| 1. |
- Enrico, Alessandro
(författare)
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Bright Lights: Innovative Micro- and Nano-Patterning for Sensing and Tissue Engineering
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Light is the primary source of energy on our planet and has been a significant driver in the evolution of human society and technology. Light finds applications in two-dimensional (2D) photolithography and three-dimensional (3D) printing, where a pattern is transferred to a material of interest by ultraviolet (UV) light exposure, and in laser scribing and cutting, where high power lasers are used to pattern the surface of objects or cut through the bulk of the material of interest. However, conventional light-based processing has three main constraints: a) the wavelength of visible light limits resolution, b) only materials that absorb the wavelength in use can be efficiently processed, and c) intense laser light burns its target, degrading the material surrounding the exposed areas and further limiting material compatibility. Overcoming these limitations is the core of this thesis.The first part of this thesis describes three different patterning methods enabled by intelligent design and non-linear light-matter interaction. The first work reports the use of light at 365 nm to generate sub-20 nm wide nanowires (NWs) exploiting crack lithography, exceeding the possible resolution given by diffraction limit by 10-fold. The second work describes how the non-linear interaction of femtosecond laser pulses with otherwise transparent glass enables nanostructuring of borosilicate coverslips. Positively charging the nanostructured glass surfaces grants a “attract and destroy” bactericidal functionality and maintains the transparency of the substrate, creating a microscopy compatible platform to study bacteria-surface interactions and providing strategies to fight antibiotic-resistant bacteria. The third and fourth works show how femtosecond lasers can directly pattern carbon nanotube films and 2D materials (graphene, molybdenum disulfide, and platinum diselenide) without damaging the substrate or the material surrounding the exposed area. Non-linear interaction with high-energy laser pulses allows sub-300 nm resolution, circumventing the limit given by light diffraction in the linear regime. The combination of high resolution, femtosecond exposure, and ultrafast scanning speed provides a valid alternative to resist-based photolithography while eliminating the related contamination issues for these sensitive materials.The second part of this thesis describes two different 3D micromachining approaches enabled by high-intensity laser light. The fifth work presents a collagen patterning method based on laser-induced cavitation, called cavitation molding. This method represents a new biomanufacturing mode that is neither additive nor subtractive. In this study, cavitation molding enables the generation of a micro vascularized cancer-on-chip model, consisting of an in-vivo-like spheroidal mass of cancer cells surrounded by artificial blood vessels. In the sixth and final work, we used two-photon polymerization to generate 3D platforms in a biocompatible resin. This platform enables the study of the physiology of neurons and their interaction with astrocyte cells. The low autofluorescence of the printed resins allows optical readout of the neuronal activity by calcium imaging.
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| 2. |
- Frank, Göran
(författare)
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Experimental Studies of the Interaction of Atmospheric Aerosol Particles with Clouds and Fogs
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this work, cloud and fog droplet formation was studied in three joint field experiments. The instrument, the droplet aerosol analyser (DAA), has also been further developed and verified as part of this work. The DAA is an instrument especially developed for studies of cloud and fog droplet formation and growth. It measures the ambient size of individual droplets and interstitial particles in a fog or a cloud. It then measures the size of the individual dry residual particles after evaporation of the water. It also counts the number of dry particles of each size, which gives a unique three-parameter data set that connects ambient size to dry size and to the number of particles. Having access to these parameters, a number of related aerosol/cloud parameters can be determined, whereof the microstructure, i.e. the size and number of droplets and their size distribution, characterisation of the droplet activation, as defined by the Köhler equation, and the size-dependent cloud droplet nucleation scavenging of particles due to activation, are the most important. The results from one fog experiment showed that, most of the time fog consisted of unactivated droplets with a continuous size distribution in the size region 1-47 µm in diameter. There were no gaps generated by the droplet activation process, as has been observed in clouds. In the two ground-based cloud experiments, cloud droplet number concentrations increased almost linearly with particle number concentration. Droplet concentrations of up to 2000 per cubic centimetre in an experiment in northern England and up to almost 3000 per cubic centimetre in an experiment on Tenerife, Spain, were observed, thus demonstrating the influence of air pollution on cloud microstructure.
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| 3. |
- Huang, Po-Han
(författare)
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Femtosecond Laser Microfabrication of Glasses and 2D Materials for Photonics and Energy Storage
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Femtosecond laser-based fabrication technologies have seen rapid developments in the past decades, thanks to the capability of femtosecond lasers to induce localized multiphoton absorption in materials. Multiphoton absorption can result in various material modifications that can be leveraged for additive and subtractive manufacturing. Their versatile applications have demonstrated the great potential of femtosecond lasers in advancing micro- and nano-fabrication. These include (1) multiphoton crosslinking enabling 3D printing with unprecedented patterning freedom and sub-micrometer resolution,(2) the formation of self-organized structures enabling the creation of multi-functional sub-wavelength patterns in solid materials, and (3) multiphoton ablation enabling precise sculpturing of wide-ranging materials. Nevertheless, there remains a large room to explore when it comes to available materials and achievable devices. This thesis aims to advance the applications of femtosecond lasers to glasses and 2D materials for the fabrication of advanced and integrated microdevices for photonics and energy storage. The first part of this thesis presents two approaches for 3D printing of inorganic glass. These approaches are based on two unusual observations in hydrogen silsesquioxane (HSQ) upon femtosecond laser exposure: (1) multiphoton crosslinking and (2) the formation of self-organized structures. The first work reports an approach for 3D printing of solid silica glass with sub-micrometer resolution by multiphoton crosslinking of HSQ. In contrast to the alternative methods, our approach does not require any thermal treatments, which offers desirable design fidelity and integration flexibility. The second work reports the possibility of inducing material modifications (1) and (2) in HSQ simultaneously. This possibility enables additive manufacturing of self-organized nanogratings, and thus, 3D printing of hierarchical structures made of Si-rich glass. In the third work, a protocol to perform the 3D printing on optical fiber tips is developed, which enables the fabrication of fiber-tip optical microdevices for sensing and beam shaping. The second part of this thesis presents the application of femtosecond lasers to fabricating on-paper microsupercapacitors (MSCs).MSCs are promising energy-storage microdevices for self-powering electronics, and paper substrates, yet vulnerable, are attractive for their sustainability and flexibility. The material and shape of MSCelectrodes play a crucial role in the energy-storage performance, and 2D materials have emerged as suitable candidate materials. In the last two works, a scalable approach for the precise micromachining of 2D-material electrodes by multiphoton ablation is developed, preserving their electrochemical performance and the integrity of the paper substrates.
