Smart Actuators Research Articles

Bioinspired bilayer hydrogel-based actuator with rapidly bidirectional actuation, programmable deformation and devisable functionality

Smart hydrogel actuators which respond to external stimuli have attracted great attention and shown good application prospects in many fields as their simplicity and reliability, while the challenges remain in terms of the relatively low driving force, responsive velocity and deformation amplitude considering the structure-dependent actuation behavior. Here, we propose a thermosensitive hydrogel-based actuator with bioinspired bilayer structure by applying a textured airlaid paper to induce the formation of heterogeneous construction. This nature-inspired design benefits the hydrogel-based actuator rapidly bidirectional actuation, realizing excellent bending velocity (140.6° s−1 within first 5 s) and bending amplitude (850.0° within 30 s) in hot water, powerful recovery in cool water and remarkable reproducibility upon external environmental stimulus by optimizing the texture orientation and mechanical property of airlaid paper. The excellent bonding between airlaid paper and hydrogel also endows the actuator satisfactory stability for circularly operation under water environment for weeks. The programmable deformation and devisable functionality are further realized by propagable and elaborate design for architecture and component of responsive hydrogel, favoring the hydrogel-based actuator alterable ethanol-sensitive ability, photothermal drivability and regenerability. This bilayer hydrogel-based actuator provides promising potentials for the applications in soft robots, smart actuators, artificial muscles, and intelligent human-machine technologies.

Adaptive Neural Digital Control of Hysteretic Systems With Implicit Inverse Compensator and Its Application on Magnetostrictive Actuator.

Hysteresis is a complex nonlinear effect in smart materials-based actuators, which degrades the positioning performance of the actuator, especially when the hysteresis shows asymmetric characteristics. In order to mitigate the asymmetric hysteresis effect, an adaptive neural digital dynamic surface control (DSC) scheme with the implicit inverse compensator is developed in this article. The implicit inverse compensator for the purpose of compensating for the hysteresis effect is applied to find the compensation signal by searching the optimal control laws from the hysteresis output, which avoids the construction of the inverse hysteresis model. The adaptive neural digital controller is achieved by using a discrete-time neural network controller to realize the discretization of time and quantizing the control signal to realize the discretization of the amplitude. The adaptive neural digital controller ensures the semiglobally uniformly ultimately bounded (SUUB) of all signals in the closed-loop control system. The effectiveness of the proposed approach is validated via the magnetostrictive-actuated system.

Nanogel Crosslinking-Based Belousov-Zhabotinsky Self-Oscillating Polyacrylamide Gel with Improved Mechanical Properties and Fast Oscillatory Response.

The Belousov-Zhabotinsky (BZ) self-oscillating gel is a unique actuator suited for studying the behavior of intelligent soft robots. However, the traditional BZ self-oscillating polyacrylamide (PAAm) gel is easily broken and is slow to response to stimuli, which limits its practical application. Therefore, the preparation of BZ gels with sensitive responses to external stimuli and desirable, robust mechanical properties remains a challenge. In this work, PAAm-activated nanogels with unpolymerized double bonds are used as nanocrosslinkers to synthesize a nanogel crosslinking-based BZ (NCBZ) self-oscillating PAAm gel, whose mechanical properties, for example, antipuncture, cutting, and tensile properties, are superior to those of traditional PAAm BZ-self-oscillating gels. The oscillatory period of the traditional gel is much longer than that of the corresponding homogeneous BZ system, resulting from the slow response of the gel to changes in redox potential, whereas large, interconnected pores inside the NCBZ gel provide efficient channels for rapid species transport, supporting fast response of the gel, which results in almost the same period of chemomechanical oscillations as the homogeneous system under the same conditions. Scanning electron microscopy results show that the NCBZ gel is more stable than the traditional BZ PAAm gel after 7 h of oscillation. Our results make it possible to prepare robust gel motors and provide promising application prospects for smart soft robots, actuators, sensors, tissue engineering, and other applications.

