The curvature of elongated microscopic building blocks plays a crucial role on their self-assembly into orientationally ordered phases. While rod-like molecules form a handful of liquid crystal (LC) p ...
Grain texture evolution and coarsening after quenching can be achieved by curvature-driven growth and grain rotation. Here we examine grain rotation in coarsening, impurity-doped, two-dimensional coll ...
Colloid science has recently grown substantially owing to the innovative use of silane coupling agents (SCAs), especially 3-trimethoxysilylpropyl methacrylate (TPM). SCAs were previously used mainly a ...
MirandaC RBell-Davies, JoanCodina, ArranCurran, JureDobnikar, RoelP ADullens, and IgnacioPagonabarraga
J. Chem. Phys. 2024 160 184201
We present a technique for measuring the interactions between pairs of colloidal particles in two optical traps. This method is particularly suitable for measuring strongly attractive potentials, an o ...
TaikiYanagishima, JohnRusso, RoelP ADullens, and HajimeTanaka
J. Chem. Phys. 2023 159 064510
During devitrification, pre-existing crystallites grow by adding particles to their surface via a process that is either thermally activated (diffusive mode) or happens without kinetic barriers (fast ...
MirandaC RBell-Davies, ArranCurran, YanyanLiu, and RoelP ADullens
Phys. Rev. E 2023 107 064601
We perform feedback experiments and simulations in which a colloidal dumbbell particle, acting as a particle on a ring, is followed by a repulsive optical trap controlled by a continuous-time-delayed ...
Justin-AurelUlbrich, CarlaFernández-Rico, BrianRost, JacopoVialetto, LucioIsa, JeffreySUrbach, and RoelP ADullens
Phys. Rev. E 2023 107 042602
Anisotropic colloidal particles exhibit complex dynamics which play a crucial role in their functionality, transport, and phase behavior. In this Letter, we investigate the two-dimensional diffusion o ...
RuthACrothers, NicholasH POrr, Berendvan der Meer, RoelP ADullens, and TaikiYanagishima
Langmuir 2023 39 5306
We optimize and characterize the preparation of 3-trimethoxysilyl propyl methacrylate (TPM) colloidal suspensions for three-dimensional confocal microscopy. We revisit a simple synthesis of TPM micros ...
NicholasH POrr, TaikiYanagishima, IgorPDolbnya, AndreiVPetukhov, and RoelP ADullens
J. Chem. Phys. 2022 157 224903
We study the crystallization of colloidal dispersions under capillary-action-induced shear as the dispersion is drawn into flat walled capillaries. Using confocal microscopy and small angle x-ray scat ...
JosephDHutchinson, FrançoisALavergne, and RoelPADullens
Phys. Rev. Materials 2022 6 075604
Alloying has long been used to control the properties of crystalline materials. However, the microscopic details of the effects of adding impurities remains poorly understood, as directly imaging thes ...
NicholasHPOrr, TaikiYanagishima, EricMaire, and RoelPADullens
Phys. Rev. Materials 2021 5 123605
We present a method to locate and characterize grain boundaries in polycrystalline materials from the real-space coordinates of their constituent particles. The method is robust against imperfections ...
TaikiYanagishima, JohnRusso, RoelPADullens, and HajimeTanaka
Phys. Rev. Mater. 2021 127 215501
We present a method to locate and characterize grain boundaries in polycrystalline materials from the real-space coordinates of their constituent particles. The method is robust against imperfections ...
Proc. Natl. Acad. Sci. U. S. A. 2021 118 2107241118
Self-assembly of microscopic building blocks into highly ordered and functional structures is ubiquitous in nature and found at all length scales. Hierarchical structures formed by colloidal building ...
TaikiYanagishima, YanyanLiu, HajimeTanaka, and RoelPADullens
Phys. Rev. X 2021 11 021056
The rotational Brownian motion of colloidal spheres in dense suspensions reflects local hydrodynamics and contact forces, which are both key to nonlinear rheological phenomena such as shear-thickening ...
BoPeng, YanyanLiu, DirkGALAarts, and RoelPADullens
Soft Matter 2021 17 1480
Photo-catalytically active crystalline TiO2 has attracted special attention due to its relevance for renewable energy and is typically obtained by the calcination of amorphous TiO2. However, stabilisi ...
We characterise the local mechanical properties of two-dimensional colloidal crystals with hexagonal symmetry assembled at the flat interface between oil and water. Our experiments elucidate the condi ...
CarlaFernandez-Rico, JeffreySUrbach, and RoelPADullens
Langmuir 2021 37 2900
Surface roughness plays an important role in determining the mechanical properties, wettability, and self-assembly in colloidal systems. In this work, we develop a simple and fast method to produce ro ...
