Ultrafast small-scale soft electromagnetic robots

Insect-Scale Biped Robots Based on Asymmetrical Friction Effect Induced by Magnetic Torque

Multimodal and controllable locomotion in complex terrain is of great importance for practical applications of insect-scale robots. Robust locomotion plays a particularly critical role. In this study, a locomotion mechanism for magnetic robots based on asymmetrical friction effect induced by magnetic torque is revealed and defined. The defined mechanism overcomes the design constraints imposed by both robot and substrate structures, enabling the realization of multimodal locomotion on complex terrains. Drawing inspiration from human walking and running locomotion, a biped robot based on the mechanism is proposed, which not only exhibits rapid locomotion across substrates with varying friction coefficients but also achieves precise locomotion along patterned trajectories through programmed controlling. Furthermore, apart from its exceptional locomotive capabilities, the biped robot demonstrates remarkable robustness in terms of load-carrying and weight-bearing performance. The presented locomotion and mechanism herein introduce a novel concept for designing magnetic robots while offering extensive possibilities for practical applications in insect-scale robotics.

A wireless controlled robotic insect with ultrafast untethered running speeds

Running speed degradation of insect-scale (less than 5 cm) legged microrobots after carrying payloads has become a bottleneck for microrobots to achieve high untethered locomotion performance. In this work, we present a 2-cm legged microrobot (BHMbot, BeiHang Microrobot) with ultrafast untethered running speeds, which is facilitated by the complementary combination of bouncing length and bouncing frequency in the microrobot's running gait. The untethered BHMbot (2-cm-long, 1760 mg) can achieve a running speed of 17.5 BL s-1 and a turning centripetal acceleration of 65.4 BL s-2 at a Cost of Transport of 303.7 and a power consumption of 1.77 W. By controlling its two front legs independently, the BHMbot demonstrates various locomotion trajectories including circles, rectangles, letters and irregular paths across obstacles through a wireless control module. Such advancements enable the BHMbot to carry out application attempts including sound signal detection, locomotion inside a turbofan engine and transportation via a quadrotor.

Multimodal Soft Robotic Actuation and Locomotion

Diverse and adaptable modes of complex motion observed at different scales in living creatures are challenging to reproduce in robotic systems. Achieving dexterous movement in conventional robots can be difficult due to the many limitations of applying rigid materials. Robots based on soft materials are inherently deformable, compliant, adaptable, and adjustable, making soft robotics conducive to creating machines with complicated actuation and motion gaits. This review examines the mechanisms and modalities of actuation deformation in materials that respond to various stimuli. Then, strategies based on composite materials are considered to build toward actuators that combine multiple actuation modes for sophisticated movements. Examples across literature illustrate the development of soft actuators as free-moving, entirely soft-bodied robots with multiple locomotion gaits via careful manipulation of external stimuli. The review further highlights how the application of soft functional materials into robots with rigid components further enhances their locomotive abilities. Finally, taking advantage of the shape-morphing properties of soft materials, reconfigurable soft robots have shown the capacity for adaptive gaits that enable transition across environments with different locomotive modes for optimal efficiency. Overall, soft materials enable varied multimodal motion in actuators and robots, positioning soft robotics to make real-world applications for intricate and challenging tasks.

Untethered soft actuators for soft standalone robotics

Soft actuators produce the mechanical force needed for the functional movements of soft robots, but they suffer from critical drawbacks since previously reported soft actuators often rely on electrical wires or pneumatic tubes for the power supply, which would limit the potential usage of soft robots in various practical applications. In this article, we review the new types of untethered soft actuators that represent breakthroughs and discuss the future perspective of soft actuators. We discuss the functional materials and innovative strategies that gave rise to untethered soft actuators and deliver our perspective on challenges and opportunities for future-generation soft actuators.

