23 research outputs found
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Camouflage and Display for Soft Machines
Synthetic systems cannot easily mimic the color-changing abilities of animals such as cephalopods. Soft machinesâmachines fabricated from soft polymers and flexible reinforcing sheetsâare rapidly increasing in functionality. This manuscript describes simple microfluidic networks that can change the color, contrast, pattern, apparent shape, luminescence, and surface temperature of soft machines for camouflage and display. The color of these microfluidic networks can be changed simultaneously in the visible and infraredâa capability that organisms do not have. These strategies begin to imitate the functions, although not the anatomies, of color-changing animals.Chemistry and Chemical Biolog
Arthrobots
This paper describes a class of robotsââarthrobotsââ inspired, in part, by the musculoskeletal system of arthropods (spiders and insects, inter alia). An exoskeleton, constructed from thin organic polymeric tubes, provides lightweight structural support. Pneumatic joints modeled after the hydrostatic joints of spiders provide actuation and inherent mechanical compliance to external forces. An inflatable elastomeric tube (a âballoonâ) enables active extension of a limb; an opposing elastic tendon enables passive retraction. A variety of robots constructed from these structural elements demonstrate i) crawling with one or two limbs, ii) walking with four or six limbs (including an insect-like triangular gait), iii) walking with eight limbs, or iv) floating and rowing on the surface of water. Arthrobots are simple to fabricate, inexpensive, light-weight, and able to operate safely in contact with humans.Chemistry and Chemical Biolog
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Noncontact orientation of objects in three-dimensional space using magnetic levitation
This paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media.Chemistry and Chemical Biolog
Slow light in narrow paraffin-coated vapor cells
Alkali vapor cells with antirelaxation coated walls can have long atomic coherence times. However, using such coated cells in the hyperfine configuration for electromagnetically induced transparency (EIT) requires longitudinal atomic motion to be confined to less than the hyperfine wavelength. We employed a narrow (1 mm) coated cell geometry to study hyperfine EIT and slow and stored light in warm
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87
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vapor, with results comparable to those in buffer gas cells and showing the promise of such cells for several applications
Noncontact orientation of objects in three-dimensional space using magnetic levitation
International audienceThis paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media
Slit Tubes for Semisoft Pneumatic Actuators
This article describes a new principle for designing soft or semisoft' pneumatic actuators: SLiT (for SLit-in-Tube) actuators. Inflating an elastomeric balloon, when enclosed by an external shell (a material with higher Young's modulus) containing slits of different directions and lengths, produces a variety of motions, including bending, twisting, contraction, and elongation. The requisite pressure for actuation depends on the length of the slits, and this dependence allows sequential actuation by controlling the applied pressure. Different actuators can also be controlled using external sliders that act as reprogrammable on-off switches. A pneumatic arm and a walker constructed from SLiT actuators demonstrate their ease of fabrication and the range of motions they can achieve
High-Sensitivity Measurement of Density by Magnetic Levitation
This paper presents
methods that use Magnetic Levitation (MagLev)
to measure very small differences in density of solid diamagnetic
objects suspended in a paramagnetic medium. Previous work in this
field has shown that, while it is a convenient method, standard MagLev
(i.e., where the direction of magnetization and gravitational force
are parallel) cannot resolve differences in density <10<sup>â4</sup> g/cm<sup>3</sup> for macroscopic objects (>mm) because (i) objects
close in density prevent each other from reaching an equilibrium height
due to hard contact and excluded volume, and (ii) using weaker magnets
or reducing the magnetic susceptibility of the medium destabilizes
the magnetic trap. The present work investigates the use of weak magnetic
gradients parallel to the faces of the magnets as a means of increasing
the sensitivity of MagLev without destabilization. Configuring the
MagLev device in a rotated state (i.e., where the direction of magnetization
and gravitational force are perpendicular) relative to the standard
configuration enables simple measurements along the axes with the
highest sensitivity to changes in density. Manipulating the distance
of separation between the magnets or the lengths of the magnets (along
the axis of measurement) enables the sensitivity to be tuned. These
modifications enable an improvement in the resolution up to 100-fold
over the standard configuration, and measurements with resolution
down to 10<sup>â6</sup> g/cm<sup>3</sup>. Three examples of
characterizing the small differences in density among samples of materials
having ostensibly indistinguishable densitiesî¸Nylon spheres,
PMMA spheres, and drug spheresî¸demonstrate the applicability
of rotated Maglev to measuring the density of small (0.1â1
mm) objects with high sensitivity. This capability will be useful
in materials science, separations, and quality control of manufactured
objects