MICROCANTILEVER-BASED FORCE SENSING, CONTROL AND IMAGING

This dissertation presents a distributed-parameters base modeling framework for microcantilever (MC)-based force sensing and control with applications to nanomanipulation and imaging. Due to the widespread applications of MCs in nanoscale force sensing or atomic force microscopy with nano-Newton to pico-Newton force measurement requirements, precise modeling of the involved MCs is essential. Along this line, a distributed-parameters modeling framework is proposed which is followed by a modified robust controller with perturbation estimation to target the problem of delay in nanoscale imaging and manipulation. It is shown that the proposed nonlinear model-based controller can stabilize such nanomanipulation process in a very short time compared to available conventional methods. Such modeling and control development could pave the pathway towards MC-based manipulation and positioning. The first application of the MC-based (a piezoresistive MC) force sensors in this dissertation includes MC-based mass sensing with applications to biological species detection. MC-based sensing has recently attracted extensive interest in many chemical and biological applications due to its sensitivity, extreme applicability and low cost. By measuring the stiffness of MCs experimentally, the effect of adsorption of target molecules can be quantified. To measure MC\u27s stiffness, an in-house nanoscale force sensing setup is designed and fabricated which utilizes a piezoresistive MC to measure the force acting on the MC\u27s tip with nano-Newton resolution. In the second application, the proposed MC-based force sensor is utilized to achieve a fast-scan laser-free Atomic Force Microscopy (AFM). Tracking control of piezoelectric actuators in various applications including scanning probe microscopes is limited by sudden step discontinuities within time-varying continuous trajectories. For this, a switching control strategy is proposed for effective tracking of such discontinuous trajectories. A new spiral path planning is also proposed here which improves scanning rate of the AFM. Implementation of the proposed modeling and controller in a laser-free AFM setup yields high quality image of surfaces with stepped topographies at frequencies up to 30 Hz. As the last application of the MC-based force sensors, a nanomanipulator named here MM3A® is utilized for nanomanipulation purposes. The area of control and manipulation at the nanoscale has recently received widespread attention in different technologies such as fabricating electronic chipsets, testing and assembly of MEMS and NEMS, micro-injection and manipulation of chromosomes and genes. To overcome the lack of position sensor on this particular manipulator, a fused vision force feedback robust controller is proposed. The effects of utilization of the image and force feedbacks are individually discussed and analyzed for use in the developed fused vision force feedback control framework in order to achieve ultra precise positioning and optimal performance