Piezo-Wormbots for Continuous Crawling

Biomimetic soft robots are typically made of soft materials with bioinspired configurations. However, their locomotion is activated and manipulated by externally controlled soft actuators. In this study, piezo-wormbots were developed by automatically triggering the mechanical metamaterial-inspired soft actuator to mimic the continuous crawling of inchworms without manipulation, where crawling was controlled by the deformation of the piezo-wormbots themselves. We designed the flexible piezo-wormbots with an actuator to generate bending deformation under continuous inflation, piezoelectric rubber to automatically create internal excitation voltage to trigger deflation, as well as true legs and prolegs to convert the bending-recovering sequence into continuous crawling. We tailored the actuator to enhance the crawling performance and found that the response was critically affected by the leg pattern, inflation-to-deflation time duration ratio, air pressure, and ground environment. We observed satisfactory locomotion performance for the following tasks (pushing boxes and approaching a predefined target) through accurate self-actuated crawling under up to 51 continuous bending cycles. The maximum crawling velocity of the piezo-wormbots was found to be 16.6 mm/s, resulting in a maximum body length per second (BL/s) of 0.13, which is comparable to those of most natural inchworms (0.1-0.3 BL/s). This study offers new insight into bioinspired soft robotics and expands its biomimetic performance to continuously autonomous locomotion.

Sidewinder-Inspired Self-Adjusting, Lateral-Rolling Soft Robots for Autonomous Terrain Exploration

Helical structures of liquid crystal elastomers (LCEs) hold promise in soft robotics for self-regulated rolling motions. The understanding of their motion paths and potentials for terrain exploration remains limited. This study introduces a self-adjusting, lateral-rolling soft robot inspired by sidewinder snakes. The spring-like LCE helical filaments (HFs) autonomously respond to thermal cues, demonstrating dynamic and sustainable locomotion with adaptive rolling along non-linear paths. By fine-tuning the diameter, pitch, and modulus of the LCE HFs, and the environmental temperature, the movements of the LCE HFs, allowing for exploration of diverse terrains over a 600 cm2 area within a few minutes, can be programmed. LCE HFs are showcased to navigate through over nine obstacles, including maze escaping, terrain exploration, target hunting, and successfully surmounting staircases through adaptable rolling.

Optomagnetic Coordination Helical Robot with Shape Transformation and Multimodal Motion Capabilities

Soft robots with magnetic responsiveness exhibit diverse motion modes and programmable shape transformations. While the fixed magnetization configuration facilitates coupling control of robot posture and motion, it limits individual posture control to some extent. This poses a challenge in independently controlling the robot's transformation and motion, restricting its versatile applications. This research introduces a multifunctional helical robot responsive to both light and magnetism, segregating posture control from movements. Light fields assist in robot shaping, achieving a 78% maximum diameter shift. Magnetic fields guide helical robots in multimodal motions, encompassing rotation, flipping, rolling, and spinning-induced propulsion. By controlling multimodal locomotion and shape transformation on demand, helical robots gain enhanced flexibility. This innovation allows them to tightly grip and wirelessly transport designated payloads, showcasing potential applications in drug delivery, soft grippers, and chemical reaction platforms. The unique combination of structural design and control methods holds promise for intelligent robots in the future.

Principles and methods of liquid metal actuators

As a promising material, liquid metals (LMs) have gained considerable interest in the field of soft robotics due to their ability to move as designed routines or change their shape dramatically under external stimuli. Inspired by the science fiction film Terminator, tremendous efforts have been devoted to liquid robots with high compliance and intelligence. How to manipulate LM droplets is crucial to achieving this goal. Accordingly, this review is dedicated to presenting the principles driving LMs and summarizing the potential methods to develop LM actuators of high maneuverability. Moreover, the recent progress of LM robots based on these methods is overviewed. The challenges and prospects of implementing autonomous robots have been proposed.

Magnetically Actuated Trigger Transient Soft Actuators Comprising On-Demand Photo-Initiated and Thermo-Degradable Polypropylene Carbonate-Photo-Acid Generator

Lifetime-reconfigurable soft robots have emerged as a new class of robots, emphasizing the unmet needs of futuristic sustainability and security. Trigger-transient materials that can both actuate and degrade on-demand are crucial for achieving life-reconfigurable soft robots. Here, we propose the use of transient and magnetically actuating materials that can decompose under ultraviolet light and heat, achieved by adding photo-acid generator (PAG) and magnetic particles (Sr-ferrite) to poly(propylene carbonate) (PPC). Chemical and thermal analyses reveal that the mechanism of PPC-PAG decomposition occurs through PPC backbone cleavage by the photo-induced acid. The self-assembled monolayer (SAM) encapsulation of Sr-ferrite preventing the interaction with the PAG allowed the transience of magnetic soft actuators. We demonstrate remotely controllable and degradable magnetic soft kirigami actuators using blocks with various magnetized directions. This study proposes novel approaches for fabricating lifetime-configurable magnetic soft actuators applicable to diverse environments and applications, such as enclosed/sealed spaces and security/military devices.

