Deployable fiber-reinforced polymer for advanced monolithic Rigid–Soft robotics applications

Ionic Polymer-Metal Composites (IPMC) have various applications in the fields of soft robotics as actuators [1], energy conversion as ion exchange membrane in Fuel cells [2], Biomedical engineering for drug delivery [3] etc. Nafion ionomer plated with a noble metal (such as platinum) is being used successfully as actuators for soft robotic applications [1,4] and recently Aquivion [5] has been explored and proven to be a good candidate to replace Nafion. As ion exchange membrane in Fuel cells, a stable sulfonated silica-based ionomer has been proposed as a replacement for Nafion, which has a dual function as this material has shown to have a higher active surface area of platinum and have increased the performance of fuel cells. These membranes have shown stable performance with improved water management capabilities at low relative humidity, while Nafion based membranes have performed poorly. [6] With this inspiration and the aforementioned advantages we propose to study and investigate the application of sulfonated silica-based membrane to prepare IPMC actuators for soft robots. Based on the positive results these IPMC’s have provided for fuel cell performance, we expect encouraging results for actuation such as higher actuation forces, durability, higher water retainment etc. which would benefit and promote soft robotics. [1,6]

BackgroundSoft materials, with their compliant properties, enable conformity and safe interaction with human body. With the advance in actuation and sensing of soft materials, new paradigm in robotics called “soft robotics” emerges. Soft robotics has become a new approach in designing medical devices such as wearable robotic gloves and exoskeleton. However, application of soft robotics in surgical instrument inside human body is still in its infancy.AimsIn this paper, current application and design of soft robots specifically applied for endoscopy are reviewed.Materials & MethodsDifferent aspects in the implementation of soft robotics in endoscope design were reviewed. The key studies about MIS and NOTES were reviewed to establish the clinical background and extract the limitations of current endoscopic device in the last decade.Results and discussionIn this review study, the implementation of soft robotics concepts in endoscopic application, with highlights on different features of several soft endoscopes, were evaluated. The progress in different aspects of soft robotics endoscope, current state, and future perspectives were also discussed.ConclusionBased on the survey on the structural specification, actuation, sensing, and stiffening the future soft surgical endoscopes are recommended to fulfil the following specifications: safe especially from pressure leakage, fully biocompatible materials, MR‐compatible, capable for large bending in at least two antagonistic directions, modularity, adjustable stiffness.

The field of soft robotics has shown unprecedented growth in research efforts, scientific achievements, and technological advancements. Bioinspiration and biomimetics have played an instrumental role in the birth and growth of soft robotics. What is next for this field? To promote soft robotics research to the next level and have a broader impact in robotics and engineering fields, in this roadmap, we argue that two research directions should be strengthened i) more structured, formal methods and tools for designing and developing soft robots and bioinspired robots ii) more concrete applications of bioinspired soft robots in diverse sectors of human activities. This article provides a roadmap for the design of bioinspired soft robots, the integration of soft robot systems, and their applications in industry and services. Scientists and experts describe the state-of-the art and the perspectives of bioinspired, model-informed design of soft robots, outlining the challenges in developing complex soft robotic systems, and applications of soft robots in diverse fields.&#xD.

Inspired by diverse shape-shifting phenomena in nature, various man-made shape programmable materials have been developed for applications in actuators, deployable devices, and soft robots. However, fabricating mechanically robust shape-morphing structures with on-demand, rapid shape-transformation capability, and high load-bearing capacity is still a great challenge. Herein, we report a mechanically robust and rapid shape-shifting material system enabled by the volatilization of a non-fully-reacted, volatile component in a partially cured cross-linking network obtained from photopolymerization. Volume shrinkage induced by the loss of the volatile component is exploited to drive complex shape transformations. After shape transformation, the residual monomers, cross-linkers, and photoinitiators that cannot volatilize still exist in the network, which is ready for a further photopolymerization to significantly stiffen the initial material. Guided by analytic models and finite element analysis, we experimentally demonstrate that a variety of shape transformations can be achieved, including both 2D-to-3D and 3D-to-3D' transformations, such as a buckyball self-folding from a 2D hexagonal lattice sheet and multiple pop-up structures transforming from their initial compact configurations. Moreover, we show that an ultra-low-weight 3D Miura-ori structure transformed from a 2D sheet can hold more than 1600 times its weight after stiffness improvement via postcuring. This work provides a versatile and low-cost method to fabricate rapid and robust shape-morphing structures for potential applications in soft robots, deployable antennas, and optical devices.

Conventional robotic systems are built with rigid materials to deal with large forces and predetermined processes. Soft robotics, however, is an emerging field seeking to develop adaptable robots that can perform tasks in unpredictable environments and biocompatible devices that close the gap between humans and machines. Dielectric elastomers (DEs) have emerged as a soft actuation technology that imitates the properties and performance of natural muscles, making them an attractive material choice for soft robotics. However, conventional DE materials suffer from electromechanical instability (EMI), which reduces their performance and limits their applications in soft robotics. This review discusses key innovations in DE artificial muscles from a material standpoint, followed by a survey on their representative demonstrations of soft robotics. Specifically, we introduce modifications of DE materials that enable large strains, fast responses, and high energy densities by suppressing EMI. Additionally, we examine materials that allow variable stiffness and self‐healing abilities in DE actuators. Finally, we review dielectric elastomer actuator (DEA) applications in soft robotics in four categories, including automation, manipulation, locomotion, and human interaction.

