110 research outputs found
Solid State Aircraft Concept Overview
Due to recent advances in polymers, photovoltaics, and batteries a unique type of aircraft may be feasible. This is a solid-state aircraft, with no conventional mechanical moving parts. Airfoil, propulsion, energy production, energy storage and control are combined in an integrated structure. The key material of this concept is an ionic polymeric-metal composite (IPMC) that provides source of control and propulsion. This material has the unique capability of deforming in an electric field and returning to its original shape when the field is removed. Combining the IPMC with thin-film batteries and thin-film photovoltaics provides both energy source and storage in the same structure. The characteristics of the materials enables flapping motion of the wing to be utilized to generate the main propulsive force. Analysis shows that a number of design configurations can be produced to enable flight over a range of latitudes on Earth, Venus and possibly Mars
Compaction of Rods: Relaxation and Ordering in Vibrated, Anisotropic Granular Material
We report on experiments to measure the temporal and spatial evolution of
packing arrangements of anisotropic, cylindrical granular material, using
high-resolution capacitive monitoring. In these experiments, the particle
configurations start from an initially disordered, low-packing-fraction state
and under vertical vibrations evolve to a dense, highly ordered, nematic state
in which the long particle axes align with the vertical tube walls. We find
that the orientational ordering process is reflected in a characteristic, steep
rise in the local packing fraction. At any given height inside the packing, the
ordering is initiated at the container walls and proceeds inward. We explore
the evolution of the local as well as the height-averaged packing fraction as a
function of vibration parameters and compare our results to relaxation
experiments conducted on spherically shaped granular materials.Comment: 9 pages incl. 7 figure
Preparation of controlled particulate mixtures with glass beads of different sizes
A method of mixing/preparing binary and ternary mixtures of glass beads was developed using a viscous solution of glycerol
in water. After mixing, the mixture was transferred to a prismatic vessel and glycerol was washed out. The different sized beads
were differently coloured and digital pictures taken from each face were automatically treated by image analysis to determine the
coloured fraction present in each face. Statistical analysis showed that no significant deviation existed in the colour distribution of
each of the four faces.Achi-square test showed that a uniform distribution could be accepted for the beads, no segregation of bead
size nearby the edges was observed and that no wall effect was present. The two-dimensional picture obtained by image analysis
was converted to the corresponding three-dimensional distribution, from which the expected bed porositywas inferred. The porosity
previously estimatedwas compared with the experimental porosity determined by gravimetry directly on the bed.Nosignificant
deviations were found, thereby proving that the mixing method developed was reliable. Hundreds of experiments were done
showing a very high reproducibility. The developed methodwas further used for studies on mixing of binary and ternary mixtures.
In certain conditions (mixtures enriched with large size particles and having a significant difference in size) a segregation layering
effect took place and the bottom layer presented a composition corresponding to the packing with the smallest porosity possible.Fundação para a CiĂȘncia e a Tecnologia (FCT) e FEDER - POCTI/EQU/37500/2001
Force optimization of ionic polymer metal composite actuators by an orthogonal array method
Ionic liquids at electrified interfaces
Until recently, âroom-temperatureâ (<100â150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)â(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of âfirst-generationâ room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the âlater generationâ RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in âcocktailsâ of oneâs choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost âuniversalâ solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) âsister-systemsâ.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules
Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms
Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materialsâskeletal muscle, tendons and plant tissuesâand compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.</p
Mechanoelectric effects in ionic gels
Certain fluorinated ion-exchange membranes, when swollen and suitably plated
by conducting electrodes, display a spontaneous curvature increasing with
the applied electric field . There is also an inverse
effect, where an imposed curvature induces an electric field (in open
circuit conditions). We present here a compact description of these effects
in the linear regime, and in static conditions: this is based on linear
irreversible thermodynamics, with two driving forces ({E} and a water
pressure gradient ) and two fluxes (electric current and water
current). We also give some qualitative estimates of the three Onsager
coefficients which come into play
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