This dissertation presents and explores a technique to confine and manipulate single and multiple nano-objects in solution by exploiting the thermophoretic interactions with local temperature gradients. The method named thermophoretic trap uses an all-optically controlled heating via plasmonic absorption by a gold nano-structure designed for this purpose. The dissipation of absorbed laser light to thermal energy generates a localized temperature field. The spatial localization of the heat source thereby leads to strong temperature gradients that are used to drive a particle or molecule into a desired direction. The behavior of nano-objects confined by thermal inhomogeneities is explored experimentally as well as theoretically. The monograph treats three major experimental stages of development, which essentially differ in the way the heating laser beam is shaped and controlled. In a first generation, a static heating of an appropriate gold structure is used to induce a steady temperature profile that exhibits a local minimum in which particles can be confined. This simple realization illustrates the working principle best. In a second step, the static heating is replaced. A focused laser beam is used to heat a smaller spatial region. In order to confine a particle, the beam is steered in circles along a circular gold structure. The trapping dynamics are studied in detail and reveal similarities to the well-established Paul trap. The largest part of the thesis is dedicated to the third generation of the trap. While the hardware is identical to the second generation, using the real-time information on the position of the trapped object to heat only particular sites of the gold structure strongly increases the efficiency of the trap compared to the earlier versions. Beyond that, the optical feedback control allows for an active shaping of the effective virtual trapping potential by applying modified feedback rules, including e.g. a double-well or a box-like potential. This transforms the formerly pure trapping device to a versatile technique for micro and nano-fluidic manipulation. The physical and technical contributions to the limits of the method are explored. Finally, the feasibility of trapping single macro-molecules is demonstrated by the confinement of lambda-DNA for extended time periods over which the molecules center-of-mass motion as well as its conformational dynamics can be studied.

The main subject of this thesis is to examine thermo-osmotic flows, which occur on interfaces of non-uniform temperature. Such thermo-osmotic flows are purely non-thermal equilibrium phenomena. Along the non-isothermal interface, specific interaction of a liquid and its solutes with a boundary vary in strength across the interface, according to the local temperature. This boundary can be a solid, a membrane or a phase boundary. The flow is thereby continuously pumping fluid across the interface in direction of the local temperature gradient, resulting in an extended flow pattern in the bulk due to mass conservation. In a system containing particles and heat sources in a liquid under spatial confinement, the thermo-osmotic flow may drive particles in a directed manner, or can lead to collective phenomena. To approach this broad topic of (self-)thermophoresis and collective motion of active particles and quantify the role of the thermo-osmotic flow upon the latter effects, different experiments have been performed: The first experiments aim to quantify the thermo-osmotic flow at a non-isothermal liquid/solid interface for two fundamentally different substrate properties. Further, the bulk flow was investigated for two different systems. The form and spatial extension of this bulk flow pattern depends sensitively on the form of the container and the interface, as well as on the thermo-osmotic flow. The first system is a liquid film confined between two planar glass cover slips. The second case is a Janus particle immobilized on one of the glass slips. In the first case, the non-uniform temperature profile is generated by optical heating of a nanometer sized gold colloid, and in the second case, the heat source is the Janus particle. The bulk flow pattern consists, for the second case, of the flow pattern created by the glass cover slips and the one created by the Janus particle. The following experiments are focusing on the dynamics of mobile self-thermophoretic Janus particles. In particular, their dynamics and the contributions of the thermo-osmotic flow to the interaction of multiple active particles are investigated. To investigate those particles under controlled conditions and examine their interactions at low concentrations for an effectively unlimited amount of time, a real-time feedback algorithm was co-developed to gain control of the motion of multiple active particles simultaneously, called ”photon nudging”. With the help of this method, first experiments have been performed to quantify the dynamics of a Janus particle located close to a heat source.

No description available.

This dissertation presents and explores a technique to confine and manipulate single and multiple nano-objects in solution by exploiting the thermophoretic interactions with local temperature gradients. The method named thermophoretic trap uses an all-optically controlled heating via plasmonic absorption by a gold nano-structure designed for this purpose. The dissipation of absorbed laser light to thermal energy generates a localized temperature field. The spatial localization of the heat source thereby leads to strong temperature gradients that are used to drive a particle or molecule into a desired direction. The behavior of nano-objects confined by thermal inhomogeneities is explored experimentally as well as theoretically. The monograph treats three major experimental stages of development, which essentially differ in the way the heating laser beam is shaped and controlled. In a first generation, a static heating of an appropriate gold structure is used to induce a steady temperature profile that exhibits a local minimum in which particles can be confined. This simple realization illustrates the working principle best. In a second step, the static heating is replaced. A focused laser beam is used to heat a smaller spatial region. In order to confine a particle, the beam is steered in circles along a circular gold structure. The trapping dynamics are studied in detail and reveal similarities to the well-established Paul trap. The largest part of the thesis is dedicated to the third generation of the trap. While the hardware is identical to the second generation, using the real-time information on the position of the trapped object to heat only particular sites of the gold structure strongly increases the efficiency of the trap compared to the earlier versions. Beyond that, the optical feedback control allows for an active shaping of the effective virtual trapping potential by applying modified feedback rules, including e.g. a double-well or a box-like potential. This transforms the formerly pure trapping device to a versatile technique for micro and nano-fluidic manipulation. The physical and technical contributions to the limits of the method are explored. Finally, the feasibility of trapping single macro-molecules is demonstrated by the confinement of lambda-DNA for extended time periods over which the molecules center-of-mass motion as well as its conformational dynamics can be studied.

