3D printing at the macroscale has evolved from making plastic prototypes to the production of high-performance functional metal parts for industries such as medical and aerospace. By contrast, MEMS devices today are produced in large quantities using semiconductor manufacturing processes. However, the semiconductor manufacturing paradigm is not cost-effective for producing customized MEMS devices in small to medium volumes (tens to thousands of units per year), and related applications are difficult to address efficiently. 3D printing of functional MEMS devices could play an important role in filling this gap. Here, we discuss recent advances in 3D- printed functional MEMS, addressing the challenges of economical customization at smaller production volumes.

We present a fabrication process for 3D printing of glass sensors directly onto the end of optical fiber tips. Compared to conventional polymeric 3D-printed fiber-tip sensors, our method provides far superior chemical resistance and mechanical durability. We demonstrate the utility of our sensors by reliably measuring the refractive index of aggressive organic solvents - environments where polymer-based sensors are prone to swelling and deformation. This breakthrough opens new avenues for deploying robust glass sensors in demanding industrial settings, such as chemical processing plants and oil refineries, where precise and durable refractive index measurements are essential.

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.

Denna avhandling utforskar avancerade tillverkningstekniker som använder femtosekundlaserteknik för att utveckla miniatyriserade komponenter inom fotonik och energilagring. Genom att utnyttja de unika egenskaperna hos femtosekundlaserns interaktion med material, särskilt med hydrogen silsesquioxane (HSQ), introduceras här nya strategier för direkt 3D-utskrift av glasmikrostrukturer och högpresterande mikrosuperkondensatorer (MSC:er).

I avhandlingens första del studeras tre distinkta laserinteraktionsregimer, Uniform Mode, Nanograting Mode och Sphere Mode, systematiskt i HSQ. Dessa regimer möjliggör tillverkning av 3D-strukturer av kiseldioxid med olika morfologier och egenskaper. En viktig prestation är den direkta 3D-utskriften av glaskonstruktioner på spetsen av optiska fibrer med hjälp av samtliga tre regimer, vilket visar betydande framsteg i att integrera funktionella mikro-optiska komponenter på fiberbaserade plattformar. Fyra konceptvaliderande fotonikenheter demonstreras: en optisk resonator, en refraktionsindexsensor, en polarisationsstråldelare samt en mikrolins på en fiberspets. Dessa enheter uppvisar utmärkt prestanda och fastställer att direkt femtosekundlaserskrivning (DLW) är ett lovande tillvägagångssätt för integration av glasmikrostrukturer i kompakta och robusta fotoniksystem.

Den andra delen av avhandlingen fokuserar på femtosekundlasertillverkade MSC:er. Två energilagringsenheter har utvecklats. Den första använder en heterogen MXene/PEDOT:PSS-bläckformulering som mönstrats på papperssubstrat via direkt bläckskrivning (DIW) följt av ritsning med femtosekundlaser, vilket resulterar i flexibla, metallfria MSC-serier med hög kapacitans per yta och justerbar spänning. Den andra enheten använder ett 3D-utskrivet nanogitter-skelett med vertikalt orienterade plattor tillverkade i HSQ, följt av konform beläggning med ledande material. Denna design förbättrar jontransporten avsevärt och ökar elektrodytan. Resultatet är en enhet med rekordhög karakteristisk frekvens på 5 .72 kHz samt utmärkt kapacitansstabilitetöver 450 000 cykler, vilket gör den väl lämpad för växelströmsfiltrering i mikroelektronik.

Sammanfattningsvis visar detta arbete att tillverkningstekniker som använder femtosekundlaserteknik erbjuder kraftfulla och mångsidiga möjligheter för tillverkning av miniatyriserade fotoniska och energilagrande komponenter. Kombinationen av additiv 3D-mikrotillverkning, materialomvandling och strukturell kontroll öppnar nya vägar för att integrera funktionella material i kompakta system. Framtida forskning kan fokusera på utökad materialkompatibilitet, utveckling av mer komplexa fotoniska arkitekturer och integration av energilagring med mikroelektroniska kretsar. Tillsammans utgör dessa bidrag en skalbar, exakt och robust tillverkningsplattform för nästa generations mikroenheter.

