Stimuli-responsive granular crystals assembled by dipolar and multipolar interactions

Abstract

This paper describes granular crystals held together by unusual, multipolar interactions and, under application of external bias, undergoing reversible structural transitions between closed and open forms. The system is comprised...

Self-organization of agitated microspheres on various substrates

“…As mentioned briefly in the previous sections, we hypothesize that the tribocharging mechanism 44,52–55,76,77 lies at the heart of the high packing density of both silica and polystyrene particle monolayers attained on the CF x -coated substrates. To verify this hypothesis, we performed Kelvin probe force microscopy (KPFM) measurements using an atomic force microscope (AFM) to measure the surface profile and simultaneously measure the potential difference caused by the surface charge.…”

“…In earlier reports, scientists primarily engaged in studying the gravity-dominated pattern formation that emerged when disordered granular packings comprising large, mm-sized spheres or binary grain mixtures on substrates were vibrated in lateral direction. 39–45 The well-established concept of vibro-fluidization is commonly applied to mobilize solid granular material or agglomerated powders, i.e. , during vigorous horizontal or vertical vibration, granular materials behave in a fluid-like manner.…”

“…[36][37][38] In earlier reports, scientists primarily engaged in studying the gravity-dominated pattern formation that emerged when disordered granular packings comprising large, mm-sized spheres or binary grain mixtures on substrates were vibrated in lateral direction. [39][40][41][42][43][44][45] The well-established concept of vibrofluidization is commonly applied to mobilize solid granular material or agglomerated powders, i.e., during vigorous horizontal or vertical vibration, granular materials behave in a fluid-like manner. [46][47][48][49][50] Inspired by this body of work, we explore in this study if starting from disordered fine powder particles, the microspheres can be arranged in ordered structures, i.e., particle monolayers, using the same concept.…”

Triboelectric Charging of Particles, an Ongoing Matter: From the Early Onset of Planet Formation to Assembling Crystals

“…24 Lately, Grzybowski's group reported the formation of these granular crystals on supporting conductive substrates and showed that induced dipole and multipole interactions between the particles and the conductive substrate account for the stability of these granular structures. 23 Interestingly, larger crystal structures were obtained when a second conductive substrate was placed on top of the setup without touching the beads, i.e., charge transfer with the top plate was excluded (cf. Figure 3b).…”

“…Figure 3c). 23 The formation of granular crystals using electrostatic selfassembly is not restricted to spheres but could also be applied to obtain crystals of other millimeter-sized objects such as cubes (cf. Figure 3d) or rods by mechanical agitation.…”