Pattern formation, i.e., the outcome of self-organization, has fascinated scientists for centuries. A large effort was devoted to understand the formation of regular patterns in dissipative structures. More recently, it appears that self-organized structures could also be achieved near equilibrium. There is a great variety of physical and chemical systems that, near equilibrium, exhibit periodic patterns. For instance, stripes or bubbles could be observed in thin films of magnetic garnet, superconducting materials, block copolymers, liquid crystals, phospholipids, and ferrofluids. Wrinkling instability of compressed rigid membranes on soft elastic substrates leads also to the formation of periodic patterns near equilibrium. Since the seminal paper of Bowden et al. (Nature 1998), various systems were proposed to generate nano- and micrometric wrinkles via the application of compressive stresses to multilayers. In addition to its purely fundamental interest, these instabilities also offer a new route to build in a simple, cost-effective, and well-defined way nano- and microstructured surfaces without the use of the traditional, robust techniques developed in the microelectronics industry. In this thesis, we develop a new system, metal-polymer-substrate trilayers, that exhibit wrinkling when heated above the glass transition temperature of the polymer. We explain in detail the mechanism at the origin of wrinkling and expand existing models to obtain a complete description of the relevant parameters that govern both the amplitude and the wavelength of the obtained pattern. In light of this, we show that by playing with the rheological properties of the polymer we are able to control precisely the geometry of the wrinkles. Furthermore, to generate surfaces with a tailor-made buckling pattern, we develop an original variant of the experiments. We tune the boundary conditions at the polymer-substrate interface by chemically patterning the substrates with regions of high and low adhesion. In this way, we obtain patterns with wrinkles being oriented differently above the sticky and the slippery regions. This last result is very surprising since it seems, at first sight, unrealistic to imagine that the chemical nature of the substrate could affect the elastic instability of the skin through a micron-thick polymer film. To explore wrinkled patterns with complex morphologies, we couple the wrinkling instability with solvent diffusion. Molecular diffusion in the polymer layer triggers the transition from an unwrinkled to a wrinkled state, provided that stimuloresponsive mutlilayers are used. The wrinkled pattern obtained is determined by the geometry of the diffusion process. To understand this surprising observation, we explain in detail how the scalar field related to the solvent concentration affects so strongly the elastic instabilities usually determined by the tensorial stress field. This mechanism allows us thus to grant exotic stress distributions which lead to very intriguing patterns (e.g. parallel or radial folds, herringbones). Interestingly, we find that under specific conditions, a hierarchical wrinkled morphology, i.e. pattern of wrinkles branching into generations of ever-higher folds, develops. We study other manifestations of hierarchical structures existing around us. In this frame, we derive a general concept that a plate constrained at one edge (with a fixed wavelength) but free at the opposite one evolves naturally to larger wavelengths to minimize its bending energy. We show theoretically that the evolution results from a compromise between the gain in bending energy and the energetic penalties related to the change of wavelength. We demonstrate the universality of these concepts by showing that our commonplace suspended curtain behaves like nanometer-thick polystyrene films deposited on water and further compressed. We close this thesis by making a short review of the main applications related to wrinkling that are already described in literature and develop in detail one of them, the use of wrinkling to investigate cell contact guidance.

"The design and development of chemically modified surfaces for bioanalytical applications is presented. Chemical surface modification is demonstrated to be a method to control surface properties on the molecular level by selecting the appropriate substrate, linking chemistry, and terminal group functionality. These systems utilize spontaneous interactions between individual molecules that allow them to self-assemble into larger, supramolecular constructs with a predictable structure and a high degree of order. Applications investigated in this thesis include: surface patterning, switchable surface wettability, and biological sensor devices that combine surface based molecular recognition, electrochemical detection methods, and microfluidics. A multilayered approach to complex surface patterning is described that combines self-assembly, photolabile protecting groups, and multilayered films. A photolabile protecting group has been incorporated into molecular level films that when cleaved leaves a reactive surface site that can be further functionalized. Surface patterns are created by using a photomask and then further functionalizing the irradiated area through covalent coupling. Fluorophores were attached to the deprotected regions, providing visual evidence of surface patterning. This approach is universal to bind moieties containing free amine groups at defined regions across a surface, allowing for the development of films with complex chemical and physico-chemical properties. Systems with photoswitchable wettability were developed by fabricating multilayered films that include a photoisomerizable moiety, cis-/trans- dicarboxystilbene. When this functionality was incorporated into a multilayered film using non-covalent interactions, irradiation with light of the appropriate wavelength resulted in a conformational change that consequently changed the hydrophobicity of the substrate. Methods were investigated to increase the reversibility of the photoswitching process by creating surface space between the stilbene ligands. Utilizing mixed monolayers for spacing resulted in complete isomerization for one cycle, while the use of SAMs with photolabile groups produced surfaces that underwent isomerization for three complete cycles. A microfluidic device platform for ion sensing applications has been developed. The platform contains components to deliver small volumes of analyte to a surface based microelectrode array and measure changes in analyte concentration electrochemically in an analogous method to that used in conventional electrochemical cells. Crown ether derivatives that bind alkali metal ions have been synthesized and tested as ionophores for a multi-analyte device of this type, and the sensing platform was demonstrated to measure physiological relevant concentrations of potassium ions. Advantages of this design include: high sensitivity (uM to mM), small sample volumes (less than 0.1 mL), multi-analyte capabilities (multiple working electrodes), continuous monitoring (a flow through system), and the ability to be calibrated (the system is reusable). The self-assembled systems described here are platform technologies that can be combined and used in molecular level devices. Current and future work includes: photopatterning of gold and glass substrates for directed cell adhesion and growth, the design and synthesis of selective ion sensors for biological samples, multi-analyte detection in microfluidic devices, and incorporating optical as well as electrochemical transduction methods into sensor devices to allow for greater sensitivity and self-calibration."