Integration of functional materials and structures on the tips of optical fibers has enabled various applications in micro-optics, such as sensing, imaging, and optical trapping. Direct laser writing is a 3D printing technology that holds promise for fabricating advanced micro-optical structures on fiber tips. To date, material selection has been limited to organic polymer-based photoresists because existing methods for 3D direct laser writing of inorganic materials involve high-temperature processing that is not compatible with optical fibers. However, organic polymers do not feature stability and transparency comparable to those of inorganic glasses. Herein, we demonstrate 3D direct laser writing of inorganic glass with a subwavelength resolution on optical fiber tips. We show two distinct printing modes that enable the printing of solid silica glass structures (“Uniform Mode”) and self-organized subwavelength gratings (“Nanograting Mode”), respectively. We illustrate the utility of our approach by printing two functional devices: (1) a refractive index sensor that can measure the indices of binary mixtures of acetone and methanol at near-infrared wavelengths and (2) a compact polarization beam splitter for polarization control and beam steering in an all-in-fiber system. By combining the superior material properties of glass with the plug-and-play nature of optical fibers, this approach enables promising applications in fields such as fiber sensing, optical microelectromechanical systems (MEMS), and quantum photonics.

MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors (MSCs). Despite its superior electrochemical performance, only a few studies have reported MXene-based ultrahigh-rate (>1000 mV s−1) on-paper MSCs, mainly due to the reduced electrical conductance of MXene films deposited on paper. Herein, ultrahigh-rate metal-free on-paper MSCs based on heterogeneous MXene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)-stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing. With a footprint area of only 20 mm2, the on-paper MSCs exhibit excellent high-rate capacitive behavior with an areal capacitance of 5.7 mF cm−2 and long cycle life (>95% capacitance retention after 10,000 cycles) at a high scan rate of 1000 mV s−1, outperforming most of the present on-paper MSCs. Furthermore, the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal-free on-paper MSC arrays, which can also be simultaneously charged/discharged at 1000 mV s−1, showing scalable capacitive performance. The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on-paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics. 

We demonstrate a refractive index sensor additively 3D-printed in silica glass on an optical fiber tip. The sensor shows a sensitivity of 900 nm/RIU and measures a liquid volume as small as 0.6 pl.

We demonstrate a refractive index sensor additively 3D-printed in silica glass on an optical fiber tip. The sensor shows a sensitivity of 900 nm/RIU and measures a liquid volume as small as 0.6 pl.

Silica glass is a high-performance material used in many applications such as lenses, glassware, and fibers. However, modern additive manufacturing of micro-scale silica glass structures requires sintering of 3D-printed silica-nanoparticle-loaded composites at similar to 1200 degrees C, which causes substantial structural shrinkage and limits the choice of substrate materials. Here, 3D printing of solid silica glass with sub-micrometer resolution is demonstrated without the need of a sintering step. This is achieved by locally crosslinking hydrogen silsesquioxane to silica glass using nonlinear absorption of sub-picosecond laser pulses. The as-printed glass is optically transparent but shows a high ratio of 4-membered silicon-oxygen rings and photoluminescence. Optional annealing at 900 degrees C makes the glass indistinguishable from fused silica. The utility of the approach is demonstrated by 3D printing an optical microtoroid resonator, a luminescence source, and a suspended plate on an optical-fiber tip. This approach enables promising applications in fields such as photonics, medicine, and quantum-optics.

The demand for miniaturized electronics has created a need for compact, high-performance on-chip power sources. Micro supercapacitors (MSCs) have emerged as promising candidates for on-chip filtering applications due to their high specific capacitance and on-chip integrity. However, most existing MSCs suffer from significant capacitance attenuation at high frequencies, limiting their effectiveness in modern electronic circuits operating above 10 kHz. This study addresses this challenge by developing a printed on-chip MSC with open-through nanograting electrode microstructure using a high-resolution 3D printing technique. The resulting 3D nanograting structure enables on-chip MSC high capacitance while facilitating rapid ion transport, crucial for maintaining high-frequency performance. Consequently, the on-chip MSC demonstrates an ultra-compact footprint of 0.048 mm2, about 260 time smaller than conventional aluminum electrolytic capacitor (AEC), while offering two-order higher areal capacitance of 1.2 mF cm-² at 1 kHz, and retain 0.32 mF cm-² at 10 kHz. This performance is twice as large as the highest value reported among state-of-the-art. The nanograting MSC simultaneously offers both high capacitance and excellent frequency response in a compact form factor, enabling effective line-filtering up to 10 kHz and provides promising potential for miniaturized, high-frequency line-filtering applications in advanced electronic systems.