Wearable dielectric elastomer actuators (DEAs) have been greatly considered for development of biomedical devices. In particular, a DEA cuff device has the capability of minimizing venous system disorders that occur in the lower limbs such as orthostatic intolerance (OI) and deep-vein thrombosis which are a result of substantial blood pooling. Recent works have shown that DEAs could regulate and even enhance venous blood flow return. This wearable technology orders a new light, low-cost, compliant, and simple countermeasure which could be safely and comfortably worn that includes mobility. In addition, it may supplement or even provide an alternative solution to exercise and medication. This work presents the design, model, and characterization of the DEA cuff device design that is capable of generating significant pressure change. A rolled DEA strip was actuated over a simulated muscle-artery apparatus using a periodic voltage input, and fluid pressure change was directly observed. A force sensitive resistor sensor was used to achieve a more precise pressure measurement. Performance analysis was conducted through frequency response analysis. The results provide a framework for implementing dynamic modelling and control to allow various forms of actuation input.
Hydrogen gas can be harvested via the electrolysis of water. The gas is then fed into a proton exchange membrane fuel cell (PEMFC) to produce electricity with clean emission. Ionic polymer-metal composite (IPMC), which is made from electroplating a proton-conductive polymer film called Nafion encourages ion migration and dissociation of water under application of external voltage. This property has been proven to be able to act as catalyst for the electrolysis of pure water. This renewable energy system is inspired by photosynthesis. By using solar panels to gather sunlight as the source of energy, the generation of electricity required to activate the IPMC electrolyser is acquired. The hydrogen gas is collected as storable fuel and can be converted back into energy using a commercial fuel cell. The goal of this research is to create a round-trip energy efficient system which can harvest solar energy, store them in the form of hydrogen gas and convert the stored hydrogen back to electricity through the use of fuel cell with minimal overall losses. The effect of increasing the surface area of contact is explored through etching of the polymer electrolyte membrane (PEM) with argon plasma or manually sanding the surface and how it affects the increase of energy conversion efficiency of the electrolyser. In addition, the relationship between temperature and the IPMC is studied. Experimental results demonstrated that increases in temperature of water and changes in surface area contact correlate with gas generation.
Dielectric elastomer (DE) is a type of soft actuating material, the shape of which can be changed under electrical voltage stimuli. DE materials have great potential in applications involving energy harvesters, micro-manipulators, and adaptive optics. In this paper, a stripe DE actuator with integrated sensing and actuation is designed and fabricated, and characterized through several experiments. Considering the actuator’s capacitor-like structure and its deform mechanism, detecting the actuator’s displacement through the actuator’s circuit feature is a potential approach. A self-sensing scheme that adds a high frequency probing signal into actuation signal is developed. A fast Fourier transform (FFT) algorithm is used to extract the magnitude change of the probing signal, and a non-linear fitting method and artificial neural network (ANN) approach are utilized to reflect the relationship between the probing signal and the actuator’s displacement. Experimental results showed this structure has capability of performing self-sensing and actuation, simultaneously. With an enhanced ANN, the self-sensing scheme can achieve 2.5% accuracy.
In this paper, a novel artificial muscle/tendon structure is developed for achieving bio-inspired actuation and
self-sensing. The hybrid structure consists of a dielectric elastomer (DE) material connected with carbon fibers,
which incorporates the built-in sensing and actuation capability of DE and mechanical, electrical interfacing
capability of carbon fibers. DEs are light weight artificial muscles that can generate compliant actuation with
low power consumption. Carbon fibers act as artificial tendon due to their high electro-conductivity and mechanical strength. PDMS material is used to electrically and mechanically connect the carbon fibers with the
DE material. A strip actuator was fabricated to verify the structure design and characterize its actuation and
sensing capabilities. A 3M VHB 4905 tape was used as the DE material. To make compliant electrodes on
the VHB tape, carbon black was sprayed on the surface of VHB tape. To join the carbon fibers to the VHB
tape, PDMS was used as bonding material. Experiments have been conducted to characterize the actuation
and sensing capabilities. The actuation tests have shown that the energy efficiency of artificial muscle can reach
up to 0.7% and the strain can reach up to 1%. The sensing tests have verified that the structure is capable of
self-sensing through the electrical impedance measurement.
