Actuation Properties Research Articles

Human TRPV4 engineering yields an ultrasound-sensitive actuator for sonogenetics.

Sonogenetics offers non-invasive and cell-type specific modulation of cells genetically engineered to express ultrasound-sensitive actuators. Finding an ion channel to serve as sonogenetic actuator it critical for advancing this promising technique. Here, we show that ultrasound can activate human TRP channel hTRPV4. By screening different hTRPV4 variants, we identify a mutation F617L that increases mechano-sensitivity of this channel to ultrasound, while reduces its sensitivity to hypo-osmolarity, elevated temperature, and agonist. This altered sensitivity profile correlates with structural differences in hTRPV4-F617L compared to wild-type channels revealed by our cryo-electron microscopy analysis. We also show that hTRPV4-F617L can serve as a sonogenetic actuator for neuromodulation in freely moving mice. Our findings demonstrate the use of structure-guided mutagenesis to engineer ion channels with tailored properties of ideal sonogenetic actuators.

Mechanical behavior of shape memory alloys considering the effects of body fluids corrosion for biomedical applications

Abstract Shape memory alloys (SMAs) are widely used in biomedical engineering, including cardiovascular stents, artificial skeletons, and orthodontic implants. For the above applications, the body fluids corrosion processes will inevitably cause deterioration in the mechanical properties of the SMAs actuator during its service life, which will threaten the safety of human health. To analyze such problems, experimental measurements have been carried out to investigate the influence of body fluid corrosion on the mechanical properties of SMAs. Changes in the mechanical properties, such as Young’s modulus and phase transformation temperatures of SMAs under body fluids corrosion were tested firstly in the simulated body environment with the 0.9 wt. % NaCl solution at 37. With an increase of the immersion time, the results show that the Ti (titanium) percentage, austenitic (reverse) transformation start temperature, austenitic (reverse) transformation finish temperature, and maximum residual strain all increase, the Ni (nickel) percentage, martensitic transformation finish temperature, tensile strength, and yield strength decrease, and the martensitic transformation start temperature first decreases and then increases. The research in this work can provide an experimental basis for further study of the SMAs materials in biomedicine applications.

A Numerical Study of the Vibration Characteristics of a Haptic Actuator for a Dial Gear Shifter

Human–machine interaction (HMI) is becoming increasingly important, especially in the automotive industry, where advancements in automated driving and driver assistance systems are key to enhancing driver safety and convenience. Among the many HMI interfaces, tactile sensing has been widely used in automotive applications as it enables instant and direct interactions with drivers. An area that remains underexplored among the tactile HMI interfaces is the application of haptic feedback to gear shifter modules. Therefore, this study investigates the design optimization of a dial gear shifter by analyzing the vibrations transmitted to the knob surface from an integrated haptic actuator. Specifically, we first tuned the mechanical properties of the haptic actuator (in terms of the resonance frequency and vibration level) in a simulation model by referring to experimental results. Next, a numerical model of a dial gear shifter was constructed, integrated with a haptic actuator, and tuned with the experimental results. The model was further optimized based on the design of the experiment and sensitivity analyses. The optimized design yielded a 24.5% improvement in the vibration level compared with the reference design, exceeding the minimum threshold (>~2.5 m/s2 at 200 Hz) required for tactile sensing. The vibration enhancement (>22.x%) was also confirmed under the simulated hand-grabbing condition. This study is technically significant as it demonstrates that the haptic vibration in a dial gear shifter can be efficiently optimized through numerical analyses. This research will be used for the actual prototyping of a dial gear shifter to provide a safe driving experience for drivers.

Ti3C2T x MXene Based Electro-Ionic Soft Actuator with Potential for Wearable Finger Straps.

Soft electro-ionic actuators have received extensive research and attention due to their advantages such as low voltage response and adjustable deformation. However, they have not been able to enter the actual industry application like traditional rigid actuators; one of the reasons may be that the kinematic properties of actuators have been less studied. The electro-ionic actuator based on Ti3C2T x MXene-CNT/PPy electrode prepared in this paper shows good bending displacement (18.8 mm) and strain (0.63%) under 4 V voltage. In this article, the overlapping nature and exponential function relationship of the actuator end-point trajectories are preliminarily discussed, and the morphology change and cubic polynomial function relationship of the actuator body are considered. Moreover, in application, a novel proof-of-concept model of smart wearable finger straps is proposed. This study is a unique attempt and is hoped to provide a new research perspective in the field of soft electro-ionic actuators.

