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Microneedle (MN) technology offers a powerful approach for transdermal delivery enabling painless injection and facilitating self‐administration without the need for professional assistance. However, the weak mechanical strength of MNs can lead to inefficient drug delivery and serious skin irritation if the MNs fracture during administration and leave fragments under the skin. Thus, the MNs need to be mechanically robust to avoid fracture during penetration through the skin while maintaining efficient drug delivery. Herein, the polymer‐based MNs with layer‐by‐layer (LbL) films of silica (SiO₂) nanoparticles (NPs) and a polycation (poly(diallyldimethylammonium chloride) (PDADMAC)) followed by hydrothermal calcination are reinforced. The mechanical strength of the MNs is significantly improved after LbL assembly and shows lower threshold pressure to penetrate skins. Moreover, their drug loading and releasing properties are significantly enhanced due to an increase in the surface area and interfacial interaction. These SiO₂nanoparticle‐containing LbL thin films have great potential for the surface modification of 3D microstructured devices such as MNs, as evidenced by their enhanced mechanical strength and drug coating efficiency that result in a promising MN drug delivery model.

 

Understanding the dynamics of polymers in confined environments is pivotal for diverse applications ranging from polymer upcycling to bioseparations. In this study, we develop an entropic barrier model using self-consistent field theory that considers the effect of attractive surface interactions, solvation, and confinement on polymer kinetics. In this model, we consider the translocation of a polymer from one cavity into a second cavity through a single-segment-width nanopore. We find that, for a polymer in a good solvent (i.e., excluded volume, u0 > 0), there is a nonmonotonic dependence of mean translocation time (τ) on surface interaction strength, ɛ. At low ɛ, excluded volume interactions lead to an energetic penalty and longer translocation times. As ɛ increases, the surface interactions counteract the energetic penalty imposed by excluded volume and the polymer translocates faster through the nanopore. However, as ɛ continues to increase, an adsorption transition occurs, which leads to significantly slower kinetics due to the penalty of desorption from the first cavity. The ɛ at which this adsorption transition occurs is a function of the excluded volume, with higher u0 leading to an adsorption transition at higher ɛ. Finally, we consider the effect of translocation across different size cavities. We find that the kinetics for translocation into a smaller cavity speeds up while translocation to a larger cavity slows down with increasing ɛ due to higher surface contact under stronger confinement.

 

Porous materials possess numerous useful functions because of their high surface area and ability to modulate the transport of heat, mass, fluids, and electromagnetic waves. Unlike highly ordered structures, disordered porous structures offer the advantages of ease of fabrication and high fault tolerance. Bicontinuous interfacially jammed emulsion gels (bijels) are kinetically trapped disordered biphasic materials that can be converted to porous materials with tunable features. Current methods of bijel fabrication result in domains that are micrometers or larger, and non-uniform in size, limiting their surface area, mechanical strength, and interaction with electromagnetic waves. In this work, scalable synthesis of bijels with uniform and sub-micrometer domains is achieved via a two-step solvent removal process. The resulting bijels are characterized quantitatively to verify the uniformity and sub-micrometer scale of the domains. Moreover, these bijels have structures that resemble the microstructure of the scale of the white beetle Cyphochilus. We find that such bijel films with relatively small thicknesses (<150 μm) exhibit strong solar reflectance as well as high brightness and whiteness in the visible range. Considering their scalability in manufacturing, we believe that VIPS-STRIPS bijels have great potential in large-scale applications including passive cooling, solar cells, and light emitting diodes (LEDs).