Holographic microscopy is used as a new technique for measuring the 3D position of colloids. In this thesis the advantages and disadvantages of holographic microscopy are brought to light. The...Show moreHolographic microscopy is used as a new technique for measuring the 3D position of colloids. In this thesis the advantages and disadvantages of holographic microscopy are brought to light. The distance between passive colloids and a glass substrate is measured, in order to investigate how to use hologaphic microscopy to get a trustful result. The technology is not well established yet for a physical conclusion, nevertheless, this research was very helpful in understanding the technique.Show less
Flexible colloidal molecules with site-specific interaction offer many possibilities for designing flexible colloidal structures. In this project, we have analyzed how differently shaped colloidal...Show moreFlexible colloidal molecules with site-specific interaction offer many possibilities for designing flexible colloidal structures. In this project, we have analyzed how differently shaped colloidal building blocks, so called colloidal ”atoms”, can influence the flexibility and formation of colloidal molecules, which is a finite sized cluster of colloidal atoms. We investigated how particle shape and size and linker DNA control or affect the flexibility of colloidal molecules and the translational and angular displacement of the colloidal ”atom”. We also have shown preferred angles between atoms, by analyzing the location of the bonded particles on the face of the cube.Show less
The ability to guide particles through complex environments has promising applications in biological and physical departments. Catalytic active Janus particles are one of the types of particles...Show moreThe ability to guide particles through complex environments has promising applications in biological and physical departments. Catalytic active Janus particles are one of the types of particles that have the potential of being controlled. This thesis describes a method to track and analyse particles’ motion, which is essential to understand their behaviour. In particular, we focus on particles orbiting around or inside circular obstacles, analysing their speed and the interaction with each other. It is found that the speed of particles orbiting an obstacle is governed by a normal distribution, particles orbiting an obstacle have a lower speed by a factor of 0.85±0.04 than when they move freely, speed is independent of obstacle curvature, and particles orbiting an obstacle together have the same speed, which has a higher value the more particles orbit together. Furthermore, the effects of global and local fuel depletion effects are discussed.Show less
Active particles can be used to model various biological processes like groups of bacteria or even flocks of birds. Until now, the shape of active prolate ellipsoids has not been optimized to make...Show moreActive particles can be used to model various biological processes like groups of bacteria or even flocks of birds. Until now, the shape of active prolate ellipsoids has not been optimized to make these particles move in a straight line. This is particularly interesting because a straight moving particle can be used as a basis to model these biological systems. Simulations were done to optimize the shape of prolate ellipsoids for straightness of path and four variables are defined that quantify this. The paths of active prolate ellipsoids with a long semi axis of 5 μm and a short semi axis between 1 and 4.9 μm were simulated in C, and the straightness of path was compared using the variables. The simulations suggest that particles with a larger short semi axis follow straighter paths, although this needs to be supported by empirical results.Show less
We use Inline Digital Holography to measure the diffusion coefficient of spherical colloids with a 1.06mm radius in the bulk of a liquid. We obtain a diffusion coefficient of 0.23 +/- 0.03mm2/s...Show moreWe use Inline Digital Holography to measure the diffusion coefficient of spherical colloids with a 1.06mm radius in the bulk of a liquid. We obtain a diffusion coefficient of 0.23 +/- 0.03mm2/s which is in good agreement with Stokes-Einstein theory. We attempt the measurements to active Janus colloid spheres and explore the possibilities and limitations of the technique. We use the Discrete Dipole Approximation to fit the holograms to the Lorenz-Mie theory and report on the viability of the computation. We discuss the minimum necessary requirements for performing a successful fitting and analysis of the motion of Janus colloid spheres, in the bulk of a medium, using inline holographyShow less
The self-propulsion of active colloidal particles in a liquid is subject to many recent studies in soft and active matter physics. Understanding the behavior of these particles can result in a...Show moreThe self-propulsion of active colloidal particles in a liquid is subject to many recent studies in soft and active matter physics. Understanding the behavior of these particles can result in a better understanding of natural processes such as the movement of bacteria, but also find medical applications such as the directed delivery of drugs in damaged tissues. Recent studies have been performed on the swimming behavior of colloidal rods and the self-propulsion of dumbbells with one active particle attached to a passive particle. Anisotropic particles are of particular interest because the differences in sizes between the two lobs allow the study of the influence of the shape of the particle on the movement of the particle, while keeping the other variables constant. In this thesis the self-propulsion of symmetrical and asymmetrical dumbbells is discussed. Those particles with sizes in the order of micrometers are coated on one side with platinum and dispersed in hydrogen peroxide. The swimming behavior of the particles and the influence of the size ratio between the two spheres of the dumbbell are discussed. Clear differences in the angular velocity and curvature for the different dumbbell shapes are found.Show less