Molded, Solid-State Biomolecular Assemblies with Programmable Electromechanical Properties.

Piezoelectric and ferroelectric technologies are currently dominated by perovskite-based ceramics, not only due to their impressive figures of merit, but due to their versatility in size and shape. This allows the dimensions of, for example, lead zirconium titanate and potassium sodium niobate, to be tailored to the needs of thousands of applications across the automotive, medical device, and consumer electronics industries. In this Letter, we significantly advance the performance and customization of biomolecular crystal (nontoxic, biocompatible amino acids, viz., trans-4-hydroxy-L-proline, L-alanine, hydrates of L-arginine and L-asparagine, and γ-glycine) assemblies by growing them as molded, substrate-free piezoelectric elements. This methodology allows for electromechanical properties to be embedded in these assemblies by fine-tuning the chemistry of the biomolecules and thus the functional properties of the single crystal space group. Here, we report the piezoelectric, mechanical, thermal, and structural properties of these amino acid-based polycrystalline actuators. This versatile, low-cost, low-temperature growth method opens up the path to phase in biomolecular piezoelectrics as high-performance, eco-friendly alternatives to ceramics.

Increasing the damping properties of the magnetorheological actuator of the vehicle suspension control system

Introduction. In accordance with one of the ways of solving the problem of increasing the smoothness of the vehicles, a controlled suspension is proposed, which is created on the basis of the use of «smart» materials – magnetorheological elastomers, the mechanical properties of which, in particular, damping, can be changed with the help of a controlling magnetic field. This is implemented with the help of the magnetorheological actuator of the suspension control system, which has the form of an elastic bushing of the suspension arm, consisting of several electrically connected in series toroid-like coils (with a core of magnetorheological elastomer). The device is powered by current, the value of which is controlled by the operator, or automatically, depending on the road profile and driving mode. Magnetorheological actuators (elastic bushings) are placed in the holes of the suspension levers instead of standard rubber ones and combined with a controlled current source. Thus, the suspension becomes controllable, which makes it possible to set the necessary vibration damping of the vehicle body to increase its smoothness. Problem. The disadvantage of the previous designs of the magnetorheological actuator is the insufficient amount of the magnetic flux density and the unevenness of its distribution within the elastic bushings. As a result, the damping properties of such controlled suspensions become insufficiently effective, which reduces the possibility of increasing the smoothness of the vehicles. The purpose of the work is to increase the damping properties of the magnetorheological actuator of the vehicle suspension control system, which will increase the control efficiency. The task is to improve the design of the performing magnetorheological device, to carry out calculations and develop a calculation scheme of the study, to determine the average magnetic flux density value and its distribution across the cross-section of the device, to calculate the dependence of the device damping indicator on the magnetic flux density, to compare the damping indicators of the improved device with previously known ones. Methodology. Research tasks were solved on the basis of magnetic field analysis using methods of magnetic field theory and SOLIDWORKS® and FEMM software packages, as well as analysis of the dependence of the damping properties of bushings from magnetorheological elastomers on magnetic flux density. A description of the design and principle of operation of the magnetorheological actuator of the vehicle suspension characteristics control system is given, based on which the calculation scheme was developed. Results. The results of research calculations showed that the average value of magnetic flux density in the proposed design of the device reached 0.85 T, its distribution became fairly uniform, and there were no zones where it was abnormally small. For the first time, the dependence of the damping index on the magnetic flux density of the controlling magnetic field has signs of scientific novelty. It was found that this indicator for the proposed design of the device increased by 22 % compared to previous other designs, which will increase the efficiency of the control system and the smoothness of the vehicle. A positive result was achieved due to the following features of the proposed design of the suspension actuator: the elastic sleeve consists of several coaxially located actuators made of anisotropic magnetorheological elastomer, in which the conglomerates of the ferromagnetic filler during the manufacturing process are located collinear to the direction of the angular deformations of the sleeve and the control magnetic field flux density vector, and the devices have control coils located on their surfaces, which are made of conductive elastic elastomer and electrically connected in a series circuit. Originality. The control method, previous designs and construction of this controlled suspension are protected by patents of Ukraine. Practical value. The direction of further research is to optimize the parameters of the control coils in order to reduce the energy consumption for them and to protect them from overheating. References 20, figures 10.

