An elegant and precise method to fabricate asymmetrical structures and/or gradient structures was developed based on a vapor-phase sublimation and deposition process. The fabricated materials exhibited versatility and had advantages such as well-controlled pore structures and functional properties ranging from an asymmetrical distribution to a gradient hierarchy; precisely addressed interface chemistries and properties for the constructed materials; and flexibility to produce the materials at multiple scales. By using a time-dependent customization parameter to control the bulk size and/or the dispersion of molecules, fabrication of the materials was demonstrated, producing particles with hierarchical pore structures and with bulk sizes ranging from >500 μm to submicrons, as well as gradients with both continuously varied porosity and chemical functionality that were demonstrated to be in a controlled direction and varied across multiple scales (centimeter, millimeter, and micrometer). By exploiting chemical vapor deposition to enable multicomponent copolymerization during the fabrication process, multifunctional poly-p-xylylenes formed building blocks for these hierarchical materials and provided the defined surface chemistries. The proposed functional hierarchical materials were constructed and assembled in the vapor phase and in one step, and prospective materials produced by this method are expected to have novel properties and unlimited applications.

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Using a simplified yet realistic strain-relaxation model, we analyse facet-resolved non-contact AFM (NC-AFM) data of self-assembled strained germanium islands grown on Si(100) at 650 • C and extract estimates of the nucleation barrier and pyramid-to-dome shape transition barrier. We estimate the shape transition barrier of Ge dots as ∼0.5 meV/atom, and the nucleation barrier as ∼0.2 eV.

A vapor-phase process, involving the sublimation of an ice substrate/template and the vapor deposition of a maleimide-functionalized poly-p-xylylene, has been reported to synthesize an advanced porous material, with readily clickable chemical interface properties, to perform a Michael-type addition of a maleimide functionality for conjugation with a thiol group. In contrast to the conventional chemical vapor deposition of poly-p-xylylenes on a solid surface that forms thin film coatings, the process reported herein additionally results in deposition on a dynamic and sublimating ice surface (template), rendering the construction of a three-dimensional, porous, maleimide-functionalized poly-p-xylylene. The process seamlessly exploits the refined chemical vapor deposition polymerization from maleimide-substituted [2,2]paracyclophane and ensures the preservation and transformation of the maleimide functionality to the final porous poly-p-xylylene products. The functionalization and production of a porous maleimide-functionalized poly-p-xylylene were completed in a single step, thus avoiding complicated steps or post-functionalization procedures that are commonly seen in conventional approaches to produce functional materials. More importantly, the equipped maleimide functionality provides a rapid and efficient route for click conjugation toward thiol-terminated molecules, and the reaction can be performed under mild conditions at room temperature in a water solution without the need for a catalyst, an initiator, or other energy sources. The introduced vapor-based process enables a straightforward synthesis approach to produce not only a pore-forming structure of a three-dimensional material, but also an in situ-derived maleimide functional group, to conduct a covalent click reaction with thiol-terminal molecules, which are abundant in biological environments. These advanced materials are expected to have a wide variety of new applications.