Effects of actuator-substrate ratio on hydrodynamic and propulsion performances of underwater oscillating flexible structure actuated by macro fiber composites

Oscillating flexible structures driven by smart actuators are promising thrust-producing components for underwater bionic vehicles. In this study, the hydrodynamic and propulsion performances of an oscillating flexible structure driven by macro fiber composites (MFCs) are investigated at varying actuator-substrate ratios. Numerical and experimental results demonstrate that the underwater resonant frequency increases approximately linearly with increasing actuator-substrate ratio. Moreover, the ratios of the in-air and underwater resonant frequencies vary with differing actuator-substrate ratios, and are mainly determined by the equivalent mass density. The effects of the actuator-substrate ratios on several characteristic parameters related to the propulsion performance are investigated and compared. The results suggest the generated mean thrust of the fully actuated case is the largest, but the power efficiency is the lowest among all the actuator-substrate ratios investigated, because this case has the lowest characteristic velocity and Reynolds number. In contrast, the highest power efficiency and lowest generated thrust are observed in the longest substrate case with the smallest actuator-substrate ratio. An optimal balance between the power efficiency and generated thrust is achieved when the actuator-substrate ratio approaches 0.6, in which case the characteristic parameters of propulsion performance are the highest among all the cases. These findings can provide useful guidelines for the design of efficient underwater bionic devices propelled by flexible fins driven by MFCs and other smart actuators.

Modeling and analysis of an electro-magneto-elastic rotating cylindrical tube actuator

This paper presents the static modeling and analysis of a novel cylindrical tube actuator subjected to a rotation about longitudinal axis with an internally applied air pressure under an electromagnetic field. The current tube actuator belongs to a smart actuator category and is made of an electro-magneto-active polymer filled with a particular volume fraction of suitable fillers. A continuum mechanics-based electro-magneto-mechanical model is developed to predict the response of the actuator for a combined pressure and electromagnetic field loading. To validate the same, the model is compared with the outputs of an existing spring roll actuator. Parametric studies are subsequently performed for varying input pressure, electric field, magnetic field, fillers content, and actuator’s rotational speed. The output sensitivity in terms of strain intensity at inner and outer surfaces of the actuator is also checked at different controlling inputs. In addition, various electro-magneto-mechanical instability curves are drawn to examine the critical inflation of the tube actuator. In general, the developed model provides initial steps toward the modern actuator designs for applications where a precise control with high load-carrying capability of the actuator plays a significant role.

Semicrystalline polymer networks with a swelling-enhanced water-triggered two-way shape-memory effect for programmable deformation and smart actuation

A simple, effective and universal strategy is proposed to fabricate a water-triggered two-way shape-memory polymer with the highest angle reversibility of 45.2%, which can be applied as a soft gripper and water level monitor.

Water-triggered synergistic fluorescence variation and shape deformation in a Zn-TCPP metal–organic framework-based gel

A MOF-based gel with simultaneous fluorescence and morphologic changes triggered by water was developed and applied in a visible rewriting pattern and a smart artificial actuator.

Development and challenges of smart actuators based on water-responsive materials.

Water-responsive (WR) materials, due to their controllable mechanical response to humidity without energy actuation, have attracted lots of attention to the development of smart actuators. WR material-based smart actuators can transform natural humidity to a required mechanical motion and have been widely used in various fields, such as soft robots, micro-generators, smart building materials, and textiles. In this paper, the development of smart actuators based on different WR materials has been reviewed systematically. First, the properties of different biological WR materials and the corresponding actuators are summarized, including plant materials, animal materials, and microorganism materials. Additionally, various synthetic WR materials and their related applications in smart actuators have also been introduced in detail, including hydrophilic polymers, graphene oxide, carbon nanotubes, and other synthetic materials. Finally, the challenges of the WR actuator are analyzed from the three perspectives of actuator design, control methods, and compatibility, and the potential solutions are also discussed. This paper may be useful for the development of not only soft actuators that are based on WR materials, but also smart materials applied to renewable energy.

Remote MPC for Tracking Over Lossy Networks

In this work we consider the problem of remote control over lossy networks for systems subject to constraints. The objective is to devise a strategy for tracking reference signals while satisfying constraints under any network condition. We consider a remote Model Predictive Controller (MPC) and a local smart actuator able to stabilize the system when needed, in combination with a suitable mechanism to tackle packet losses. We show that the proposed algorithm allows us to enforce constraints without any assumption on the network, while we prove the convergence to constant desired references under mild assumptions. Simulations with real Wi-Fi communication data show the benefits of the algorithm with respect to other networked MPCs. The proposed solution is useful to combine high performances of advanced control technologies that cannot be implemented on-board and safety of locally controlled systems.

