PVC Gel Research Articles

Modular multilayered PVC gel soft actuators for novel lightweight humanoid facial robot

Electroactive multilayered poly (vinyl chloride) (PVC) gel actuators (MPGAs) have attracted increasing interest in the field of soft robotics. However, they still face problems such as relatively low contraction strain, poor durability, and robustness. Herein, we report a new modular multilayered PVC gel actuator (M-MPGA) based on stainless steel meshed electrodes. The output characteristics of the actuator were notably improved by adjusting the plasticizer content in the gel and optimizing the structural parameters of the meshed anode electrodes. The effect of the number of stacked layers on the performance of the actuator was investigated and a dynamic model was derived for the actuator modular design. Actuator modules with multidirectional degrees of actuation were established and applied to a humanoid facial robot for the first time. The developed actuator with a meshed electrode size of #60 was found to exhibit a high contraction strain of over 20 %, which is almost twice that of the traditional MPGAs with an electrode size of #100. In addition, the fabricated actuator module had a low loss rate (1.152 %), high operating bandwidth (9.7 Hz), fast response (∼45 ms), and exceptional stability (95.24 % retention at 10,000 s actuation) without any distortion of the actuation performance. Furthermore, the developed prototype humanoid facial robot demonstrated the advantages of ultralight weight (754 g), smooth facial expression, and ease of control.

In-situ characterization of dynamic electromechanical properties for PVC gel actuators

PVC gel actuator possesses the advantages including low driving voltage, substantial deformation, and high output force, making it ideal for applications in micro-lenses, assistive rehabilitation, and soft robotics. However, there remains a lack of in-situ characterization and quantitative analysis of plasticizer migration and charge transfer within PVC gel, resulting in an unclear understanding of changes in the plasticizer content, mechanical and electrical properties of the enrichment layer. In this study, we conducted in-situ characterization of plasticizer migration and charge transfer within PVC gel, and analyzed the change of plasticizer content, mechanical and electrical properties. In-situ Raman spectroscopy results revealed that plasticizer migration takes time to reach equilibrium, resulting in a gradient distribution of plasticizer content within the enrichment layer. Furthermore, in-situ broadband impedance analysis demonstrated that stimulation voltage induces changes in the material's electrical properties, transitioning from uniform electrical characteristics to distinct properties between the gel layer and the enrichment layer. Notably, we established a mathematical relationship between modulus and plasticizer content, revealing a gradient distribution of modulus within the enrichment layer. This study not only contributes to understanding the underlying mechanisms of mechanical and electrical properties variations within PVC gel, but also provides valuable insights for optimizing the actuation performance of PVC gel actuators.

Emergence of chaos in an electroactive artificial muscle PVC gel under state-varying electromechanical parameters

The deformation mechanism of artificial muscle materials based on the natural method has always been one of the frontier topics in the field of biophysics. Electroactive PVC gel is a composite material that mimics the response of natural muscles, making it highly advantageous for various bionic mechanical applications. The existing literature primarily focuses on enhancing the performance and exploring applications of PVC gel, with particular emphasis on optimizing its ability to simulate muscle deformation. However, the existing literature lacks research on the theoretical mechanism and modeling of large deformation, particularly regarding the investigation of nonlinear dynamic behavior under state-varying electromechanical parameters. The present research establishes a novel theoretical model for PVC gel and investigates its dynamic response to voltage, mechanical force, and inertia force. Firstly, the electromechanical constitutive model of PVC gel actuator was elucidated, and the nonlinear dynamics control equation of PVC gel actuator was established based on the Gent model. Secondly, we investigate the vibration characteristics of PVC gel material by analyzing four key parameters: size, tensile strength, applied voltage amplitude, and excitation frequency. Through this analysis, we determine the relevant parameters and operational range of the PVC gel actuator when subjected to voltage excitation. Meanwhile, the phase trajectories and Poincaré maps were generated based on the control equation calculation results to investigate the vibration stability and chaotic characteristics of the PVC gel actuator under electromechanical coupling conditions. The deformation of PVC gel is influenced by various nonlinear factors, wherein the alteration in frequency induces harmonic, subharmonic, and super-harmonic resonance phenomena within the frequency response. By revising the size, voltage, and frequency of these three factors, with particular emphasis on regulating the frequency, chaotic behavior in the PVC gel will be facilitated. Finally, the bifurcation analysis of the electromechanical vibration behavior of the PVC gel actuator was carried out, and the stability of the PVC gel vibration was further quantitatively determined by the Lyapunov exponent.