Dielectric elastomers (DEs) have significant applications in artificial muscle and other biomedical equipment
and device fabrications. Metallic thin films by thin film transfer and sputter coating techniques can provide conductive
surfaces on the DE samples, and can be used as electrodes for the actuators and other biomedical sensing devices. In the
present study, 3M VHB 4910 tape was used as a DE for the coating and electrical characterization tests. A 150 nm
thickness of gold was coated on the DE surfaces by sputter coating under vacuum with different pre-strains, ranging
from 0 to 100%. Some of the thin films were transferred to the surface of the DEs. Sputter coating, and direct
transferring gold leaf coating methods were studied and the results were analyzed in detail in terms of the strain rates and
electrical resistivity changes. Initial studies indicated that the metallic surfaces remain conductive even though the DE
films were considerably elongated. The coated DEs can be used as artificial muscle by applying electrical stimulation
through the conductive surfaces. This study may provide great benefits to the readers, researchers, as well as companies
involved in manufacturing of artificial muscles and actuators using smart materials.
This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.
Dielectric elastomers are soft actuation materials with promising applications in robotics and biomedical de- vices. In this paper, a bio-inspired artificial muscle actuator with artificial tendons is developed for robotic arm applications. The actuator uses dielectric elastomer as artificial muscle and functionalized carbon fibers as artificial tendons. A VHB 4910 tape is used as the dielectric elastomer and PDMS is used as the bonding material to mechanically connect the carbon fibers to the elastomer. Carbon fibers are highly popular for their high electrical conductivities, mechanical strengths, and bio-compatibilities. After the acid treatments for the functionalization of carbon fibers (500 nm - 10 μm), one end of carbon fibers is spread into the PDMS material, which provides enough bonding strength with other dielectric elastomers, while the other end is connected to a DC power supply. To characterize the actuation capability of the dielectric elastomer and electrical conductivity of carbon fibers, a diaphragm actuator is fabricated, where the carbon fibers are connected to the actuator. To test the mechanical bonding between PDMS and carbon fibers, specimens of PDMS bonded with carbon fibers are fabricated. Experiments have been conducted to verify the actuation capability of the dielectric elastomer and mechanical bonding of PDMS with carbon fibers. The energy efficiency of the dielectric elastomer increases as the load increases, which can reach above 50%. The mechanical bonding is strong enough for robotic arm applications.
The manta ray, Manta birostris, demonstrates excellent swimming capabilities; generating highly efficient thrust
via flapping of dorsally flattened pectoral fins. In this paper, we present an underwater robot that mimics the
swimming behavior of the manta ray. An assembly-based fabrication method is developed to create the artificial
pectoral fins, which are capable of generating oscillatory with a large twisting angle between leading and trailing
edges. Ionic polymer-metal composite (IPMC) actuators are used as artificial muscles in the fin. Each fin consists
of four IPMC beams bonded with a compliant poly(dimethylsiloxane) (PDMS) membrane. By controlling each
individual IPMC strips, we are able to generate complex flapping motions. The fin is characterized in terms of tip
deflection, tip blocking force, twist angle, and power consumption. Based on the characteristics of the artificial
pectoral fin, a small size and free-swimming robotic manta ray is developed. The robot consists of two artificial
pectoral fins, a rigid body, and an on-board control unit with a lithium ion rechargeable battery. Experimental
results show that the robot swam at a speed of up to 0.055 body length per second (BL/sec).
Ionic polymer-metal composites (IPMC) are soft actuation materials with promising applications in robotics
and biomedical devices. In this paper, a MEMS-based approach is presented for monolithic, batch fabrication of
IPMC pectoral fin actuators that are capable of complex deformation. Such an actuator consists of multiple, individually
controlled IPMC regions that are mechanically coupled through compliant, passive regions. Prototypes
of artificial pectoral fins have been fabricated with the proposed method, and sophisticated deformation modes,
including bending, twisting, and cupping, have been demonstrated, which shows the promise of the pectoral fin
in robotic fish applications.
