Thermocapillary dewetting of liquids and molten films has recently emerged as a viable alternative to conventional microprocessing methods. As this thermal gradient-induced mechanism is universal, it can be applied to any material. This work explores the sequential dewetting of materials with varying melting points, including polymers and metals, to create aligned morphologies. The variation in melting point allows for the dewetting of single layers at a time or mobility-limited simultaneous dewetting. As a result, a variety of multimaterial structures can be produced with built-in alignment, such as arrays of concentric circles, lines with periodic segmentation, or islands on holes. This approach employs photothermal methods to induce the necessary thermal gradient, manipulating several variables in order to influence the consequent structures. Adjusting laser power and light intensity allows for the control of temperature for selective dewetting of films; altering beam size and exposure time affects the extent of dewetting in terms of diameter size; overlap effects and simultaneous dewetting can result in complex architectures. This controlled writing of patterns also presents a technique to create both masks at low temperatures for conductive multilayers as well as templates for electrospray deposition.

Focused laser spike (FLaSk) excitation has been demonstrated as a reliable technique for the patterning of micro-to-nanoscale features locally by thermocapillary shear of thin films. Recent work on polymer thin films has revealed that overlapping laser scans can leverage coupled thermal and fluid effects to create subwavelength patterns. Compared to polymeric films, metallic thin films possess both a lower melt viscosity and higher surface tension. Here, we investigate overlapping effects in the dewetting of ∼15 nm gold thin films on borosilicate and quartz glass substrates with a 532 nm continuous wave laser. During this process, FLaSk initiates capillary and thermocapillary dewetting simultaneously. Further, the low oxidation potential and high vapor pressure of gold lead to nonequilibrium vaporization during heating. Since the parameters of overlapping scans control the amount of material that is heated and to what temperature it is heated, selection of laser power, scanning distance, writing speed, and numerical aperture results in particles with different sizes and spacing deposited on the writing substrates or a positioned superstrate through a laser-induced localized physical vapor deposition (LILPVD) process. If the laser parameters are selected within a specific working range, uniform or periodic particle distributions can be repeatably deposited in this fashion, which can then be used as seeds for nanomaterial growth. In addition, if the substrate melts during FLaSk, the viscous force of the liquid-on-liquid dewetting broadens the range of patterning conditions by resisting the motion of the gold leading to more uniform particles over a large range of parameters.

To create macropore‐infused nanocomposite emulsion thermosets (MINET), a mixing pathway is demonstrated in which a viscous fluid is kinetically trapped by high shear mixing of immiscible liquids, surfactant, and nanoparticles. The MINETs are prepared from common ingredients that are widely employed in industry, including epoxy resin, vegetable oil, epoxidized soybean oil, and different types of nanoparticles such as silica, activated carbon, alumina, and zinc oxide. MINETs prepared by the presented route are processed at ambient conditions and exhibit low shrinkage (<2%). Furthermore, they are suitable to form macro‐ to microscale structures with high precision and various controlled porosity. The interconnected porous architecture of MINET is even preserved in molded micrometer‐scale features and thus ensures mass transport through multiscale structures. In combination with standard microembossing or photolithography, the high throughput microfabrication of microstructured architectures with tunable pore sizes in a wide range (≈100 nm to ≈10 µm) is possible. As one application example, the parallel production of multiplexed electrospray emitters is demonstrated.

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<p>To create microporous nanocomposite epoxy thermosets (MiNET), a mixing pathway is demonstrated in which a bicontinuous emulsion gel (bijel) like viscous fluid is kinetically trapped by high shear mixing of immiscible liquids, surfactant, and nanoparticles. The MiNETs are prepared from common ingredients, that are widely employed in industry, including epoxy resin, vegetable oil, epoxidized soybean oil, and different types of nanoparticles such as silica, activated carbon, alumina, and zinc oxide. MiNETs prepared by the presented route are processed at ambient conditions and exhibit low shrinkage (less than 2%). Furthermore, they are suitable to erect macro- to microscale structures with high precision and various porosity. The interconnected porous architecture of MiNET is even preserved in microscale features and thus ensures the mass transport in microstructures. With facile processability and tunability of pore sizes in a wide range (~100 nm to few microns), the proposed route overcomes the two major roadblocks – difficulty in fabrication and large domain size (on the order of 5µm or larger) – of bijel-like materials to apply in catalysis, energy storage, and molecular encapsulation. </p>