Actuator Devices Research Articles

Smart Textile‐Based Personal Thermal Comfort Systems: Current Status and Potential Solutions

AbstractThermophysiological comfort in humans is sought universally but seldom achieved due to biological and physiological variances. Most people in developed parts of the world rely on highly energy‐intensive, and inefficient central heating/cooling systems to achieve thermophysiological comfort which is rarely satisfactory. A potential solution to this issue is a wearable personal thermal comfort system (PTCS) consisting of textile‐based temperature and moisture sensors, thermal and moisture responsive actuators, and/or heating/cooling devices, that can sense the environment and physiology of the wearer, and accordingly provide an individualized thermal environment. Moving thermal regulation away from the built environment to the microclimate surrounding the human body using textiles has the potential to provide personalized thermal comfort and energy savings. Such a system may employ thermal comfort models and leverage the Internet of Things (IoT) and machine learning (ML) to understand individuals' comfort requirements. Herein, the current state of textile‐based active and passive comfort systems/technologies are summarized, including their environmental impact, major thermal comfort models, and factors influencing comfort. Also, active and passive textile‐based devices (sensors, actuators, and flexible heating/cooling devices) that may be incorporated into a textile‐based wearable PTCS are comprehensively discussed with an emphasis on their advantages, limitations, and prospects.

A novel adaptive balance-drive mechanism for industrial robots using a series elastic actuator

ABSTRACT To compensate the joint torque of Axis-II caused by end loading and mass of links in industrial robots, static balancing mechanisms are generally used. There are several existing balancing mechanism techniques. However, as these techniques lack autonomy, continuity and dynamics, they cannot completely compensate the joint torque in the presence of dynamic or multiple types of loads. In this paper, a new balancing mechanism technique for industrial robots, based on series elastic actuator (SEA) devices is presented. Simulation and experimental results prove that the devices combine the effects of the balancing mechanism and driving motor of Axis-II, as well as increase load capacity and flexibility. Therefore, this technique can be used to devise a novel dynamic balancing cylinder for heavily loaded industrial robots with active control ability, and simultaneously improve the load-to-weight ratio.

Structure and Dielectric Properties of Electroactive Tetraaniline Grafted Non-Polar Elastomers

Intrinsic modification of polybutadiene and block copolymer styrene–butadiene–styrene with the electrically conducting emeraldine salt of tetraaniline (TANI) via a three-step grafting method, is reported in this work. Whilst the TANI oligomer grafted at a similar rate to both polybutadiene and styrene–butadiene–styrene under the same conditions, the resulting elastomers exhibited vastly different properties. 1 mol% TANI-PB exhibited an increased relative permittivity of 5.9, and a high strain at break of 156%, whilst 25 mol% TANI-SBS demonstrated a relative permittivity of 6.2 and a strain at break of 186%. The difference in the behaviour of the two polymers was due to the compatibilisation of TANI by styrene in SBS through π-π stacking, which prevented the formation of a conducting TANI network in SBS at. Without the styrene group, TANI-PB formed a phase separated structure with high levels of TANI grafting. Overall, it was concluded that the polymer chain structure, the morphology of the modified elastomers, and the degree of grafting of TANI, had the greatest effect on the mechanical and dielectric properties of the resultant elastomers. This work paves the way for an alternative approach to the extrinsic incorporation of conducting groups into unsaturated elastomers, and demonstrates dielectric elastomers with enhanced electrical properties for use in actuation devices and energy harvesting applications.