A comparative analysis between deep neural network-based 1D-CNN and LSTM models to harness the self-sensing property of the shape memory alloy wire actuator for position estimation

The article presents a performance-based comparative analysis of popular deep neural network (DNN) models such as 1-dimensional convolutional neural network (1D-CNN) and long short-term memory (LSTM) for position estimation of shape memory alloy (SMA)-based wire actuator. These DNN models utilize the self-sensing property (SSP) for position estimation of the SMA actuator. The phase-dependent electrical resistivity of SMA wire acts as SSP, where the electrical resistivity in the form of SMA wire resistance acts as inputs to the proposed models for precise estimation of the current position of the SMA actuator. For effective position control of the SMA actuator, accurate position sensor feedback is required, utilizing SSP results in the elimination of this external sensor. This will improve the overall system in terms of compactness and reduced interface complexity. Coming to DNN models, 1D-CNN has been meagerly explored in the current literature landscape for self-sensing estimation of SMA actuators. These 1D-CNN models are becoming quite popular for time series prediction for various applications and are emerging as an alternative to widely used LSTM models. In this paper, a novel implementation of a 1D-CNN model for SMA actuator position estimation has been done. A comparative analysis between 1D-CNN and LSTM has been done for prediction capability and inference speed based on performance measures such as Mean Square Error (MSE), Mean Absolute Error (MAE), symmetric Mean Absolute Percentage Error (sMAPE), data distribution, and average inference speed. The proposed comparative results show that 1D-CNN has a matching performance with the LSTM model with respect to prediction capability, however, 1D-CNN offers faster inference speed. The analysis of the proposed work can be useful for choosing a suitable DNN model for deployment on low computing platforms such as microcontrollers for SMA actuator-based real-time applications where time latency is a critical parameter.

Large Local Internal Stress in an Elastically Bent Molecular Crystal Revealed by Raman Shifts.

The structural dynamics involved in the mechanical flexibility of molecular crystals and the internal stress in such flexible materials remain obscure. Here, the study reports an elastically bending lipidated molecular crystal that shows systematic shifts in characteristic vibrational frequencies across the bent crystal region - revealing the nature of structural changes during bending and the local internal stress distribution. The blueshifts in the bond stretching modes (such as C═O and C-H modes) in the inner arc region and redshifts in the outer arc region of the bent crystals observed via micro-Raman mapping are counterintuitive to the bending models based on intermolecular hydrogen bonds. Correlating these shifts with the trends observed from high-pressure Raman studies on the crystal reveals the local stress difference between the inner arc and outer arc regions of the bent crystal to be ≈2GPa, more than an order of magnitude higher than the previously proposed value in elastically bending crystals. High local internal stress can have direct ramifications on the properties of molecular piezoelectric energy harvesters, actuators, semiconductors, and flexible optoelectronic materials.

Core–Shell Nanostructured Assemblies Enable Ultrarobust, Notch‐Resistant and Self‐Healing Materials

AbstractActuators based on stimulus‐responsive soft materials have attracted widespread attention due to their significant advantages in flexibility and structural adaptability over traditional rigid actuators. However, the development of fast‐actuating, mechanical robust and self‐healing actuators without compromising flexibility remains an ongoing challenge. Here, this study presents a photo‐responsive flexible actuator by incorporating core–shell liquid metal nano‐assemblies into a polyurethane matrix to construct a dynamic supramolecular interface. The nano‐assemblies are endowed with adaptive characteristics to external loading, being expected to dissipate energy via the reversible reconstruction of hydrogen bonding and deformation of nano‐assemblies. The obtained composites exhibit excellent mechanical strength (31 MPa), low modulus (2.02 MPa), high stretchability (1563.95%), autonomous self‐healing (92.5%), and NIR‐responsive actuation properties. Furthermore, the combination of high cohesive energy but fluxible nano‐liquid metal core, and strong dynamic interface not only achieves the balance of high tensile strength and high flexibility but also endows the actuators with outstanding notch‐resistant performance (fracture energy≈58.8 kJ m−2) through multiphase energy dissipation. This work provides a promising strategy for developing soft yet tough self‐healing materials in the fields of flexible robotics and artificial muscles.

