Depletion force induces the flocculation of colloidal particles, providing a means to influence the stable states of colloidal structures. By determining the depletion force across various sizes...Show moreDepletion force induces the flocculation of colloidal particles, providing a means to influence the stable states of colloidal structures. By determining the depletion force across various sizes and concentrations of depletants, we identified the optimal size and concentration range for effective depletion forces. Our results highlight the existence of an optimal depletant size. Steric interactions obstruct the proximity of colloids, hindering small depletants from creating depletion force. On the other side of the spectrum, larger polymers either adhere to colloidal surfaces \cite{Kuhl1996} or generate a lower depletion force due to their lower number density. Nevertheless, the force magnitude remains significant. The advantage of larger depletants, is that they offer a larger interaction range, enabling the formation of colloidal hysterons. All polymers measured create sporadically strong attractive interactions between colloids, creating unpredictability in the control of colloidal structures.Show less
This research investigates the influence of variations in temperature and relative humidity on the color of aging bloodstains, pertaining to the ulti- mate objective to develop a method of...Show moreThis research investigates the influence of variations in temperature and relative humidity on the color of aging bloodstains, pertaining to the ulti- mate objective to develop a method of bloodstain age estimation for crime scene investigations. It was found that bloodstain color is not strongly influenced by fluctuations in temperature and relative humidity. Further- more, a triphasic exponential fit of red-values and its derivatives show po- tential for future forensic applications. Although more research is needed under various climate and bloodstain conditions, colorimetric analysis ap- pears to be a promising method for the age estimation of bloodstains.Show less
In this work, magnetic tweezers were used to study the locomotion of active particles in bulk. For this purpose half platinum-coated magnetic spherical Janus particles were suspended in a 5% H2O2...Show moreIn this work, magnetic tweezers were used to study the locomotion of active particles in bulk. For this purpose half platinum-coated magnetic spherical Janus particles were suspended in a 5% H2O2 solution, by which active locomotion was induced. The substrate-particle distance was varied by means of a magnetic field in a magnetic tweezers set-up. By recording the diffraction pattern and the (x,y) positions of these particles during locomotion, the velocity and translational diffusion coefficients were calculated from their Mean-Squared Displacement (MSD) and compared to near-wall locomotion. Although not enough data was gathered to draw conclusions on the influence of the wall on the locomotion of the particles, the applied method appears promising to do so in future research. Namely, it is shown that the magnetic particles can clearly be elevated and be retained in a range of height in bulk. The method is discussed extensively and suggestions for improvements or other approaches are given in the discussion.Show less
Colloidal molecules are a recent development in the field of physics, with specific tailoring towards certain properties such as directional bonding and flexibility. The advantage of using colloids...Show moreColloidal molecules are a recent development in the field of physics, with specific tailoring towards certain properties such as directional bonding and flexibility. The advantage of using colloids is that they provide an excellent starting point to understanding and emulating the dynamics of their molecular counterpart. These parallels can be drawn since colloidal molecules are still sensitive to thermal fluctuations and move much slower than molecules, meaning direct observations can be made. In this thesis, we explore building a ring-like structure out of spherical and cubic colloid supported lipid bilayers (CSLB). The unique aspect of this project, is that in this combined use there is both directional bonding, flexibility and constrained internal motion. The overarching aim is to understand the conformations of a 8 particle ring formed from alternating sphere and cube colloids, with the cubes being on the corners. To do this, we analyse individual angles to look at the conformations as well the structural changes, done using mode analysisShow less
This thesis describes how 3D-printing at micrometer scale can be used to differentiate propulsion methods for active colloidal particles. Two sizes of colloidal particles with a shape resembling...Show moreThis thesis describes how 3D-printing at micrometer scale can be used to differentiate propulsion methods for active colloidal particles. Two sizes of colloidal particles with a shape resembling Star Trek voyagers are printed and as they are activated, by a platinum coating and putting them into a hydrogen peroxide solution, multiple experiments with varying circumstances are performed. In these experiments different behavior such as a unexpected direction reversal is observed and literature is reviewed to interpret the observed behavior. The role of the substrate is concluded to be very significant as the voyagers seem to be trapped when moving backwards and the role of the coating seems to be able to reverse the direction of the colloids as the gradient of platinum thickness could effect the proton current. In the end, four different follow-up experiments are proposed, to further examine the active motion of platinum coated swimmers.Show less
Two different types of colloidal particles were synthesized: 3-(Trimethoxysilyl)propyl methacrylate (TPM) particles with a diameter of 1.00 ± 0.04 μm and cross-linked polystyrene (PS) particles...Show moreTwo different types of colloidal particles were synthesized: 3-(Trimethoxysilyl)propyl methacrylate (TPM) particles with a diameter of 1.00 ± 0.04 μm and cross-linked polystyrene (PS) particles with a diameter of 1.38 ± 0.03 μm. These colloids were used to form close-packed colloidal clusters using a Salting Out-Quenching technique developed by Yake et al. [1] By analysing optical microscopy images, the cluster size distribution was determined. Finally, the colloidal clusters were swollen with toluene or monomer to permanently fuse the colloids together. During the swelling process, the particles folded back into close-packed structures to minimise the second moment of the mass distribution.Show less
