In this study, polymethyl methacrylate (PMMA) is joined with fused silica using pulsed femtosecond laser transmission micro‐welding. This technique enables the welding of transparent materials to each other without the need for intermediate opaque layers, through localized energy deposition. The laser parameters – peak fluence, scanning speed, and hatch distance – are systematically optimized to maximize joint shear strength. The ATR‐FTIR spectroscopic analysis has proven that mechanical interlocking is the primary mechanism of joint formation between the two materials. An analytical model based on heat accumulation is developed to describe the joining process, with a good predictive quality confirmed by comparison with the experimental results. This joining approach is applied to seal a hybrid PMMA‐fused silica microfluidic chip. The device has successfully passed a static leakage test by withstanding pressures up to the full‐scale value of the employed microfluidic pump at 2 bar, demonstrating the effectiveness of femtosecond laser transmission welding for fabricating robust and reliable joints in hybrid microfluidic devices.

In this work, femtosecond laser cutting of quartz wafers was demonstrated as an environmentally friendly alternative to the standard etching methods for production of sensitive sensor devices. The proposed approach employed milling channels for processing of the entire wafer thickness. The laser parameters examined for this procedure were the pulse energy, the number of scans and the channel width. Subsequent analysis of each channel focused on evaluating its depth, the angle of tapering, and the overall quality of the cut. The laser system operated at a central wavelength of 515 nm, delivering pulses with a temporal width of 390 femtoseconds. After identifying the optimal laser parameters for achieving the best channel quality through the wafer thickness (280 μ m), the method was used to directly laser-cut quartz microresonators in a tuning-fork geometry. The resonant performance of laser-cut tuning forks was simulated and experimentally validated using a laser-vibrometer under photoacoustic excitation. The results matched standard quartz-tuning-fork behavior, with the junction quality between the body and prongs significantly impacting performance. This study confirms femtosecond laser cutting as an efficient, eco-friendly method for producing quartz micro-devices, enabling single prototype fabrication not achievable with conventional methods.

Standing Surface Acoustic Waves (SSAWs) generated on a piezoelectric substrate are largely used to create stable surface force patterns in active lab‐on‐a‐chip devices. This study presents the development and experimental validation of a full‐domain 3D digital twin for a SSAW device based on 128° YX LiNbO ₃ , commonly used for acoustofluidic applications. The model is developed in COMSOL Multiphysics to accurately capture the electromechanical interactions that govern SSAW generation and its interaction with the substrate. Its predictive accuracy is validated through electrical characterization with a vector network analyzer and surface displacement mapping with a laser Doppler vibrometer, demonstrating strong agreement between simulations and experimental data. This validation proves the reliability of digital twins for predictive modeling and design optimization of SSAW devices, offering a more precise and efficient alternative to traditional models and trial‐and‐error approaches.

Quartz is widely employed in optoelectronic and sensing applications owing to its excellent mechanical and chemical properties. However, its intrinsic transparency up to 5 μm limits its direct use as a photodetection substrate across the near- and mid-infrared spectral regions. Laser surface texturing for the fabrication of the so-called black quartz represents a promising strategy to overcome this limitation. In this work, different femtosecond (fs) laser texturing strategies were investigated on a 1 mm thick α-quartz wafer, namely uniform milling, grid-patterned grooves, and localized arrays of ablated craters. The fs-laser-treated quartz samples showed a transmittance reduction of up to 60% within the quartz transparency window in the infrared range, with crater matrices providing the most effective blackening performance. The enhanced absorption was attributed to light-trapping effects induced by the tapered crater geometry, which promotes multiple internal reflections and increased optical confinement within the substrate. The proposed strategy demonstrates a reliable, maskless, and chemical-free surface functionalization strategy for the fabrication of quartz-based substrates for broadband infrared photodetection in sensing applications.

Surface functionalisation of polymers is essential for enhancing properties such as wettability and mechanical resistance. This study presents a scalable, coating-free approach to fabricate hydrophobic and superhydrophobic Polydimethylsiloxane (PDMS) surfaces. Aluminium (AA2024) moulds were microstructured using a TruMicro femtosecond laser system to generate grid patterns with controlled hatch distances and depths, as well as laser-induced periodic surface structures (LIPSSs). These features were accurately replicated onto PDMS, as confirmed by scanning electron miscoscopy (SEM) and profilometry. Contact angle measurements showed a marked increase in hydrophobicity, reaching superhydrophobicity for optimised parameters, with surface stability maintained over four months without degradation.

On-chip label-free detection of microparticles is a key challenge for developing miniaturized platforms for real-time sensing in liquids. A promising strategy involves exploiting photoacoustic and thermoelastic effects to convert optical absorption into detectable acoustic signals. Understanding these processes at the single-particle level is essential for advancing next-generation diagnostic and analytical platforms. In this work, we present a numerical investigation of the thermal, mechanical, and acoustic dynamics of a dye-free polystyrene microsphere in water under pulsed optical excitation. We developed a fully coupled finite-element model to simulate heat transfer, thermoelastic deformation, and acoustic wave propagation. The effect of optical pulse duration, from nanoseconds to milliseconds, was systematically analysed. This provides a crucial link between the temporal profile of the photonic excitation and the resulting optomechanical response. Simulations reveal a transition from an impulsive thermoelastic regime for nanosecond pulses, characterized by elastic ringing, to a quasi-static regime for longer pulses. While near-field pressure depends on pulse duration, far-field propagation becomes largely independent of excitation conditions due to acoustic attenuation in water. These findings offer key design rules for tailoring laser source specifications to optimize energy conversion efficiency. Ultimately, this work establishes a comprehensive predictive framework for the development of integrated on-chip photonics and photoacoustic sensing architectures.