The vibration dynamics of relatively large granular grains is extensively treated in literature, but comparable studies on the self-assembly of smaller agitated beads are lacking. In this work, we investigate...
Particle (monolayer) assembly is essential to various scientific and industrial applications, such as the fabrication of photonic crystals, optical sensors, and surface coatings. Several methods, including rubbing, have been developed for this purpose. Here, we report on the serendipitous observation that microparticles preferentially partition onto the fluorocarbon-coated parts of patterned silicon and borosilicate glass wafers when rubbed with polydimethylsiloxane slabs. To explore the extent of this effect, we varied the geometry of the pattern, the substrate material, the ambient humidity and the material and size of the particles. Partitioning coefficients amounted up to a factor 12 on silicon wafers, and even ran in the 100's on borosilicate glass wafers at zero humidity. Using Kelvin Probe Force Microscopy, the observations can be explained by tribo-electrification, inducing a strong electrostatic attraction between the 1 particles and the fluorocarbon zones, while the interaction with the non-coated zones is insignificant or even weakly repulsive.
Triboelectrification is the spontaneous charging of two bodies when released from contact. Even though its manifestation is commonplace, in for instance triboelectric nanogenerators, scientists find the tribocharging mechanism a mystery. The primary aim of this mini-review is to provide an overview of different tribocharging concepts that have been applied to study and realize the formation of ordered stable structures using different objects on various length scales. Relevance spans from materials to planet formations. Especially, dry assembly methods of particles of different shapes based on tribocharging to obtain crystal structures or monolayers are considered. In addition, the current technology employed to examine tribocharging in (semi)dry environments is discussed as well as the relevant forces playing a role in the assembly process. In brief, this mini-review is expected to provide a better understanding of tribocharging in assembling objects on the nano-and micrometer scales.
The present contribution
reports on a study aiming to find the
most suitable rubbing method for filling arrays of separated and interconnected
micromachined pockets with individual microspheres on rigid, uncoated
silicon substrates without breaking the particles or damaging the
substrate. The explored dry rubbing methods generally yielded unsatisfactory
results, marked by very large percentages of empty pockets and misplaced
particles. On the other hand, the combination of wet rubbing with
a patterned rubbing tool provided excellent results (typically <1%
of empty pockets and <5% of misplaced particles). The wet method
also did not leave any damage marks on the silicon substrate or the
particles. When the pockets were aligned in linear grooves, markedly
the best results were obtained when the ridge pattern of the rubbing
tool was moved under a 45° angle with respect to the direction
of the grooves. The method was tested for both silica and polystyrene
particles. The proposed assembly method can be used in the production
of medical devices, antireflective coatings, and microfluidic devices
with applications in chemical analysis and/or catalysis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.