yet simple circuits to embed multiple computation functions in soft electronic systems above the centimeter scale is still a tough challenge. Herein, utilizing smooth cyclic motions of magnetic liquid metal droplets (MLMD) in specially designed and surface-modified circulating channels, a soft reconfigurable circulator (SRC) consisting of three simple and reconfigurable basic modules is described. Through these modules, MLMD can utilize their conductivity and extreme deformation capabilities to transfer their simple cyclic motions as input signals to programmable electrical output signals carrying computing information. The obtained SRCs make it possible for soft robots to perform complex computing tasks, such as logic, programming, and self-adaptive control (a combination of programming and feedback control). Following, a digital logic-based grasping function diagnosis, a locomotion reprogrammable soft car, and a self-adaptive control-based soft sorting gripper are demonstrated to verify SRCs' capabilities. The unique attributes of MLMD allow complex computations based on simple configurations and inputs, which provide new ways to enhance soft robots' computing capabilities.

Bioinspired Multimodal Multipose Hybrid Fingers for Wide-Range Force, Compliant, and Stable Grasping.

The increasing demand for grasping diverse objects in unstructured environments poses severe challenges to the existing soft/rigid robotic fingers due to the issues in balancing force, compliance, and stability, and hence has given birth to several hybrid designs. These hybrid designs utilize the advantages of rigid and soft structures and show better performance, but they are still suffering from narrow output force range, limited compliance, and rarely reported stability. Owing to its rigid-soft coupling structure with flexible switched multiple poses, human finger, as an excellent hybrid design, shows wide-range output force, excellent compliance, and stability. Inspired by human finger, we propose a hybrid finger with multiple modes and poses, coupled by a soft actuator (SA) and a rigid actuator (RA) in parallel. The multiple actuation modes formed by a pneumatic-based rigid-soft collaborative strategy can selectively enable the RA's high force and SA's softness, whereas the multiple poses derived from the specially designed underactuated RA skeleton can be flexibly switched with tasks, thus achieving high compliance. Such hybrid fingers also proved to be highly stable under external stimuli or gravity. Furthermore, we modularize and configure these fingers into a series of grippers with excellent grasping performance, for example, wide graspable object range (diverse from 0.1 g potato chips to 27 kg dumbbells for a 420 g two-finger gripper), high compliance (tolerate objects with 94% gripper span size and 4 cm offset), and high stability. Our study highlights the potential of fusing rigid-soft technologies for robot development, and potentially impacts future bionics and high-performance robot development.

Stiffness Preprogrammable Soft Bending Pneumatic Actuators for High-Efficient, Conformal Operation.

Soft pneumatic actuators (SPAs) are extensively investigated due to their simple control strategies for producing sophisticated motions. However, the motions or operations of homogeneous SPAs show obvious limitations in some varying curvature interaction scenarios because of the profile mismatch of homogeneous SPAs and specific interacted objects. Herein, a stiffness preprogrammable soft pneumatic actuator (SPSPA) is proposed by discretely presetting gradient geometrical or materials distributions. Through finite element analysis and experimental validation, a mathematical model of behavior prediction of SPSPA was built to relate the geometrical parameters/materials with its morphing behaviors, making it possible to reversely obtain designed parameters. This design strategy enables conformal and efficient interaction in some curvature varying scenarios. Specifically, higher effective contact area, perimeter utilization ratio, and conformal ability can be obtained while interacting with those inhomogeneous curvature objects, for example, more than 434.7% improvement in contact area rates and 12.5% enhancement in perimeter utilization ratios toward a typical equilateral triangle object. Further, a serial of SPSPAs that have conformal grasping/interactive capability, better contact sensing behaviors were demonstrated. For example, an SPSPA and an SPSP robot were demonstrated, which showed better kinetic, kinematic characterizations and sensing capability compared with the homogeneous one while coming across varying curvature objects. Moreover, underactuated finger rehabilitation SPSPAs were demonstrated with customized profiles and coupled joint motion. This customized scheme can be potentially used in those specific-purposed, single, and repetitive application scenarios where varying curvature, conformal and efficient interaction are needed.

Anisotropic Shear-Sensitive Tactile Sensors with Programmable Elastomers for Robotic Manipulations.

High-performance tactile sensors are urgently demanded in various intensive interactive scenarios, e.g., texture detection, robotic interaction with fragile objects, and motion direction recognition, where dynamic conditions are involved with complex tangential forces or vibrations. Although many microstructured/porous sensors can perceive tangential forces, their isotropic structures that lack programmability lead them to be incapable of sensing the direction of forces and restrain their tunability for complex situations, e.g., a wide sensing range for large forces and high sensitivity for gentle forces. Here, by tuning the programmable microstructures (microcolumns and microfilms) of an elastomeric active layer, we propose a simple principle to flexibly tune the shear sensitivity of an anisotropic porous sensor and bring a 10-fold distinction of anisotropy with a wide range of shear sensitivity (from 0.07 to 0.7 N-1). The fabricated tactile sensors can be used in various robotic manipulations resiliently, for instance, morphology and topology identification of curved surfaces, delicate interactive manipulations, and recognizing the relative motion of two contacting objects. Our work introduces a simple and effective strategy for tailoring flexible shear-sensitive sensors for diverse dexterous robotic manipulations during complex interactions.