Smart Networking of Company

Abstract: This paper simulate IoT based smart companies and make our networking infrastructure effective, efficient and most importantly accurate with security. The simulator used is Cisco Packet Tracer, this tool has been used form many years in networking. Main strength of the tool is the offering of a variety of network components that simulate a real network, devices would then need to be interconnected and configured in order to create a network. Technology plays a critical role in all daily activities of the present day. One of these needs is to create a smart office that controls operation and turns off electronic devices via a smartphone. This implementation can be implemented effectively using package tracking software that includes IoT functions to control and simulate a smart office. The latest version of the tool Cisco introduced IoT functionalities, and now it is possible to add to the network smart devices, components, sensors, actuators and also devices that simulate microcontrollers such as Arudino or Raspberry Pi. All the IoT devices can be run on standard programs or can be customized by programming them with Java, Phyton or Blockly. This makes Cisco Packet Tracer an ideal tool for building IoT practical simulations. Smart-Industrial smart-company office offer simulation of a power plant that produces and stores electricity via solar panels and wind turbines. All the electricity is produced by smart devices, then stored and utilized to power a production chain filled with smart sensor and actuators. IoT security features are also introduced in the simulations. Keywords: Internet of things (IOT), Campus Network (CN), networking, wide area network (WAN).

Bio-Mimetic Actuators of a Photothermal-Responsive Vitrimer Liquid Crystal Elastomer with Robust, Self-Healing, Shape Memory, and Reconfigurable Properties.

Soft actuators with apparent uniqueness in exhibiting complex shape morphing are highly desirable for artificial intelligence applications. However, for the majority of soft actuators, in general, it is challenging to achieve versatility, durability, and configurability simultaneously. Enormous works are devoted to meet the multifunctional smart actuators, to little effect. Herein, self-healing and bio-mimetic smart actuators are proposed based on azobenzene chromophores and dynamic disulfide bonds. Benefiting from the dynamic and drivable vitrimer liquid crystal elastomer (V-LCE) materials, a series of actuators with single or compound dynamic three-dimensional structures were fabricated, which were capable of double-stimuli response and complex "bionic" motions, such as the blooming of a flower, grasping and loosening an object, and so forth. Moreover, these flexible actuators showed fascinating properties, such as high robustness, excellent elasticity-plasticity shape-memory properties (Rf and Rr are close to 100%), easily reconfigurable property, and self-healing. This smart V-LCE provides a guideline to design and fabricate soft versatility actuators, which has prospects for developing smart bionic and artificial intelligence devices.

An Electrospinning Anisotropic Hydrogel with Remotely-Controlled Photo-Responsive Deformation and Long-Range Navigation for Synergist Actuation

As a soft/wet intelligent material, hydrogel actuators with multiple stimuli-responsiveness have been widely developed. However, it is still greatly difficult for them to integrate bi/multiple responsiveness together for bio-mimetic synergistic actuation. Here, we have explored a high-strength anisotropic bi-layer hydrogel actuator with P(NIPAM-ABP) layer and Fe3O4/PAN layer via electrospinning technique, which can provide programmable bi-functional synergistic movement. The Fe3O4/PAN layer can provide magnetic responsive navigation for long-range transportation on account of the magnetism of the Fe3O4 nanoparticles. Furthermore, the ultrahigh photothermal conversion efficiency of the Fe3O4 nanoparticles in the Fe3O4/PAN layer, can endow the P(NIPAM-ABP) layer with fast remotely-controlled photothermal-responsive deformation. Most importantly, this hydrogel actuator can achieve complex higher-level programmable movements than before based on the synergy of remotely-controlled deformation and the long-range transportation, which can be utilized to design various novel bio-mimetic soft-robots. Last but not least, the introduction of the electrospinning, not only can achieve high strength (4.59 MPa of tensile strength) of this bi-layer hydrogel, but also can provide both ultrafast (178°/s) and programmable complex photothermal-responsiveness, owing to the ultrahigh specific surface area (ultra-thin and porous structure) and excellent orientation of the thermal-responsive P(NIPAM-ABP) nanofibers respectively. This work will provide a general method via electrospinning for anisotropic hydrogel actuator with bi/multiple-functional synergy and will provide a new strategy for smart actuators and other bio-mimetic intelligent materials/systems.

