Evaporation-induced particle aggregation in drying droplets is of significant importance in the prevention of pathogen transfer due to the possibility of indirect fomite transmission of the infectious virus particles. In this study, particle aggregation was directionally controlled using contact line dynamics (pinned or slipping) and geometrical gradients on microstructured surfaces by the systematic investigation of the evaporation process on sessile droplets and sprayed microdroplets laden with virus-simulant nanoparticles. Using this mechanism, we designed robust particle capture surfaces by significantly inhibiting the contact transfer of particles from fomite surfaces. For the proof-of-concept, interconnected hexagonal and inverted pyramidal microwall were fabricated using ultravioletbased nanoimprint lithography, which is considered to be a promising scalable manufacturing process. We demonstrated the potentials of an engineered microcavity surface to limit the contact transfer of particle aggregates deposited with the evaporation of microdroplets by 93% for hexagonal microwall and by 96% for inverted pyramidal microwall. The particle capture potential of the interconnected microstructures was also investigated using biological particles, including adenoviruses and lung-derived extracellular vesicles. The findings indicate that the proposed microstructured surfaces can reduce the indirect fomite transmission of highly infectious agents, including norovirus, rotavirus, or SARS-CoV-2, via respiratory droplets.

Nanowire structures have attracted attention in various fields, since new characteristics could be acquired in minute regions. Especially, Anodic Aluminum Oxide (AAO) is widely used in the fabrication of nanostructures, which has many nanosized pores and well-organized nano pattern. Using AAO as a template for replication, nanowires with a very high aspect ratio can be fabricated. Herein, we propose a facile method to fabricate a nano-micro hybrid structure using nanowires replicated from AAO, and surface treatment. A polymer resin was coated between Polyethylene terephthalate (PET) and the AAO filter, roller pressed, and UV-cured. After the removal of aluminum by using NaOH solution, the nanowires aggregated to form a micropattern. The resulting structure was subjected to various surface treatments to investigate the surface behavior and wettability. As opposed to reported data, UV-ozone treatment can enhance surface hydrophobicity because the UV energy affects the nanowire surface, thus altering the shape of the aggregated nanowires. The hydrophobicity of the surface could be further improved by octadecyltrichlorosilane (OTS) coating immediately after UV-ozone treatment. We thus demonstrated that the nano-micro hybrid structure could be formed in the middle of nanowire replication, and then, the shape and surface characteristics could be controlled by surface treatment.

Reverse offset printing (ROP) is receiving increasing attention as an emerging technology for printed electronics due to its rapid, environment‐friendly fabrication processes. A tunable ROP process is proposed by exploiting the controlled elastic deformation of a stretchable blanket. First, the flat elastomeric blanket is elastically stretched before coating with the printing ink. Next, Ag ink is coated on the surface of a supporting substrate and sequentially transferred to a prestrained elastomeric blanket. Second, the patterned cliché is rolled over the prestrained blanket surface by applying an optimized pressure for patterning. Finally, releasing the strain in the patterned elastomeric blanket leads to a pattern deformation on pitch and sizes. A decrease in the line width and pitch is demonstrated using a tunable ROP process with a stretchable blanket. This unique tunable printing process offers the capability of low‐cost fabrication of various microstructures from a single cliché using simple mechanical stretching and releasing.

No abstract

The cover page shows the illustration of controlled pattern shrinkage in reverse offset printing. Young Tae Cho and co‐workers demonstrate in their article, number http://doi.wiley.com/10.1002/adem.202001537, that the pattern size reduction by a flexible blanket material with simple mechanical stretching and releasing shed light on the low‐cost, scalable, and high‐resolution printing for printed electronics.