As evidenced by the growth of additive manufacturing, there is extensive value in customization, both in terms of chemistry and structure. Direct laser writing is a promising approach to the maskless patterning of a broad range of nano to microscale materials. We employ a methodology using laser-induced solvothermal voxels, which combines the control of solvothermal chemistry for nanoparticle synthesis with the patterning abilities of direct laser writing, enabling the integration of nanocrystalline oxides, metals, and mixed metal oxides and alloys. We present an expanded range of materials that can be easily fabricated through this method and explore how this process can be used for 2.5D topographical patterning and layering with potential applications for catalysis and sensing.

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Micellar solubilization is a transport process occurring in surfactant-stabilized emulsions that can lead to Marangoni flow and droplet motility. Active droplets exhibit self-propulsion and pairwise repulsion due to solubilization processes and/or solubilization products raising the droplet's interfacial tension. Here, we report emulsions with the opposite behavior, wherein solubilization decreases the interfacial tension and causes droplets to attract. We characterize the influence of oil chemical structure, nonionic surfactant structure, and surfactant concentration on the interfacial tensions and Marangoni flows of solubilizing oil-in-water drops. Three regimes corresponding to droplet "attraction", "repulsion" or "inactivity" are identified. We believe these studies contribute to a fundamental understanding of solubilization processes in emulsions and provide guidance as to how chemical parameters can influence the dynamics and chemotactic interactions between active droplets.

Fabrication and processing approaches that facilitate the ease of patterning and the integration of nanomaterials into sensor platforms are of significant utility and interest. In this work, we report the use of laser-induced thermal voxels (LITV) to fabricate microscale, planar gas sensors directly from solutions of metal salts. LITV offers a facile platform to directly integrate nanocrystalline metal oxide and mixed metal oxide materials onto heating platforms, with access to a wide variety of compositions and morphologies including many transition metals and noble metals. The unique patterning and synthesis flexibility of LITV enable the fabrication of chemically and spatially tailorable microscale sensing devices. We investigate the sensing performance of a representative set of n-type and p-type LITV-deposited metal oxides and their mixtures (CuO, NiO, CuO/ZnO, and Fe 2 O 3 /Pt) in response to reducing and oxidizing gases (H 2 S, NO 2 , NH 3 , ethanol, and acetone). These materials show a broad range of sensitivities and notably a strong response of NiO to ethanol and acetone (407 and 301% R/R 0 at 250 °C, respectively), along with a 5-to 20-fold sensitivity enhancement for CuO/ZnO to all gases measured over pure CuO, highlighting the opportunities of LITV for the creation of mixed-material microscale sensors.

Metal-organic frameworks (MOFs) have emerged as promising candidates for a wide range of applications due to their high surface area and customizable structures, however, the minimal external hydrophilicity of MOFs...