In this paper, a model is proposed for a biomimetic robotic fish propelled by an ionic polymer metal composite
(IPMC) actuator with a rigid passive fin at the end. The model incorporates both IPMC actuation dynamics
and the hydrodynamics, and predicts the steady-state speed of the robot under a periodic actuation voltage.
Experimental results have shown that the proposed model can predict the fish motion for different tail dimensions.
Since its parameters are expressed in terms of physical properties and geometric dimensions, the model is expected
to be instrumental in optimal design of the robotic fish.
Ionic polymer-metal composites (IPMCs) form an important category of electroactive polymers. In this paper,
a nonlinear, physics-based model is proposed for IPMC actuators. A key component in the proposed model
is the nonlinear capacitance of IPMC, demonstrated by the nonlinear relationship between an applied step
voltage and the induced charge. A nonlinear partial differential equation (PDE) is fully considered in analytical
derivation of the capacitance of IPMC. The nonlinear capacitance is incorporated into a circuit model, which
includes additionally the pseudo capacitance, the ion diffusion resistance, and the nonlinear DC resistance of the
polymer. The model is verified in experiments.
Ionic polymer-metal composites (IPMCs) have built-in sensing and actuation capabilities which make them attractive in
many biomedical and biological applications. In this paper a physics-based but control-oriented dynamic model is proposed
for IPMC actuators. The modeling work starts from the governing partial differential equation (PDE) that describes the
charge redistribution dynamics under external electrical field, electrostatic interactions, ionic diffusion, and ionic migration
along the thickness direction. It is further extended by incorporating the effect of distributed surface resistance. The
electrical impedance model is obtained by deriving the exact solution to the governing PDE in the Laplace domain. By
assuming a linear electromechanical coupling, an actuation model which relates bending displacement to voltage input
is derived. The model is represented as an infinite-dimensional transfer function, which is amenable to model reduction
and real-time control design while capturing fundamental physics. It thus bridges the traditional gap between the physics-based
perspective and the system-theoretic perspective on modeling of IPMC materials. The model is expressed in terms
of fundamental material parameters and dimensions of the IPMC, and is therefore geometrically scalable. The latter has
been further confirmed in experiments.
Compact sensing schemes are desirable for feedback control of ionic polymer-metal composite (IPMC) actuators
in their targeted bio, micro, and nano applications. In this paper, a novel integrated sensory actuator with both
position and force feedback is designed by combining IPMC with polyvinylidene fluoride (PVDF) films. The
design adopts differential configurations for both the sensor-actuator structure and the sensing circuit, and thus
eliminates capacitive coupling between IPMC and PVDF, minimizes the internal stress at bonding interfaces,
and enables excellent immunity to thermal and electromagnetic noises. Closed-loop position control of the IPMC
output is demonstrated together with simultaneous tip force measurement, based upon the integrated PVDF
position and force sensors.
Compact sensing methods are desirable for ionic polymer-metal composite (IPMC) actuators in microrobotic and biomedical applications. In this paper a novel sensing scheme for IPMC actuators is proposed by integrating an IPMC with a PVDF (polyvinylidene fluoride) thin film. The problem of feedthrough coupling from the actuation signal to the sensing signal, arising from the proximity of IPMC and PVDF, presents a significant challenge in real-time implementation. To reduce the coupling while minimizing the stiffening effect, the thickness of the insulating layer is properly chosen based on the Young's modulus measurement of the IPMC/PVDF structures. Furthermore, a nonlinear circuit model is proposed to capture the dynamics of the still significant coupling effect, and its parameters are identified through a nonlinear fitting process. A compensation scheme based on this model is then implemented to extract the correct sensing signal. Experimental results show that the developed IPMC/PVDF structure, together with the compensation algorithm, can perform effective, simultaneous actuation and sensing. As a first application, the sensori-actuator has been successfully used for the open-loop micro-injection of living Drosophila embryos.
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