Wavelength-selective responsive hybrid structures utilizing shape memory poly(aryl ether ketone)

Wavelength-selective responsive shape memory polymers (SMPs) are able to achieve significantly programmable deformations upon light irradiations with different wavelengths, which are expected to play the important roles in diverse smart devices. At present, the most of wavelength-selective responsive SMPs exhibit poor strength and thermo-stability, which restrict their utilizations in sensor and aerospace structures. Here, we constructed the light responsive poly(aryl ether ketone) (PAEK) hybrid structures with enhanced strength and wavelength-selective responses, which exhibited programmable multistage deformations under light irradiations of different wavelengths (365 nm and 254 nm). Besides, we designed “man” and “flower” smart structures with photo-responsive PAEK components to demonstrate wavelength-selective responsive motions. The smart “man” could spontaneously open his limbs and the “flower” could bloom via diverse programmable paths, which could be tuned by manipulating the arrangement of photosensitive components and light irradiation wavelengths. The wavelength-selective shape memory hybrid structures could be widely utilized in the fields of soft robots, smart actuators, and deformed devices.

Pressure and Temperature Induced Dual Responsive Molecular Crystals: Effect of Polymorphism

The rapid conversion of energy into mechanical motion is a crucial requirement in the design of advanced flexible sensors and optoelectronic devices. Responsive materials that show mechanical movement when exposed to different external stimuli such as heat, pressure, humidity, or light can serve as technomimetics in smart actuator and microrobotic devices. However, it is quite challenging to design molecular crystals which can respond to two or more external stimuli. Herein, we report dimorphic forms (1a and 1b) of 2-hydroxy-3,5-dibromobenzylidine-4-fluoro-3-nitroaniline (Crystal 1) where form 1a is brittle and form 1b is elastically bendable. Both polymorphs exhibit progressive thermosalient responses which are seemingly different in nature. One polymorph (1a) shows jumping, while the other (1b) shows bending. The property difference is solely attributed to the inherent crystal packing and linked to the differences in the molecular conformations, structural packing, and intermolecular interactions. 2-Hydroxy-3-bromo-5-chlorobenzylidine-4-fluoro-3-nitroaniline (Crystal 2) was nonthermosalient but was mechanically flexible. Variable temperature powder X-ray diffractometry revealed anisotropic crystallographic face expansion─a possible explanation for the different thermosalient behaviors of the dimorphs.

An asymmetric clay film for smart moisture actuators: Film actuation and characterization

Exploring low-cost materials and convenient fabrication is crucial for the development of humidity responsive actuators. Montmorillonite (Mt.), one of the natural layered clays, provides the great potential in the field of smart actuators. We present the self-assembling Mt.bilayer film, which was simply prepared by sequential vacuum filtration of Mt. and organic montmorillonite (OMt) dispersions. When exposed to the uniform humidity, the obtained Mt./OMt bilayer film shows good stable actuation and a large bending deformation with a curvature up to 360°. Several biomimetic devices (window cutain, flower and gripper) was designed using Mt./OMt films and their smart actuation was demonstrated through programmable bendings. Importantly, more complex shape-deformations and more intelligent actuators can be realized by simply printing glue arrays on OMt side of the bilayer film. Additionally, the obtained Mt./OMt film is sensitive to various solvents and shows different bending behaviors upon exposure to the organic solvents vapors. This work may demonstrate a new, simple and promising strategy for potential application of layered clay in flexible robots, biomimetic devices, and solvent sensors.

Giant single-crystal-to-single-crystal transformations associated with chiral interconversion induced by elimination of chelating ligands

Numerous single crystals that exhibit single-crystal-to-single-crystal (SCSC) transformations have been reported, and some of them show great promise for application to advanced adsorption materials, magnetic switches, and smart actuators. However, the development of single crystals with super-adaptive crystal lattices capable of huge and reversible structural change remains a great challenge. In this study, we report a ZnII complex that undergoes giant SCSC transformation induced by a two-step thermal elimination of ethylene glycol chelating ligands. Although the structural change is exceptionally large (50% volume shrinkage and 36% weight loss), the single-crystal nature of the complex persists because of the multiple strong hydrogen bonds between the constituent molecules. This allows the reversible zero-dimensional to one-dimension and further to three-dimensional structural changes to be fully characterized by single-crystal X-ray diffraction analyses. The elimination of chelating ligands induces a chiral interconversion in the molecules that manifests as a centric-chiral-polar symmetric variation of the single crystal. The study not only presents a unique material, featuring both a periodic crystal lattice and gel-like super-ductility, but also reveals a possible solid-state reaction method for preparing chiral compounds via the elimination of chelating ligands.

