Direct observation of impact propagation and absorption in dense colloidal monolayers

Abstract

SignificanceSingle-particle characterization of the impact response has unveiled design principles to focus and control stress propagation in macroscopic granular crystalline arrays. We demonstrate that similar principles apply to aqueous monolayers of microparticles excited by localized mechanical pulses. By inducing extreme local deformation rates and tracking the motion of each particle with velocities that reach up to few meters per second, we reveal that a regime of elastic collisions, typically forbidden due to overdamping, becomes accessible. This provides insights on the stress propagation and energy absorption of dense suspensions upon fast deformation rates.

Heat‐Free Fabrication of Metallic Interconnects for Flexible/Wearable Devices

“…Successful screen‐printing relies on deposition under low shear stress without triggering solidification. We inferred that interparticle Hertzian interactions, and associated hydrodynamics mediated elastic scattering of shear stress, in a colloidal suspension permits dispersion without mechanical fracture of the particles. Increased viscosity of the carrier fluid and stochastic (anisotropic) particle distribution renders faster and more isotropic energy absorption abetted by Stokes' drag and interparticle carrier fluid lubricity .…”

“…We inferred that interparticle Hertzian interactions, and associated hydrodynamics mediated elastic scattering of shear stress, in a colloidal suspension permits dispersion without mechanical fracture of the particles. Increased viscosity of the carrier fluid and stochastic (anisotropic) particle distribution renders faster and more isotropic energy absorption abetted by Stokes' drag and interparticle carrier fluid lubricity . Since ULMCS particles have smooth deformable surfaces, high shear stresses are required to transfer stress into the particles due to surface roughness dependent elastic deformation limit, hence high concentration of these particles can be used.…”

Collapse mechanisms and extreme deformation of particle-laden interfaces

“…The coalescence of particle-coated drops with planar interfaces has been studied to visualize the evolution of the contact area [83] and to determine the velocity threshold for coalescence under impact [84]. The damped, oscillatory dynamics after coalescence is affected by the interfacial rheology of the particle monolayer [80]. [85].…”

Silver‐Nanowire‐Based Interferometric Optical Tweezers for Enhanced Optical Trapping and Binding of Nanoparticles

“…To quantify the perfection and stability of the assembled optical matter arrays, a local orientational bond order parameter is used. For a given particle n , the local hexagonal order parameter ϕ 6 ( n ) is defined aswhere M is the total number of nearest neighbors of particle n and is the angle between a fixed axis (here the x ‐axis) and the bond joining the particle n with another particle m . For a single monolayer particle assembly, the hexagonal order parameter (ψ 6 ) is treated as the average of the local parameters of all the particleswhere N is the total number of particles.…”