Non-contact femtosecond laser-based methods for investigating glass mechanics at small scales

With the progress made in miniaturizing systems over the last decades, understanding materialsâ behavior at small scales has become a necessity. In this context, glass behavior has remained largely unknown, partly for technological reasons and partly due to the inherent difficulties associated with its brittle fracture behavior. Despite their importance for technological implementation, questions such as its failure statistics or its behavior under constant load remain unanswered. This thesis aims at filling the gap of the available methodologies and instrumentation for the mechanical testing of glass at the micro-/nano- scale. Until recently, suitable methods for manufacturing arbitrary shapes in glass were missing, hampering the implementation of appropriate testing methods. Fortunately, recent progress in the field of femtosecond laser processing has opened new opportunities for designing specific tools adapted to the investigation of glass micromechanics. In addition, the careful observation of nanoscale self-organization processes taking place during laser exposure offers a novel means for observing fracture statistical behavior. Here, we use this novel glass processing method to introduce two novel experimental approaches: one based on novel concept of contactless micro-/nano-monolithic tensile tester, and a second one, based on statistical observations of an intermittent behavior occurring during laser exposure. Using these two approaches, we are able not only to load the material to unprecedented high level of stress and this, in a pure tensile mode, but also to study stress relaxation effects and finally, to explore its fracture statistical behavior. From the technology development perspective, this thesis offers an experimental framework for contactless testing of glass materials that, in particular for silica, set guidelines for microsystems designers. In parallel, this work demonstrates the use of unconventional methods, inherited from other scientific disciplines, as a means for extracting relevant brittle fracture parameters, usually difficult to obtain at the microscale and requiring extensive numbers of experiments

A Monolithic Micro-Tensile Tester for Investigating Silicon Dioxide Polymorph Micromechanics, Fabricated and Operated Using a Femtosecond Laser

Mechanical testing of materials at the microscales is challenging. It requires delicate procedures not only for producing and handling the specimen to be tested, but also for applying an accurate and controlled force. This endeavor is even more challenging when it comes to investigating the behavior of brittle materials such as glass. Here, we present a microtensile tester for investigating silica glass polymorphs. The instrument is entirely made of silica and for which the same femtosecond laser is not only used for fabricating the device, but also for operating it (loading the specimen) as well as for performing in situ measurements. As a proof-of-concept, we present a stress-strain curve of fused silica for unprecedented high tensile stress of 2.4 GPa, as well as preliminary results of the elastic modulus of femtosecond laser-affected zones of fused silica, providing new insights on their microstructures and mechanical behavior

Femtosecond laser direct-write waveplates based on stress-induced birefringence

The use of femtosecond lasers to introduce controlled stress states has recently been demonstrated in silica glass. We use this technique, in combination with chemical etching, to generate and control stress-induced birefringence over a well-defined region of interest, demonstrating direct-write wave plates with precisely tailored retardance levels. This tailoring enables the fabrication of laser-written polarization optics that can be tuned to any wavelength for which silica is transparent and with a clear aperture free of any laser modifications. Using this approach, we achieve sufficient retardance to act as a quarter-wave plate. The stress distribution within the clear aperture is analyzed and modeled, providing a generic template that can be used as a set of design rules for laser-machined polarization devices.Comment: 14 pages, 8 figures Revised version, with updated title and abstract to reflect use of stress-induced birefringence. Sections 4.1 and 4.3 also updated (1D and 2D model) with more accurate descriptions of stressor region and to correct an implementation error in the 2D mode

CO2 laser polishing of microfluidic channels fabricated by femtosecond laser assisted carving

In this study, we investigate the effects of CO2 laser polishing on microscopic structures fabricated by femtosecond laser assisted carving (FLAC). FLAC is the peripheral laser irradiation of 2.5D structures suitable for low repetition rate lasers and is first used to define the microwell structures in fused silica followed by chemical etching. Subsequently, the bottom surface of patterned microwells is irradiated with a pulsed CO2 laser. The surfaces were characterized using an atomic force microscope (AFM) and scanning electron microscope (SEM) in terms of roughness and high quality optical imaging before and after the CO2 laser treatment. The AFM measurements show that the surface roughness improves more than threefold after CO2 laser polishing, which promises good channel quality for applications that require optical imaging. In order to demonstrate the ability of this method to produce low surface roughness systems, we have fabricated a microfluidic channel. The channel is filled with polystyrene bead-laden fluid and imaged with transmission mode microscopy. The high quality optical images prove CO2 laser processing as a practical method to reduce the surface roughness of microfluidic channels fabricated by femtosecond laser irradiation. We further compared the traditional and laser-based glass micromachining approaches, which includes FLAC followed by the CO2 polishing technique. � 2016 IOP Publishing Ltd

Hybrid Nanosecond Laser Processing and Heat Treatment for Rapid Preparation of Super-Hydrophobic Copper Surface

The super-hydrophobic copper surface was obtained by using a nanosecond pulsed laser. Different micro- and nano-structures were fabricated by changing the laser scanning interval and scanning speed, before heating in an electric heater at 150 °C for two hours to explore the effect of laser parameters and heat treatment on the wettability of the copper surface. It was found that the laser-treated copper surface is super-hydrophilic, and then, after the heat treatment, the surface switches to hydrophobic or even super-hydrophobic. The best super-hydrophobic surface’s apparent contact angle (APCA) was 155.6°, and the water sliding angle (WSA) was 4°. Super-hydrophobic copper is corrosion-resistant, self-cleaning, and dust-proof, and can be widely used in various mechanical devices

A Monolithic Micro-Tensile Tester for Investigating Silicon Dioxide Polymorph Micromechanics, Fabricated and Operated Using a Femtosecond Laser

The authors would like to make the following changes to the published paper [1]: Equation (5) should be written as follows:[...

Microscopy Conference 2017 (MC 2017) - Proceedings

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

Microscopy Conference 2017 (MC 2017) - Proceedings

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2017", die vom 21. bis 25.08.2017, in Lausanne stattfand

MC 2019 Berlin Microscopy Conference - Abstracts

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2019", die vom 01. bis 05.09.2019, in Berlin stattfand