Abstract: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-simulan… Show more
“…Further, to provide clearer evidence of the high surface energy of the epidermal seed surfaces, we investigated the aggregated particle patterns after drying sprayed droplets of a particle-laden solution on the biological and synthetic seed surfaces. According to our previous study 30 , the evaporation-induced particle residues differed depending on the surface wettability. For hydrophilic or super-hydrophilic surfaces, the sprayed microdroplets tend to coalesce, leading to the typical Wenzel state on the structured sur-faces (Fig.…”
Section: Resultsmentioning
confidence: 82%
“…The PUA resin was cured with ultraviolet (UV) light (λ = 365 nm) for few seconds. The detailed UV NIL process has been described in our previous work 30 , 46 . Figure 5 The two-step replication process of Allium seed surfaces.…”
Section: Methodsmentioning
confidence: 99%
“…To separate the structural effect on the wetting properties from chemical/molecular interactions, we also studied the wetting behavior after adjusting the surface energy of the replicated seed surfaces through oxygen plasma treatment 26 – 29 . Furthermore, to verify the effect of the constituent material on the wetting of seed surfaces, we investigated particle aggregation patterns on the biological seeds and replicated surfaces after evaporation of sprayed nanoparticle-laden droplets 30 . These results support our understanding of the interplay between surface characteristics and wetting properties and provide direct evidence related to the wettability of the outermost waxes or constituent materials of the seed surfaces.…”
Biological surfaces in plants are critical for controlling essential functions such as wettability, adhesion, and light management, which are linked to their adaptation, survival, and reproduction. Biomimetically patterned surfaces replicating the microstructures of plant surfaces have become an emerging tool for understanding plant–environment interactions. In this study, we developed a two-step micro-replication platform to mimic the microstructure of seed surfaces and demonstrated that this initial platform can be used to study seed surface–environment interactions. The two-step process involved the extraction of a simplified seed surface model from real seeds and micro-replication of the simplified seed surface model using nanoimprint lithography. Using Allium seeds collected from Mongolia and Central Asia as the model system, we studied the wettability of biological and synthetic seed surfaces. We could independently control the material properties of a synthetic seed surface while maintaining the microstructures and, thereby, provide clear evidence that Allium seed surfaces were highly wettable owing to the high surface energy in the epidermal material rather than a microstructural effect. We expect that this platform can facilitate study of the independent effect of microstructure on the interaction of seed surfaces with their surroundings and contribute to research on the evolution of plant–environment interactions.
“…Further, to provide clearer evidence of the high surface energy of the epidermal seed surfaces, we investigated the aggregated particle patterns after drying sprayed droplets of a particle-laden solution on the biological and synthetic seed surfaces. According to our previous study 30 , the evaporation-induced particle residues differed depending on the surface wettability. For hydrophilic or super-hydrophilic surfaces, the sprayed microdroplets tend to coalesce, leading to the typical Wenzel state on the structured sur-faces (Fig.…”
Section: Resultsmentioning
confidence: 82%
“…The PUA resin was cured with ultraviolet (UV) light (λ = 365 nm) for few seconds. The detailed UV NIL process has been described in our previous work 30 , 46 . Figure 5 The two-step replication process of Allium seed surfaces.…”
Section: Methodsmentioning
confidence: 99%
“…To separate the structural effect on the wetting properties from chemical/molecular interactions, we also studied the wetting behavior after adjusting the surface energy of the replicated seed surfaces through oxygen plasma treatment 26 – 29 . Furthermore, to verify the effect of the constituent material on the wetting of seed surfaces, we investigated particle aggregation patterns on the biological seeds and replicated surfaces after evaporation of sprayed nanoparticle-laden droplets 30 . These results support our understanding of the interplay between surface characteristics and wetting properties and provide direct evidence related to the wettability of the outermost waxes or constituent materials of the seed surfaces.…”
Biological surfaces in plants are critical for controlling essential functions such as wettability, adhesion, and light management, which are linked to their adaptation, survival, and reproduction. Biomimetically patterned surfaces replicating the microstructures of plant surfaces have become an emerging tool for understanding plant–environment interactions. In this study, we developed a two-step micro-replication platform to mimic the microstructure of seed surfaces and demonstrated that this initial platform can be used to study seed surface–environment interactions. The two-step process involved the extraction of a simplified seed surface model from real seeds and micro-replication of the simplified seed surface model using nanoimprint lithography. Using Allium seeds collected from Mongolia and Central Asia as the model system, we studied the wettability of biological and synthetic seed surfaces. We could independently control the material properties of a synthetic seed surface while maintaining the microstructures and, thereby, provide clear evidence that Allium seed surfaces were highly wettable owing to the high surface energy in the epidermal material rather than a microstructural effect. We expect that this platform can facilitate study of the independent effect of microstructure on the interaction of seed surfaces with their surroundings and contribute to research on the evolution of plant–environment interactions.