Reliability Testing of 3D-Printed Polyamide Actuators

3D printing is a rapidly emerging low-cost, high-yield, and high-speed manufacturing technique that has already been utilized in fabricating sensor and actuator devices. Here we investigate the cyclic fatigue and the effect of heating on 10 $\times$ 10 mm2-sized, 3D-printed polyamide-based laser scanning electromagnetic actuators, which are intended for integration with miniaturized laser-scanning imagers to yield a wide variety of optical imaging modalities. The tested actuators offer compact sizes and high-scan angles, comparable to their MEMS counterparts. We have tested N = 15 devices, at 5 different total optical scan angles between 40° - 80°, and observed their lifetimes (up to 108 cycles ≈ 10 days each), as well as the variability in their scan angle and mechanical resonance. A selected scanner was also tested under increased temperature conditions up to 60 °C for 10 hours, showing no sign of fatigue when returned to room temperature. Overall, it is concluded that 3D printed polymeric actuators are promising low-cost alternatives for short-term use in disposable opto-medical imaging units.

Synthesis of Three-Dimensional Carbon Nanostructure/Copper Nanowire for Additive Interface Layer of Ionic Polymer Metal Composite.

Additive interface materials for improved ionic polymer metal composite (IPMC) actuator performance are being investigated. In this study, three-dimensional carbon nanostructure/copper nanowire (3DC Cu-NW) with a novel structure was synthesized via low-pressure chemical vapor deposition. An IPMC actuator with a 3DC Cu-NW interface layer was fabricated, which exhibited improved actuation performance, long-term stability, and electrochemical properties. The proposed 3DC consists of carbon nanotubes (CNTs) and graphene, grown using an Fe catalyst and CH4 gas, respectively. We optimized the growth conditions (Fe catalyst: 12.5 mg/L, CH4: 20 sccm) to achieve a 3DC with an appropriate thickness and a large specific surface area. The 3DC Cu-NW benefited from a Cu oxidation prevention property and a large specific surface area. The electrochemical properties and actuation performance of the IPMC actuator improved with an increased 3DC Cu-NW concentration. An IPMC actuator with a 0.6 wt% 3DC Cu-NW interface layer exhibited 1.3- and 5.6-fold electrochemical property and actuation performance improvement, respectively, over an IPMC actuator with no 3DC Cu-NW interface layer. These results show that the proposed 3DC Cu-NW has potential as an IPMC actuator interface material, and that 3DC Cu-NW synthesis and application technology can be applied to future research on sensor, actuator, and flexible devices.

Nanocrystallization in FINEMET-Type Fe73.5Nb3Cu1Si13.5B9 and Fe72.5Nb1.5Mo2Cu1.1Si14.2B8.7 Thin Films.

A growing variety of microelectronic devices and magnetic field sensors as well as a trend of miniaturization demands the development of low-dimensional magnetic materials and nanostructures. Among them, soft magnetic thin films of Finemet alloys are appropriate materials for sensor and actuator devices. Therefore, one of the important directions of the research is the optimization of thin film magnetic properties. In this study, the structural transformations of the Fe73.5Nb3Cu1Si13.5B9 and Fe72.5Nb1.5Mo2Cu1.1Si14.2B8.7 films of 100, 150 and 200 nm thicknesses were comparatively analyzed together with their magnetic properties and magnetic anisotropy. The thin films were prepared using the ion-plasma sputtering technique. The crystallization process was studied by certified X-ray diffraction (XRD) methods. The kinetics of crystallization was observed due to the temperature X-ray diffraction (TDX) analysis. Magnetic properties of the films were studied by the magneto-optical Kerr microscopy. Based on the TDX data the delay of the onset crystallization of the films with its thickness decreasing was shown. Furthermore, the onset crystallization of the 150 and 200 nm films began at the temperature of about 400–420 °C showing rapid grain growth up to the size of 16–20 nm. The best magnetic properties of the films were formed after crystallization after the heat treatment at 350–400 °C when the stress relaxation took place.

Improving the Electrochemical Performance and Stability of Polypyrrole by Polymerizing Ionic Liquids.