Nanomanipulation and In-situ Transport Measurements on Carbon Nanotubes

With the advent of microelectronics and micromechanical systems, the benefits of miniaturized technology became evident. With the discovery of carbon nanotubes by Iijima in 1991, a material has been found that offers superior porperties such as high tensile strength, excellent electrical and heat conductivity while being lightweight, flexible and tunable by the specific atomic arrangement in its structure. The first part of this thesis deals with a new synthesis approach, which combines the known routes of chemical vapour deposition and laser ablation. The results concerning diameter and yield fit well within an established model for the nucleation and growth of carbon nanotubes and extend it by considering a larger parameter space. Furthermore, conventional laser ablation has been used to synthesize C-13 augmented carbon nanotubes, whose diameters depend among the usual synthesis parameters also on the C-13 content, an influence which is in line with the changed thermal conductivities of isotope mixtures. Manipulation of carbon nanotubes inside a transmission electron microscope forms the second part of this thesis. With the help of an in-situ nanomanipulator, several experiments involving the mechanical and electrical properties of carbon nanotubes have been performed. Two-probe resistances of individual nanotubes have been measured and the observation of individual shell failures allowed for the determination of current limits per carbon shell. With the help of electrical current, a nanotube was modified in its electrical characteristics by reshaping its structure. By application of DC-currents or square current pulses, the filling of iron- or cementite-filled multi-wall carbon nanotubes has been found to move in a polarity-defined direction guided by the nanotube walls. Depending on the current, nanotube shape, and composition of the filling different regimes of material transport have been identified, including the reworking of the inner nanotube shells. The application of a high driving current leads to a complete reworking of the host nanotube and the current-induced growth of carbonaceous nanostructures of changed morphology. Utilizing the obtained results, a transport mechanism involving momentum transfer from the electron wind to the filling atoms and a solid filling core during transport is developed and discussed. Finally, measurements of mechanical properties using electrically induced resonant or non-resonant vibrations inside the transmission electron microscope have been observed and important mechanical parameters have been determined with the help of a modified Euler-Bernoulli-beam approach.Mit dem Aufkommen von Mikroelektronik und mikromechanischen Systemen wurden die Vorteile miniaturisierter Geräte augenscheinlich. Mit der Entdeckung von Kohlenstoff-Nanoröhren durch Iijima 1991 wurde ein Material gefunden, welches überlegene Eigenschaften wie hohe Festigkeit, exzellente elektrische und Wärmeleitfähigkeit zeigt, während es zeitgleich leicht und flexibel ist. Diese Eigentschaften können durch eine Änderung der spezifischen atomaren Anordnung in der Nanoröhrenhülle beeinflusst werden. Der erste Teil dieser Dissertationsschrift behandelt einen neuartigen Syntheseansatz, welche die bekannten Syntheserouten der chemischen Gasphasenabscheidung und Laserablation kombiniert. Die Ergebnisse bezüglich des Durchmessers und der Ausbeute lassen sich gut mit einem etablierten Modell der Nukleation und des Wachstums von Kohlenstoff-Nanoröhren beschreiben - sie erweitern es, indem sie einen größeren Parameterraum berücksichtigen. Des Weiteren wurde konventionelle Laserablation benutzt, um C-13 angereicherte Kohlenstoff-Nanoröhren herzustellen, deren Durchmesser nicht nur von den üblichen Parametern, sondern auch vom C-13 Anteil abhängt. Diese Abhängigkeit geht mit der veränderten thermischen Leitfähigkeit von Isotopenmischungen einher. Die Manipulation von Kohlenstoff-Nanoröhren in einem Transmission-Elektronenmikroskop formt den zweiten Teil der Dissertationschrift. Mit Hilfe eines in-situ Manipulators wurden vielfältige Experimente durchgeführt, um die mechanischen und elektrischen Eigenschaften der Kohlenstoff-Nanoröhren zu bestimmen. Zweipunktmessungen des Widerstands einzelner Nanoröhren und die Beobachtung des Versagens einzelner Kohlenstoffschichten erlaubte die Bestimmung der Stromtragfähigkeit einzelner Hüllen. Mit Hilfe eines elektrischen Stromes konnte eine Nanoröhre durch die veränderung der Struktur in ihren elektrischen Eigenschaften verändert werden. Unter Verwendung dauerhaften oder gepulsten Gleichstroms konnte die Eisen- oder Zementit-Füllung der Kohlenstoff-Nanoröhren in eine polaritätsabhängige Richtung bewegt werden. Die Füllung wurde dabei durch die Wände der Nanoröhre geführt. Abhängig von Strom, Form der Nanoröhre und Zusammensetzung der Füllung ließen sich verschiedene Bereiche des Materialtransports identifizieren, u.a. das Umarbeiten einiger innerer Kohlenstoffschichten. Ein hoher Strom hingegen bewirkt eine Umarbeitung der kompletten Nanoröhre und strominduziertes Wachstum von Kohlenstoff-Nanostrukturen mit veränderter Morphologie. Mit Hilfe der gewonnenen Resultate wurde ein Transportmodell entwickelt, welches den Impulstransfer von Elektronen an Füllungsatome sowie einen festen Füllungskern während des Transports diskutiert. Messungen der mechanischen Eigenschaften, welche mit Hilfe von resonanter oder nicht-resonanter elektrischer Anregung von Schwingungen im Transmissions-Elektronenmikroskop durchgeführt wurden bilden den Abschluss der Arbeit. Durch die Beobachtungen konnten mit einem modifizierten Euler-Bernoulli-Balkenmodell wichtige mechanische Eigenschaften bestimmt werden

Cutting Edge Nanotechnology

The main purpose of this book is to describe important issues in various types of devices ranging from conventional transistors (opening chapters of the book) to molecular electronic devices whose fabrication and operation is discussed in the last few chapters of the book. As such, this book can serve as a guide for identifications of important areas of research in micro, nano and molecular electronics. We deeply acknowledge valuable contributions that each of the authors made in writing these excellent chapters

