Abstract
Hemispherical Janus particles that were coated with silver or nickel on the equatorial plane of hemispherical polymer microparticles were prepared and dispersed in water and the responses to AC electric and stationary magnetic fields applied were investigated. Both of the particles are so oriented that the equatorial plane is parallel to the AC electric field, owing to electric-field induced dipole orientation, which is the response proportional to the quadratic electric field. The nickel coated particles are self-assembled to make a chain-like structure aligned in the direction of the stationary magnetic field. In addition, when both AC electric and stationary magnetic fields are applied, the orientation of a nickel-coated hemispherical particle is uniquely determined in such a way that the equatorial plane is parallel to both electric and magnetic fields. Because the particle is magnetized on the plane, its direction is reversed when the magnetic field is reversed, which is the response that is proportional to the magnetic field. Utilizing these features, mirrors are fabricated that can switch the transmittance and reflectance with electric and magnetic fields. Such features of the Janus particles as to be controlled by an electric and magnetic fields will find wide applications in the fields of microoptics and microfluidics.
Highlights
A Janus particle is a particle having surface and shape with two or more different physical and chemical properties [1]
We have investigated the response of the particles that are dispersed in water to an applied AC electric field
We have examined what kind of phenomenon occurs with ferromagnetic-metal coated hemispherical Janus particles, too
Summary
A Janus particle is a particle having surface and shape with two or more different physical and chemical properties [1]. As an essential feature of the Janus particle, anisotropy due to its asymmetric structure should be stressed. Because of this anisotropy, it possesses various physical and chemical functions. Janus particles are expected to be applied to basic science, such as biochemistry, physics, and colloid chemistry, and to practical applications, such as drug delivery, electronic devices, optical biosensors, etc. The feature having self-propelled or external-field driven mobility [2,3,4,5,6] is expected to be applied to drug delivery
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