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Janus particles

Sébastien Michelin, Eric Lauga
Catalytic swimmers have attracted much attention as alternatives to biological systems for examining collective microscopic dynamics and the response to physico-chemical signals. Yet, understanding and predicting even the most fundamental characteristics of their individual propulsion still raises important challenges. While chemical asymmetry is widely recognized as the cornerstone of catalytic propulsion, different experimental studies have reported that particles with identical chemical properties may propel in opposite directions...
February 13, 2017: Scientific Reports
Xiao-Ting Sun, Ying Zhang, Dong-Hua Zheng, Shuai Yue, Chun-Guang Yang, Zhang-Run Xu
A visualized sensing method for glucose and cholesterol was developed based on the hemispheres of the same Janus hydrogel microparticles. Single-phase and Janus hydrogel microparticles were both generated using a centrifugal microfluidic chip. For glucose sensing, concanavalin A and fluorescein labeled dextran used for competitive binding assay were encapsulated in alginate microparticles, and the fluorescence of the microparticles was positively correlated with glucose concentration. For cholesterol sensing, the microparticles embedded with γ-Fe2O3 nanoparticles were used as catalyst for the oxidation of 3,3',5,5'-Tetramethylbenzidine by H2O2, an enzymatic hydrolysis product of cholesterol...
February 7, 2017: Biosensors & Bioelectronics
Seung Yeol Lee, Jongkook Choi, Jong-Ryul Jeong, Jung H Shin, Shin-Hyun Kim
Photonic Janus particles are created by alternately sputtering silica and titania on microspheres in order to obtain a structural color gradient. In addition, the microspheres are rendered magnetoresponsive. The Janus microspheres with optical and magnetic anisotropy enable on-demand control over orientation and structural color through manipulation of an external magnetic field, thereby being useful as active color pigments for reflection-mode displays.
February 6, 2017: Advanced Materials
Mihail Nicolae Popescu, William Uspal, Siegfried Dietrich
Chemically active colloids move by creating gradients in the composition of the surrounding solution and by exploiting the differences in their interactions with the various molecular species in solution. If such particles move near boundaries, e.g., the walls of the container confining the suspension, gradients in the composition of the solution are also created along the wall. This give rise to chemi-osmosis (via the interactions of the wall with the molecular species forming the solution), which drives flows coupling back to the colloid and thus influences its motility...
January 31, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Ning Li, Hao Cai, Lei Jiang, Jiani Hu, Ashika Bains, Jesse Hu, Qiyong Gong, Kui Luo, Zhongwei Gu
In this study, we prepared a smart polymeric vehicle for the hydrophobic drug paclitaxel (PTX) that allowed a maximum steady-state circulation and a fast intracellular release in tumors. PTX was linked to the Janus PEGylated (PEG = poly(ethylene glycol)) peptide dendrimer via an enzyme-sensitive linker glycylphenylalanylleucylglycine tetrapeptide by efficient click reaction, resulting in Janus dendritic prodrug with 20.9% PTX content. The prodrug self-assembled into nanoscale particles with appropriate nanosizes, compact morphology, and negative surface charge...
February 15, 2017: ACS Applied Materials & Interfaces
Jaffar Hasnain, Georg Menzl, Swetlana Jungblut, Christoph Dellago
Based upon recent experiments in which Janus particles are made into active swimmers by illuminating them with laser light, we explore the effect of applying a light pattern on the sample, thereby creating activity inducing zones or active patches. We simulate a system of interacting Brownian diffusers that become active swimmers when moving inside an active patch and analyze the structure and dynamics of the ensuing stationary state. We find that, in some respects, the effect of spatially inhomogeneous activity is qualitatively similar to a temperature gradient...
February 7, 2017: Soft Matter
Tomohiro G Noguchi, Yasutaka Iwashita, Yasuyuki Kimura
Amphiphilic Janus particles (AJP), composed of hydrophilic and hydrophobic hemispheres, are one of the simplest anisotropic colloids, and they exhibit higher surface activities than particles with homogeneous surface properties. Consequently, a ternary system of AJP, water, and oil can form extremely stable Pickering emulsions, with internal structures that depend on the Janus structure of the particles and the system composition. However, the detail of these structures has not been fully explored, especially for the composition range where the amount of the minority liquid phase and AJP are comparable, where one would expect the Janus characteristics to be directly reflected...
