Title Promoter Affiliations Abstract "Feasible self-assembly models" "Jan VAN DEN BUSSCHE" "Databases and Theoretical Computer Science" "Self-assembly is the process in which intricate structures are obtained by spontaneous assembly of smaller building blocks. Self-assembly is present in a wide range of processes, and appears at various scales in nature. For example, the spontaneous formation of a molecular crystal and even the development of a sin- gle cell to a full-grown multicellular organism may be seen as (highly-involved) self-assembly processes. Self-assembly techniques are fundamental for the de- velopment of nanotechnology. The computing potential of self-assembly has recently been considered and partially experimentally verified. While there are self-assembly models avail- able, their computational power is often too large to be either physically implementable or successfully analyzable. Therefore, I aim to consider distinctly less powerful models, which enjoy other attractive properties. This landscape of attractive properties for self-assembly has currently been only scarcely explored. This project will uncover the fundamental computational features of self-assembly, and provide a natural unifying hierarchy of computational self-assembly models, containing representatives of each ""sweet spot"" in the above landscape. This, e.g., allows designers of artificial self-assembly processes to make informed decisions about which features to incorporate in order to derive enough computational power while maintaining sufficient analyzability." "Fault tolerance in self-assembly models" "Jan VAN DEN BUSSCHE" "Databases and Theoretical Computer Science" "Self-assembly is the spontaneous assembly of simple building blocks into intricate structures, and takes place both in nature and artificially. Because artificial top-down construction is becoming increasingly problematic when operating on smaller scales, self-assembly is fundamental for nanotechnology. In nature, self-assembly appears at virtually all scales: from, e.g., the spontaneous folding of RNA molecules via the development of single cells and multicellular organisms to ant colonies. Self-assembly should be fault tolerant, i.e., obtain a working product even in the face of (modest) errors. It has been demonstrated (both in theory and experimentally) that one can compute by selfassembly. Recently, some mechanisms for fault tolerance has been designed and implemented for computational self-assembly. Unfortunately, every fault-tolerance mechanism comes with a cost. This project will uncover new and improve existing fundamental fault-tolerance mechanisms for computational self-assembly, and will fit them in a unifying framework. Emphasis here is on determining the cost and obtained fault tolerance of combining several fault-tolerance mechanism within a single self-assembly system. This, e.g., allows designers of artificial self-assembly processes to make informed decisions about which fault-tolerance mechanisms to incorporate together in order to derive a reasonable tradeoff between fault tolerance and cost." "Molecular self-assembly under 2D lateral nanoconfinement: Capabilities and prospects" "Steven De Feyter" "Molecular Imaging and Photonics" "Molecular self-assembly is omnipresent. Think about the DNA molecules in your body or soap dissolving fat. However, fundamental knowledge about the early self-assembly stages is limited and hinders controlling the process at will, sought after in numerous fields of applications. To that end, confinement of self-assembly has emerged as a strategy to obtain more insight into the early stages. Our group has developed a two-dimensional confinement approach where molecular self-assembly is forced into small spaces, or nanocorrals, on a covalently modified surface. In this thesis, the current capabilities of the approach were demonstrated and new additions to the method were developed, enabling multiple new prospects. We showed that the addition of chemisorbed species on the surface and the presence of an impurity can respectively add more or less disorder for an aperiodic tiling system. For multicomponent systems, confinement induced strain on a three-component network, enabled access to the early self-assembly events of a two-component system, granting polymorphic control, and revealed that no single aligned domains form inside nanocorrals upon adding a second competing component.Two different routes were presented to incorporate more flexibility in the confinement approach. In the first route, an atomic force microscope replaces the scanning tunneling microscope for corral fabrication and the subsequent study of the confined network. In the second approach, iodonium salts were used instead of diazonium salts, expanding the library of available functionalities at the surface." "Cellulose nanocrystal self-assembly to 1D-structures" "Wim Thielemans" "Chemical Engineering, Kulak Kortrijk Campus" "Self-assembly, where particles cluster together autonomically, is an approach to create new materials for applications, such as electronic devices. However, the control over long-rangeordering of the formed structures needs more research to drive technological advancement. The shape and the range of the ordered structure is dictated by the properties on the particle surface as well as the conditions at which the self-assembly takes place. In this study, the nanoparticles used are nano-sized rod-like things made of cellulose, the building block of all plant material.Cellulose as a fibre has ordered and disordered sections from which the ordered sections can be isolated as cellulose nanocrystals (CNC) that have reactive surfaces that can be readily modified.The CNC surface can be selectively modified to contain groups to steer their self-assembly behaviour. Moreover, the other end of the crystal can be modified to direct the