Physiochemical microparticle sensors based on nonlinear magnetic oscillations

Fabrication, Assembly, and Application of Patchy Particles

“…Janus particles were initially introduced by Casagrade et al in 1989, [21] but it took the mention of Janus grains in de Gennes' Nobel Lecture [23] in 1991 to bring these particles to the general attention of researchers worldwide. Over the last two decades, many fabrication methods for Janus particles have been developed, [14] including scalable ones, and the particles are now being implemented in new technologies such as emulsions, [44,45] electronic paper, [46][47][48] tunable liquid optics, [49] sensors [50] and microrheological probes. [51][52][53] Fabrication methods for various types of Janus particles, ranging from bicompartmental and dumbbell-like to half-rasberry, arconand snowman-like particles, have been comprehensively reviewed by Perro and co-workers.…”

Surface-anisotropic spherical colloids in geometric and field confinement

“…Depending on the nature of the colloid, this response can be monitored (i.e., fluorescence) enabling the probing of interactions with the surrounding fluid. For example, Kopleman's group [65,68] has shown that magnetically modulated optical nanoprobes (magMOONs) can be used as rheological probes by monitoring the critical slipping rate (Ω c ). Ω c can be determined by measuring the rotation rate of a magMOON at an external rotational rate Ω larger than Ω c .…”

“…One can now determine physical values of the surrounding medium by measuring an average nonlinear rotation rate (δΘ/δt) where Θ is the rotation angle of the sphere with respect to the applied field and solving Eq. (1) for m, B, κ, η, or V. In their studies, McNaughton et al [68] have applied this approach to the determination of the interparticle magnetic moment of magnetic colloids, the temperature-dependence of the viscosity of glucose, the dynamics of binding of molecules to the probe particle, and the estimation of shape factors.…”

Slipping friction of an optically and magnetically manipulated microsphere rolling at a glass-water interface

“…Such measurements are straightforward using optically anisotropic probes such as half-coated microspheres or dimers of particles [13]. For the microspheres used in the experiments described here, incorporation of optical anisotropy is ideal as long as the particle surface roughness remains unaffected.…”

“…Drastic changes in the rotational motion of micro-objects are characteristic of the behavior of overdamped driven nonlinear oscillators [4,[12][13][14][15]. Such systems exhibit two classes of motional behavior: (1) linear phase-locked rotation at low external driving frequencies and (2) nonlinear phase-slipping rotation at high external driving frequencies.…”