Polypyrrole (PPy) based electroactive materials are important building blocks for the development of flexible electronics, bio-sensors and actuator devices. As the properties and behavior of PPy depends strongly on the operating environment—electrolyte, solvent, etc., it is desirable to plant immobile ionic species into PPy films to ensure stable response. A premade ionic polymer is not optimal in many cases, as it enforces its own structure on the conducting polymer, therefore, polymerization during fabrication is preferred. Pyrrole (Py) was electropolymerized at low temperature together with a polymerizable ionic liquid (PIL) monomer in a one-step polymerization, to form a stable film on the working electrode. The structure and morphology of the PPyPIL films were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy and solid-state NMR (ssNMR) spectroscopy. The spectroscopy results confirmed the successful polymerization of Py to PPy and PIL monomer to PIL. The presence of (TFSI–) anions that balance the charge in PPyPIL was confirmed by EDX analysis. The electrical properties of PPyPIL in lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) aqueous and propylene carbonate solutions were examined with cyclic voltammetry (CV), chronoamperometry, and chronopotentiometry. The blend of PPyPIL had mixed electronic/ionic conductive properties that were strongly influenced by the solvent. In aqueous electrolyte, the electrical conductivity was 30 times lower and the diffusion coefficient 1.5 times higher than in the organic electrolyte. Importantly, the capacity, current density, and charge density were found to stay consistent, independent of the choice of solvent.

Characterization of optofluidic devices for the sorting of sub-micrometer particles.

In this work, we investigate methods of fabricating a device for the optical actuation of nanoparticles. To create the microfluidic channel, we pursued three fabrication methods: SU-8 to molded polydimethylsiloxane soft lithography, laser etching of glass, and deep reactive ion etching of fused silica. We measured the surface roughness of the etched sidewalls, and the laser power transmission through each device. We then measured the radiation pressure on 0.5-µm particles in the best-performing fabricated device (etched fused silica) and in a square glass capillary.

BIoTA: A Buildout IoT Application Language

Domain-Specific Languages (DSLs) serve a wide variety of purposes in the development of complex applications. The Internet of Things (IoT) brings additional complexity to software development due to its inherent distribution and inclusion of a massive number of heterogeneous devices (sensors and actuators). The process of developing software architectures for IoT involves the interaction of several components that play distinct roles. In this paper, we propose a language called BIoTA (Buildout IoT Application Language), a DSL whose objective is to assist and streamline the building of software architectures for IoT. The specification and implementation of the BIoTA language involve a grammar and a compiler, responsible for syntax and semantic analysis, as well as code generation. They facilitate the formalization of software architectures using automata, which would otherwise be created in an informal and ad-hoc manner to address specific IoT scenarios. We developed an IDE (Integrated Development Environment) capable of reading and creating software architectures using the BIoTA language. With the BIoTA IDE, we demonstrate three examples of software architectures for IoT smart applications in public buildings, irrigation, and parking. The IDE also makes it possible to export architectures to a software distribution package pattern based on containers (Docker Compose) for future deployment.

Ground vehicles hydraulic system pneumatic hydraulic valve

Hydraulic systems equipped with working bodies hydraulic drives are widely used in ground vehicles. The researches show that one of the modern hydraulic drives problems is the destruction of flexible high-pressure hoses and the unauthorized pressure fluid discharge into the atmosphere. The analysis of the machines hydraulic drive protecting existing methods shows that the urgency of their improvement problem remains, since, for most of them the loss is between 3 and 10 l when operating, for example, pneumatic electric protection system - 6 … 8 l., float protection system is up to 10 l. As can be seen from the analysis, after the protection system locking device actuation leakage of the pressure fluid is preserved. The hydromechanical hydraulic drive protection system is the closest in technical essence and the achieved technical result. However, it also has a disadvantage, for example, when the locking device is actuated a hydraulic shock occurs, and leads to an oscillatory process of the plunger, an increase in the overlap time of the damaged hydraulic line, a decrease in the speed of the locking device and its operational reliability. To eliminate these shortcomings, the authors propose a new technical solution.