Delivery of a desired ‘active’ compound (for example, starch (as an energy substrate)) to the gastrointestinal (GI) tract is most easily achieved by oral administration. Unfortunately, the efficacy of most actives is greatly reduced due to the aggressive nature of digestive enzymes and processes which occur in this environment. A commonly applied strategy to prevent deactivation of the active prior to absorption at the target site is to encapsulate the active in another ‘sacrificial’ or non-degradable polymer matrix. Traditionally, the active and matrix is processed into a microparticle format for easy oral delivery (dispersed in a liquid or paste). However, established encapsulation methods which rely on bulk-phase processing to produce these microparticles (e.g. emulsification) are far from ideal as they lack control over the final microparticle size, size distribution, composition and shape. The lack of control in the physical properties of the resultant microparticles in turn results in an inherent lack of control over the kinetics of release of the active at the target site. In contrast, recent advances in microfluidic device fabrication and methodology development have firmly proven that these new generation devices can produce monodisperse droplets and microparticles in a continuous, controllable and predictable manner. Their potential as a processing tool for the production of highly tailored microparticles for targeted delivery, however, remains to be fully explored. Both the physical and chemical (physicochemical) properties of microparticles made from a single polymer system may be altered by the deposition of one or more additional polymer layers onto the microparticle surface (for example, alternating layers of oppositely charged polyelectrolytes to produce core-shell like particles), and this method has proven to be favorable with regards to retarding the release of active compounds. However, this addition of alternate layers of oppositely charged polyelectrolytes (so called Layer-by-Layer (LbL) deposition or assembly) does increase the number of processing steps the particles must undergo prior to storage or delivery. Further, the overall effectiveness of this additional processing is still highly dependent on the properties of the original (core) microparticles. In this thesis, a microfluidic technique was developed to encapsulate starch granules in alginate-based microparticles. Using this continuous technique, the size of the microparticles produced were shown to be monodisperse and reproducible. The developed microfluidic device included a drop formation section, followed by a gelation region and a transfer section, where the particles made on-chip are transferred from the carrier oil phase to an aqueous phase prior to collection. The microparticles collected from this microfluidic device were found to be stable for several weeks and in stark contrast to particles produced via a standard bulk emulsification routes, no aggregation was observed over this time frame. The release profile of glucose (as a result of starch hydrolysation) from microparticles produced using both a standard bulk emulsification method and the developed microfluidic-based method were compared. It was found that the monodisperse particles produced using the microfluidic method showed significantly more retardation to release compared to the glucose release profile from bulk-processed particles. This retardation effect was more pronounced when a thin layer of an oppositely charged polyelectrolyte (chitosan) was adsorbed onto the negatively charged surface (alginate is an anionic polyelectrolyte) of the microfluidic-processed microparticle. The microfluidic device developed within this thesis and the resulting tailored microparticles thus show significant potential with regards to offering a new generation of microparticle delivery systems with highly deterministic delivery over extended lifetimes.

