Kirigami, a traditional paper‐cutting art, is a promising method for creating mechanically robust circuitry for unconventional devices capable of extreme stretchability through structural deformation. In this study, this design approach is expanded upon by introducing Liquid Metal based Elastic Kirigami Electrodes (LM‐eKE) in which kirigami‐patterned soft elastomers are coated with eutectic gallium‐indium (EGaIn) alloy. Overcoming the mechanical and electrical limitations of previous efforts with paper‐like kirigami, the all soft LM‐eKE can be stretched to 820% strain while the electrical resistance only increases by 33%. This is enabled by the fluidic properties of the EGaIn coating, which maintains high electrical conductivity even as the elastic substrate undergoes extreme deformation. Applying the LM‐eKE to human knee joints and fingers, the resistance change during physical activities is under 1.7%, thereby allowing for stable electrical operation of wearable health monitoring devices for tracking electroencephalogram (EEG) signals and other physiological activity.
have developed machines capable of multimodal locomotion that are able to maneuver in unstructured environments for the application like search and rescue operation, [2] monitoring and defence. [3] Such multimodality is typically achieved through either i) shape morphing of the body, ii) gait change, or iii) using different mechanisms of actuation or propulsion. A popular approach is to use distinct propulsive mechanisms that are specialized for locomotion within a corresponding environment (e.g., propeller for flying and swimming and a wheel for locomotion on land [4,5] ). However, multiple propulsive mechanisms can complicate design and add extra weight to such systems. Likewise, using a single propulsive mechanism capable of achieving distinct gaits and locomotion modes can simplify the design but often results in more limited mobility within certain environments. [6][7][8] A promising alternative is to utilize reversible shape morphing of the body, so that a common set of actuators or robotic limbs can be re-oriented to perform new modes of ground contact or fluid-structure interactions (see for examples).Soft robots are especially well-suited for reversible shape change due to their mechanical deformability and morphological response in response to controlled stimuli. Recently, Baines et al. proposed a shape morphing limb that can transform between a flipper and a leg by taking advantage of stiffness tuning. [12] The limb is implemented on a turtle-inspired robot [6] to facilitate amphibious locomotion. Shah et al. presented a Matching the rich multimodality of natural organisms, i.e., the ability to transition between crawling and swimming, walking and jumping, etc., represents a grand challenge in the fields of soft and bio-inspired robotics. Here, a multimodal soft robot locomotion using highly compact and dynamic bistable soft actuators is achieved. These actuators are composed of a prestretched membrane sandwiched between two 3D printed frames with embedded shape memory alloy (SMA) coils. The actuator can swiftly transform between two oppositely curved states and generate a force of 0.3 N through a snapthrough instability that is triggered after 0.2 s of electrical activation with an input power of 21.1 ± 0.32 W (i.e., electrical energy input of 4.22 ± 0.06 J. The consistency and robustness of the snap-through actuator response is experimentally validated through cyclical testing (580 cycles). The compact and fast-responding properties of the soft bistable actuator allow it to be used as an artificial muscle for shape-reconfigurable soft robots capable of multiple modes of SMA-powered locomotion. This is demonstrated by creating three soft robots, including a reconfigurable amphibious robot that can walk on land and swim in water, a jumping robot (multimodal crawler) that can crawl and jump, and a caterpillar-inspired rolling robot that can crawl and roll.
Soft materials that exhibit compliance, programmability, and reconfigurability can have a transformative impact as electronic skin for applications in wearable electronics/soft robotics. There has been significant progress in soft conductive materials; however, achieving electrically controlled and reversible changes in conductivity and circuit connectivity remains challenging. To overcome this limitation, a soft material architecture with reconfigurable conductive networks of silver flakes embedded within a hydrogel matrix is presented. The conductive networks can be reversibly created/disconnected through various stimuli, including current, humidity, or temperature. Such stimuli affect electrical connectivity of the hydrogel by controlling its water content, which can be modulated by evaporation under ambient conditions (passive dehydration), evaporation through electrical Joule heating (active dehydration), or absorption of additional water (rehydration). The resulting change in electrical conductivity is reversible and repeatable, endowing the composite with on‐demand reconfigurable conductivity. To highlight this material's unique properties, it is shown that conductive traces can be reconfigured after severe damage and revert to lower conductivity after rehydration. Additionally, a quadruped robot is demonstrated that can respond to stimuli by changing direction following exposure to excess water, thereby achieving reprogrammable locomotion behaviors.
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