Nanoporous Polymer-Infiltrated Nanoparticle Films with Uniform or Graded Porosity <i>via</i> Undersaturated Capillary Rise Infiltration

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Polymer‐infiltrated nanoparticle films (PINFs) that have high volume fractions (>50 vol%) of nanoparticles (NPs) possess enhanced properties making them ideal for various applications. Capillary rise infiltration (CaRI) of polymer and solvent‐driven infiltration of polymer (SIP) into pre‐assembled NP films have emerged as versatile approaches to fabricate PINFs. Although these methods are ideal for fabricating PINFs with homogenous structure, several applications including separations, and photonic/optical coatings would benefit from a method that enables scalable manufacturing of heterostructured (i.e., films with variation in structural properties such as porosity, composition, refractive indices, etc.) PINFs. In this work, a new technique is developed for fabricating heterostructured PINFs with cavities based on CaRI. A bilayer composed of densely packed inorganic NP layer atop polymer NP layer is thermally annealed above the glass transition temperature of the polymer NP, which induces CaRI of the polymer into the interstices of the inorganic NP layer. Exploiting the difference in the sizes of the two particles, heterostructured double stack PINFs composed of a PINF and a layer with large cavities are produced at a moderate temperature (<200 °C). Using these heterostructured PINFs, Bragg reflectors that can detect the presence of wetting agents in water are fabricated.

Section: Resultsmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heterostructured Polymer‐Infiltrated Nanoparticle Films with Cavities via Capillary Rise Infiltration

Kim

Qiang

Turner

et al. 2020

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Lubricant Depletion‐Resistant Slippery Liquid‐Infused Porous Surfaces via Capillary Rise Lubrication of Nanowire Array

Tran

Kim

Ternon

et al. 2021

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Despite their promise in diverse applications, lubricant depletion over time presents an important challenge for slippery lubricant‐infused porous surfaces (SLIPS). The main source of lubricant depletion is the growth of a wetting ridge around a droplet of foreign liquid that removes the infused lubricant from the porous surface when the droplet slides off. This work describes the fabrication of liquid‐infused ZnO nanowire array by capillary rise lubrication and the effect of array morphology on suppressing wetting ridge formation. The orientation of nanowires strongly affects lubricant infiltration and the stability of SLIPS properties. The infiltrated lubricant in random ZnO nanowire arrays does not form a visible wetting ridge around a water droplet because of the strong capillarity that retains the lubricant confined in the nanoporous structure. The lack of wetting ridge gives rise to a stable SLIPS that exhibits self‐recovery of the infused lubricant. Such a structure retains lubricant under a strong centrifugal force, showing high stability. This study provides a straightforward, robust, and potentially scalable approach for making stable SLIPS that suppresses lubricant depletion by taking advantage of the unique morphology of the random nanowire arrays and capillary rise lubrication.

Condensation‐Controlled Toposelective Vapor Deposition in Nano‐ and Microcavities: Theory, Methods, Applications, and Related Technologies

Lovikka¹

2022

fabricable while we are facing increasing complexity in, for example, microelectronics. [6,7] For these reasons, challenges such as bad pattern alignment, [8,9] or pinch-off of pores and void formation [10][11][12][13] in top-down fabrication need to be addressed. On the other hand, a continuous film causes tradeoffs in desirable properties in many nanotechnological applications, such as losing mesoporosity while increasing the mechanical properties of an aerogel [14] or reducing catalytic activity while increasing catalyst stability against sintering. [15] To counter these problems, even atomic layer deposition (ALD), a method known for its superior conformality, has been expanded into area-selective fabrication by the addition of etching and functionalization steps in the workflow. [16][17][18][19] However, additional steps make the workflow increasingly slow, complex, and dependent on surface chemistries. There is also a growing interest in area-selectivity based on properties of precursors and substrates in ALD, [20] but new requirements on precursors would narrow down potential reagents. Furthermore, even conformal methods would leave voids inside ink-bottle-shaped pores and under composite undercuts [21] because conformal methods would clog the pore mouths before filling the internal parts. These problems have very recently revoked calls for profound changes and even a paradigm shift toward selective functionalization in the nanoscale. [18,20,[22][23][24][25] Special attention should be paid to inherently non-conformal methods, especially if they are surface-selective towards cavities. This includes both surface-selective subconformal coatings, those that coat only extremities and protrusions of a substrate, and surface-selective superconformal coatings, those that fill or coat cavities.Bottom-up approaches could eliminate the aforementioned problems while reducing the needed steps for surface-selective treatments-instead of breaking or carving things smaller and using miniaturized techniques (top-down), coatings could be grown self-aligning (bottom-up). One bottom-up category is surface-shape-selective deposition. Currently, this category has limited approaches, which are often based on either anisotropic processes such as directional plasma etching [26] or reagent flux, force fields, [27] competitive adsorption, [28] or reagents and additives with specific properties. [22] Truly bottom-up gap-filling technologies, especially those free of line-of-sight limitations, Nanotechnology drives technological progress in many frontiers, from electronics to medicine, from tougher composites to adaptive surfaces. As the feature sizes are made smaller, the importance of surfaces is increased. Many of the most powerful methods for surface manipulation are variants of vapor deposition (VD). However, VD is typically not surface-selective and, therefore, extra work steps are needed to integrate the methods into nanofabrication routines. Furthermore, many fields are moving toward 3D nanostructures, which unavoidably means...