Battery-free, wireless, and electricity-driven soft swimmer for water quality and virus monitoring

Miniaturized mobile electronic system is an effective candidate for in situ exploration of confined spaces. However, realizing such system still faces challenges in powering issue, untethered mobility, wireless data acquisition, sensing versatility, and integration in small scales. Here, we report a battery-free, wireless, and miniaturized soft electromagnetic swimmer (SES) electronic system that achieves multiple monitoring capability in confined water environments. Through radio frequency powering, the battery-free SES system demonstrates untethered motions in confined spaces with considerable moving speed under resonance. This system adopts soft electronic technologies to integrate thin multifunctional bio/chemical sensors and wireless data acquisition module, and performs real-time water quality and virus contamination detection with demonstrated promising limits of detection and high sensitivity. All sensing data are transmitted synchronously and displayed on a smartphone graphical user interface via near-field communication. Overall, this wireless smart system demonstrates broad potential for confined space exploration, ranging from pathogen detection to pollution investigation.

Fast and Facile Liquid Metal Printing via Projection Lithography for Highly Stretchable Electronic Circuits

Soft electronic circuits are crucial for wearable electronics, biomedical technologies, and soft robotics, requiring soft conductive materials with high conductivity, high strain limit, and stable electrical performance under deformation. Liquid metals (LMs) have become attractive candidates with high conductivity and fluidic compliance, while effective manufacturing methods are demanded. Digital light processing (DLP)-based projection lithography is a high-resolution and high-throughput printing technique for primarily polymers and some metals. If LMs can be printed with DLP as well, the entire soft devices can be fabricated by one printer in a streamlined and highly efficient process. Herein, fast and facile DLP-based LM printing is achieved. Simply with 5-10 s of patterned ultraviolet (UV)-light exposure, a highly conductive and stretchable pattern can be printed using a photo-crosslinkable LM particle ink. The printed eutectic gallium indium traces feature high resolution (≈20 µm), conductivity (3 × 106 S m-1 ), stretchability (≈2500%), and excellent stability (consistent performance at different deformation). Various patterns are printed in diverse material systems for broad applications including stretchable displays, epidermal strain sensors, heaters, humidity sensors, conformal electrodes for electrography, and multi-layer actuators. The facile and scalable process, excellent performance, and diverse applications ensure its broad impact on soft electronic manufacturing.

Mechanically-Guided 3D Assembly for Architected Flexible Electronics

Architected flexible electronic devices with rationally designed 3D geometries have found essential applications in biology, medicine, therapeutics, sensing/imaging, energy, robotics, and daily healthcare. Mechanically-guided 3D assembly methods, exploiting mechanics principles of materials and structures to transform planar electronic devices fabricated using mature semiconductor techniques into 3D architected ones, are promising routes to such architected flexible electronic devices. Here, we comprehensively review mechanically-guided 3D assembly methods for architected flexible electronics. Mainstream methods of mechanically-guided 3D assembly are classified and discussed on the basis of their fundamental deformation modes (i.e., rolling, folding, curving, and buckling). Diverse 3D interconnects and device forms are then summarized, which correspond to the two key components of an architected flexible electronic device. Afterward, structure-induced functionalities are highlighted to provide guidelines for function-driven structural designs of flexible electronics, followed by a collective summary of their resulting applications. Finally, conclusions and outlooks are given, covering routes to achieve extreme deformations and dimensions, inverse design methods, and encapsulation strategies of architected 3D flexible electronics, as well as perspectives on future applications.

