This PhD-thesis presents a study on micron-sized particles, so-called colloids. By controlling the chemical and physical properties of these particles, such as the interparticle interaction... Show moreThis PhD-thesis presents a study on micron-sized particles, so-called colloids. By controlling the chemical and physical properties of these particles, such as the interparticle interaction and the particles’ shape, colloids can act as building blocks that self-assembly into larger structures. This could lead to the development of materials with novel properties such as ‘smart’ materials with the ability to adapt their structure to the environment. In this thesis spherical colloids are used as a starting point to make complex colloidal building blocks and larger microstructures. Anisotropic particles were formed by introducing surface roughness, dents, protrusions and chemical functionalization on the particle surface. Complex structures were obtained by assembling and reconfiguring clusters of spheres. Here, a balance of several phenomena including, the interfacial and potential energy, entropy and geometric constraints, determined the final geometry of the assembled structure. The work also shows how anisotropic elongated particles distorted the hexagonal order in crystals of spheres, either locally or over long distances. These distortions are known to influence the optical, mechanical and electronic properties of colloidal crystals. The complex particles and assemblies made in this study are therefore an important step towards the development of materials with novel and adaptable properties. Show less
This work discusses the flow of granular materials (e.g. sand). Even though a single particle is a simple object, the collective behavior of billions of particles can be very complex. In a... Show moreThis work discusses the flow of granular materials (e.g. sand). Even though a single particle is a simple object, the collective behavior of billions of particles can be very complex. In a surprisingly large amount of cases, it is not exactly known how a granular material behaves, and this while these kinds of materials are omnipresent in everyday life, industry, and nature Similar to materials such as water, which can occur as ice, liquid water and vapor, sand can also exist in different phases of matter. If you for instance walk on the beach, sand behaves like a solid, but if you pour it out of your shoes afterwards, it flows like a liquid. This thesis is dedicated to experiments where we investigate what happens when you try to "liquefy" sand by weakly vibrating it. We use an experimental setup which enables us to study how much stress is required to make sand flow, depending on the desired flow rate and the amount of vibrations. These experiments reveal several physical principles that turn out to be important towards understanding the unique behavior of these kinds of materials Show less