“…Such strategies include tailoring the particle shape, 29 inter-particle interactions, 38,39 particle wettability, 40 substrate structuring. 41,42 Further, bulk heating of substrate/liquids, 31,43,44 introducing additives into the liquid, 30,45 and applying an electric/magnetic field 46,47 have also been employed to suppress the CRE. However, passive methods are not applicable to situations where real-time control over the assembly process is required.…”
Section: ■ Introductionmentioning
confidence: 99%
“…Control over the assembly of nano/microparticles is realized by modulating the CRE, following either passive − or active strategies. − The passive techniques depend on modifying the chemical/physical properties of the particles, substrate, or liquid. Such strategies include tailoring the particle shape, inter-particle interactions, , particle wettability, substrate structuring. , Further, bulk heating of substrate/liquids, ,, introducing additives into the liquid, , and applying an electric/magnetic field , have also been employed to suppress the CRE. However, passive methods are not applicable to situations where real-time control over the assembly process is required.…”
Optically controlled assembly of suspended particles from evaporating sessile droplets is an emerging method to realize on-demand patterning of particles over solid substrates. Most of the reported strategies rely either on additives or surface texturing to modulate particle deposition. Though dynamic control over the assembly of microparticles is possible, limited success has been achieved in nanoparticle patterning, especially in the case of metallic nanoparticles. This work demonstrates a simple light-directed patterning of gold (Au) nanoparticles based on the thermoplasmonically controlled liquid flow. Excitation at the plasmonic wavelength (532 nm) generates the required temperature gradient, resulting in the particle assembly at the irradiation zone in response to the thermocapillary flow created inside the droplet. Particle streak velocimetry experiments and analysis confirm the existence of a strong thermocapillary flow, which counteracts the naturally occurring evaporative convection flows. By modulating the illumination conditions, we could achieve patterns with various morphologies, including center deposit, off-center deposit, multi-spot deposit, and lines. We successfully applied the developed strategy for realizing closely packed hybrid particle assembly containing different particles: Au and polystyrene particles (PS). We performed optical microscopy, 3D profilometry, and SEM analysis to characterize the particle deposit. We analyzed the periodicity of Au-PS hybrid assembly using fast Fourier transform and radial distribution function analysis. PS particles formed a hexagonal close-packed arrangement at the irradiation zone, with Au NPs residing inside the voids. We believe that the presented strategy could significantly enhance the applicability of the evaporative lithography from sessile droplets for the programmable patterning of metallic nanoparticles.
The sustained water repellency of interconnected micropatterned surfaces is explored over an extended duration, with a focus on their resilience during a 90‐day water‐immersion test. Initially, the microstructure surfaces exhibit high water repellency, a characteristic of the Cassie–Baxter state. However, subsequent detailed temporal analyses reveal varying responses depending on the structural topology. The interconnected micropatterned surfaces exhibit remarkable long‐term resistance to water; this is attributed to the formation of large and stable air pockets enabled by their unique microcavity structures. In comparison, hierarchical microcavity surfaces with micropillars exhibit a notable decrease in water repellency, as evidenced by reduced contact angles, suggesting a transition to a wetting state owing to the emergence of surface hydrophilicity during long‐term water exposure. This study demonstrates the importance of stable air‐pocket effects, particularly in applications where the long‐term stability of liquid repellency is critical, and suggests the role of interconnected structures in maintaining water repellency over time.
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