CarlaFernandez-Rico, MassimilianoChiappini, TaikiYanagishima, Heidide Sousa, DirkGALAarts, MarjoleinDijkstra, and RoelPADulllens
Science 2020 369 950
Understanding the impact of curvature on the self-assembly of elongated microscopic building blocks, such as molecules and proteins, is key to engineering functional materials with predesigned structu ...
DavidOMorley, AliceLThorneywork, RoelPADullens, and MarkWilson
Phys. Rev. E 2020 101 042309
The properties of a wide range of two-dimensional network materials are investigated by developing a generalized network theory. The methods developed are shown to be applicable to a wide range of sys ...
NimaHSiboni, AliceLThorneywork, AliciaDamm, RoelPADullens, and JuergenHorbach
Phys. Rev. E 2020 101 042609
The effect of hydrodynamic interactions (HI) on the long-time self-diffusion in quasi-two-dimensional fluids of paramagnetic colloidal particles is investigated using a combination of experiments and ...
We report a straightforward, model-free approach for measuring pair potentials from particle-coordinate data, based on enforcing consistency between the pair distribution function measured separately ...
JoshuaLAbbott, ArthurVStraube, DirkGALAarts, and RoelPADullens
New J. Phys. 2019 21 083027
A colloidal particle is driven across a temporally oscillating one-dimensional optical potential energy landscape and its particle motion is analysed. Different modes of dynamic mode locking are obser ...
FrancoisALavergne, ArranCurran, DirkGALAarts, and RoelPADullens
Eur. Phys. J. B 2019 92 142
We discuss the various mechanisms involved in the spontaneous shrinkage of circular grain boundaries in two-dimensional colloidal crystals. We provide experimental evidence that these grain boundary l ...
YanyanLiu, TaikiYanagishima, ArranCurran, KazemVEdmond, StefanoSacanna, and RoelPADullens
Langmuir 2019 35 7962
We describe the synthesis and application of 3-(trimethoxysilyl)propyl methacrylate (TPM) particles as a colloidal model system for three-dimensional (3D) confocal scanning laser microscopy. The effec ...
CarlaFernandez-Rico, TaikiYanagishima, ArranCurran, DirkGALAarts, and RoelPADullens
Adv. Mater. 2019 31 1807514
The bulk synthesis of fluorescent colloidal SU-8 polymer rods with tunable dimensions is described. The colloidal SU-8 rods are prepared by shearing an emulsion of SU-8 polymer droplets and then expos ...
JoshuaLAbbott, JamesASpiers, YongxiangGao, DirkGALAarts, and RoelPADullens
J. Phys. D: Appl. Phys 2019 52 024002
We study the static and dynamic behaviour of colloidal rods in an optical potential energy landscape. We explore the stable states of a colloidal rod in a single optical trap close to a flat wall. Her ...
KiraEKlop, RoelPADullens, PaulMLettinga, SergeiASergei, and DirkGALAarts
Mol. Phys. 2018 116 2864
We confine a colloidal liquid crystal between parallel plates separated down to several times the rod length. By connecting the system to a reservoir we effectively create a grand canonical system, in ...
Colloidal particles with asymmetric catalytic activities are emerging micro/nanomotors that harvest chemical energy for propulsion in fluids. It is of general interest to produce such particles with h ...
AliceLThorneywork, SimonKSchnyder, DirkGALAarts, JuergenHorbach, RolandRoth, and RoelPADullens
Mol. Phys. 2018 116 3245
Hard disks are one of the simplest interacting many-body model system in two dimensions (2D). Here, we present a comprehensive set of measurements of the static structure factors for quasi-2D monodisp ...
FrancoisALavergne, ArranCurran, DirkGALAarts, and RoelPADullens
P. Natl. Acad. Sci. USA 2018 115 6922
The formation and kinetics of grain boundaries are closely related to the topological constraints imposed on their complex dislocation structure. Loop-shaped grain boundaries are unique structures to ...
We apply Henderson's method for measuring the cavity distribution function y(r) [J. Henderson, Mol. Phys. 48, 389 (1983)] to obtain the pair distribution function at contact, g(sigma(+)). In contrast ...
BoPeng, XinglinXinglin, DirkGALAarts, and RoelPADullens
Nat. Nanotechnol. 2018 13 478
Recent progress in synthetic nanotechnology and the ancient use of metals in food preservation and the antibacterial treatment of wounds have prompted the development of nanometallic materials for ant ...
DanielStopper, AliceLThorneywork, RoelPADullens, and RolandRoth
J. Chem. Phys. 2018 148 104501
Using dynamical density functional theory (DDFT), we theoretically study Brownian self-diffusion and structural relaxation of hard disks and compare to experimental results on quasi two-dimensional co ...
