Shape-morphing uses a single actuation source for complex-task-oriented multiple patterns generation, showing a more promising way than reconfiguration, especially for microrobots, where multiple actuators are typically hardly available. Environmental stimuli can induce additional causes of shape transformation to compensate the insufficient space for actuators and sensors, which enriches the shape-morphing and thereby enhances the function and intelligence as well. Here, making use of the ionic sensitivity of alginate hydrogel microstructures, we present a shape-morphing strategy for microrobotic end-effectors made from them to adapt to different physiochemical environments. Pre-programmed hydrogel crosslinks were embedded in different patterns within the alginate microstructures in an electric field using different electrode configurations. These microstructures were designed for accomplishing tasks such as targeting, releasing and sampling under the control of a magnetic field and environmental ionic stimuli. In addition to structural flexibility and environmental ion sensitivity, these end-effectors are also characterized by their complete biodegradability and versatile actuation modes. The latter includes global locomotion of the whole end-effector by self-trapping magnetic microspheres as a hitch-hiker and the local opening and closing of the jaws using encapsulated nanoparticles based on local ionic density or pH values. The versatility was demonstrated experimentally in both in vitro environments and ex vivo in a gastrointestinal tract. Global locomotion was programmable and the local opening and closing was achieved by changing the ionic density or pH values. This ‘structural intelligence’ will enable strategies for shape-morphing and functionalization, which have attracted growing interest for applications in minimally invasive medicine, soft robotics, and smart materials.
Efforts to impart responsiveness to environmental stimuli in artificial hydrogel fibers are crucial to intelligent, shape-memory electronics and weavable soft robots. However, owing to the vulnerable mechanical property, poor processability, and the dearth of scalable assembly protocols, such functional hydrogel fibers are still far from practical usage. Herein, we demonstrate an approach toward the continuous fabrication of an electro-responsive hydrogel fiber by using the self-lubricated spinning (SLS) strategy. The polyelectrolyte inside the hydrogel fiber endows it with a fast electro-response property. After solvent exchange with triethylene glycol (TEG), the maximum tensile strength of the hydrogel fiber increases from 114 kPa to 5.6 MPa, far superior to those hydrogel fiber-based actuators reported previously. Consequently, the flexible and mechanical stable hydrogel fiber is knitted into various complex geometries on demand such as a crochet flower, triple knot, thread tube, pentagram, and hollow cage. Additionally, the electrochemical-responsive ionic hydrogel fiber is capable of acting as soft robots underwater to mimic biological motions, such as Mobula-like flapping, jellyfish-mimicking grabbing, sea worm-mimicking multi-degree of freedom movements, and human finger-like smart gesturing. This work not only demonstrates an example for the large-scale production of previous infeasible hydrogel fibers, but also provides a solution for the rational design and fabrication of hydrogel woven intelligent devices.
The in vitro reproduction of three-dimensional (3D) cellular constructs to physiologically mimic human liver is highly desired for drug screening and clinical research. However, the fabrication of a liver-mimetic 3D model using traditional bottom-up technologies is challenging owing to the complex architecture and specific functions of real liver tissue. This work proposes a versatile strategy for spatially assembling gear-like microstructures encapsulating multiple cell types, and reorganizing them into 3D lobule-like micro-architecture with physiological relevance to native liver tissue. Gear-like microstructures were fabricated by photo-crosslinking poly(ethylene glycol) diacrylate (PEGDA) hydrogel mixed with hepatocytes and fibroblasts, in a digital micromirror device (DMD)-based microfluidic channel. The microstructures were assembled through coordinated micromanipulation based on local fluid force, and spatially self-aligned through hydrophilic–hydrophobic interactions into a 3D integrated construct with lobule-like morphology and a perfusable central lumen. The resulting 3D lobule-like constructs allowed long-term co-culture of hepatocytes and fibroblasts with high cell viability. The co-cultured constructs enhanced hepatocyte proliferation and spreading, as well as liver functions including a 50% increase in albumin secretion and urea synthesis. For hepatotoxicity assessment, the 3D lobule-like construct enabled drug perfusion through its built-in lumen for simulation of drug diffusion in the liver, which could improve the response sensitivity and efficiency to hepatotoxic drug. These results demonstrated that this method provides a valuable 3D co-culture model with perfusable lobule-like architecture and physiological functions, which has potential applications in drug discovery and tissue engineering applications.
Fabricated microscale tissues that replicate in vivo architectures have shown huge potential in regenerative medicine and drug discovery. Owing to the spatial organization of cell-encapsulated hydrogel microstructures, three-dimensional (3D) tissue structures have been broadly applied as novel pathological or pharmacological models. However, the spatial reorganization of arbitrary microstructures with tissue-specific shapes into 3D in vitro microtissues that mimic the physiological morphology and nutrient diffusion of native tissues presents a major challenge. Here, we develop a versatile method that engineers permeable 3D microtissues into tissue-specific microscopic architectures. The customized, arbitrarily shaped hollow micromodules are prepared by photocopolymerizing poly(ethylene glycol) diacrylate (PEGDA) with acryloyl-PEG-Arg-Gly-Asp-Ser (RGDS). These micromodules are spatially reorganized and self-aligned by a facile assembly process based on hydrodynamic interactions, forming an integrated geometry with tissue-specific morphology and a vessel-mimetic lumen. The RGD linkages create cell-adhesive structures in the PEGDA hydrogel, greatly increasing the long-term cell viability in 3D microtissue cultures. Meanwhile, the mechanical properties for fast cell spreading inside the microstructures can be optimized by modulating the PEGDA concentration. The 3D microtissues, with their different geometries and permeable tubular lumens, maintained cell proliferation over 14 days. The cell viabilities exceeded 98%. We anticipate that our method will regenerate complex tissues with physiological importance in future tissue engineering.
Systems with programmable and complex shape morphing are highly desired in many fields wherein sensing, actuation, and manipulation must be performed. Living organisms use nonuniform distributions of their body structural composition to achieve diverse shape morphing, motion, and functionality. However, for the microrobot fabrication, these designs often involve complicated robotic architectures requiring time-consuming and arduous fabrication processes. This paper proposes a single-step aniso-electrodeposition method for fabricating modular microrobots (MMRs) with distinct functions in each modular segment. By programming the electric field, the microscale stripe-shaped structure can be endowed with diverse shape-morphing capabilities, such as spiraling, twisting, bending, and coiling. The proposed fabrication method can develop MMRs with multiple independent modules onto which cells, drugs, and magnetic nanoparticles can be loaded to achieve multifunctionality. Thus, MMRs can perform multiple tasks, such as propulsion, grasping, and object delivery, simultaneously under magnetic control and ionic and pH stimuli.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.