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.

Dynamic braille display based on surface-structured PVC gel

Braille displays are a class of human–computer interaction electromechanical devices that display dynamic braille through an array of actuators. However, existing actuators for braille displays suffer from issues such as bulky size, heavy weight, and small tactile displacement, leading to difficulties in improving their resolution and readability. To address the above issues, we developed a novel electroactive artificial muscle actuator and applied it to braille displays. The novel actuator consists of a surface-structured PVC gel and planar electrodes. To investigate the effect of surface structure on the performance of novel PVC gel actuators, four types of surface-structured PVC gels were fabricated by a casting process, and their actuation performance was tested. The results show that the conical and frustum conical array structures are more favorable for improving the displacement of novel PVC gel actuators, while the cylindrical and quadrangular array structures are more favorable for improving their recovery forces. We observed both surface structure and dynamic electrical actuation, suggesting that the actuation of the novel actuator is mainly caused by the deformation of the surface structure of the array. We also analyzed electrowetting effects in PVC gels using the Lippmann–Young equation, to explain the differences in the performance of surface-structured PVC gels with different contact angles. Moreover, six multilayer actuators composed of PVC gels with a conical surface array structure are applied to the braille display unit to display the braille digits from 0 to 9. It has been shown that the novel PVC gel actuator has excellent mechanical properties, which makes it an ideal solution for braille displays.

Design of a Novel Robotic Fish Structure Utilizing PVC Gel Actuators

Design of a Novel Robotic Fish Structure Utilizing PVC Gel Actuators

Tunable focus poly(vinyl chloride) gel microlens Array fabricated by shaping in patterned electric field

AbstractIn this work, we demonstrate a poly(vinyl chloride) (PVC)‐gel‐based microlens array (MLA) with tunable focus. The MLA is fabricated using a PVC solution and a glass substrate with a ring‐array‐patterned electrode. By coating the solution on the substrate and applying a direct current (DC) voltage to the electrode, a PVC gel membrane with a convex surface profile on the inner region of the electrode (anode) is formed with the solvent evaporation. After the complete evaporation of the solvent and removing the voltage, the solidified PVC gel membrane exhibits an MLA character. When an inverse DC voltage is applied to the electrode, the PVC gel accumulated on the inner region will shift toward the outer electrode connected to the anode, leading the curvature of the convex surface to decrease and the focal length to increase accordingly. The variable surface profile with voltage is precisely measured by a laser confocal microscope and the result shows that the focal length of the MLA can be tuned within a large range.

Plasticizer structural effect for sustainable and high-performance PVC gel-based triboelectric nanogenerators

A triboelectric nanogenerator (TENG) produces electrical energy by the accumulation of electric charges when two different materials rub against each other. In this study, the characteristics, and stabilities of adipate PVC gels with different adipate plasticizers were investigated for the development of triboelectric nanogenerators (TENGs) for sustainable energy harvesting. Various plasticizers with different numbers of carbon atoms in the alkyl chain were used to synthesize PVC gels, and their triboelectric properties, permittivities, and electrical conductivities were evaluated. In particular, we investigated the relationship between the surface charge dissipation rate and electrical resistivity of the PVC gel, which can maximize the TENG performance. The DOA5-based PVC gel TENG showed the highest output performance (198 V, 15.6 µA, and 384 µW/cm2) and stable output performance without plasticizer leakage for over 30 days at a high temperature. The developed TENG can be used as a power source for small electronic devices, maintaining a stable and high-output performance with high durability, making it ideal for self-powered systems in harsh environments requiring continuous power supply.