Nanotribology of metallic glasses in corrosive environments

Metallic glasses (MGs) are promising materials for micromechanical systems, where miniaturized components involving mechanical contact require control of friction. Nanotribological experiments on MGs in corrosive aqueous solutions are carried out using atomic force microscopy (AFM), focusing on the role of surface oxide films formed during corrosion. A new method is developed to study in situ the structure of surface oxide films. The surface oxide film has a bilayer structure as revealed by repeated scanning with the AFM tip. The dependence of friction on electrochemical potential reveals the growth mechanism of the oxide film. Friction and adhesion after different immersion times in different solutions allow to compare the physicochemical processes of surface dissolution at the interfaces of the two layers of surface films and elucidate their influence on friction. An irregular atomic-scale stick-slip friction is observed and attributed to the amorphous nature of corroded surfaces. Finally, we show three different friction processes occurring at increasing normal loads: removal of the dissolution layer at low-load regime; stress-assisted tribo-oxidation in intermediate-load regime; and tribochemical wear in high-load regime. The chemical sensitivity of nanotribology studies demonstrates a novel route to explore fundamental mechanisms of corrosion at the microscopic scale.Metallische Gläser (MG) sind vielversprechende Materialien für mikromechanische Systeme, in denen der mechanische Kontakt eine Kontrolle über Reibung erfordert. Mit Hilfe der Rasterkraftmikroskopie (AFM) wurden nanotribologische Experimente auf MG in korrosiven wässrigen Lösungen durchgeführt, wobei die Rolle von Oxidfilmen im Fokus stand. Eine neuartige Methode für die in situ-Untersuchung der Struktur der Oberflächenoxidfilme wurde entwickelt. Der Oberflächenoxidfilm weist eine zweilagige Struktur auf, die durch wiederholtes Rastern mit der AFM-Spitze nachgewiesen wurde. Die Abhängigkeit der Reibung vom elektrochemischen Potential zeigt die Wachstumsmechanismen der Oxidfilme an. Reibung und Adhäsion nach verschieden langer Immersion erlauben den Vergleich der physikochemischen Prozesse der Oberflächenauflösung an der Grenzfläche der beiden Lagen. Es wurde eine unregelmäßige stick-slip Reibung auf atomarer Skala beobachtet und auf die amorphe Natur der korrodierten Oberflächen zurückgeführt. Schließlich beschreiben wir drei verschiedene Reibungsprozesse, die mit zunehmender Normalkraft auftreten: die Abtragung der abgeschiedenen Lage bei niedrigen Auflagekräften, eine durch mechanische Spannung unterstützte Tribo-Oxidation bei mittleren Kräften sowie tribochemischen Verschleiß bei hohen Kräften. Die chemische Empfindlichkeit der nanotribologischen Studien zeigt eine neue Möglichkeit auf, grundsätzliche Mechanismen der Korrosion auf der mikroskopischen Skala zu erforschen

Ald processes development for hybrid nanodevices-like nanostructures

194 p.The development of new and innovative atomic structures displaying multifunctional properties goes together with progress in advanced processes which enable atomic level control. One leading deposition technique is Atomic layer deposition (ALD), which has emerged as a powerful tool for bond-specific functionalization and the growth of stoichiometric films over wafer scale and high area uniformity. ALD offers a wide range of functionalization routes by means of four processes such as vapor phase metalation (VPM), multiple pulsed vapor-phase infiltration (MPI), ALD and molecular layer deposition (MLD). As an example of VPM on soft molecules, Zn metalation on Enterobactin (H6EB) and FeEnterobactin (FeH3EB) were studied experimentally and theoretically. Thus, we showed that the VPM process could become a route to functionalize soft organic molecules with potential applications in the pharmaceutical field. Extending Zn metalation-VPM growth to hybrid nanostructures, in this case ML-(NH4)V7O16. nanostructured square and Mw-H2Ti3O7 nanotubes. Zn metalation-VPM process provides a way to functionalize soft nanostructured materials in order to change their crystal structure and thereby their magnetic and optical properties, without affect their morphology. The use of DEZn/H2O in MPI, promotes the nucleation of ZnO nanoparticles around the nanotube (cactus-like) affecting the morphology and surface properties. It was found that the electronic energy gap decreases with increasing Zn content, making the (ZnO)Ti3O7 nanoparticle/nanotube nanocomposites potentially useful as photoanode for dye-sensitized solar cells (DSCs) and sensors. The ALD growth of uniform MxOy thin films where M stands for V, Mn, Sn or Zn was undertaken. The preliminary results show successful deposition of ¿-MnO2, ¿-V2O5, SnxOy and ZnO stoichiometric films, uniform over large areas. This points towards the possible growth of these oxides which can be considered as energy materials. Finally, the growth of alucone thin films (AlO-T and AlO-A, T: terephthalate and A: adipate) by ALD and MLD was explored. Stoichiometric thin films with large area uniformity were obtained in both cases. The use of bifunctional monomers (aromatic and aliphatic carboxylate) in the growth of AlO-T and AlO-A thin films leads to a lamellar phase and to an amorphous one, respectively. The structure of AlO-T is obtained by optimizing four models and correlating experimental data with DFT calculations. The analysis of the electronic band gap using frontier orbital (HOMO-LUMO), alongside the uniform LiPF6 distribution through the AlO-T, point to future studies of AlO-T for anode and electrolyte nanomembranes with potential applications in carboxylates-based energy storage concepts. Thus, in this thesis we have shown the versatility of ALD processes to realize novel thin films and pursue various functionalization strategies