Mechanisms of Genipin and MCNT effects on the actuation properties and failure of chitosan gel bionic artificial muscles

Mechanisms of Genipin and MCNT effects on the actuation properties and failure of chitosan gel bionic artificial muscles

Photochromic Carbon Nanomaterials: An Emerging Class of Light-Driven Hybrid Functional Materials.

Photochromic molecules have remarkable potential in memory and optical devices, as well as in driving and manipulating molecular motors or actuators and many other systems using light. When photochromic molecules are introduced into carbon nanomaterials (CNMs), the resulting hybrids provide unique advantages and create new functions that can be employed in specific applications and devices. This review highlights the recent developments in diverse photochromic CNMs. Photochromic molecules and CNMs are also introduced. The fundamentals of different photochromic CNMs are discussed, including design principles and the types of interactions between CNMs and photochromic molecules via covalent interactions and non-covalent bonding such as π-π stacking, amphiphilic, electrostatic, and hydrogen bonding. Then the properties of photochromic CNMs, e.g., in photopatterning, fluorescence modulation, actuation, and photoinduced surface-relief gratings, and their applications in energy storage (solar thermal fuels, photothermal batteries, and supercapacitors), nanoelectronics (transistors, molecular junctions, photo-switchable conductance, and photoinduced electron transfer), sensors, and bioimaging are highlighted. Finally, an outlook on the challenges and opportunities in the future of photochromic CNMs is presented. This review discusses a vibrant interdisciplinary research field and is expected to stimulate further developments in nanoscience, advanced nanotechnology, intelligently responsive materials, and devices.

Optimized Design of a Soft Actuator Considering Force/Torque, Bendability, and Controllability via an Approximated Structure

Abstract This paper introduces a novel design method that enhances the force/torque, bendability, and controllability of soft pneumatic actuators (SPAs). The complex structure of the soft actuator is simplified by approximating it as a cantilever beam. This allows us to derive approximated nonlinear kinematic models and a dynamical model, which is explored to understand the correlation between natural frequency and dimensional parameters of SPA. The design problem is then transformed into an optimization problem, using kinematic equations as the objective function and the dynamical equation as a constraint. By solving this optimization problem, the optimal dimensional parameters are determined. Six prototypes are manufactured to validate the proposed approach. The optimal actuator successfully generates the desired force/torque and bending angle, while its natural frequency remains within the constrained range. This work highlights the potential of using optimization formulation and approximated nonlinear models to boost the performance and dynamical properties of soft pneumatic actuators.

Thermally Driven 3D Seamless Textile Actuators for Soft Robotic Applications

Soft wearable robotic devices have emerged as a promising solution for human mobility assistance and rehabilitation, yet current solutions suffer from issues such as bulkiness, high cost, nonscalability, noise, and limited portability. This study introduces a novel approach to soft robotic assistive devices using untethered, soft actuators with seamlessly integrated sensing, heating, and actuation properties through digital machine knitting and low‐boiling liquid. The proposed soft actuator operates under a voltage of less than 12.5 V, generating a tip force of up to 50 mN. This actuator achieves a bending motion when filled with 2 mL of low‐boiling liquid and supplied with 15 W. The dynamic response of the actuator is examined under consistent parameters, revealing a 60‐second inflation time and a subsequent natural cooling period of 30 s at room temperature. Notably, over 12 cycles, the tip force of the actuator exhibits minimal variation, highlighting its durability for prolonged usage. The proposed approach paves the way for overcoming the limitations of existing technologies, particularly in terms of motion assistance and rehabilitation applications, with an emphasis on at‐home usage during daily activities.