Das Influenza A Virus (IAV) stellt weltweit eine ernstzunehmende Bedrohung für Gesundheit und Wirtschaft der Menschheit dar. Ein universeller und langanhaltender Impfstoff konnte noch nicht entwickelt werden und klinisch zugelassene Medikamente verlieren durch die rasante Entstehung von resistenten Stämmen zunehmend ihre Wirkung. Aus diesem Grund gewinnt die Erforschung neuer antiviraler Strategien zur Bekämpfung des Influenzavirus an Bedeutung zum Schutze unserer Gesellschaft. Eine vielversprechende Zielstruktur für die Entwicklung neuer antiviraler Medikamente stellt das virale Hämagglutinin (HA) dar. Das HA liegt in hoher Dichte auf Influenzaviren vor und ermöglicht die Bindung an Sialinsäuren (SA) auf Wirtszellen und die Verschmelzung mit deren Lipidmembran. HA-bindende Moleküle entfalten eine hemmende Wirkung bereits bei dem ersten Kontakt mit Zellen, sodass eine Infektion erst gar nicht stattfinden kann. Aufgrund einer hohen HA-Dichte auf der Virusoberfläche eignen sich besonders multivalente SA tragende Nanopartikel für die Hemmung einer viralen Infektion. Aufbauend auf diesen Erkenntnissen, wurden in der vorliegenden Arbeit neue multivalente Binder gegenüber dem viralen Hämagglutinin (HA) entwickelt und studiert. Im Gegensatz zu bereits bekannten multivalenten Sialosiden, die in einer undefinierten räumlichen Orientierung auf Polymergerüsten präsentiert wurden, konnten in der vorliegenden Arbeit strukturelle Aspekte identifiziert werden, um Gerüstsysteme mit optimaler Rezeptorpräsentation gegenüber der Influenza A Virusoberfläche zu generieren. Neben SA-basierten Polymersystemen wurde auch ein gegen HA gerichtetes Peptid aus einem Antikörper identifiziert, welches sich auch für eine multivalente Interaktion mit IAV eignet. Diese Arbeit ermöglicht neue Einblicke in die Auswahl geeigneter Trägersysteme, eines optimalen Rezeptorabstandes und der Verwendung alternativer Rezeptoren mit dem Ziel einer Infektionshemmung von IAV. / Influenza A virus (IAV) still poses a serious threat to global health and economy of mankind. So far, a universal, long-lasting vaccine could not be developed, and clinically approved drugs are prone to lose activity due to the fast development of resistant strains. Because of this, research on new antiviral compounds and strategies to combat influenza viruses is of great importance for the protection of our society. A promising candidate for the development of novel antiviral drugs is the viral hemagglutinin (HA) protein. HA is present at high density on the viral envelope, which allows binding to sialic acid (SA) molecules on host cells and fusion with their membrane. Following, HA binding molecules have an inhibitory effect at the very first step of the infection cycle, leading to the inability of an infection. Based on a high HA density on the viral surface, SA carrying nanoparticles qualify for the inhibition of a viral infection. Based on this knowledge the study at hand demonstrates the development of new multivalent binders against viral HA and discusses them critically. In contrast to published multivalent sialosides, which are displayed in an undefined fashion on polymer scaffolds, the results of this thesis support the identification of structural requirements for the design of new scaffold systems with an optimal match to the viral surface. Beside sialoside based polymer systems, completely new peptide based systems, based on an HA binding antibody, were developed. Similar to polyglycerolsialosides, such multivalent peptide-decorated polymers were able to achieve nanomolar binding inhibition constants, too. In summary, this thesis enables new insights into the choice of a suitable carrier system, the optimal receptor spacing, and the use of alternative receptors with the ultimate goal of virus neutralization.

The main subject of this thesis is to examine thermo-osmotic flows, which occur on interfaces of non-uniform temperature. Such thermo-osmotic flows are purely non-thermal equilibrium phenomena. Along the non-isothermal interface, specific interaction of a liquid and its solutes with a boundary vary in strength across the interface, according to the local temperature. This boundary can be a solid, a membrane or a phase boundary. The flow is thereby continuously pumping fluid across the interface in direction of the local temperature gradient, resulting in an extended flow pattern in the bulk due to mass conservation. In a system containing particles and heat sources in a liquid under spatial confinement, the thermo-osmotic flow may drive particles in a directed manner, or can lead to collective phenomena. To approach this broad topic of (self-)thermophoresis and collective motion of active particles and quantify the role of the thermo-osmotic flow upon the latter effects, different experiments have been performed: The first experiments aim to quantify the thermo-osmotic flow at a non-isothermal liquid/solid interface for two fundamentally different substrate properties. Further, the bulk flow was investigated for two different systems. The form and spatial extension of this bulk flow pattern depends sensitively on the form of the container and the interface, as well as on the thermo-osmotic flow. The first system is a liquid film confined between two planar glass cover slips. The second case is a Janus particle immobilized on one of the glass slips. In the first case, the non-uniform temperature profile is generated by optical heating of a nanometer sized gold colloid, and in the second case, the heat source is the Janus particle. The bulk flow pattern consists, for the second case, of the flow pattern created by the glass cover slips and the one created by the Janus particle. The following experiments are focusing on the dynamics of mobile self-thermophoretic Janus particles. In particular, their dynamics and the contributions of the thermo-osmotic flow to the interaction of multiple active particles are investigated. To investigate those particles under controlled conditions and examine their interactions at low concentrations for an effectively unlimited amount of time, a real-time feedback algorithm was co-developed to gain control of the motion of multiple active particles simultaneously, called ”photon nudging”. With the help of this method, first experiments have been performed to quantify the dynamics of a Janus particle located close to a heat source.