1 research outputs found
Toward the Assembly of 2D Tunable Crystal Patterns of Spherical Colloids on a Wafer-Scale
Entering an era of miniaturization prompted scientists
to explore
strategies to assemble colloidal crystals for numerous applications,
including photonics. However, wet methods are intrinsically less versatile
than dry methods, whereas the manual rubbing method of dry powders
has been demonstrated only on sticky elastomeric layers, hindering
particle transfer in printing applications and applicability in analytical
screening. To address this clear impetus of broad applicability, we
explore here the assembly on nonelastomeric, rigid substrates by utilizing
the manual rubbing method to rapidly (≈20 s) attain monolayers
comprising hexagonal closely packed (HCP) crystals of monodisperse
dry powder spherical particles with a diameter ranging from 500 nm
to 10 μm using a PDMS stamp. Our findings elucidate that the
tribocharging-induced electrostatic attraction, particularly on relatively
stiff substrates, and contact mechanics force between particles and
substrates are critical contributors to attain large-scale HCP structures
on conductive and insulating substrates. The best performance was
obtained with polystyrene and PMMA powder, while silica was assembled
only in HCP structures on fluorocarbon-coated substrates under zero-humidity
conditions. Finally, we successfully demonstrated the assembly of
tunable crystal patterns on a wafer-scale with great control on fluorocarbon-coated
wafers, which is promising in microelectronics, bead-based assays,
sensing, and anticounterfeiting applications