Femtosecond laser-based 3D printing of micro- and nano components in silica glass for optics and energy storage
Time: Fri 2025-11-28 09.00
Location: F3, Lindstedtvägen 26
Language: English
Subject area: Electrical Engineering
Doctoral student: Lee-Lun Lai , Mikro- och nanosystemteknik
Opponent: Professor Dan M. Marom, Hebrew University of Jerusalem, Jerusalem, Israel
Supervisor: Professor Kristinn Gylfason B., Mikro- och nanosystemteknik; Professor Frank Niklaus, Mikro- och nanosystemteknik; Professor Göran Stemme, Mikro- och nanosystemteknik
QC 20251027
Abstract
This thesis explores advanced femtosecond laser fabrication techniques for the development of miniaturized components in photonics and energy storage. By leveraging the unique characteristics of femtosecond laser–material interactions, particularly with hydrogen silsesquioxane (HSQ), this work introduces novel strategies for direct 3D printing of glass microstructures and high-performance microsupercapacitors (MSCs).
In the first part of the thesis, three distinct femtosecond laser interaction regimes, Uniform Mode, Nanograting Mode, and Sphere Mode, are systematically investigated in HSQ. These regimes enable the fabrication of silica-based 3D microstructures with different morphologies and properties. A key achievement is the direct 3D printing of silica glass structures on optical fiber tips using all three modes, demonstrating a significant advancement in integrating functional micro-optics into fiber-based platforms. Four proof-of-concept photonic devices are demonstrated: an optical resonator, a refractive index sensor, a polarization beam splitter, and a fiber-tip microlens. These devices show excellent performance and establish the feasibility of using femtosecond direct laser writing (DLW) for glass microstructure integration in compact and robust photonic systems.
The second part of the thesis focuses on femtosecond-laser-enabled MSCs. Two energy storage devices have been developed. The first employs a heterogeneous MXene/PEDOT:PSS ink formulation patterned via direct ink writing (DIW) and femtosecond laser scribing on paper substrates, creating flexible, metal-free MSC arrays with high areal capacitance and voltage tunability. The second device utilizes a 3D-printed nanograting skeleton with vertically aligned plates fabricated in HSQ, followed by conformal coating with conductive layers. This design significantly improves ion transport and increases the electrode surface area. The resulting device achieves a record-high characteristic frequency of 5.72 kHz, along with excellent capacitance retention over 450,000 cycles, making it suitable for AC line-filtering applications in microelectronic circuits.
Overall, this work demonstrates that femtosecond laser fabrication offers powerful and versatile capabilities for miniaturized photonic and energy storage devices. The combination of additive 3D microfabrication, material conversion, and structural control opens new pathways for integrating functional materials into compact systems. Future research directions include expanding material compatibility, developing more complex photonic architectures, and integrating energy storage with microelectronic circuitry. Together, these contributions point toward a scalable, precise, and robust fabrication platform for next-generation microdevices.