self-assembly toform end-to-end interactions leading to a wire-like 1D-assembly. Additionally, the CNCs can be produced in a manner that leaves the CNCs already in an end-to-end associated assembly. This assembly could be preserved through selectively modifying the surfaces of the crystal, so that 1Dassemblies would emerge. Though 1D self-assembled structures have been reported before, CNC based 1D-assemblies would be a completely new approach in the field. We also aim to develop the method to fully control the structures we make in a scalable fashion." "Self-assembly under nanoconfinement conditions" "Steven De Feyter" "Molecular Imaging and Photonics" "Molecular self-assembly of organic building blocks has often been used for fabricating complex functional surfaces. A sizeable part of this discipline consists of understanding the complexity of molecular recognition processes transpiring during the assembly process which occurs at the interface between an organic liquid and a crystalline solid. ln the last two decades, a wide variety of structurally diverse molecular layers have been fabricated ranging from simple lamellae to sophisticated multicomponent networks. Scanning tunneling microscopy (STM), a powerful technique that provides often submolecular resolution if the substrate is conductive, crystalline and atomically flat, have been also used to see these molecular clearly. The aim of this research has been molecule-based two dimensional (2D) crystal engineering which encompasses the control of supramolecular interactions to build complex patterns in a programmed fashion. Analogous to crystallization in bulk, the self-assembly of molecules at the liquid-solid interface is believed to proceed in discrete stages namely, nucleation, growth and ripening. A number of experimental parameters have been identified that have an impact on the surface composition and structure at the liquid-solid interface (LSl). These parameters include the type of solvent, concentration of molecules, type of substrate, temperature at which the self-assembly takes place and thermal history of the sample. Highly oriented pyrolytic graphite (HOPG), a conductive material composed of stacked graphene sheets, is an appealing susbstrate to study nucleation and growth processes by molecular self-assembly in 'corrals’, which are monolayer-deep, flat-bottomed, circular pits. Compartmentalizing the assembling molecules in corrals and on surrounding terraces can provide a handle on studying the processes that are otherwise too fast or coupled with each other. Meanwhile, extraction of crucial parameters relevant to the energetics and kinetics of the assembly process in turn will help to resolve the existing conundrum surrounding self-assembly at the LSl. Last but not the least, the knowledge gained from such studies could be used as an additional handle to influence the assembly process." "Cellulose nanocrystal self-assembly to 1D-structures" "Wim Thielemans" "Chemical Engineering, Kulak Kortrijk Campus" "Self-assembly, where particles cluster together autonomically, is an approach to create new materials for applications, such as electronic devices. However, the control over long-range ordering of the formed structures needs more research to drive technological advancement. The shape and the range of the ordered structure is dictated by the properties on the particle surface as well as the conditions at which the self-assembly takes place. In this study, the nanoparticles used are nano-sized rod-like things made of cellulose, the building block of all plant material. Cellulose as a fibre has ordered and disordered sections from which the ordered sections can be isolated as cellulose nanocrystals (CNC) that have reactive surfaces that can be readily modified. The CNC surface can be selectively modified to contain groups to steer their self-assembly behaviour. Moreover, the other end of the crystal can be modified to direct the self-assembly to form end-to-end interactions leading to a wire-like 1D-assembly. Additionally, the CNCs can be produced in a manner that leaves the CNCs already in an end-to-end associated assembly. This assembly could be preserved through selectively modifying the surfaces of the crystal, so that 1Dassemblies would emerge. Though 1D self-assembled structures have been reported before, CNC based 1D-assemblies would be a completely new approach in the field. We also aim to develop the method to fully control the structures we make in a scalable fashion. " "Implementation of block copolymer based directed self-assembly for advanced lithography." "Guido Groeseneken" "Department of Electrical Engineering (ESAT), Electronic Circuits and Systems (ECS)" "Optical lithography technology has been one of the key enablers for Moore’s Law for over four decades, allowing semiconductor devices to shrink down by approximately a factor of two every two years. This has brought astounding benefits to the industry, as transistors become cheaper, more powerful and faster as they grow smaller. However, current technology, 193 nm immersion lithography, has reached its fundamental resolution limit and, as such, manufacturers have resorted to expensive multiple patterning processes. This economic reality has spurred interest in alternative patterning technologies. Among these, directed self-assembly of block copolymers stands out due to its ability to generate well-controlled sub-20 nm features. Block copolymers are unique soft materials that can self-assemble through microphase separation into various periodic nanostructures such as lamellae, spheres and cylinders, driven by the incompatibility between the different blocks. Of these morphologies, the lamellar and cylindrical phases are of high interest for the lithographic community. Specifically, the cylindrical features, directed by a topographic pre-pattern through a grapho-epitaxy process, are