High performance fiber-constrained plasticized PVC gel actuators for soft robotics

Plasticized Poly (vinyl chloride) (PVC) gel actuators, a type of electroactive soft actuator, have recently attracted increasing interest in soft robotics. Herein, we report a novel planar PVC gel actuator with flexible electrodes and a fiber-constrained structure for electroactive artificial muscles. PET adhesive fibers were evenly affixed on both sides of the unidirectional pre-stretched PVC gel membranes in one direction, resulting in a human-muscle-like unidirectional contraction and expansion movement. The fibers can constrain the bending motion of the PVC gel membranes, and the unidirectional pre-stretch in the direction of the attached fibers further makes the membrane anisotropic, leading to easy and fast actuation in the direction normal to the pre-stretch. The developed fiber-constrained plasticized PVC gel actuator (FCPPGA) unit exhibited high strain (>40%) and stress (>0.5 MPa) with a fast response time of about 0.1 s under a relatively low driving DC field (<15 V/μm). The simulated data were in good agreement with the experimental results. Furthermore, the designed FCPPGA was successfully used to demonstrate the mimicry of lower jaw motions in a skeleton model.

Modeling of Fiber-Constrained Planar PVC Gel Actuators.

In recent years, plasticized poly (vinyl chloride) (PVC) gel has attracted increasing attention in soft robotics. However, there is scarce research on the deformation mechanism and modeling of PVC gel actuators. In this study, to investigate the deformation mechanism of fiber-constrained planar PVC gel actuators, we propose a complex nonlinear model based on traditional thermodynamic electroactive polymer (EAP) multi-field coupling theory. The proposed model can reveal the dielectric breakdown strength of PVC gels and predict the deformation of planar PVC gel actuators with varying levels of pre-stretching. The theoretical results were in good agreement with the experimental results, indicating the feasibility of the proposed model.

Investigation of a Simple Viscoelastic Model for a PVC-Gel Actuator under Combined Mechanical and Electrical Loading.

PVC gels are gaining more attention in the applications of soft actuators. While their characteristics have been extensively studied experimentally, precise models that predict the deformation due to imposed mechanical and electrical forces are not yet available. In this work, a viscoelastic model based on a combination of a Maxwell and a Kelvin-Voigt model is developed to describe the responsive deformation of the actuator. The model parameters are tuned using data obtained from a unique experimental setup. The PVC gel used in the actuator is made from PVC and dibutyl adipate (DBA) together with a tetrahydrofuran (THF) solvent. A full factorial test campaign with four and three levels for the mechanical and electrical forces, respectively, are considered. The results showed that some of the viscoelastic response could be captured by the model to some extent but, furthermore, the stiffness behavior of the PVC gel seemed to be load-type-dependent, meaning that the PVC-gel material changed stiffness due to the magnitude of the electrical force applied and this change was not equal to a similar change in mechanical force.

A PVC plasticization electrically active laminated metamaterial with tunable sound insulating performance

In this paper, we introduce an electrically driven laminated active acoustic metamaterial with PVC plasticization, which the structure is composed of electroactive PVC gel membrane, wire mesh electrodes, and conductive fabric in a sandwich form, that can achieve excellent sound-damping performance with tunable sound insulation. Compared with the previous tunable acoustic metamaterial, this structure requires lower driving voltage and better sound insulation performance. The specific researches are as follows: Firstly, we studied the strain rate of different laminated structure parameters after applying voltage was explored through experiments, and the design parameter combination with better strain rate was obtained by comparing the results. Then, the sound insulation performance of the laminated structure before and after the application of the electric field was studied, and it was concluded that the structure had better adjustable stiffness and damping characteristics under the action of the electric field, and improved the sound insulation performance in a wide frequency range. This provides a new way of adjustable sound insulation, which is expected to be used in heavy equipment such as automobiles.

Synergistic and counteractive effects of Bi-component plasticizers on structure and electric field-induced bending actuation behaviors of poly (vinyl chloride) (PVC) gels