January 19, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Qi Xiao, Zhichun Wang, Dewight Williams, Pawaret Leowanawat, Mihai Peterca, Samuel E Sherman, Shaodong Zhang, Daniel A Hammer, Paul A Heiney, Steven R King, David M Markovitz, Sabine André, Hans-Joachim Gabius, Michael L Klein, Virgil Percec
Nonlamellar lipid arrangements, including cubosomes, appear in unhealthy cells, e.g., when they are subject to stress, starvation, or viral infection. The bioactivity of cubosomes-nanoscale particles exhibiting bicontinuous cubic structures-versus more common vesicles is an unexplored area due to lack of suitable model systems. Here, glycodendrimercubosomes (GDCs)-sugar-presenting cubosomes assembled from Janus glycodendrimers by simple injection into buffer-are proposed as mimics of biological cubic membranes...
December 28, 2016: ACS Central Science
Taras Y Molotilin, Vladimir Lobaskin, Olga I Vinogradova
In this work, we use molecular dynamics and lattice-Boltzmann simulations to study the properties of charged Janus particles in an electric field. We show that for a relatively small net charge and a thick electrostatic diffuse layer, mobilities of Janus particles and uniformly charged colloids of the same net charge are identical. However, for higher charges and thinner diffuse layers, the Janus particles always show lower electrophoretic mobility. We also demonstrate that the Janus particles align with the electric field and the angular deviation from the field's direction is related to their dipole moment...
December 28, 2016: Journal of Chemical Physics
Ningwei Li, Nima Sharifi-Mood, Fuquan Tu, Daeyeon Lee, Ravi Radhakrishnan, Tobias Baumgart, Kathleen J Stebe
Inspired by proteins that generate membrane curvature, sense the underlying membrane geometry, and migrate driven by curvature gradients, we explore the question: Can colloids, adhered to lipid bilayers, also sense and respond to membrane geometry? We report the migration of Janus microparticles adhered to giant unilamellar vesicles elongated to present spatially varying curvatures. In our experiments, colloids migrate only when the membranes are tense, suggesting that they migrate to minimize membrane area...
December 30, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Ji Hoon Park, Nuri Han, Ji Eun Song, Eun Chul Cho
A surfactant-free approach is proposed to synthesize nonspherical Janus particles with temperature-dependent wettability on hydrophobic surfaces. Sub-micrometer-sized particles comprising poly(styrene-co-divinylbenzene) core and a thermally responsive poly(N-isopropylacrylamide-co-methacrylic acid) shell are first synthesized to stabilize styrene droplets in water, producing a Pickering emulsion. Upon heating to 80 °C and subsequent addition of initiators to the aqueous phase, styrene droplets are polymerized and combine with the core-shell particles to construct dumbbell-shaped nonspherical particles...
December 22, 2016: Macromolecular Rapid Communications
Wenping He, Johannes Frueh, Narisu Hu, Liping Liu, Meiyu Gai, Qiang He
Current wound sealing systems such as nanoparticle-based gluing of tissues allow almost immediate wound sealing. The assistance of a laser beam allows the wound sealing with higher controllability due to the collagen fiber melting which is defined by loss of tertiary protein structure and restoration upon cooling. Usually one employs dyes to paint onto the wound, if water absorption bands are absent. In case of strong bleeding or internal wounds such applications are not feasible due to low welding depth in case of water absorption bands, dyes washing off, or the dyes becoming diluted within the wound...
December 2016: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Yong Dou, Charles A Cartier, Wenjie Fei, Shashank Pandey, Sepideh Razavi, Ilona Kretzschmar, Kyle J M Bishop
We investigate the dynamics of metallodielectric Janus particles moving via contact charge electrophoresis (CCEP) between two parallel electrodes. CCEP uses a constant voltage to repeatedly charge and actuate conductive particles within a dielectric fluid, resulting in rapid oscillatory motion between the electrodes. In addition to particle oscillations, we find that micrometer-scale Janus particles move perpendicular to the field at high speeds (up to 600 μm/s) and over large distances. We characterize particle motions and propose a mechanism based on the rotation-induced translation of the particle following charge transfer at the electrode surface...