Delivery of a desired ‘active’ compound (for example, starch (as an energy substrate)) to the gastrointestinal (GI) tract is most easily achieved by oral administration. Unfortunately, the efficacy of most actives is greatly reduced due to the aggressive nature of digestive enzymes and processes which occur in this environment. A commonly applied strategy to prevent deactivation of the active prior to absorption at the target site is to encapsulate the active in another ‘sacrificial’ or non-degradable polymer matrix. Traditionally, the active and matrix is processed into a microparticle format for easy oral delivery (dispersed in a liquid or paste). However, established encapsulation methods which rely on bulk-phase processing to produce these microparticles (e.g. emulsification) are far from ideal as they lack control over the final microparticle size, size distribution, composition and shape. The lack of control in the physical properties of the resultant microparticles in turn results in an inherent lack of control over the kinetics of release of the active at the target site. In contrast, recent advances in microfluidic device fabrication and methodology development have firmly proven that these new generation devices can produce monodisperse droplets and microparticles in a continuous, controllable and predictable manner. Their potential as a processing tool for the production of highly tailored microparticles for targeted delivery, however, remains to be fully explored. Both the physical and chemical (physicochemical) properties of microparticles made from a single polymer system may be altered by the deposition of one or more additional polymer layers onto the microparticle surface (for example, alternating layers of oppositely charged polyelectrolytes to produce core-shell like particles), and this method has proven to be favorable with regards to retarding the release of active compounds. However, this addition of alternate layers of oppositely charged polyelectrolytes (so called Layer-by-Layer (LbL) deposition or assembly) does increase the number of processing steps the particles must undergo prior to storage or delivery. Further, the overall effectiveness of this additional processing is still highly dependent on the properties of the original (core) microparticles. In this thesis, a microfluidic technique was developed to encapsulate starch granules in alginate-based microparticles. Using this continuous technique, the size of the microparticles produced were shown to be monodisperse and reproducible. The developed microfluidic device included a drop formation section, followed by a gelation region and a transfer section, where the particles made on-chip are transferred from the carrier oil phase to an aqueous phase prior to collection. The microparticles collected from this microfluidic device were found to be stable for several weeks and in stark contrast to particles produced via a standard bulk emulsification routes, no aggregation was observed over this time frame. The release profile of glucose (as a result of starch hydrolysation) from microparticles produced using both a standard bulk emulsification method and the developed microfluidic-based method were compared. It was found that the monodisperse particles produced using the microfluidic method showed significantly more retardation to release compared to the glucose release profile from bulk-processed particles. This retardation effect was more pronounced when a thin layer of an oppositely charged polyelectrolyte (chitosan) was adsorbed onto the negatively charged surface (alginate is an anionic polyelectrolyte) of the microfluidic-processed microparticle. The microfluidic device developed within this thesis and the resulting tailored microparticles thus show significant potential with regards to offering a new generation of microparticle delivery systems with highly deterministic delivery over extended lifetimes.

Delivery of a desired ‘active’ compound (for example, starch (as an energy substrate)) to the gastrointestinal (GI) tract is most easily achieved by oral administration. Unfortunately, the efficacy of most actives is greatly reduced due to the aggressive nature of digestive enzymes and processes which occur in this environment. A commonly applied strategy to prevent deactivation of the active prior to absorption at the target site is to encapsulate the active in another ‘sacrificial’ or non-degradable polymer matrix. Traditionally, the active and matrix is processed into a microparticle format for easy oral delivery (dispersed in a liquid or paste). However, established encapsulation methods which rely on bulk-phase processing to produce these microparticles (e.g. emulsification) are far from ideal as they lack control over the final microparticle size, size distribution, composition and shape. The lack of control in the physical properties of the resultant microparticles in turn results in an inherent lack of control over the kinetics of release of the active at the target site. In contrast, recent advances in microfluidic device fabrication and methodology development have firmly proven that these new generation devices can produce monodisperse droplets and microparticles in a continuous, controllable and predictable manner. Their potential as a processing tool for the production of highly tailored microparticles for targeted delivery, however, remains to be fully explored. Both the physical and chemical (physicochemical) properties of microparticles made from a single polymer system may be altered by the deposition of one or more additional polymer layers onto the microparticle surface (for example, alternating layers of oppositely charged polyelectrolytes to produce core-shell like particles), and this method has proven to be favorable with regards to retarding the release of active compounds. However, this addition of alternate layers of oppositely charged polyelectrolytes (so called Layer-by-Layer (LbL) deposition or assembly) does increase the number of processing steps the particles must undergo prior to storage or delivery. Further, the overall effectiveness of this additional processing is still highly dependent on the properties of the original (core) microparticles. In this thesis, a microfluidic technique was developed to encapsulate starch granules in alginate-based microparticles. Using this continuous technique, the size of the microparticles produced were shown to be monodisperse and reproducible. The developed microfluidic device included a drop formation section, followed by a gelation region and a transfer section, where the particles made on-chip are transferred from the carrier oil phase to an aqueous phase prior to collection. The microparticles collected from this microfluidic device were found to be stable for several weeks and in stark contrast to particles produced via a standard bulk emulsification routes, no aggregation was observed over this time frame. The release profile of glucose (as a result of starch hydrolysation) from microparticles produced using both a standard bulk emulsification method and the developed microfluidic-based method were compared. It was found that the monodisperse particles produced using the microfluidic method showed significantly more retardation to release compared to the glucose release profile from bulk-processed particles. This retardation effect was more pronounced when a thin layer of an oppositely charged polyelectrolyte (chitosan) was adsorbed onto the negatively charged surface (alginate is an anionic polyelectrolyte) of the microfluidic-processed microparticle. The microfluidic device developed within this thesis and the resulting tailored microparticles thus show significant potential with regards to offering a new generation of microparticle delivery systems with highly deterministic delivery over extended lifetimes.