Quality analysis of material jetted silicone material for soft robotics application

Light‐driven liquid crystal elastomers (LCEs) have drawn a great deal of attention as one kind of the most attractive and exciting soft active materials because of their wide application in biomimetic devices, artificial muscles, sensors, and soft robotics. Recently, photothermal effect based LCE actuators have emerged as a promising material with features of biocompatibility, high tissue penetration ability, and the ease and flexibility in materials design. However, to achieve polarized light‐driven LCE actuators, where the polarization can serve as an additional manipulation degree of freedom for actuators manipulation, is still a challenge. Herein, a strategy of constructing a linearly polarization dependent light‐driven soft actuator based on dichroic dye (DD) doped LCEs is demonstrated. Three polarization‐dependent photothermal effect based LCE actuators, including oscillators, bionic dog swinging tail, and light‐mill are experimentally investigated for the first time. The polarization of light is proved to perform as controlling parameter and provides an additional degree of freedom to photothermal effect based light‐driven LCE actuators besides the wavelength and intensity of light. The DD‐doped LCE actuator with good polarization dependence shows great potential applications in soft robotics and biomimetic field.

Liquid metal composites are promising soft conductors for applications in soft electronics, sensors, and soft robotics. Existing liquid metal composites usually have a high‐volume fraction of liquid metal, which not only increases the density but also the material cost. Future applications in soft electronics and robotics highly demand liquid metal composites with low density and high conductivity for large‐scale, low‐cost, lightweight, and more sustainable applications. In this work, lightweight and highly conductive composites embedded with liquid metal fiber networks are synthesized. This new paradigm of liquid metal composites consists of an interconnected liquid metal fiber network embedded in a compliant rubber matrix. The liquid metal fiber network serves as an ultra‐lightweight conductive pathway for electrons. Experiments indicate that this soft conductive composite also possesses nearly strain‐insensitive conductance and superior cyclic stability. Potential applications of the composite films as stretchable interconnects, electrodes, and sensors are demonstrated.

Compared to rigid-structure robots, soft robots possess higher degrees of freedom and stronger environmental adaptability, which has aroused increasing attention in the robotic field. Among them, soft pneumatic robots have excellent performances in various practical applications. However, the nonlinearity and instability of pressure response of soft actuators caused by lateral expansion come to a great challenge. To address this problem, we proposed to embed a spring constraint layer around each single air chamber. Following the design concept, we obtained single-cavity and multi-DoF pneumatic actuators and evaluated their elongation and bending characteristics. Experimental results demonstrated that our proposed actuators have more linear pressure response as well as higher consistency. Eventually, through robotic applications, including soft robotic hand and gripper our proposed actuators could facilitate flexible manipulation and elaborate performance.

A shape-memory soft actuator integrated with reversible electric/moisture actuating and strain sensing

Durable semi-interpenetrating polymer network containing dynamic boroxine bonds for multi-shape manipulated deformation

This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.

Visible light responsive soft actuator based on functional anthracene dye

Magnetorheological elastomers are one of the promising options for stiffness variation of soft robots due to their field-dependent behavior producing high stiffness change rapidly. In this study, we have developed a multiphysics finite element model to investigate this unique behavior with a possible application in soft robotics. Sample magnetorheological elastomers were produced, and an experimental setup was developed. Cantilever bending experiments were performed under varying external magnetic field to tune the model. Results show that the elastic modulus increases with increasing external magnetic field as well as dependency on the volume fraction. Additionally, a possible implementation of magnetorheological elastomers as a stiffening module for a soft continuum robot is discussed as well.

ABSTRACTTwisted and coiled artificial muscles (TAMs) have been extensively studied in the field of soft robots due to their exceptional properties, including high energy density, large load‐to‐weight ratio, large deformation, low driving voltage, and low hysteresis. The advancements of TAMs hold the potential for enhancing the performance and broadening their functional capabilities of soft robots, thus demonstrating substantial practical value. This review outlines the recent progress in TAMs and their diverse applications in soft robots. First, the commonly used materials to fabricate TAMs, including inorganic fibers, composite fibers, organic fibers, and natural fibers, are discussed along with their characteristics. Then, the actuation strategies are summarized across four aspects: thermal method, solvent method, electrochemical method and other non‐contact methods. Moreover, the configurations of TAMs are classified into single, parallel and braided structures. In addition, various soft robots driven by TAMs are introduced according to their functions, including manipulation, locomotion, smart textile, and sensor. Finally, the research hotspots and development trends of TAMs are evaluated. It is expected that this review article can serve as a valuable reference and source of inspiration for researchers in the field of soft actuators and robots.