Dielectric elastomers (DEs) are a relatively new electroactive polymer (EAP) transducer technology. They are capable of over 100% strain when actuated, and can be used as sensors to measure large strains. In actuation mode, the DE is subject to an electric field; in sensing mode, the capacitance of the dielectric elastomer is measured. In this work, a dielectric elastomer configured as a circular membrane clamped around its outer edge over a sealed chamber and inflated by a bias pressure is studied in order to characterize its static and dynamic electromechanical behavior. In both cases, the experiments were conducted with prestretched dielectric elastomer actuators fabricated from 0.5 mm or 1 mm thick polyacrylate films and unless stated otherwise carbon grease electrodes were used. The static tests investigate the effect of flexible electrodes and passive layers on the electromechanical response of dielectric elastomer membrane actuators and sensors. To study the effect of the flexible electrodes, four compliant electrodes were tested: carbon grease, silver grease, graphite spray, and graphite powder. The electrode experiments show that carbon grease is the most effective electrode of those tested. To protect the flexible electrodes from environmental hazards, the effect of adding passive elastic layers to the transducers was investigated. A series of tests were conducted whereby the position of the added layers relative to the transducer was varied: (i) top passive layer, (ii) bottom passive layer, and (iii) passive layers on both the bottom and top of the transducer. For the passive layer tests, the results show that adding elastic layers made of the same material as the DE dramatically changes both the mechanical and electrical response of the actuator. The ability to use capacitance measurements to determine the membrane's maximum stretch was also investigated. The experiments demonstrate that the capacitance response can be used to sense large mechanical strains in the membrane ï ³ 25%. In addition, a numerical model was developed which correlates very well with the experimental results especially for strains up to 41%. The dynamic experiments investigate the dynamic response of a dielectric elastomer membrane due to (i) a time-varying pressure input and (ii) a time-varying voltage input. For the time-varying pressure experiments, the prestretched membrane was inflated and deflated mechanically while a constant voltage was applied. The membrane was cycled between various predetermined inflation states, the largest of which was nearly hemispherical, which with an applied constant voltage of 3 kV corresponded to a maximum strain at the pole (center of membrane) of 28%. These experiments show that for higher voltages, the volume displaced by the membrane increases and the pressure inside the chamber decreases. For the time varying voltage experiments, the membrane was passively inflated to various predetermined states, and then actuated. Various experiments were conducted to see how varying certain system parameters changed the membrane's dynamic response. These included changing the chamber volume and voltage signal offset, as well as measuring the displacement of multiple points along the membrane's radius in order to capture its entire motion. The chamber volume experiments reveal that increasing the size of the chamber onto which the membrane is clamped will cause the resonance peaks to shift and change in number. For these experiments, the pole strains incurred during the inflation were as high as 26 %, corresponding to slightly less than a hemispherical state. Upon actuation using a voltage signal with an amplitude of 1.5 kV, the membrane would inflate further, causing a maximum additional strain of 12.1%. The voltage signal offset experiments show that adding offset to the input signal causes the membrane to oscillate at two distinct frequencies rather than one. Lastly, experiments to capture the entire motion of the membrane revealed the different mode shapes the membrane's motion resembles. / Master of Science

Problematics of sensing position metal darts in targets is new and in this time is no too explored problem. This work analyses accessible method, what can realize this scan. There are lot of accessible methods like best applicable reflect method inductive, based on change inductivity and method capacitive, based on change capacities tabular condenser. Capacitive sensing should be realized by the plate couple, where stiring electrode supplies signal.Sensing electrode receiving this signal. On the basis changes thorough electrostatic field measures change capacities. By the changes capacities fit algorithm we can evaluate, whether is in sensing field visible foreign subject – dart. For capacitive method is also designed driving and scanning unit. Various method were to be laboratory tested and was achieved satisfactory results.

Fluid suspended biological particles (bioparticles) flowing through a non-uniform electric field are actuated by the induced dielectrophoretic (DEP) force, known to be dependent upon the bioparticles’ dielectric phenotypes. In this work: a 10-1000 kHz DEP actuation potential applied to a co-planar microelectrode array (MEA) induces a DEP force, altering passing bioparticle trajectories as monitored using: (1) an optical assay, in which the lateral bioparticle velocities are estimated from digital video; and (2) a capacitive cytometer, in which a 1.478 GHz capacitance sensor measures the MEA capacitance perturbations induced by passing bioparticles, which is sensitive to the bioparticles’ elevations. The experimentally observed and simulated lateral velocity profiles of actuated polystyrene microspheres (PSS) and viable and heat shocked Saccharomyces cerevisiae cells verify that the bioparticles’ dielectric phenotypes can be inferred from the resultant trajectories due to the balance between the DEP force and the viscous fluid drag force.

Fluid suspended biological particles (bioparticles) flowing through a non-uniform electric field are actuated by the induced dielectrophoretic (DEP) force, known to be dependent upon the bioparticles’ dielectric phenotypes. In this work: a 10-1000 kHz DEP actuation potential applied to a co-planar microelectrode array (MEA) induces a DEP force, altering passing bioparticle trajectories as monitored using: (1) an optical assay, in which the lateral bioparticle velocities are estimated from digital video; and (2) a capacitive cytometer, in which a 1.478 GHz capacitance sensor measures the MEA capacitance perturbations induced by passing bioparticles, which is sensitive to the bioparticles’ elevations. The experimentally observed and simulated lateral velocity profiles of actuated polystyrene microspheres (PSS) and viable and heat shocked Saccharomyces cerevisiae cells verify that the bioparticles’ dielectric phenotypes can be inferred from the resultant trajectories due to the balance between the DEP force and the viscous fluid drag force.