**Delayed feedback control of active particles: a controlled journey towards the destination**

*Khadem, Seyed Mohsen Jebreiil ; Klapp, Sabine H. L.* (2019-06-07)

We explore theoretically the navigation of an active particle based on delayed feedback control. The delayed feedback enters in our expression for the particle orientation which, for an active particle, determines (up to noise) the direction of motion in the next time step. Here we estimate the orientation by comparing the delayed position of the particle with the actual one. This method does n...

**Anomalous transport of magnetic colloids in a liquid crystal–magnetic colloid mixture**

*Shrivastav, Gaurav P. ; Klapp, Sabine H. L.* (2019-01-03)

We report an extensive molecular dynamics study on the translational dynamics of a hybrid system composed of dipolar soft spheres (DSS), representing ferromagnetic particles, suspended in a liquid crystal (LC) matrix. We observe that the LC matrix strongly modifies the dynamics of the DSS. In the isotropic regime, the DSS show a crossover from subdiffusive to normal diffusive behavior at long t...

**Heat flow due to time-delayed feedback**

*Loos, Sarah A. M. ; Klapp, Sabine H. L.* (2019-02-21)

Many stochastic systems in biology, physics and technology involve discrete time delays in the underlying equations of motion, stemming, e. g., from finite signal transmission times, or a time lag between signal detection and adaption of an apparatus. From a mathematical perspective, delayed systems represent a special class of non-Markovian processes with delta-peaked memory kernels. It is wel...

**Manipulating shear-induced non-equilibrium transitions in colloidal films by feedback control**

*Vezirov, Tarlan A. ; Gerloff, Sascha ; Klapp, Sabine H. L.* (2015)

Using Brownian Dynamics (BD) simulations we investigate non-equilibrium transitions of sheared colloidal films under controlled shear stress sigma(xz). In our approach the shear rate (gamma) over dot is a dynamical variable, which relaxes on a time scale tau(c) such that the instantaneous, configuration-dependent stress sigma(xz)(t) approaches a pre-imposed value. Investigating the dynamics und...

**Tunable structures of mixtures of magnetic particles in liquid-crystalline matrices**

*Peroukidis, Stavros D. ; Lichtner, Ken ; Klapp, Sabine H. L.* (2015)

We investigate the self-organization of a binary mixture of similar sized rods and dipolar soft spheres by means of Monte-Carlo simulations. We model interparticle interactions by employing anisotropic Gay-Berne, dipolar and soft-sphere interactions. In the limit of vanishing magnetic moments we obtain a variety of fully miscible liquid crystalline phases including nematic, smectic and lamellar...

**Generic model for tunable colloidal aggregation in multidirectional fields**

*Kogler, Florian ; Velev, Orlin D. ; Hall, Carol K. ; Klapp, Sabine H. L.* (2015)

Based on Brownian Dynamics computer simulations in two dimensions we investigate aggregation scenarios of colloidal particles with directional interactions induced by multiple external fields. To this end we propose a model which allows continuous change in the particle interactions from point-dipole-like to patchy-like (with four patches). We show that, as a result of this change, the non-equi...

**Effects of magnetic field gradients on the aggregation dynamics of colloidal magnetic nanoparticles**

*Heinrich, Dirk ; Goñi, Alejandro R. ; Osán, Tristán ; Cerioni, L. M. C. ; Smessaert, Anton ; Klapp, Sabine H. L. ; Faraudo, Jordi ; Pusiol, Daniel Jose ; Thomsen, Christian* (2015)

We have used low-field H-1 nuclear-magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) to investigate the aggregation dynamics of magnetic particles in ionic ferrofluids (IFFs) in the presence of magnetic field gradients. At the beginning of the experiments, the measured NMR spectra were broad and asymmetric, exhibiting two features attributed to different dynamical environments o...

**Self-assembly of three-dimensional ensembles of magnetic particles with laterally shifted dipoles**

*Yener, Arzu B. ; Klapp, Sabine H. L.* (2016)

We consider a model of colloidal spherical particles carrying a permanent dipole moment which is laterally shifted out of the particles' geometrical centres, i.e. the dipole vector is oriented perpendicular to the radius of the particles. Varying the shift delta from the centre, we analyse ground state structures for two, three and four hard spheres, using a simulated annealing procedure. We al...

**The effect of charge separation on the phase behavior of dipolar colloidal rods**

*Rutkowski, David M. ; Velev, Orlin D. ; Klapp, Sabine H. L. ; Hall, Carol K.* (2016)

Colloids with anisotropic shape and charge distribution can assemble into a variety of structures that could find use as novel materials for optical, photonic, electronic and structural applications. Because experimental characterization of the many possible types of multi-shape and multipolar colloidal particles that could form useful structures is difficult, the search for novel colloidal mat...

**Orientational order and translational dynamics of magnetic particle assemblies in liquid crystals**

*Peroukidis, Stavros D. ; Klapp, Sabine H. L.* (2016)

Implementing extensive molecular dynamics simulations we explore the organization of magnetic particle assemblies (clusters) in a uniaxial liquid crystalline matrix comprised of rodlike particles. The magnetic particles are modelled as soft dipolar spheres with diameter significantly smaller than the width of the rods. Depending on the dipolar strength coupling the magnetic particles arrange in...

**Multidirectional colloidal assembly in concurrent electric and magnetic fields**

*Bharti, Bhuvnesh ; Kogler, Florian ; Hall, Carol K. ; Klapp, Sabine H. L. ; Velev, Orlin D.* (2016)

Dipolar interactions between nano- and micron sized colloids lead to their assembly into domains with well-defined local order. The particles with a single dipole induced by an external field assemble into linear chains and clusters. However, to achieve the formation of multidirectionally organized nano-or microassemblies with tunable physical characteristics, more sophisticated interaction too...