Ald processes development for hybrid nanodevices-like nanostructures

194 p.The development of new and innovative atomic structures displaying multifunctional properties goes together with progress in advanced processes which enable atomic level control. One leading deposition technique is Atomic layer deposition (ALD), which has emerged as a powerful tool for bond-specific functionalization and the growth of stoichiometric films over wafer scale and high area uniformity. ALD offers a wide range of functionalization routes by means of four processes such as vapor phase metalation (VPM), multiple pulsed vapor-phase infiltration (MPI), ALD and molecular layer deposition (MLD). As an example of VPM on soft molecules, Zn metalation on Enterobactin (H6EB) and FeEnterobactin (FeH3EB) were studied experimentally and theoretically. Thus, we showed that the VPM process could become a route to functionalize soft organic molecules with potential applications in the pharmaceutical field. Extending Zn metalation-VPM growth to hybrid nanostructures, in this case ML-(NH4)V7O16. nanostructured square and Mw-H2Ti3O7 nanotubes. Zn metalation-VPM process provides a way to functionalize soft nanostructured materials in order to change their crystal structure and thereby their magnetic and optical properties, without affect their morphology. The use of DEZn/H2O in MPI, promotes the nucleation of ZnO nanoparticles around the nanotube (cactus-like) affecting the morphology and surface properties. It was found that the electronic energy gap decreases with increasing Zn content, making the (ZnO)Ti3O7 nanoparticle/nanotube nanocomposites potentially useful as photoanode for dye-sensitized solar cells (DSCs) and sensors. The ALD growth of uniform MxOy thin films where M stands for V, Mn, Sn or Zn was undertaken. The preliminary results show successful deposition of ¿-MnO2, ¿-V2O5, SnxOy and ZnO stoichiometric films, uniform over large areas. This points towards the possible growth of these oxides which can be considered as energy materials. Finally, the growth of alucone thin films (AlO-T and AlO-A, T: terephthalate and A: adipate) by ALD and MLD was explored. Stoichiometric thin films with large area uniformity were obtained in both cases. The use of bifunctional monomers (aromatic and aliphatic carboxylate) in the growth of AlO-T and AlO-A thin films leads to a lamellar phase and to an amorphous one, respectively. The structure of AlO-T is obtained by optimizing four models and correlating experimental data with DFT calculations. The analysis of the electronic band gap using frontier orbital (HOMO-LUMO), alongside the uniform LiPF6 distribution through the AlO-T, point to future studies of AlO-T for anode and electrolyte nanomembranes with potential applications in carboxylates-based energy storage concepts. Thus, in this thesis we have shown the versatility of ALD processes to realize novel thin films and pursue various functionalization strategies

Simultaneous Fluorescence and Atomic Force Microscopy to study Mechanically-Induced Bacterial Death in Real Time

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de la Materia Condensada. Fecha de lectura: 18-09-2020In the last decades, advanced imaging techniques have improved our ability to analyze biological systems at the micro and nanoscale, and in real time. Microscopy techniques have their own strengths and limitations, so their combination has the potential to provide a more comprehensive understanding of biological processes. This thesis is focused on the development and application of simultaneous fluorescence and atomic force microscopy (AFM) to study mechanically-induced bacterial death. The results reported here provide a quantitative understanding of the mechanical interactions between the AFM tip and bacteria, in the context of emerging mechano-bactericidal nanomaterials. This manuscript is divided into six chapters and one appendix. Chapter 1 provides an overview of the bacterial world and the strategies used over the years to combat the increasing bacterial contamination of surfaces, emphasizing the recent strategy based on mechanical damage. It also describes the microscopy techniques used, highlighting the strengths and weaknesses of each one, and discussing why correlative microscopy is more suitable to study this kind of processes. Chapter 2 describes the general materials and methods applied in this thesis and the software used to analyze experimental data. Chapter 3 provides the groundwork to develop a methodology to successfully combine AFM nanoindentation and fluorescence microscopy simultaneously using fluorescent polymer beads, focusing on the challenges that may arise when simultaneous measurements are performed. In Chapter 4, the methodology was adapted to image bacteria in physiological conditions, and optimal protocols to perform reproducible experiments on living bacteria were found. This optimized methodology in combination with a fluorescent cell membrane integrity marker was successfully applied to quantify the forces needed to rupture the bacterial cell wall. Moreover, a correlation between the forces exerted on bacteria and the kinetics of the fluorescence response is found. Chapter 4 is complemented by Appendix A, which provides the mechanical characterization of the bacterial wall below the rupture point, in order to give a more complete overview of the mechanical properties of the bacterial surface. Chapter 5 explores a different method to assess bacterial viability upon nanoindentation by monitoring the oscillation of the Min system, which reflects bacterial physiology. This method reveals that forces below the breakage point of the cell wall produce a fatigue effect, and provides a quantitative framework to understand low force collisions between bacteria and nanomaterials. These experiments also emphasize the limitation of integrity markers to provide a comprehensive view of bacterial response. The aim of Chapter 6 is to provide coherence and perspective to the main results of the thesis, as well as an outlook on how advanced microscopy methods and future experiments may impact the study of interactions between bacteria and nanotopographical features in the context of mechano-bactericidal nanomaterial