AliceLThorneywork, JoshuaLAbbott, DirkGALAarts, PeterKeim, and RoelPADullens
J. Phys-Condens. Mat. 2018 30 104003
Recently, the full phase behaviour of 2D colloidal hard spheres was experimentally established, and found to involve a first order liquid to hexatic transition and a continuous hexatic to crystal tran ...
YongxiangGao, FlavioRomano, RoelPADullens, JonathanKDoye, and DirkGALAarts
Phys. Rev. Materials 2018 2 015601
Alignment of anisometric particles into liquid crystals (LCs) often results from an entropic competition between their rotational and translational degrees of freedom at dense packings. Here we show t ...
FrancoisALavergne, DirkGALAarts, and RoelPADullens
Phys. Rev. X 2017 7 041064
Understanding grain growth is key for controlling the microstructure and the mechanical properties of most polycrystalline materials, including metals, alloys, and ceramics. However, the precise mecha ...
YongxiangGao, VioletFarkas, RoelPADullens, and DirkGALAarts
Soft Matter 2017 13 8678
Confocal microscopy was used to directly observe the structural coarsening of the first layer of short colloidal rods sedimented onto a flat wall. Based on an image analysis algorithm we devised, quan ...
AliceLThorneywork, JoshuaLAbbott, DirkG A LAarts, and RoelP ADullens
Phys. Rev. Lett. 2017 118 158001
We study the melting of quasi-two-dimensional colloidal hard spheres by considering a tilted monolayer of particles in sedimentation-diffusion equilibrium. In particular, we measure the equation of st ...
SimonKSchnyder, ThomasO ESkinner, AliceLThorneywork, DirkG A LAarts, JuergenHorbach, and RoelP ADullens
Phys. Rev. E 2017 95 032602
A binary mixture of superparamagnetic colloidal particles is confined between glass plates such that the large particles become fixed and provide a two-dimensional disorderedmatrix for the still mobile small particles, which form a fluid. By varying fluid and matrix area fractions and tuning the i ...
LouisB GCortes, YongxiangGao, RoelP ADullens, and DirkG A LAarts
J. PHYS.-CONDENS. MAT. 2017 29 064003
We report on the confinement of colloidal liquid crystals in three dimensional chambers with a square footprint. To this end we use colloidal silica rods and exploit their relatively large density difference with respect to the dispersing solvent to study isotropic, nematic and smectic phases confin ...
AliceLThorneywork, DirkG A LAarts, JuergenHorbach, and RoelP ADullens
Phys. Rev. E 2017 95 012614
We present a systematic experimental study of the dynamic behavior of monodisperse and bidisperse twodimensional colloidal hard-sphere fluids. We consider the diffusive behavior of the two types of particles for systems with a variety of compositions and total area fractions. In particular, we measu ...
MichaelP NJuniper, UrsZimmermann, ArthurVStraube, RutBesseling, DirkG A LAarts, HartmutLoewen, and RoelP ADullens
NEW J. PHYS. 2017 19 013010
In this article we examine the dynamics of a colloidal particle driven by a modulated force over a sinusoidal optical potential energy landscape. Coupling between the competing frequencies of the modulated drive and that of particle motion over the periodic landscape leads to synchronisation of part ...
RaamanandRChauhan, RoelP ADullens, KrassimirPVelikov, and DirkG A LAarts
RSC Adv. 2017 7 28780
We study the effects of concentration, surface area and surface chemistry of fractal fumed silica aggregates on a model fat-structured food system. We use oscillatory stress sweep rheology to determine the storage modulus, the length of the linear viscoelastic region and the rate of network breakdow ...
RaamanandRChauhan, RoelP ADullens, KrassimirPVelikov, and DirkG A LAarts
Food Funct. 2017 8 352
We investigate the role of a colloidal model system in the crystallization and network formation of lipids. This system consists of fractal fumed silica aggregates. We look at the influence of different solid fat concentrations and fumed silica concentrations on the resulting gel network. Oscillat ...
FrancoisALavergne, SamuelDiana, DirkG A LAarts, and RoelP ADullens
LANGMUIR 2016 32 12716
We investigate the segregation of impurities to grain boundaries in colloidal polycrystalline monolayers using video microscopy. A model colloidal alloy is prepared by embedding large spherical impurities in a polycrystalline monolayer of small host colloidal hard spheres, which stops grain growth a ...