December 13, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Alina Kirillova, Claudia Marschelke, Jens Friedrichs, Carsten Werner, Alla Synytska
Herein, we report a new strategy for the design of antifouling surfaces by using hybrid hairy Janus particles. The amphiphilic Janus particles possess either a spherical or a plateletlike shape and have core-shell structures with an inorganic core and hydrophilic/hydrophobic polymeric shells. Subsequently, these bifunctional Janus particles enable the fabrication of surfaces with modularity in chemical composition and final surface topography, which possess antifouling properties. The antifouling and fouling-release capability of the composite Janus particle-based surfaces is investigated using the marine biofilm-forming bacteria Cobetia marina...
November 30, 2016: ACS Applied Materials & Interfaces
Minggan Li, Dehi Joung, Janusz A Kozinski, Dae Kun Hwang
A microfluidic flow lithography approach was investigated to synthesize highly porous nonspherical particles and Janus particles in a one-step and high-throughput fashion. In this study, using common solvents as porogens, we were able to synthesize highly porous particles with different shapes using ultraviolet (UV) polymerization-induced phase separation in a microfluidic channel. We also studied the pore-forming process using operating parameters such as porogen type, porogen concentration, and UV intensity to tune the pore size and increase the pore size to submicron levels...
December 20, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Bas G P van Ravensteijn, Willem K Kegel
Chemically anisotropic dumbbell-shaped colloids are prepared starting from cross-linked polymer seed particles coated with a chlorinated outer layer. These chlorinated seeds are swollen with monomer. Subsequently, a liquid protrusion is formed on the surface of the seed particle by phase separation between the monomer and the swollen polymer network. Solidification of these liquid lobes by polymerization leads to the desired dumbbell-shaped colloids. The chlorine groups remain confined on the seed lobe of the particles, ensuring chemical anisotropy of the resulting particles...
March 15, 2017: Journal of Colloid and Interface Science
Yijiang Liu, Jiankang Hu, Xiaotian Yu, Xinyu Xu, Yong Gao, Huaming Li, Fuxin Liang
Two Janus-type catalysts were synthesized by selective modification and further functionalization with metal nanoparticles on one or both beads of snowman-like Janus particles. The catalytic performance of Janus-type catalysts both in homogeneous and interfacial reaction systems was systematically investigated using the reduction of nitro-compound as model reaction. The results showed that Janus-type catalysts have excellent catalytic activity in homogeneous reaction system and they are easy to recycle. Further, the Janus-type catalysts exhibited more efficient catalytic activity at emulsion interface than that of oil-water biphasic interface due to the exposed Au nanoparticles on snowman-like Janus particles offer high accessibility to reactants...
March 15, 2017: Journal of Colloid and Interface Science
Lucero Sanchez, Yi Yi, Yan Yu
Controlling the internalization of synthetic particles by immune cells remains a grand challenge for developing successful drug carrier systems. Polyethylene glycol (PEG) is frequently used as a protective coating on particles to evade immune clearance, but it also hinders the interactions of particles with their intended target cells. In this study, we investigate a spatial decoupling strategy, in which PEGs are coated on only one hemisphere of particles, so that the other hemisphere is available for functionalization of cell-targeting ligands without the hindrance effect from the PEGs...
January 7, 2017: Nanoscale
Pingwei Cai, Yuan Hong, Suqin Ci, Zhenhai Wen
Electrochemical catalysis of O2-incorporated reactions is a promising strategy for metal-air batteries. The performance of metal-air batteries is determined by the catalytic activities of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Therefore, developing efficient catalysts with superior activities for the ORR and OER is of great significance to expand the application range of metal-air batteries. Herein, CoFe alloy nanoparticles adhered to the inside wall of nitrogen doped carbon nanotubes (CoFe@NCNTs) are synthesized and can function as a Janus particle to efficiently catalyze the ORR and OER with desirable activities in 0...
December 8, 2016: Nanoscale
Jing Liu, Hong-Lian Guo, Zhi-Yuan Li
Controlled propulsion of microparticles and micromachines in fluids could revolutionize many aspects of technology, such as biomedicine, microfluidics, micro-mechanics, optomechanics, and cell biology. We report the self-propelled cyclic round-trip motion of metallo-dielectric Janus particles in static line optical tweezers (LOT). The Janus particle is a 5 μm-diameter polystyrene sphere half-coated with 3 nanometer thick gold film. Both experiment and theory show that this cyclic translational and rotational motion is a consequence of the collective and fine action of the gold-face orientation dependent propulsion optical force, the gradient optical force, and the spontaneous symmetry breaking induced optical torque in different regions of the LOT...
December 1, 2016: Nanoscale
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