Silveira Fiates Braun, Ana LuizaAna LuizaSilveira Fiates Braun2025-11-102025-11-102025-10-16https://media.suub.uni-bremen.de/handle/elib/23238https://doi.org/10.26092/elib/4910Silica aerogels are porous materials with high specific surface area, open porosity, and low thermal conductivity. These unique properties make them promising candidates for applications such as catalyst supports and thermal insulation. Although silica aerogels have already been incorporated in microsystems; their high shrinkage and fragile behaviour have limited their use to particles, thin films and droplets. This work investigates (I) a process for realising shrinkage-free silica aerogel monoliths inside microfluidic channels and (II) their application as catalytic supports in hydrogen combustion microdevices. The silica aerogels were realised using a sol-gel method with a two-step catalysis. Tetraethyl orthosilicate was used as the silica precursor. To overcome the shrinking and improve the mechanical strength of the aerogels, CO2 supercritical drying and mechanical additives (polyethylene glycol and carbon nanotubes) were applied. Critical process parameters observed were the filling of the microchannels during gelation to avoid shrinkage inside the channel; one week aging time; and twenty exchange cycles during drying to completely remove the ethanol from the pores and avoid pore collapse. The resulting aerogels were successfully integrated in the microchannels without shrinkage. The various compositions of aerogels exhibited high specific surface areas, in a range of 374 to 551 m2/g and mesoporosity. The aerogels were also successfully reinforced by polyethylene glycol and carbon nanotubes (2 to 8 wt.%). The reinforced aerogel monoliths showed an increase of the compressive strength up to three times higher than pure silica aerogels. To explore catalytic applications, the aerogels were functionalized with platinum and ruthenium nanoparticles with concentrations of 2 to 10 wt.%. For this study, a new chip design was used, featuring a polyimide membrane-based open cavity with platinum thermal structures, enabling both the nanoparticle integration and in-situ reaction characterization. Nanoparticles were dispersed in ethanol and infiltrated into the aerogel after drying, ensuring deep penetration and uniform distribution. The catalytic system was characterised using SEM, STEM, EXD, XRD and H2 chemisorption. Additionally, the catalytic combustion was monitored directly in the chip by measuring the resistance change of the thermistor. The final nanoparticle integrated aerogel system could initiate hydrogen combustion in the chip at different loading of Platinum (2 to 10 wt%) and gas composition (0.5 – 2 % vol H2/air). The catalytic reaction also proceeded independently of pre-heating of the system, where a variation of 40oC was measured. Overall, this work establishes a scalable methodology for integrating silica aerogels into microfluidic channels without shrinkage and demonstrates their viability as catalytic supports for platinum nanoparticles in hydrogen combustion devices.enhttps://creativecommons.org/licenses/by/4.0/aerogelmicrotechnologyH₂ Combustion Devices500 Naturwissenschaften und Mathematik::530 PhysikDissertation10.26092/elib/4910urn:nbn:de:gbv:46-elib232386