Dynamic large strain formulation for nematic liquid crystal elastomers

Liquid crystal elastomers (LCEs) are a class of materials which exhibit an anisotropic behavior in their nematic state due to the main orientation of their rod-like molecules called mesogens. The reorientation of mesogens leads to the well-known actuation properties of LCEs, i.e. exceptionally large deformations as a consequence of particular external stimuli, such as temperature increase. Another key feature of nematic LCEs is the capability to undergo deformation by constant stresses while being stretched in a direction perpendicular to the orientation of mesogens. During this plateau stage, the mesogens rotate towards the stretching direction. Such characteristic is defined as semisoft elastic response of nematic LCEs. We aim at modeling the semisoft behavior in a dynamic finite element method based on a variational-based mixed finite element formulation. The reorientation process of the rigid mesogens relative to the continuum rotation is introduced by micropolar drilling degrees of freedom. Responsible for the above-mentioned characteristics is an appropriate free energy function. Starting from an isothermal free energy function based on the small strain theory, we aim to widen it into the framework of large strains by identifying tensor invariants. In this work, we analyze the isothermal influence of the tensor invariants on the mechanical response of the finite element formulation and show that its space-time discretization preserves mechanical balance laws in the discrete setting.

Optimizing Performance of PVC Gel Actuators: Temperature Influence and Characterizations

PVC gels are in high demand for actuators, so choosing the optimal route for preparing PVC gel is crucial. In this study, PVC gel samples were prepared using polymer PVC, plasticizer Di-butyl adipate (DBA), and solvent tetrahydrofuran (THF) at temperatures ranging from 40°C to 70°C. The samples obtained at different temperatures were labeled as PVC40, PVC50, PVC60, and PVC70. Rheological properties of all PVC gel samples were analyzed, revealing, that the rheological behavior of the PVC70 gel sample differed significantly from the others due to THF evaporation at 70°C, resulting in inadequate PVC gel preparation. However, PVC40, PVC50, and PVC60 gel samples were chosen for further characterizations, including scanning electron microscopy (SEM), actuation, and mechanical properties evaluation. Moreover, a self-assembled setup was fabricated using electrodes and PVC gel to test the performance of the planar actuator. The maximum displacement of PVC60 was measured at approximately 0.74 mm, with a response time of 0.75 sec under an applied voltage of 1000V. It was observed that the homogeneity of the gel and the solubility of the raw materials, based on resin were influenced by the reaction temperature, suggesting that uniformity could be achieved through dipole-dipole interactions or hydrogen bonding between PVC and DBA (Cl-H…. O=C). Finally, our findings have the potential to contribute to the development of innovative PVC gel actuators.

Bioinspired H-Bonding Connected Gradient Nanostructure Actuators Based on Cellulose Nanofibrils and Graphene.

The construction of flexible actuators with ultra-fast actuation and robust mechanical properties is crucial for soft robotics and smart devices, but still remains a challenge. Inspired by the unique mechanism of pinecones dispersing seeds in nature, a hygroscopic actuator with interlayer network-bonding connected gradient structure is fabricated. Unlike most conventional bilayer actuator designs, the strategy leverages biobased polyphenols to construct strong interfacial H-bonding networks between 1D cellulose nanofibers and 2D graphene oxide, endowing the materials with high tensile strength (172MPa) and excellent toughness (6.64MJm-3). Furthermore, the significant difference in hydrophilicity between GO and rGO, along with the dense interlayer H-bonding, enables ultra-fast water exchange during water absorption and desorption processes. The resulted actuator exhibits ultra-fast driving speed (154°s-1), excellent pressure-resistant and cyclic stability. Taking advantages of these benefits, the actuator can be fabricated into smart devices (such as smart grippers, humidity control switches) with significant potential for practical applications. The presented approach to constructing interlayer H-bonding in gradient structures is instructive for achieving high performance and functionalization of biomass nanomaterials and the complex of 1D/2D nanomaterials.

Theoretical study of vacuum-powered artificial muscles with inner support and flexible skin

In the theoretical study of vacuum-powered artificial muscles, the inhomogeneous and nonlinear deformation properties of the skin have not been fully investigated, and the effect of the skin material on their performance has not been considered in the model. This work presents a theoretical analysis for the support-skin vacuum-powered artificial muscles and extends the skin to more general flexible materials, which endows the results with a strong generalization ability. The influence of various factors including structural parameters, axial force, negative pressure, and material parameter on the skin deformation are comprehensively analyzed, which is directly related to the actuation behaviors. Besides, the theoretical analysis is able to make an accurate prediction of the wrinkling behavior of the skin, including the critical boundary and wrinkling region. The experimental verification on the theoretical predicted configuration and wrinkled area of the skin have been carried out, which verifies the correctness of the results of the theoretical analysis. We believe that this work will provide an effective way for guiding the design and analyzing the actuation properties of such artificial muscles.