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| 4. |
- Pagliano, Simone
(författare)
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Additive Manufacturing and Integration of 3D MEMS using Ultrafast Lasers and Magnetic Assembly
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The geometry of MEMS devices is limited by the technologies used to fabricate them. Today, microsystems are manufactured with patterning technologies that allow only for 2D and 2.5D geometries. These miniaturized devices are widely used in industry, including the automotive, electronics, and biomedical sectors, and their adoption in our society is expected to increaseeven further with the advance of the Internet of Things. 3D MEMS can contribute to this development enabling novel applications and improvedperformances, by exploiting more complex device geometries, and reducing device footprint, by integrating more functionalities onto smaller areas. In recent years, new technologies have been proposed to realize 3D microdevices by directly patterning 3D microstructures and by integrating together microchips manufactured with standard technologies. In this thesis, we develop 3D MEMS devices and fabrication technologies based on both paradigms using femtosecond laser micromachining and the magnetic assembly of tinychips.The first part of the thesis describes how laser micromachining with ultrashort pulses can be leveraged to achieve both additive and subtractive MEMS manufacturing. Two-photon polymerization of photosensitive resins enables additive manufacturing of 3D microstructures with sub-micron resolution. However, the kinds of devices, geometries, and materials that can be currently printed by two-photon polymerization are still limited, thus we set out to address some of these limitations. In the first work, we fabricate functional 3D printed accelerometers combining self-shadow masking features with directional metallization. In the second work, we demonstrate the realization of long overhanging structures (∼ 1mm) using the consecutive printing of short sections. In the third work, we 3D print polyimide, a high-performing polymer that can be used in harsh environments, where typical 3D printedpolymers are not suitable. Subtractive manufacturing by laser micromachining is demonstrated in the fourth work, where through-silicon-holes with high quality are formed using water-assisted drilling in a simple fabrication setup ,where the laser is focused on the front side of a silicon substrate and water is in contact with the backside.The second part of the thesis describes the integration of fragile and tiny MEMS devices coated with ferromagnetic thin films into silicon and polymeric substrates. The micromachined magnetized chips are integrated into receiving structures using permanent magnets. Magnetic interactions allow the non-contact handling and the vertical placement of chips at a scale and speed that is challenging for industry standard pick-&-place tools. In the fifth work, thin silicon chips for electrochemical sensing are magnetically assembled in vertical position and laterally wire bonded. In the sixth work, silicon micromachined spray nozzle chips with a diameter below 300 μm are magnetically assembled and sealed on acrylic sheets, to be used in portable soft mist inhalers.
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| 5. |
- Wang, Xiaojing
(författare)
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Heterogeneous Integration Technologies Based on Wafer Bonding and Wire Bonding for Micro and Nanosystems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heterogeneous integration realizes assembly and packaging of separately manufactured micro-components and novel functional nanomaterials onto the same substrate. It has been a key technology for advancing the discrete micro- and nano-electromechanical systems (MEMS/NEMS) devices and micro-electronic components towards cost-effective and space-efficient multi-functional units. However, challenges still remain, especially on scalable solutions to achieve heterogeneous integration using standard materials, processes, and tools. This thesis presents several integration and packaging methods that utilize conventional wafer bonding and wire bonding tools, to address scalable and high-throughput heterogeneous integration challenges for emerging applications.The first part of this thesis reports three large-scale packaging and integration technologies enabled by wafer bonding. Two low-temperature wafer-level vacuum packaging approaches are realized using narrow footprint metal-based sealing rings (Cu-Cu and Al-Au bonding, respectively). As Cu and Al are standard materials used in complementary metal-oxide-semiconductor (CMOS) wafers, these two methods can be used for system-on-chip (SoC) integration of vacuum packaged MEMS with CMOS circuits. Then, an integration method for transferring large-area 2D materials, including graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2), from their growth substrates to target substrates and formation of graphene/h-BN heterostructures by adhesive wafer bonding is demonstrated. Such a method would facilitate large-scale fabrication of novel 2D material-based devices.The second part of this thesis describes two different heterogeneous assembly approaches enabled by wire bonding. The first work realizes scalable vertical integration of microchips that are in-plane fabricated from the source wafer into a separate receiving substrate. The contactless assembly of microchips is realized by magnetic assembly and the electrical contacting is achieved by wire bonding on the sidewalls of the vertically assembled microchips. The second work deals with transfer of carbon nanotubes and Si micro-structures from their growth/fabrication substrates to target substrates by utilizing wire bonder as an automated manipulation tool. These methods could be useful for high-throughput 3D integration of microstructures and nanomaterials for various applications.
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