Self-propelling microparticles are of great interest to microtechnology, but research on complex particle shapes remains limited as few methods exist to produce such particles. Microscale 3D...Show moreSelf-propelling microparticles are of great interest to microtechnology, but research on complex particle shapes remains limited as few methods exist to produce such particles. Microscale 3D-printing could be a very useful tool in solving this problem. Here the method of 3D-printed particles is applied to create particles shaped like half-grooved rods with platinum-coated tips, with the goal of investigating the theory that slip has a significant influence on the movement of Janus swimmers. These particles exhibited a spread in velocities of which the average was slightly higher if the grooved side was facing towards the substrate than if it was facing away from it. It was also hypothesized that fluid flow and slip might have an influence on the preferred axial orientation of the particle, but no significant difference was found in the distributions of orientation compared to particles in water. A control group of rods without grooves showed an average velocity that was significantly slower than that of the grooved rods in either orientation. These results support the idea that the velocity of active particles is influenced by the particles' slip.Show less
In this thesis, a state-of-the-art Nanoscribe 3D printer is used to fabricate micron-sized particles. These particles are then partly covered with platinum and suspended in hydrogen peroxide to...Show moreIn this thesis, a state-of-the-art Nanoscribe 3D printer is used to fabricate micron-sized particles. These particles are then partly covered with platinum and suspended in hydrogen peroxide to become chemically propelled, active particles. First, it is shown that 3D-printing can indeed be used to fabricate active particles, by fabricating some relatively simple 4 µm spheres. Subsequently, different helical particles are designed and fabricated to discover that some designs can be printed consistently with the same outcome and that some cannot. A consistently printed helical particle is then analyzed to investigate the relationships between its active motion and its helical shape.Show less
An important goal in soft matter physics is to steer microscale self-assembly processes. Here we show linear structures made of colloids and the energy landscape that describes the angular mobility...Show moreAn important goal in soft matter physics is to steer microscale self-assembly processes. Here we show linear structures made of colloids and the energy landscape that describes the angular mobility. It was done by functionalizing isotropic and anisotropic colloids with a lipid bilayer and insert DNA linkers that have a specific binding group. The DNA linkers are fully mobile along the particle surface and colloids functionalized with DNA linkers are able to form flexible polymers. Specifically, we looked at polymers consisting of four monomers: tetramers and found very mobile clusters that had an averaged joint mobility of 154 +- 3 deg2/s. In the energy landscape that we experimentally and theoretically found, we can conclude the preferred angles are 180/180 degrees. For polymers made of two dumbbell particles we found a mobile bilayer, but no mobile clusters were found. Our tunable tetramers could be the design for a model of controlled self-assembly in even larger structures and define the cluster properties.Show less
Theoretical models have shown that the geometry of cell membranes affects the diffusion rate of both proteins and lipids in the cell membrane. In this thesis we present a setup that has been...Show moreTheoretical models have shown that the geometry of cell membranes affects the diffusion rate of both proteins and lipids in the cell membrane. In this thesis we present a setup that has been developed to study two different diffusion effects. The first is the effect of curvature on a field of lipids and the second is the effect of curvature on diffusing colloidal particles. The setup consists of microsized 3D printed structures characterized by different curvatures combined with colloidal particles DNA linked to the structures. Quantitative data has been collected on the motion of the lipids in spherically curved bilayers on the structures, as well as qualitative data on the mobility of different colloids. The setup has been developed to the point that it can soon be used for collecting quantitative data on the colloidal motion.Show less