Static and dynamic instability modeling of electro-magneto-active polymers with various entanglements and crosslinks

Electro-magneto-active (EMA) polymers-based smart actuators suffer from electro-magneto-mechanical instability (EMMI) phenomena arising due to the positive feedback between the applied electric and magnetic fields and reduction in the polymer thickness. This work presents a theoretical investigation of EMMI phenomena of an EMA polymeric actuator in both static and DC dynamic modes of operation. A physics-based non-affine material model is adopted here for capturing the effect of the polymer chain entanglements and crosslinks on the instability phenomena. Simultaneously, a computationally efficient energy approach for obtaining the DC dynamic instability parameters is constructed, which depends on the energy balance at the position of maximal overshoot in an oscillation cycle. The findings from the current study illustrate the trends of variation in the deformation, electric field, and magnetic field at the onset of static and dynamic EMMI with the polymeric entanglements and crosslinks parameters. It is observed that large entanglements and crosslinks in polymer chains improve the stable operation travel range, which positively impacts the actuator performance.

Smart actuation of liquid crystal elastomer elements: cross-link density-controlled response

Liquid crystal elastomers (LCEs) exhibit some remarkable physical properties, such as the reversible large mechanical deformation induced by proper environmental stimuli of different nature, such as the thermal stimulus, allowing their use as soft actuators. The unique features displayed by LCE are originated from their anisotropic microstructure characterized by the preferential orientation of the mesogen molecules embedded in the polymer network. An open issue in the design of LCEs is how to control their actuation effectiveness: the amount of mesogens molecules, how they are linked to the network, the nematic order degree, the cross-link density are some controllable parameters whose spatial distribution, in general, cannot be tuned except for the last one. In this paper, we develop a theoretical micromechanical-based framework to model and explore the effect of the network cross-link density on the mechanical actuation of LCE elements. In this context, the light-induced polymerization (photopolymerization) for obtaining the elastomers’ cross-linked network is of particular interest, being suitable for precisely tuning the cross-link density distribution within the material. This technology enables to obtain a molecular-scale architected LCEs, allowing the optimal design of the obtainable actuation. The possibility to properly set the cross-link density arrangement within the smart structural element (LCE microstructure design and optimization), represents an intriguing way to create molecular-scale engineered LCE elements having a material microstructure encoding the desired actuation capabilities.

Influence of CNT fillers in the vibration characteristics of natural fiber reinforced composite plates

Flax epoxy composites can be massively adopted in internal applications of automobiles and aircraft. This research work mainly deals with flax fiber composite in which unidirectional flax fibers are reinforced in epoxy matrix and are used in combination with CNT fillers. Such composite plate structures are manufactured and are tested using a smart actuation system. This experimental research work aims to find out the variations of the natural frequencies of composite plates made of flax fibers and CNT fillers. The consequence of various parameters like size, number of layers, etc. on CNT reinforced flax epoxy composite is discussed. The percentage of CNT fillers is varied and results for several parametric studies are presented.

Investigation of the Long‐Term Storage Stability of Shape Memory Epoxy Prepolymer

Epoxy‐based shape memory polymers (ESMPs) are important types of thermoset shape memory polymers due to their unique thermomechanical properties, which have great potential in applications ranging from smart actuators to deformable structures. The long‐term storage stability is important for ESMPs, especially when pursuing the same batch of materials for alternatives. Stable storage of ESMP preplomyers in the long term and taking it out for curing when needed are of great benefit to engineering applications which highly require the same batch of materials for high production efficiency, such as in deployable space structures, semiconductor, and electronic packaging. However, this important storage stability of ESMP has not been studied so far. Herein, a series of ESMPs with tunable glass transition temperatures (Tgs) ranging from 100 to 170 °C is prepared. The effect of long‐term storage at low temperatures on rheological, thermal, thermomechanical, mechanical, and shape memory properties is systematically investigated. The ESMP after storage shows an improvement of crosslinking density, Tgs, and mechanical strength, while maintaining chemical structures and excellent shape memory properties. This feasible method of low‐temperature storage realizes overall long‐term stability and enhancement of strength in ESMPs, making it more promising for engineering applications.