Ant-nest-inspired porous structure for MXene composites with high-performance energy-storage and actuating multifunctions

Integrating energy-storage devices(supercapacitors)and shape-deformation devices(actuators)advances the miniaturization and multifunctional development of soft robots.However,soft robots necessitate supercapacitors with high energy-storage performance and actuators with excellent actuation capability.Here,inspired by ant nests,we present a porous structure fabricated by MXene-graphene-methylcellulose(M-GMC)composite,which overcomes the self-stacking of MXene nanosheets and offers a larger specific surface area.The porous structure provides more channels and active sites for electrolyte ions,resulting in high energy storage performance.The areal capacitance of the M-GMC electrode reaches up to 787.9 mF·cm^(−2),significantly superior to that of the pristine MXene electrode(449.1 mF·cm^(−2)).Moreover,the M-GMC/polyethylene bilayer composites with energy storage and multi-responsive actuation functions are developed.The M-GMC is used as the electrode and the polyethylene is used as the encapsulation layer of the quasi-solid-state supercapacitor.Meanwhile,the actuators fabricated by the bilayer composites can be driven by light or low voltage(≤9 V).The maximum bending curvature is up to 5.11 cm^(−1).Finally,a smart gripper and a fully encapsulated smart integrated circuit based on the M-GMC/polyethylene are designed.The smart gripper enables programmable control with multi-stage deformations.The applications realize the intelligence and miniaturization of soft robots.The ant-nest-inspired M-GMC composites would provide a promising development strategy for soft robots and smart integrated devices.

Plant-leaf-inspired MXene-silk composite for intelligent solar steam generation combined with mechanical actuation

Solar steam generators based on photothermal materials are important in producing fresh water.However,conventional solar steam generators are difficult to self-adapt to the complex external environment as organisms.Herein,inspired by the plant leaf,we propose a photothermal composite based on MXene and silk to add more functionality.On one hand,the composite achieves an evaporation rate of 1.51 kg·m^(−2)·h^(−1)and a conversion efficiency of 86.9%under a solar intensity of 1 kW·m^(−2),mimicking the water transpiration of plant leaf.On the other hand,the MXene-silk-based actuator shows a maximum bending curvature of 0.91 cm^(−1)under a solar intensity of 5 kW·m^(−2).Furthermore,an intelligent solar system is constructed utilizing the synergy of solar steam generator and actuator,which advances the research from the material level to the system level.Mimicking the behavior of plant leaf,the system can automatically open during the day to generate steam and fresh water.And at night or in bad weather,it will automatically close to prevent external pollution such as dust,achieving intelligent anti-fouling.This research will have good application prospects in less developed areas.Meanwhile,it also provides a certain reference value for exploring multi-functional photothermal devices in the future.

Monolithic superaligned carbon nanotube composite with integrated rewriting, actuating and sensing multifunctions

Multifunctionality has become a mainstream trend in the development of smart clothing and flexible wearable devices.Nevertheless,it remains a grand challenge to realize multiple functions,such as sensing,actuating and information displaying,in one single multifunctional material.Here,we present one multifunctional integration strategy by employing monolithic superaligned carbon nanotube(SACNT)composite,which can leverage three different functions through fascinating features of SACNT.Firstly,by using thermochromic dye as a color-memorizing component and SACNT as a photothermal converter,the composite film can be utilized as a flexible rewritable medium.It demonstrates excellent rewriting performances(reversibility>500 times).Secondly,the composite can be tailored to fabricate an actuator,when its length direction is along the SACNT alignment.The actuator shows a bending-morphing when illuminated by near-infrared light.The morphing is attributed to a large difference in volume change between the SACNT and polymer when the SACNT absorbs the optical energy and heats the composite.Thirdly,owing to the unique anisotropy of SACNT,the composite is easily to be stretched in the direction perpendicular to the SACNT alignment,accompanied by a change in electrical resistance.Therefore,the composite is able to be used as a strain sensor.Finally,we fabricate two smart wearable devices to demonstrate the applications,which realize the functions of human-motion detection(sensing)and rewritable information display(rewriting)simultaneously.This multifunctional SACNT composite is expected to have potential applications in the next-generation wearable devices,smart clothing and so on.

Photo-thermoelectric generator integrated in graphene-based actuator for self-powered sensing function

Smart actuators integrated with sensing functions are taking a significant role in constructing intelligent robots.However,the detection of sensing signals in most actuators requires external electrical power,lacking in the self-powered feature.Herein,we report a graphene-based light-driven actuator with self-powered sensing function,which is designed by integrating a photothermoelectric generator into the actuator intelligently.When one part of the actuator is irradiated by near-infrared light,it shows a deformation with bending curvature up to 1.5 cm^(−1),owing to the mismatch volume changes between two layers of the actuator.Meanwhile,the temperature difference across the actuator generates a voltage signal due to the photo-thermoelectric effect.The Seebeck coefficient is higher than 40μV/K.Furthermore,the self-powered voltage signal is consistent with the deformation trend,which can be used to characterize the deformation state of actuator without external electrical power.We further demonstrate a gripper and a bionic hand.Their deformations mimic the motions of human hand(or finger),even making complex gestures.Concurrently,they can output self-powered voltage signals for sensing.We hope this research will pave a new way for selfpowered devices,state-of-the-art intelligent robots,and other integrated multi-functional systems.