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.