Study on novel Fe-based core-shell structured soft magnetic composites with remarkable magnetic enhancement by in-situ coating nano-ZnFe2O4 layer

Soft magnetic composites based on spherical supersendust (Fe85Si8Al4Ni3) powder were made by gas atomization. The nano-ZnFe2O4 layer was coated on the surface of Fe85Si8Al4Ni3 powder particles by in-situ oxidation. Core-shell structured microspheres were achieved and then mixed with epoxy-modified silicone resin. Lorentz-transmission electron microscopy confirmed the core-shell structure of the Fe85Si8Al4Ni3-ZnFe2O4 microspheres. The uniform surface layer consisted of nano-ZnFe2O4 layer was clarified by scanning electron microscopy and energy dispersive spectroscopy X-ray analysis. The ferromagnetic nano-ZnFe2O4 layer effectively reduces magnetic dilution, while high electrical resistivity of both ZnFe2O4 and ESR provides satisfactory insulation of the SMCs, giving rise to simultaneous high permeability and extraordinary low core loss. Magnetic properties were determined using a vibrating sample magnetometer and an auto testing system for magnetic materials (SY8258B-H/m). The results show that the samples prepared at 1200 MPa and 550 ℃ exhibited distinguished magnetic properties, with core loss of 89 W/kg (100 kHz, 50 mT) and amplitude permeability of 50 whose frequency stability is up to 170 kHz. The Fe85Si8Al4Ni3 SMCs with excellent soft magnetic properties provide great potential for application of various fields such as transformers, sensors and electromagnetic actuation devices. Our approach can be expanded to other Fe-based SMCs.

A data modeling conceptual framework for ubiquitous computing based on context awareness

This paper introduces a framework for data modeling to support ubiquitous computing based on context-awareness. Data always grow in term of volume, variety, velocity, and value. The problem arises when it grows exponentially. Consequently, data is anywhere and requirements change in early data definitions then data design become not as the plan. Therefore, suitable approach with new paradigm and methods of data modeling needs to be enhanced to solve the problems in the real world. Data model must consider the active object that related to each other. Any objects may interact with each other in a ubiquitous way and recorded in digital technology. Sensors, actuator devices, and radio frequency identification technology may support communication between objects through ubiquitous computing. The data model in Ubiquitous Computing needs to restructure to become active and dynamic. Ubiquitous computing is a model that enable all objects around the people to communicate and invisible. In order to support this paradigm, a new perspective of how data are designed and stored on each object is needed. Furthermore, using ubiquitous computing, the pervasive network can request and response information, which means the devices may communicate and has the initiative to solve a problem without human intervention. Human wants more intelligence objects. Therefore, more sensors and memory are required. Data structures need to enhance or embedded into any devices that interact with the human.

High-Order Model-Free Adaptive Iterative Learning Control of Pneumatic Artificial Muscle With Enhanced Convergence

Pneumatic artificial muscles (PAMs) have been widely used in actuation of medical devices due to their intrinsic compliance and high power-to-weight ratio features. However, the nonlinearity and time-varying nature of PAMs make it challenging to maintain high-performance tracking control. In this article, a high-order pseudopartial derivative-based model-free adaptive iterative learning controller (HOPPD-MFAILC) is proposed to achieve fast convergence speed. The dynamics of PAM is converted into a dynamic linearization model during iterations; meanwhile, a high-order estimation algorithm is designed to estimate the pseudopartial derivative component of the linearization model by only utilizing the input and output data in previous iterations. The stability and convergence performance of the controller are verified through theoretical analysis. Simulation and experimental results on PAM demonstrate that the proposed HOPPD-MFAILC can track the desired trajectory with improved convergence and tracking performance.