Shape memory alloys (SMAs) are a unique class of smart materials exhibiting extraordinary properties with a wide range of applications in engineering, biomedical, and aerospace technologies. In this study, an advanced, efficient, low-cost, and highly scalable laser-assisted imprinting method with low environmental impact to create thermally controllable surface patterns is reported. Two different imprinting methods were carried out mainly on Ni50Ti50 (at. %) SMAs by using a nanosecond pulsed Nd:YAG laser operating at 1064 nm wavelength and 10 Hz frequency. First, laser pulses at selected fluences were directly focused on the NiTi surface, which generated pressure pulses of up to a few gigapascal (GPa), and thus created micro-indents. Second, a suitable transparent overlay serving as a confining medium, a sacrificial layer, and a mesh grid was placed on the NiTi sample, whereafter the laser was focused through the confinement medium, ablating the sacrificial layer to create plasma and pressure, and thus pushing and transferring the grid pattern onto the sample. Scanning electron microscope (SEM) and laser profiler images show that surface patterns with tailorable sizes and high fidelity could be obtained. The depth of the patterns was shown to increase and later level off with the increase in laser power and irradiation time. Upon heating, the depth profile of the imprinted SMA surfaces changed where the maximum depth recovery ratio of 30 % was observed. Recovery ratio decreased and saturated at about 15 % when the number of pulses were increased. A numerical simulation of the laser irradiation process was performed showing that considerably high pressure and temperature could be generated depending on the laser fluence. The stress wave closely followed the rise time of the laser pulse to its peak value and followed by the rapid attenuation and dispersion of the stress through the sample.

As devices and new technologies continue to shrink, nanocrystalline multi-metal compounds are becoming increasingly important for high efficiency and multifunctionality. However, synthetic methods to make desirable nanocrystalline multi-metallics are not yet matured. In response to this deficiency, we have developed several solution-based methods to synthesize nanocrystalline binary alloy and intermetallic compounds. This dissertation describes the processes we have developed, as well as our investigations into the use of lithographically patterned surfaces for template-directed self-assembly of solution dispersible colloids. We used a modified polyol process to synthesize nanocrystalline intermetallics of late transition and main-group metals in the M-Sn, Pt-M’, and Co-Sb systems. These compounds are known to have interesting physical properties and as nanocrystalline materials they may be useful for magnetic, thermoelectric, and catalytic applications. While the polyol method is quite general, it is limited to metals that are somewhat easy to reduce. Accordingly, we focused our synthetic efforts on intermetallics comprised of highly electropositive metals. We find that we can react single-metal nanoparticles with zero-valent organometallic Zinc reagents in hot, coordinating amine solvents via a thermal decomposition process to form several intermetallics in the M’’-Zn system. Characterization of the single-metal intermediates and final intermetallic products shows a general retention of morphology throughout the reaction, and changes in optical properties are also observed. Following this principle of conversion chemistry, we can employ the high reactivity of nanocrystals to reversibly convert between intermetallic phases within the Pt-Sn system, where PtSn2 ↔ PtSn ↔ Pt3Sn. Our conversion chemistry occurs in solution at temperatures below 300 °C and within 1 hour, highlighting the high reactivity of our nanocrystalline materials compared to the bulk. Some evidence of the generality for this process is also presented. Our nanocrystalline powders are dispersible in solution, and as such are amenable to solution-based processing techniques developed for colloidal dispersions. Accordingly, we have investigated the use of lithographically patterned surfaces to control the self-assembly of colloidal particles. We find that we can rapidly crystallize 2-dimensional building blocks, as well as use epitaxial templates to direct the formation of interesting superlattice structures comprised of a bidisperse population of particles.

