1. The Evolution of Active Particles: Toward Externally Powered Self-Propelling and Self- Reconfiguring Particle Systems 
C. Wyatt Shields, Orlin D. Velev 
Chem 
Volume 3, Issue 4, Pages (October 2017)
DOI: /j.chempr
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2. Chem 2017 3, DOI: ( /j.chempr )
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3. Figure 1
Evolution of Active Particles: From Self-Assembly to Autonomous Propulsion
Major evolutionary thrusts in colloidal science include (chronologically) (A) the assembly of simple spheres, (B) the assembly and manipulation of Janus and patchy spheres, and (C) the propulsion and reconfiguration of active particles of engineered shape and morphology.
Chem 2017 3, DOI: ( /j.chempr )
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4. Figure 2 EHD Effects Leading to Particle Propulsion
The mobilization of ions around a particle in response to an applied electric field induces liquid motion.
(A) In the case of a sphere, these flow patterns are symmetrical around the particle, thus not generating any translational movement. Adapted with permission from Woehl et al.66 Copyright 2014 American Chemical Society.
(B) When this symmetry is broken, as in the doublet, asymmetric flows are generated, thus contributing to EHD-based self-propulsion. The direction of propulsion of this particle is frequency-dependent, as shown by Ma et al.44
Chem 2017 3, DOI: ( /j.chempr )
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5. Figure 3 ICEP for Particle Self-Propulsion
(A) Schematic of a Janus particle in a half cycle of an AC electric field. The electric double layer on the conductive (gold) side is more strongly polarized and thus drives a stronger electroosmotic slip than the dielectric side, resulting in ICEP motion in a direction of the dielectric side.
(B) Optical micrographs of Janus particles in a planar 140 V/cm field with a frequency of 1 kHz. These particles propel away from their conductive (dark) side and toward their dielectric side. Reprinted with permission from Gangwal et al.47 Copyright 2008 American Physical Society.
Chem 2017 3, DOI: ( /j.chempr )
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6. Figure 4 Electroosmotic Flow for Diode Self-Propulsion
(A) Schematic of a diode particle propelling due to rectification of an applied AC electric field. The origin of the localized electroosmotic flow and the equivalent electrical circuit are shown.
(B) Time-lapse photographs of a millimeter-sized diode floating on water and shuttling back and forth on demand by introducing a short-duration DC component into the applied AC electric signal. Reprinted with permission from Sharma et al.48 Copyright 2015 John Wiley & Sons, Inc.
Chem 2017 3, DOI: ( /j.chempr )
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7. Figure 5 Examples of Magnetically Powered Active Particles
(A) A paramagnetic doublet is shown to propel along one axis as a result of a magnetic field precessing about a perpendicular axis. Reprinted with permission from Tierno et al.51 Copyright 2008 American Chemical Society.
(B) A nanomotor containing nickel propellers and a gold head connected by silver wires is shown to propel along its central axis. Reprinted with permission from Gao et al.52 Copyright 2010 American Chemical Society.
(C) Helical microstructures draw energy from a weak rotating magnetic field to propel through liquids of low Reynolds numbers. Reprinted with permission from Tottori et al.53 Copyright 2013 American Chemical Society.
(D) A hybrid nanomotor is shown to propel in different directions depending on the type of stimulation, i.e., from acoustic energy (left) or magnetic energy (right). Reprinted with permission from Li et al.55 Copyright 2015 American Chemical Society.
Chem 2017 3, DOI: ( /j.chempr )
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8. Figure 6 Examples of Acoustically Powered Active Particles
(A) Metallic nanorods propel, rotate, and assemble in response to stimulation from acoustic perturbations. Reprinted with permission from Wang et al.56 Copyright 2012 American Chemical Society.
(B) A nanowire with a magnetic center and a surface modified with bioreceptors is propelled by forces from an acoustic traveling wave and is steered magnetically to capture and transport biological entities. Adapted with permission from Garcia-Gradilla et al.80 Copyright 2013 American Chemical Society.
(C) Polymeric particles containing bubble-filled cavities are designed to move in response to acoustic perturbations in different ways on the basis of their geometry. Reprinted from Ahmed et al.57
(D) A microswimmer produces microstreamed vortices formed from the rapid oscillations of its flagellum to power its locomotion.58
Chem 2017 3, DOI: ( /j.chempr )
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9. Figure 7
Examples of Multicomponent Reconfigurable Materials Made from Magnetic Micro- and Nanoparticles
(A) Magnetic microparticles confined to a liquid-air interface are stimulated by a planar alternating magnetic field, which drives their assembly into out-of-equilibrium structures that can self-propel when connected to a large, symmetry-breaking bead. Reprinted from Kokot et al.93 and with permission from Snezhko et al.91 (Copyright 2009 American Physical Society).
(B) Magnetic assembly of nanoparticles into flexible and magnetically responsive filaments by nanocapillarity (top). Micrographs of particles in lipid dispersions (i) before assembly, (ii) after assembly with the magnetic field on, and (iii) after assembly with the magnetic field off (bottom). Scale bar, 50 μm. Reprinted from Bharti et al.95
Chem 2017 3, DOI: ( /j.chempr )
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10. Figure 8
Examples of Multicomponent Reconfigurable Materials from Janus Spheres and Rods
(A) Janus spheres with gold-coated hemispheres in a vertical electric field generated between two layers of conductive indium tin oxide (left) forming reconfigurable clusters (middle) and chains (right). Reprinted with permission from Yan et al.97 Copyright 2016 Macmillan Publishers Limited.
(B) Precessing magnetic spheres synchronously rotate with the applied field (left) to form filaments with several unique cross sections (right). Reprinted with permission from Yan et al.16 Copyright 2012 Macmillan Publishers Limited.
(C) Reconfigurable colloidal fibers formed from gold Janus rods, which controllably actuate in response to applied electric fields. Reprinted with permission from Shah et al.100 Copyright 2014 Macmillan Publishers Limited.
Chem 2017 3, DOI: ( /j.chempr )
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11. Figure 9
Examples of Multicomponent Reconfigurable Materials from Complex-Shaped Particles
(A) Patchy cubes assemble into “AB” or “AA” segments that cannot and can reconfigure by removal of the external magnetic field, respectively.
(B) Examples of “microbots” of different sequences that store energy from their environment and reversibly self-fold in the absence of a global magnetic field as a result of stored energy within the “microbots.” Reprinted from Han et al.102
Chem 2017 3, DOI: ( /j.chempr )
Copyright © 2017 Elsevier Inc. Terms and Conditions