Fabrication of Asymmetrical and Gradient Hierarchy Structures of Poly-p-xylylenes on Multiscale Regimes Based on a Vapor-Phase Sublimation and Deposition Process

Abstract

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.

Vapor Sublimation and Deposition to Fabricate a Porous Methyl Propiolate-Functionalized Poly-p-xylylene Material for Copper-Free Click Chemistry

“…The ultimate results of the two processes rendered the construction of a three-dimensional porous material of propiolate-functionalized poly- p -xylylene with controllable pore size and porosity, and the outlook architecture in terms of shape and size dimensions replicated the ice template. Similar to other porous poly- p -xylylene reported [ 33 ], pore sizes ranging from 18.7 μm ± 6.7 μm to 35.6 μm ± 8.2 μm and porosities of approximately 54.3–67.6% were measured based on microscopic, porosimetry, and gas adsorption techniques. The resultant porous constructs were also visualized by SEM (scanning electron microscopy), as shown in Figure 1 c, where porous cubes of propiolate-functionalized poly- p -xylylene with the same dimensions (300 μm × 300 μm × 300 μm) were observed to be consistent with the ice templates, and an average pore size of 25.9 μm ± 9.3 μm was measured.…”

Synergistic and Regulatable Bioremediation Capsules Fabrication Based on Vapor-Phased Encapsulation of Bacillus Bacteria and its Regulator by Poly-p-Xylylene

“…The resultant construct consisted of a three-dimensional porous poly- p -xylylene matrix with encapsulated B. CMC1 bacteria in the matrix ( Figure 1 ). The shape of the final capsule construct replicated the shape of the transformed ice template, which was theoretically shaped by molding, sculpting, or solidifying droplets to obtain various sizes and geometries [ 15 ]. Ideally, shrinkage or dislocation of the construct is avoided owing to the continuous sublimation and deposition process [ 16 ].…”

“…A vapor-deposited polymeric matrix system of poly- p -xylylenes of United States Pharmacopeia (USP) class VI with high biocompatibility and chemical resistance to strong acids, bases, and solvents was used for encapsulation during the fabrication process. The fabrication is performed in one step with a dry and clean vapor phase, which is desirable for sensitive biological substances such as cells, enzymes, growth factors, and other functional peptides and proteins [ 14 , 15 ]. The overall encapsulation process was realized based on our previously reported mechanism to deposit a vapor-phased poly- p -xylylene polymer on a template substrate that is eventually sublimated, and by manipulating the mass transport during the processing conditions, diverse species with distinct thermodynamic properties were subjected to sublimation and deposition within the confined space of the templates.…”

“…Finally, transformation of the template resulted in the construction of composite materials with defined physical properties in terms of porosity, bulk size and geometry, and chemical functionality by the compartmentalized functional entities and the devised interfacial chemistries [ 16 ]. With respect to the vapor sublimation and deposition process, which has been reported to result in the precise localization and distribution of substances such as metals, molecules, and liquids to form composites with controlled homogeneity or anisotropy from various materials [ 15 , 17 ], we hypothesized that the benign and versatile vapor-phased process was able to encapsulate (i) unmodified native bacteria of the Bacillus species CMC1 (hereafter referred to as B. CMC1 ) with specific enzymatic function and the same precision to localize and distribute B. CMC1 due to the encapsulation technique, enabling well-controlled bacterial growth activities and functions, and (ii) a regulator molecule, carboxymethyl cellulose (CMC), with a customizable encapsulation concentration to provide the same customizable stimulation dosages to regulate the enzymatic functions of the neighboring B. CMC1 bacteria. The fabricated and encapsulated capsules were composed of inhabitant bacteria from (i) and the surrounding conditioning regulator molecules from (ii), and the synergistic activities exhibited by (i) and (ii) were able to deliver a combination of controlled enzymatic factors for bioremediation in the devised microenvironments ( Figure 1 a).…”

Special Issue: Biointerface Coatings for Biomaterials and Biomedical Applications

“…cSAPs can be the next-generation material at biointerfaces. As more stringent specifications are required for designing the surface properties of prospective materials and the development of new devices is pursued with complicated geometries and minimized sizes, the surface properties of such materials/devices now also require a more defined and flexible presentation of the chemical functionalities (e.g., multifunctional or gradient distribution) and the precise confinement of these chemical conducts in relevant locations of interest [33]. The emerging applications of the existing technologies and/or new technologies from two dimensions into more sophisticated three-dimensional regions [34] are challenging the field of biointerfaces science, and further research developments are expected on this path.…”