suitable for patterning contacts and vias in integrated circuits. Before directed self-assembly can be employed as a via patterning approach in integrated circuit manufacturing, it needs to be demonstrated that these self-assembled patterns can be generated with a pattern quality adequate for device manufacturing. This dissertation focuses on an experimental investigation of the parameters that need to be controlled to achieve this. First, it is demonstrated that control over the interfacial energy between the pre-pattern template and the different blocks of the copolymer is required to properly direct the assembly. Several techniques for surface modification of the pre-pattern were developed for this purpose. Next, the influence of template fill, which is related to the circuit design, is addressed. Subsequently, it is shown that the pattern quality of specific features can be significantly improved by adding homopolymer of the right molecular weight to the block copolymer. Finally, the patterning of a representative 7 nm node logic via layout is demonstrated." "Self-assembly in colloidal and bacterial systems studied with high resolution microscopy techniques." "Jan Vermant" "Centre of Microbial and Plant Genetics, Soft Matter, Rheology and Technology Section" "Self-assembly refers to the process by which colloidal particles or other discrete components, such as viruses or bacteria, spontaneously organize into ordered, macroscopic structures. Essential is that the colloidal building blocks undergo this restructuring process either through direct interactions, such as interparticle forces, or indirectly using a template or an external field. Recent advances have highlighted the similarity between the self-organization in bacterial systems and those observed in certain colloidal systems, when the latter mimic the properties of the bacteria as far as shape and size are concerned. Too often in the biological literature, intricate genetic mechanisms are proposed to explain the self-assembly, whereas simple physicochemical or hydrodynamic mechanisms are not considered.Bacterial swarming, the rapid spreading of a colony over surfaces, is a process triggered by a depletion of available food sources. Hence, it is a natural reaction to an unfavorable state and a potential survival strategy used by biological organisms. Although the active nature and the motility of bacteria have long been considered to be the main contributors, the importance of interfacial effects in the efficiency as well as the pattern formation have recently been suggested. Other mechanisms, such as hydrodynamics and viscoelasticity effects, have not yet been studied, whereas this may be key in understanding the phenomena of bacterial cell transport. The knowledge in this efficient structuring by self-assembly can be used to arrest the spreading of unwanted bacterial species or vice versa to create optimal growth and bioavailability of bacteria. This thesis aims at a rational approach to study the similarity and differences of self-assembly in active and passive systems, and to understand the physicochemical mechanisms that drive self-assembly in bacterial systems." "Modifying graphene by nanostructuring via molecular self-assembly" "Steven De Feyter" "Molecular Imaging and Photonics" "This research focuses on using chirality as a tool to study different aspects of supramolecular self-assembly of molecular building blocks on the highly ordered pyrolytic graphic (HOPG), at the liquid-solid interface. A well-known class of molecules in the field of supramolecular assembly on surfaces, alkoxylated dehydrobenzo[12]annulene (DBA) derivatives, are selected as the objects of study, as in addition to the vast amount of information on their self-assembly behavior, protocols are in place to functionalize them. They show a rich phase behavior and, in particular, the low-density porous networks they form are of interest. The investigation of the supramolecular chemistry of chiral DBA derivatives or their mixtures with achiral analogues is central to this work. There are still several open issues in understanding and directing the outcome of supramolecular self-assembly processes on surfaces. The following questions are addressed: 1) What are the dynamics involved and what are the timescales? 2) Can multiple self-assembly pathways act simultaneously and how can one distinguish and control them? 3) What is needed to extend 2D monolayer formation in the third dimension?" "Hierarchical nanostructured materials through nanoparticle self-assembly." "Wim Thielemans" "Chemical Engineering, Kulak Kortrijk Campus" "Nature builds very complex, multifunctional systems by assembling simple building blocks in a directed manner compared to which most manmade structures are relatively simple. In a biomimetic approach, we aim to create hierarchical multi-functional one-, two- and three-dimensional structures with controlled long-range order through self-assembly of multifunctional rodlike nanoparticles. To achieve this, we will modify the surface of rod-like cellulose nanocrystals at their three distinct surface functionalities: primary and secondary hydroxyl groups and aldehydes. Using the difference in reactivity of their lateral surface primary and secondary hydroxyl groups and of the aldehydes located at one cellulose chain end extremity, we will introduce assembly-directing groups, as well as other functionalities such as fluorescence, (electro)chromism, and redox and electron hopping capability. Ordered structures will be formed by self-assembly on solid surfaces, at liquid-liquid and liquid-gas interfaces, in bulk, and under flow, with and without addition of metal nanoparticles or di- or multifunctional linkers. Flexibility and spacing of the grafts will provide additional control over the self-assembly behaviour and performance of the additional functionalities."