As devices and new technologies continue to shrink, nanocrystalline multi-metal compounds are becoming increasingly important for high efficiency and multifunctionality. However, synthetic methods to make desirable nanocrystalline multi-metallics are not yet matured. In response to this deficiency, we have developed several solution-based methods to synthesize nanocrystalline binary alloy and intermetallic compounds. This dissertation describes the processes we have developed, as well as our investigations into the use of lithographically patterned surfaces for template-directed self-assembly of solution dispersible colloids. We used a modified polyol process to synthesize nanocrystalline intermetallics of late transition and main-group metals in the M-Sn, Pt-M', and Co-Sb systems. These compounds are known to have interesting physical properties and as nanocrystalline materials they may be useful for magnetic, thermoelectric, and catalytic applications. While the polyol method is quite general, it is limited to metals that are somewhat easy to reduce. Accordingly, we focused our synthetic efforts on intermetallics comprised of highly electropositive metals. We find that we can react single-metal nanoparticles with zero-valent organometallic Zinc reagents in hot, coordinating amine solvents via a thermal decomposition process to form several intermetallics in the M''-Zn system. Characterization of the single-metal intermediates and final intermetallic products shows a general retention of morphology throughout the reaction, and changes in optical properties are also observed. Following this principle of conversion chemistry, we can employ the high reactivity of nanocrystals to reversibly convert between intermetallic phases within the Pt-Sn system, where PtSn2 ↔ PtSn ↔ Pt3Sn. Our conversion chemistry occurs in solution at temperatures below 300 °C and within 1 hour, highlighting the high reactivity of our nanocrystalline materials compared to the bulk. Some evidence of the generality for this process is also presented. Our nanocrystalline powders are dispersible in solution, and as such are amenable to solution-based processing techniques developed for colloidal dispersions. Accordingly, we have investigated the use of lithographically patterned surfaces to control the self-assembly of colloidal particles. We find that we can rapidly crystallize 2-dimensional building blocks, as well as use epitaxial templates to direct the formation of interesting superlattice structures comprised of a bidisperse population of particles.

<p>A variety of intriguing surface patterns have been observed on developing natural systems, ranging from corrugated surface of white blood cells at nanometer scales to wrinkled dog skins at millimeter scales. To mimetically harness functionalities of natural morphologies, artificial transformative skin systems by using soft active materials have been rationally designed to generate versatile patterns for a variety of engineering applications. The study of the mechanics and design of these dynamic surface patterns on soft active materials are both physically interesting and technologically important. </p><p>This dissertation starts with studying abundant surface patterns in Nature by constructing a unified phase diagram of surface instabilities on soft materials with minimum numbers of physical parameters. Guided by this integrated phase diagram, an electroactive system is designed to investigate a variety of electrically-induced surface instabilities of elastomers, including electro-creasing, electro-cratering, electro-wrinkling and electro-cavitation. Combing experimental, theoretical and computational methods, the initiation, evolution and transition of these instabilities are analyzed. To apply these dynamic surface instabilities to serving engineering and biology, new techniques of Dynamic Electrostatic Lithography and electroactive anti-biofouling are demonstrated.</p> / Dissertation

This thesis focuses on the surface patterning by using nanoporous block copolymer (BCP) stamps. Polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) was used as model BCP. Nanoporous BCP stamps were fabricated by replication of lithographically patterned silicon molds. Nanopores inside of BCP stamps were generated by swelling‐induced pore formation. A method for scanner-based capillary stamping (SCS) with spongy nanoporous BCP stamps was developed. First, in the course of stamps design using replication molding of PS-b-P2VP against surface-modified macroporous silicon molds, PS-b-P2VP fiber rings remaining on the macroporous silicon molds were obtained that allow immobilization of water drops on the hydrophobically modified surfaces of the macroporous silicon molds. Water drops immobilized by these rings can be prevented from dewetting within the PS‐b‐P2VP fiber rings. Second, after spongy nanoporous PS-b-P2VP stamps had been obtained, preliminary experiments with non-inked PS-b-P2VP stamps revealed that parts of the stamps’ contact elements can be lithographically transferred onto counterpart surfaces. As a result, arrays of nanostructured submicron PS‐b‐P2VP dots with heights of ∼100 nm onto silicon wafers and glass slides were produced. Lastly, the SCS technique was developed, which overcomes the limitation of time-consuming re-inking procedures associated with classical soft lithography including microcontact printing (µCP) and polymer pen lithography (PPL) with solid stamps, as well as the limitations regarding throughput of scanning probe‐based serial writing approaches such as nanoscale dispensing (NADIS) and other micropipetting techniques. In addition, sizes of stamped droplets can be controlled by adjusting surface wettability and dwell time.