Metamaterials exhibit exotic properties derived from their geometric structures. A procedure has recently been developed to build reconfigurable structures from convex polyhedra. While initally...Show moreMetamaterials exhibit exotic properties derived from their geometric structures. A procedure has recently been developed to build reconfigurable structures from convex polyhedra. While initally characterized as rigid, we found that some of these structures possess multiple stable configurations. In the present study we develop numerical tools to simulate all possible deformations that can be applied to these structures, mapping the corresponding energy landscape. We use the simulation to identify the additional stable configurations and study their dependence on key physical parameters. Based on the results found, we explain the mechanism behind the observed multistability and suggest its validity as fundamental ingredient for a general designing rule. Finally, we explore the possibility of implementing our results into the development of a reconfigurable, multistable and multifunctional 3D material.Show less
Theoretical results have shown that in cells and other biological systems the geometry of the membrane controls diffusion of membrane associated proteins. Our aim is to develop an artificial system...Show moreTheoretical results have shown that in cells and other biological systems the geometry of the membrane controls diffusion of membrane associated proteins. Our aim is to develop an artificial system using colloidal particles on SLB to study this phenomenon. In quantitatively analyzing the linking mechanism of the Avidin-Biotin bond with respect to particle mobility we have conducted a series of experiments dedicated to optimizing the conditions of our system.Show less
In this project, Janus particles are obtained by swelling linear, crosslinked and chlorine functionalised polystyrene colloids with styrene. Firstly, linear polystyrene colloids of 800 nm in size...Show moreIn this project, Janus particles are obtained by swelling linear, crosslinked and chlorine functionalised polystyrene colloids with styrene. Firstly, linear polystyrene colloids of 800 nm in size with a polydispersity lower than 5% were synthesised using a surfactant-free emulsion polymerisation method. These colloids were used as seeds in a crosslinking synthesis. The obtained crosslinking spheres were larger than one micrometer. These crosslinked colloids were functionalised with chlorine groups by swelling with vinylbenzyl chloride. The chlorine groups were visualised with confocal microscopy by the addtion of fluoreceinamine to the colloids. Finally, the chlorine functionalised crosslinked seeds were swollen with styrene to obtain anisotropic Janus particles.Show less
We seek to study the in uence of substrate geometry on di usion of substrate attached particles by building a model system in which colloidal particles are attached to a supported lipid bilayer on...Show moreWe seek to study the in uence of substrate geometry on di usion of substrate attached particles by building a model system in which colloidal particles are attached to a supported lipid bilayer on TPA suitable material. We test a variety of lipid compositions and polyelectrolyte cushioning with respect to lipid mobility. Our experimental e orts show that DOPC/DOPE-PEG2000 uid lipid bilayers on glass and ORMOCER can be created. DNA linkers with cholesterol anchors are adsorbed in this bilayer and polystyrene colloids coated with complementary DNA linkers are coupled to the linkers in the bilayer. We show that the colloids di use in a two dimensional fashion on a glass substrate.Show less
We worked on a new ”ultimate” patchy particle. Silica colloids are coated with a lipid bilayer composed of a mixture of saturated and unsaturated, charged and zwitterionic lipids. The lipids are...Show moreWe worked on a new ”ultimate” patchy particle. Silica colloids are coated with a lipid bilayer composed of a mixture of saturated and unsaturated, charged and zwitterionic lipids. The lipids are shown to be mobile on these colloids and phase separation is induced using the right lipid mixture. DNA attached to cholesterol partitioned to one of the phases is used as a linker, creating specific interaction on patches. Giant unilamellar vesicles are used as a model system to study phase separation in a lipid bilayer and the partitioning of the DNA attached to cholesterol.Show less
There has been tried to develop a suitable experimental setup to study the ordering of anisotropic colloidal clusters at liquid-liquid interfaces. PMMA colloids and glycerol - CHB-decalin...Show moreThere has been tried to develop a suitable experimental setup to study the ordering of anisotropic colloidal clusters at liquid-liquid interfaces. PMMA colloids and glycerol - CHB-decalin interfaces have been used for this system. Different configurations of interfaces have been made and analyzed. A suitable tracking code has been developed to analyze the ordering of anisotropic colloidal clusters as well. This code can track colloidal clusters in two and three dimensional space.Show less
We seek to create close packed tetrahedral clusters. Our method uses a glue particle to which cluster particles attach. We expand on previous methods by allowing the cluster particles to remain...Show moreWe seek to create close packed tetrahedral clusters. Our method uses a glue particle to which cluster particles attach. We expand on previous methods by allowing the cluster particles to remain mobile during clustering. We do this by using unpolymerised TPM droplets as glue particles and use lipid biotin linkers which diffuse over the surface of this droplet. NeutrAvidin coated polystyrene beads are used as the cluster particles. We describe the protocol for creating these clusters and verify the mobility of the cluster particles.Show less