Bilayer Hydrogel Actuators with High Mechanical Properties and Programmable Actuation via the Synergy of Double-Network and Synchronized Ultraviolet Polymerization Strategies.

Bilayer hydrogel actuators, consisting of an actuating layer and a functional layer, show broad applications in areas such as soft robotics, artificial muscles, drug delivery and tissue engineering due to their inherent flexibility and responses to stimuli. However, to achieve the compatibility of good stimulus responses and high mechanical properties of bilayer hydrogel actuators is still a challenge. Herein, based on the double-network strategy and using the synchronous ultraviolet (UV) polymerization method, an upper critical solution temperature (UCST)-type bilayer hydrogel actuator was prepared, which consisted of a poly(acrylamide-co-acrylic acid)[MC] actuating layer and an agar/poly(N-hydroxyethyl acrylamide-co-methacrylic acid)[AHA] functional layer. The results showed that the tensile stress/strain of the bilayer hydrogel actuator was 1161.21 KPa/222.07%. In addition, the UCST of bilayer hydrogels was ~35 °C, allowing the bilayer hydrogel actuator to be curled into an "◎" shape, which could be unfolded when the temperature was 65 °C, but not at a temperature of 5 °C. Furthermore, hydrogel actuators of three different shapes were designed, namely "butterfly", "cross" and "circle", all of which demonstrated good actuating performances, showing the programmable potential of bilayer hydrogels. Overall, the bilayer hydrogels prepared using double-network and synchronous UV polymerization strategies realized the combination of high mechanical properties with an efficient temperature actuation, which provides a new method for the development of bilayer hydrogel actuators.

A Molecular Rheology Dynamics Study on 3D Printing of Liquid Crystal Elastomers.

This work presents a rheological study of a biocompatible and biodegradable liquid crystal elastomer (LCE) ink for three dimensional (3D) printing. These materials have shown that their structural variations have an effect on morphology, mechanical properties, alignment, and their impact on cell response. Within the last decade LCEs are extensively studied as potential printing materials for soft robotics applications, due to the actuation properties that are produced when liquid crystal (LC) moieties are induced through external stimuli. This report utilizes experiments and coarse-grained molecular dynamics to study the macroscopic rheology of LCEs in nonlinear shear flow. Results from the shear flow simulations are in line with the outcomes of these experimental investigations. This work believes the insights from these results can be used to design and print new material with desirable properties necessary for targeted applications.

Property of Cu and PbSrZrTiO3 multilayer actuator fabricated by cofiring with wet reduction

Traditional co-firing processes involving noble metals are costly, thereby prompting a shift to base metals, such as Cu, to reduce manufacturing expenses. This study explored the use of Cu as an internal electrode for fabricating piezoelectric multilayer devices using a Pb0.98Sr0.02(Zr0.48Ti0.52)O3 (PSZT) ceramic material. The compatibility of Cu with PSZT in ambient air and the subsequent wet-reduction was investigated. The addition of polyvinylidene fluoride (PVDF) to the Cu electrode expedited the reduction process; however, this prompted void formation. Thus, epoxy resin was injected to post-reduction to enhance its mechanical property and address this issue. The impact of the PVDF content on the reduction rates, microstructure, and electrical/mechanical properties was analyzed. The experimental results highlighted the successful fabrication of Cu/PSZT devices with performances comparable to those of traditional noble metal (AgPd) counterparts. The polarization and strain of the Cu/PSZT device with 10% PVDF were comparable to those of the AgPd/PSZT. Subsequently, the incorporation of epoxy resin and Cu electroplating greatly improved the mechanical strength of Cu/PSZT to values comparable to that of AgPd/PSZT, as confirmed by the successful fabrication of a piezoelectric ultrasonic device and vibration measurement at 60 kHz. Therefore, this proposed process is a viable alternative for fabricating low-cost and stable multilayer ceramic devices.