Rapid vacuum-driven monolayer assembly of microparticles on the surface of perforated microfluidic devices

Self-organization of agitated microspheres on various substrates

“…To circumvent the strong interaction forces, micro-or nanoparticles are often suspended in liquids to study the selfor directed organization of these particles on substrates using a variety of techniques, such as manipulation by means of electric and magnetic fields, or solvent evaporation. [17][18][19][20][21][22][23][24][25][26][27] In this respect, a profound understanding of the competing interparticle forces and the adhesion force between the particle and substrate is key to attain well-controlled particle patterns 20,28,29 which are relevant in various applications, e.g., bio-inspired approaches to materials engineering, paints, photonic crystals, self-cleaning anti-reflective coatings, optical and biological sensors, chemical catalysis, biomimicry. [30][31][32][33][34] However, as the wet assembly techniques rely on optimized conditions, such as solvent evaporation rate, surface wettability, pH, it tends to be challenging to attain perfect ordered crystals, without any cracks, on a large scale.…”

Impact-induced generation of single airborne microspheres and the subsequent vacuum-driven assembly of ordered arrays

“…Many of these wet assembly techniques, e.g., convective assembly, capillary assembly, or spin-coating, apply delicate self-assembly processes on (non-) patterned substrates, where a slight deviation in one of the required parameters, such as pH, relative humidity and temperature, can yield defects in the assembled monolayers comprising microspheres or nanospheres [9,10]. Other wet assembly techniques use electric and magnetic fields or a vacuumdriven force to attain an ordered monolayer from a dispersion of nanoand microparticles [6,[11][12][13] Recently, it has been shown that these close-packed assembled arrays can be transformed into non-closely packed arrays using reactive ion etching (RIE) to tune the spacing between neighbouring particles [14,15]. However, a drawback of this method is that the particle's morphology and surface roughness can be altered by dry etching.…”

Wafer-Scale Particle Assembly in Connected and Isolated Micromachined Pockets via PDMS Rubbing

“…Nevertheless, wet assembly methods are in studies still generally preferred over dry methods as the interaction forces between particles in suspensions are noticeably weaker than in a dry state. 22 , 23 …”

“…Alternatively, a large-scale dry particle assembly process has been proposed by the Jeong group. , This was successfully applied for the formation of large-area colloidal monolayers on flat, curved, and prepatterned substrates by means of unidirectional rubbing of dry powder using an elastomeric material. Nevertheless, wet assembly methods are in studies still generally preferred over dry methods as the interaction forces between particles in suspensions are noticeably weaker than in a dry state. , …”

“…Nevertheless, wet assembly methods are in studies still generally preferred over dry methods as the interaction forces between particles in suspensions are noticeably weaker than in a dry state. 22,23 Whereas the aforementioned studies mainly focused on the production of particle arrays and layers on flat or weakly structured surfaces, the present study focuses on the possibility to assemble microspheres (5 and 10 μm diameter) in arrays of micromachined pockets wherein the particles can be completely sunk into the substrate (depth of the pocket ≥ diameter of the particle). Particle assembly is achieved using PDMS rubbing.…”