Electroactive dielectric polymer gels (DPGs) have important applications in soft robots, wearable electronics, and biomedical devices etc. However, the relationship between structure and electromechanical properties of DPGs have not been fully understood so far. In this work, the effect of the bi-component plasticizers on the structure, mechanical properties, dielectric properties, and electric field induced dynamic bending actuation behaviors of plasticized poly (vinyl chloride) (PVC) gels with free electrodes were investigated using the dibutyl adipate (DBA) as major plasticizer and the branch structured bio-based triethyl 2-acetylcitrate (ATEC) or triethyl citrate (TEC) as minor second plasticizer (30 wt% of bi-component plasticizer). The PVC gel films bend towards the anode side when applied electric field under free electrodes measurement condition. The electric field induced capacitance change of PVC gels was important factor to influence the bending displacement, which were influenced by the interactions between plasticizers and PVC chains in PVC gels. The bending displacement of PVC/DBA/TEC and PVC/DBA/ATEC gels is about 80% and 140% of PVC/DBA at 7.2 kV (corresponding to 180 V/mm of nominal electric field), respectively. The synergistic and counteractive effects of bi-component plasticizers on the bending actuation of PVC gels are mainly attributed to the competition between plasticization effect of PVC and interactions of inter-plasticizers. Our results provide a new insight for the design of high performance electroactive dielectric polymer gel materials.

PVC gel bio-inspired adhesives with variable modulus and its application in a gripper

PVC gel bio-inspired adhesives with variable modulus and its application in a gripper

Development of a PVC Gel Actuator with a Particulate Structure

Actuators are usually driven in a uniaxial direction, which limits their ability to be driven with multiple degrees of freedom. In this study, we propose an actuator that is not limited to a uniaxial direction. We developed a polyvinyl chloride gel actuator with a particulate structure. The actuator can change its surface shape by displacing each particle in the structure. As the first step in this experiment, each particle was displaced independently, by applying a voltage to the anode to change the actuator’s surface into an uneven shape.

The electrical response and self-sensing of the fully flexible PVC gel actuator based on flexible electrodes

There has recently been a substantial increase in interest in research on PVC gel actuators because of its numerous advantages over traditional actuators, such as low mass density, large actuation strain, great compliance, and simple manufacturing. However, the current PVC gel actuator is mainly based on the research of rigid electrodes, and there are few researches based on flexible electrodes. In this paper, a fully flexible actuator based on PVC gel film and carbon grease electrode has been prepared. The mechanical properties of the prepared PVC gels with different plasticizer ratios were tested. Three commonly used hyperelastic models (Neo-Hookean, Mooney-Rivlin and Yeoh models) were used to characterize the mechanical properties of PVC gels, and only the Yeoh model was found to be better for the characterization of the mechanical properties of PVC gels. In addition, we used the Prony series to successfully characterize the viscoelasticity of PVC gels. Then, the fully flexible PVC gel actuator (FFPGA) with long-time static and dynamic response characteristics was studied. It was found that the FFPGA has strong viscoelasticity when working. Finally, we proposed to simplify the FFPGA into a capacitor and designed a high-pass filter in the driving circuit. The self-sensing function of the FFPGA was achieved by superimposing a high-frequency low-voltage sensing signal on the low-frequency high-voltage driving signal as the input signal.

Enhancing of broadband sound absorption through soft matter.

This paper proposed a metamaterial design method that uses soft matter for constructing a unique soft acoustic boundary to effectively improve broadband sound absorption performance. Specifically, attaching a flexible polyvinyl chloride (PVC) gel layer with an elastic modulus as low as a few kilopascals and a thickness of a few millimeters to the inner wall of a cavity-type sound-absorbing metamaterial structure significantly improved the absorption performance of the composite structure in low-frequency broadband ranges. The sound absorption enhancement mechanism differed from those proposed in previous research. On the one hand, the soft PVC gel layer acted as a soft acoustic boundary, substantially reducing the sound speed and reflection and producing considerable elastic strain energy at the interface between two different media to improve the sound absorption performance. On the other hand, this PVC gel layer displayed extremely low stiffness and high damping, producing an abundance of plasmon-like resonance modes in low-frequency broadband ranges, achieving a resonance absorption effect. Since this sound absorption enhancement method did not require an increase in the external dimensions or a change in the structural parameters of the original absorber and achieved robust enhancement in a wide frequency band, it displayed potential application value in various engineering fields.

Direct Writing Corrugated PVC Gel Artificial Muscle via Multi-Material Printing Processes.