Multimaterial 3D and 4D Bioprinting of Heterogenous Constructs for Tissue Engineering

Additive manufacturing (AM), which is based on the principle of layer-by-layer shaping and stacking of discrete materials, has shown significant benefits in the fabrication of complicated implants for tissue engineering (TE). However, many native tissues exhibit anisotropic heterogenous constructs with diverse components and functions. Consequently, the replication of complicated biomimetic constructs using conventional AM processes based on a single material is challenging. Multimaterial 3D and 4D bioprinting (with time as the fourth dimension) has emerged as a promising solution for constructing multifunctional implants with heterogenous constructs that can mimic the host microenvironment better than single-material alternatives. Notably, 4D-printed multimaterial implants with biomimetic heterogenous architectures can provide a time-dependent programmable dynamic microenvironment that can promote cell activity and tissue regeneration in response to external stimuli. This paper first presents the typical design strategies of biomimetic heterogenous constructs in TE applications. Subsequently, the latest processes in the multimaterial 3D and 4D bioprinting of heterogenous tissue constructs are discussed, along with their advantages and challenges. In particular, the potential of multimaterial 4D bioprinting of smart multifunctional tissue constructs is highlighted. Furthermore, this review provides insights into how multimaterial 3D and 4D bioprinting can facilitate the realization of next-generation TE applications.

A Review of Single-Cell Microrobots: Classification, Driving Methods and Applications

Single-cell microrobots are new microartificial devices that use a combination of single cells and artificial devices, with the advantages of small size, easy degradation and ease of manufacture. With externally driven strategies such as light fields, sound fields and magnetic fields, microrobots are able to carry out precise micromanipulations and movements in complex microenvironments. Therefore, single-cell microrobots have received more and more attention and have been greatly developed in recent years. In this paper, we review the main classifications, control methods and recent advances in the field of single-cell microrobot applications. First, different types of robots, such as cell-based microrobots, bacteria-based microrobots, algae-based microrobots, etc., and their design strategies and fabrication processes are discussed separately. Next, three types of external field-driven technologies, optical, acoustic and magnetic, are presented and operations realized in vivo and in vitro by applying these three technologies are described. Subsequently, the results achieved by these robots in the fields of precise delivery, minimally invasive therapy are analyzed. Finally, a short summary is given and current challenges and future work on microbial-based robotics are discussed.

Elastic pinch biomechanisms can yield consistent launch speeds regardless of projectile mass

Energetic trade-offs are particularly pertinent to bio-ballistic systems which impart energy to projectiles exclusively during launch. We investigated such trade-offs in the spring-propelled seeds of Loropetalum chinense, Hamamelis virginiana and Fortunearia sinensis. Using similar seed-shooting mechanisms, fruits of these confamilial plants (Hamamelidaceae) span an order of magnitude in spring and seed mass. We expected that as seed mass increases, launch speed decreases. Instead, launch speed was relatively constant regardless of seed mass. We tested if fruits shoot larger seeds by storing more elastic potential energy (PE). Spring mass and PE increased as seed mass increased (in order of increasing seed mass: L. chinense, H. virginiana, F. sinensis). As seed mass to spring mass ratio increased (ratios: H. virginiana = 0.50, F. sinensis = 0.65, L. chinense = 0.84), mass-specific PE storage increased. The conversion efficiency of PE to seed kinetic energy (KE) decreased with increasing fruit mass. Therefore, similar launch speeds across scales occurred because (i) larger fruits stored more PE and (ii) smaller fruits had higher mass-specific PE storage and improved PE to KE conversion. By examining integrated spring and projectile mechanics in our focal species, we revealed diverse, energetic scaling strategies relevant to spring-propelled systems navigating energetic trade-offs.

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.