ColinPReynolds, DavidRobinson, DirkG A LAarts, MarkWilson, WilliamWSampson, and RoelP ADullens
EPL-Europhys. Lett. 2016 116 28001
We establish a direct relation between the distribution of coordination numbers for individual particles and the mean cluster size using simple statistical considerations. We test our probabilistic theory against an experimental model system of superparamagnetic colloidal particles, which form cha ...
YanyanLiu, KazemVEdmond, ArranCurran, CharlesBryant, BoPeng, DirkG A LAarts, StefanoSacanna, and RoelP ADullens
Adv. Mater. 2016 28 8001
A new colloidal system that consists of core-shell "probe" particles embedded in an optically transparent "host" particle suspension is developed. This system enables simultaneous fast confocal imaging and optical tweezing in dense 3D colloidal materials. ...
We study the freezing of a dispersion of colloidal silica particles in water, focusing on the formation of segregated ice in the form of ice lenses. Local temperature measurements in combination with video microscopy give insight into the rich variety of factors that control ice lens formation. We o ...
MichaelP NJuniper, ArthurVStraube, DirkG A LAarts, and RoelP ADullens
Phys. Rev. E 2016 93 012608
We study the motion of colloidal particles driven by a constant force over a periodic optical potential energy landscape. First, the average particle velocity is found as a function of the driving velocity and the wavelength of the optical potential energy landscape. The relationship between average ...
AliceLThorneywork, DirkG A LAarts, JuergenHorbach, and RoelP ADullens
Soft Matter 2016 12 4129
We study the behaviour of the self-intermediate scattering function and self-van Hove correlation function for quasi-two-dimensional colloidal hard sphere fluids at a range of area fractions. We compute these functions first directly from the particle coordinates and secondly from the mean squared d ...
AliceLThorneywork, RobertoERozas, RoelP ADullens, and JuergenHorbach
Phys. Rev. Lett. 2015 115 268301
We compare experimental results from a quasi-two-dimensional colloidal hard sphere fluid to a Monte Carlo simulation of hard disks with small particle displacements. The experimental short-time self-diffusion coefficient D-S scaled by the diffusion coefficient at infinite dilution, D-0, strongly dep ...
YongxiangGao, AndrewKBalin, RoelP ADullens, JuliaMYeomans, and DirkG A LAarts
Phys. Rev. Lett. 2015 115 248301
We report an entropy-driven orientational hopping transition in a magnetically confined colloidal Janus rod. In a magnetic field, the sedimented rod randomly hops between horizontal and vertical states: the latter state comes at a substantial gravitational cost at no reduction of magnetic potential ...
ColinPReynolds, KiraEKlop, FrancoisALavergne, SarahMMorrow, DirkG A LAarts, and RoelP ADullens
J. Chem. Phys. 2015 143 214903
We study the irreversible aggregation kinetics of superparamagnetic colloidal particles in two dimensions in the presence of an in-plane magnetic field at low packing fractions. Optical microscopy and image analysis techniques are used to follow the aggregation process and in particular study the pa ...
KiraEKlop, ChrisLFarmer, RoelP ADullens, and DirkG A LAarts
Mol. Phys. 2015 113 2693
We report a method to calculate distortion energies of a colloidal liquid crystal from single-particle data via a triangulation of the particle positions followed by a linear interpolation of the particle orientations. Our method provides local information on the strength and type of distortions pre ...
DouglasJAshton, SamanthaJIvell, RoelP ADullens, RobertLJack, NigelBWilding, and DirkG A LAarts
Soft Matter 2015 11 6089
We report experimental and simulation studies of the structure of a monolayer of indented (“lock and key”) colloids, on a planar surface. On adding a non-absorbing polymer with prescribed radius and volume fraction, depletion interactions are induced between the colloids, with controlled range a ...
SitiASetu, RoelP ADullens, AuroraHernandez-Machado, IgnacioPagonabarraga, DirkG A LAarts, and RodrigoLedesma-Aguilar
Nat. Commun. 2015 6 7297
Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinem ...
FrancoisALavergne, DirkG A LAarts, and RoelP ADullens
J. PHYS.-CONDENS. MAT. 2015 27 194117
Grain boundaries are solid-solid interfaces whose dynamics is driven by their local curvature. As they are fluctuating interfaces and have a width comparable to the lattice spacing of the surrounding grains, the determination of their local geometrical characteristics is difficult. Here we present a ...
MichaelP NJuniper, ArthurVStraube, RutBesseling, DirkG A LAarts, and RoelP ADullens
Nat. Commun. 2015 6 7187
Synchronization of coupled oscillators has been scrutinized for over three centuries, from Huygens' pendulum clocks to physiological rhythms. One such synchronization phenomenon, dynamic mode locking, occurs when naturally oscillating processes are driven by an externally imposed modulation. Typical ...