Electroactive PVC gel is a new artificial muscle material with good performance that can mimic the movement of biological muscle in an electric field. However, traditional manufacturing methods, such as casting, prevent the broad application of this promising material because they cannot achieve the integration of the PVC gel electrode and core layer, and at the same time, it is difficult to create complex and diverse structures. In this study, a multi-material, integrated direct writing method is proposed to fabricate corrugated PVC gel artificial muscle. Inks with suitable rheological properties were developed for printing four functional layers, including core layers, electrode layers, sacrificial layers, and insulating layers, with different characteristics. The curing conditions of the printed CNT/SMP inks under different applied conditions were also discussed. The structural parameters were optimized to improve the actuating performance of the PVC gel artificial muscle. The corrugated PVC gel with a span of 1.6 mm had the best actuating performance. Finally, we printed three layers of corrugated PVC gel artificial muscle with good actuating performance. The proposed method can help to solve the inherent shortcomings of traditional manufacturing methods of PVC gel actuators. The printed structures have potential applications in many fields, such as soft robotics and flexible electronic devices.

Performance Evaluation and Parameter Optimization of Moving Bed Biofilm Reactor (MBBR) along with Electrocoagulation for Removal of Azithromycin

Antibiotics from hospital discharge wastewater are known to be one of the most significant water contaminants. Environmental researchers suggest the attainment of effective and biological approaches for the elimination of these contaminants. This work aims to study the efficiency of an azithromycin (AZX) removal using moving bed biofilm reactor (MBBR) combined with electrocoagulation and parameters optimization using a response surface methodology for hospital wastewater (RSM), i.e., MLSS (A), pH (B), HRT (C) and Electrode distance (D). The present research was conducted using PVC gel on a pilot scale for removing a detergent from the wastewater of hospital reactors with continuous hydraulic flux. The impact on the device concentration of independent variables, including duration of touch, percentage of the media, and the concentrations of 1200-3200 mg/l of mixed liquor suspended solids (MLSS). Closed laboratory procedure for measuring AZX concentration, azithromycin (AZX), and chemical oxygen requirement (COD) 1500-2400 mg/l is used. The findings showed that AZX and COD with PVC gel retention times are 92.3 and 95.8 percent, respectively, of 24 hours, with an MLSS concentration of approximately 3,200 mg/l. It was shown that the MBBR device has great productivity in detergent deletion from hospital waste wastewater as a bio-friendly compatible process and can produce regular performance effluents at an appropriate period. The experiment was performed using an electrochemical process, electrolysis with independently variable electrical electrodes, i.e., voltage, duration of touch, and electrolyte concentration. The complete process was optimized for the said reaction using Design-Expert software. The response surface method was used to optimize the operational parameters and show that a contact period of 35 minutes, voltage 12 V, electrolyte concentration of 0.35 M with electrode distance 1.25 cms gives 89% removal efficiency. The model for the three variables recommended by the response surface is a quadratic response.

Soft bidirectional haptic I/O module based on bi-convex patterned PVC gel

In this paper, we propose a bidirectional soft haptic I/O module that not only senses the haptic force but also generates a mechanical vibrotactile sensation. Under external pressure, the distance between the moving plate and lower electrode layer decreases, and the bi-convex patterned poly vinyl chloride (bpPVC) gel gets compressed. These two motions make the capacitance of the proposed module change. Moreover, the application of external electric field (EF) creates an electrostatic force between the upper and lower electrode layers and generates the electric-field-induced deformation of the bpPVC gel simultaneously. As soon as the external EF disappears, the proposed module regains its original shape through the elastic restoring forces of the bpPVC gel and planar springs. Therefore, the applied AC voltage makes the proposed module vibrate. The dielectric and mechanical properties of the bpPVC gel are measured to investigate the optimal weight ratio of the PVC and plasticizers. Experiments are conducted to measure the haptic sensing and actuating performance of the proposed method. The capacitance of the proposed haptic I/O module increases from 17.4 pF to 54.8 pF when the external pressure varied from 0 kPa to 100 kPa. On the other hand, the haptic output of the proposed I/O module is observed as 0.81g (g = 9.8 m s−2) at 100 Hz. The results clearly indicate that the proposed haptic I/O module not only senses the static and dynamic pressure but also controls the amplitude of vibrotactile sensation. Owing to its mechanically soft structure, we expect that the proposed haptic I/O module has the potential to be applied or attached to various flexible/soft devices or the human body.