Experimental demonstration of a Smart Homes Network in Rome

According to the European Strategy Energy Technology (SET) Plan, the resident-user engagement into the national energy strategy is pivotal to the project as it is considered to be one of the most important challenges. The Italian Minister of Economic Development and ENEA have entered into a Programme Agreement for the execution of the research and development lines of General Interest for the National Electricity System. In particular, as part of the “Development of an integrated model of the Urban Smart District” a Smart Home network experimentation has been carried out in the Centocelle district of Rome. This project aims to develop a replicable model able to monitor energy consumption, the degree of comfort and safety in residential buildings and to transmit raw data to a higher level ICT platform where they are analysed and aggregated to provide the user and the community with a series of constructive and valuable feedback that can shed light on their usage patterns and what ought to be improved to increase their energy awareness. The heart of the system is the Energy Box (EB) that allows the control of the devices (sensors and actuators) and transforms each and every home into an active node of a smart network, which allows the user to share data and information with the outside world, as to increase the dwellings' sense of participation and belonging to the community by providing them with useful tools for new forms of interaction. In perspective, the system architecture developed in the project will also be able to transform each user from a simple consumer into an active participant in the energy market, allowing individual residences to control demand (demand-side management). Finally, the brand-new home digital infrastructure has paved the way to a series of additional services, such as assisted living and home security.

High Electromechanical Deformation Based on Structural Beta-Phase Content and Electrostrictive Properties of Electrospun Poly(vinylidene fluoride- hexafluoropropylene) Nanofibers.

The poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) polymer based on electrostrictive polymers is essential in smart materials applications such as actuators, transducers, microelectromechanical systems, storage memory devices, energy harvesting, and biomedical sensors. The key factors for increasing the capability of electrostrictive materials are stronger dielectric properties and an increased electroactive β-phase and crystallinity of the material. In this work, the dielectric properties and microstructural β-phase in the P(VDF-HFP) polymer were improved by electrospinning conditions and thermal compression. The P(VDF-HFP) fibers from the single-step electrospinning process had a self-induced orientation and electrical poling which increased both the electroactive β-crystal phase and the spontaneous dipolar orientation simultaneously. Moreover, the P(VDF-HFP) fibers from the combined electrospinning and thermal compression achieved significantly enhanced dielectric properties and microstructural β-phase. Thermal compression clearly induced interfacial polarization by the accumulation of interfacial surface charges among two β-phase regions in the P(VDF-HFP) fibers. The grain boundaries of nanofibers frequently have high interfacial polarization, as they can trap charges migrating in an applied field. This work showed that the combination of electrospinning and thermal compression for electrostrictive P(VDF-HFP) polymers can potentially offer improved electrostriction behavior based on the dielectric permittivity and interfacial surface charge distributions for application in actuator devices, textile sensors, and nanogenerators.

Composition-dependent phase evolution and enhanced electrostrain properties of (Bi0.5Na0.5)TiO3–BaTiO3–Bi(Li0.5Ta0.5)O3 lead-free ceramics

Exploring lead-free materials to substitute the commercialized PZT-based compounds is in great demand for the development of miniaturized and nonhazardous actuator devices. Here, a new ternary lead-free (1-x)(Bi0.5Na0.5)1-yBayTiO3-xBi(Li0.5Ta0.5)O3 (BNBTy-xBLT) solid solution system is designed to optimize the electrostrain performance of the well-studied BNT ceramics, and the effects of BLT and Ba substitutions on phase evolution as well as electrical performances of BNT ceramics are systematically investigated. All the compositions prepared by solid-state sintering process exhibit similar pseudocubic phase with rhombohedral/tetragonal distortions in nanoregions. Through optimizing the BLT and Ba contents, the composition with 6.9 mol% Ba and 0.8 mol% BLT exhibits the maximum unipolar strain of ∼0.39% (equivalent normalized strain d33*∼654 pm/V, 60 kV/cm). Moreover, the origin of the excellent electrostrain response is emphatically analyzed from microscopic (domain structure evolution) and macroscopic (TF-R shifting) perspectives, which results from the electric-field-induced reversible relaxor-ferroelectric phase transition. These results suggest the composition-optimized BNT-BT-BLT system as a potential alternate to lead-based systems in actuator applications.