Coaxially printed magnetic mechanical electrical hybrid structures with actuation and sensing functionalities

Soft electromagnetic devices have great potential in soft robotics and biomedical applications. However, existing soft-magneto-electrical devices would have limited hybrid functions and suffer from damaging stress concentrations, delamination or material leakage. Here, we report a hybrid magnetic-mechanical-electrical (MME) core-sheath fiber to overcome these challenges. Assisted by the coaxial printing method, the MME fiber can be printed into complex 2D/3D MME structures with integrated magnetoactive and conductive properties, further enabling hybrid functions including programmable magnetization, somatosensory, and magnetic actuation along with simultaneous wireless energy transfer. To demonstrate the great potential of MME devices, precise and minimally invasive electro-ablation was performed with a flexible MME catheter with magnetic control, hybrid actuation-sensing was performed by a durable somatosensory MME gripper, and hybrid wireless energy transmission and magnetic actuation were demonstrated by an untethered soft MME robot. Our work thus provides a material design strategy for soft electromagnetic devices with unexplored hybrid functions.

Ultracompact single-nanowire-morphed grippers driven by vectorial Lorentz forces for dexterous robotic manipulations

Ultracompact and soft pairwise grippers, capable of swift large-amplitude multi-dimensional maneuvering, are widely needed for high-precision manipulation, assembly and treatment of microscale objects. In this work, we demonstrate the simplest construction of such robotic structures, shaped via a single-nanowire-morphing and powered by geometry-tailored Lorentz vectorial forces. This has been accomplished via a designable folding growth of ultralong and ultrathin silicon NWs into single and nested omega-ring structures, which can then be suspended upon electrode frames and coated with silver metal layer to carry a passing current along geometry-tailored pathway. Within a magnetic field, the grippers can be driven by the Lorentz forces to demonstrate swift large-amplitude maneuvers of grasping, flapping and twisting of microscale objects, as well as high-frequency or even resonant vibrations to overcome sticky van de Waals forces in microscale for a reliable releasing of carried payloads. More sophisticated and functional teamwork of mutual alignment, precise passing and selective light-emitting-diode unit testing and installation were also successfully accomplished via pairwise gripper collaborations. This single-nanowire-morphing strategy provides an ideal platform to rapidly design, construct and prototype a wide range of advanced ultracompact nanorobotic, mechanical sensing and biological manipulation functionalities.

Soft Electromagnetic Vibrotactile Actuators with Integrated Vibration Amplitude Sensing

Soft vibrotactile devices have the potential to expand the functionality of emerging electronic skin technologies. However, those devices often lack the necessary overall performance, sensing-actuation feedback and control, and mechanical compliance for seamless integration on the skin. Here, we present soft haptic electromagnetic actuators that consist of intrinsically stretchable conductors, pressure-sensitive conductive foams, and soft magnetic composites. To minimize joule heating, high-performance stretchable composite conductors are developed based on in situ-grown silver nanoparticles formed within the silver flake framework. The conductors are laser-patterned to form soft and densely packed coils to further minimize heating. Soft pressure-sensitive conducting polymer-cellulose foams are developed and integrated to tune the resonance frequency and to provide internal resonator amplitude sensing in the resonators. The above components together with a soft magnet are assembled into soft vibrotactile devices providing high-performance actuation combined with amplitude sensing. We believe that soft haptic devices will be an essential component in future developments of multifunctional electronic skin for future human-computer and human-robotic interfaces.

A Soft Robot Driven by a Spring-Rolling Dielectric Elastomer Actuator with Two Bristles

Confined space searches such as pipeline inspections are widely demanded in various scenarios, where lightweight soft robots with inherent compliance to adapt to unstructured environments exhibit good potential. We proposed a tubular soft robot with a simple structure of a spring-rolled dielectric elastomer (SRDE) and compliant passive bristles. Due to the compliance of the bristles, the proposed robots can work in pipelines with inner diameters both larger and smaller than the one of the bristles. Firstly, the nonlinear dynamic behaviors of the SRDE were investigated experimentally. Then, we fabricated the proposed robot with a bristle diameter of 19 mm and then studied its performance in pipelines on the ground with inner diameters of 18 mm and 20 mm. When the pipeline's inner diameter was less than the outer diameter of the bristles, the bristles remained in the state of bending and the robot locomotion is mainly due to anisotropic friction (1.88 and 0.88 body lengths per second horizontally and vertically, respectively, in inner diameter of 18 mm and 0.06 body length per second in that of 16 mm). In the case of the pipeline with the larger inner diameter, the bristles were not fully constrained, and a small bending moment applied on the lower bristle legs contributed to the robot's locomotion, leading to a high velocity (2.78 body lengths per second in 20 mm diameter acrylic pipe). In addition, the robot can work in varying geometries, such as curving pipes (curve radius ranges from 0.11 m to 0.31 m) at around two body lengths per second horizontally and on the ground at 3.52 body lengths per second, showing promise for pipeline or narrow space inspections.