Effects of initial stresses on guided wave propagation in multilayered PZT-4/PZT-5A composites: A polynomial expansion approach

Effects of initial stresses on the dispersion curves of Lamb and SH waves in multilayered PZT-4/PZT-5A composites are investigated using the polynomial expansion approach. The piezoelectric layers are considered with arbitrary crystal orientations with a result that only Lamb or SH waves may be transmitted. The problem is solved employing the Legendre polynomial approach that poses the advantages of numerically stability and effectiveness over conventional matrix method. The solution is validated by comparing the wave propagation behavior of piezoelectric materials with those reported in literature, and the convergence properties are examined. Numerical results demonstrate that initial stress has profound influences on the guided wave propagation in multilayered PZT-4/PZT-5A laminates. The phase velocity of Lamb and SH waves increases with initial tensile stresses. In addition, the effects of initial stresses rely on the wave mode and thickness of constituent layers and the stacking sequence of the constituent materials. The results are useful for understanding and optimization of new designs for actuator, electromechanical sensor and acoustic wave devices made of PZT-4/PZT-5A composites.

Fabrication and characterization of a novel bionic manipulator using a laser processed NiTi shape memory alloy

The thermo-mechanical properties of NiTi shape memory alloys (SMAs) have sparked significant research efforts seeking to exploit their bionic capabilities. Currently, the performance capabilities of NiTi-based devices have been inhibited by the retention of only one thermo-mechanical response in the as-received material, namely the shape memory effect (SME) or superelasticity (SE), which mainly depend on the transformation temperatures of the base material. In this work, a novel monolithic bionic manipulator was developed using a NiTi SMA by laser processing, which included both the shape memory and superelastic effects in a single Ni-rich monolithic structure. The device actuation and bending were achieved by resistive heating, which activates the SME of different laser processed regions. Each laser processed region has unique phase transformation onset temperatures and thermo-mechanical recovery characteristics thus providing distinct actuation characteristics. Additionally, the functional fatigue of the part was determined for rehabilitation training of patients including the fingers pairing and grabbing modes.

Robust thermoelastic microactuator based on an organic molecular crystal

Mechanically responsive molecular crystals that reversibly change shape triggered by external stimuli are invaluable for the design of actuators for soft robotics, artificial muscles and microfluidic devices. However, their strong deformations usually lead to their destruction. We report a fluorenone derivative (4-DBpFO) showing a strong shear deformation upon heating due to a structural phase transition which is reproducible after more than hundred heating/cooling cycles. Molecular dynamic simulations show that the transition occurs through a nucleation-and-growth mechanism, triggered by thermally induced rotations of the phenyl rings, leading to a rearrangement of the molecular configuration. The applicability as actuator is demonstrated by displacing a micron-sized glass bead over a large distance, delivering a kinetic energy of more than 65 pJ, corresponding to a work density of 270 J kg−1. This material can serve as a prototype structure to direct the development of new types of robust molecular actuators.

Radio frequency controlled wireless drug delivery devices

Drug delivery devices have revolutionized the course of therapeutic treatment in the recent past. These devices provide a firm foundation for diverse strategies to overcome the limitations of systemic administration that cannot provide a high drug potency at the specific disease infected body tissues. The ongoing developments in the pharmaceutical industry have focused on exploring the reliable actuating mechanisms that can provide therapy and dispense drugs precisely to control therapeutic effects with minimum toxicity. The wireless actuation of drug delivery devices has been considered as an intervening noninvasive approach to release encapsulated drug compounds. This review paper highlights implantable and transdermal drug delivery devices that are based on wirelessly controlled microchips, micropumps, microvalves, and magnetic robots. Their key features, such as working principle, dimensions, materials, operating frequency, and wireless actuation through radio frequency for drug delivery are explained. The interaction of radio waves with electrically conductive and magnetic nanoparticles is also discussed for drug delivery. Furthermore, the radio frequency assisted data telemetry and wireless power transfer techniques are elucidated for drug delivery devices. The opportunities to enhance the patients' control on therapeutic indexes and release mechanisms are still possible by incorporating advanced wireless sensors for concocting future innovations in the wirelessly controlled drug delivery devices.