4D Printing of Humidity-Driven Seed Inspired Soft Robots

Geraniaceae seeds represent a role model in soft robotics thanks to their ability to move autonomously across and into the soil driven by humidity changes. The secret behind their mobility and adaptivity is embodied in the hierarchical structures and anatomical features of the biological hygroscopic tissues, geometrically designed to be selectively responsive to environmental humidity. Following a bioinspired approach, the internal structure and biomechanics of Pelargonium appendiculatum (L.f.) Willd seeds are investigated to develop a model for the design of a soft robot. The authors exploit the re-shaping ability of 4D printed materials to fabricate a seed-like soft robot, according to the natural specifications and model, and using biodegradable and hygroscopic polymers. The robot mimics the movement and performances of the natural seed, reaching a torque value of ≈30 µN m, an extensional force of ≈2.5 mN and it is capable to lift ≈100 times its own weight. Driven by environmental humidity changes, the artificial seed is able to explore a sample soil, adapting its morphology to interact with soil roughness and cracks.

GaOOH Crystallite Growth on Liquid Metal Microdroplets in Water: Influence of the Local Environment

Gallium-based liquid metals form alloys with a melting point close to or below room temperature. On the surface of these liquid metals, a thin oxide skin is formed once in contact with oxygen, and this oxide skin can be leveraged to stabilize liquid metal micro- and nanodroplets in a liquid. During sonication and storage of these droplets in aqueous solution, gallium oxide hydroxide (GaOOH) forms on these droplets, and given enough time or treatment with heat, a full shape transition and dealloying are observed. In this article, we show that GaOOH can be grown at room temperature and that the growth is dependent on both the local environment and temperature. GaOOH growth on liquid metal microdroplets located at the air/water interface is considerably faster than in the bulk phase. Interestingly, hydrolysis to GaOOH is hampered and stops at 15 °C in bulk water after 6 h. In contrast, hydrolysis commences even at 15 °C for liquid metal microdroplets located at the air/water interface, and full surface coverage is obtained after around 24 h (compared to 12 h at 25 °C at the air/water interface). The X-ray photoelectron spectroscopy (XPS) measurement suggests that gallium oxide is dissolved and Ga(OH)₃ is formed as a precursor that reacts in a downstream reaction toward GaOOH. This improved understanding of the GaOOH formation can be leveraged to control the liquid metal micro- and nanodroplet shape and composition (i.e., for biomedical applications).

The Dynamic Mortise-and-Tenon Interlock Assists Hydrated Soft Robots Toward Off-Road Locomotion

Natural locomotion such as walking, crawling, and swimming relies on spatially controlled deformation of soft tissues, which could allow efficient interaction with the external environment. As one of the ideal candidates for biomimetic materials, hydrogels can exhibit versatile bionic morphings. However, it remains an enormous challenge to transfer these in situ deformations to locomotion, particularly above complex terrains. Herein, inspired by the crawling mode of inchworms, an isotropic hydrogel with thermoresponsiveness could evolve to an anisotropic hydrogel actuator via interfacial diffusion polymerization, further evolving to multisection structure and exhibiting adaptive deformation with diverse degrees of freedom. Therefore, a dynamic mortise-and-tenon interlock could be generated through the interaction between the self-deformation of the hydrogel actuator and rough terrains, inducing continual multidimensional locomotion on various artificial rough substrates and natural sandy terrain. Interestingly, benefiting from the powerful mechanical energy transfer capability, the crawlable hydrogel actuators could also be utilized as hydrogel motors to activate static cargos to overstep complex terrains, which exhibit the potential application of a biomimetic mechanical discoloration device. Therefore, we believe that this design principle and control strategy may be of potential interest to the field of deformable materials, soft robots, and biomimetic devices.