Rolling and ageing in T-ramp soft adhesion

• Published in: arXiv.org
• Main Authors: Boniello, Giuseppe, Tribet, Christophe, Emmanuelle, Marie, Croquette, Vincent, Zanchi, Dražen
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 09.09.2017
• Subjects: Adhesion; Adsorption; Brownian motion; Colloids; Diffusion rate; Flat plates; Microparticles; Physics - Soft Condensed Matter; Polymer coatings; Polymers; Residence time distribution; Substrates
• DOI: 10.48550/arxiv.1709.02971

Immediately before adsorption to a horizontal substrate, sinking polymer-coated colloids can undergo a complex sequence of landing, jumping, crawling and rolling events. Using video tracking we studied the soft adhesion to a horizontal flat plate of micron-size colloids coated by a controlled molar fraction \(f\) of the polymer PLL-g-PNIPAM which is temperature sensitive. We ramp the temperature from below to above \(T_c=32\pm 1^{\circ}\)C, at which the PNIPAM polymer undergoes a transition triggering attractive interaction between microparticles and surface. The adsorption rate, the effective in-plane (\(x-y\)) diffusion constant and the average residence time distribution over \(z\) were extracted from the Brownian motion records during last seconds before immobilisation. Experimental data are understood within a rate-equations based model that includes ageing effects and includes three populations: the untethered, the rolling and the arrested colloids. We show that pre-adsorption dynamics casts analyze a characteristic scaling function \(\alpha (f)\) proportional to the number of available PNIPAM patches met by soft contact during Brownian rolling. In particular, the increase of in-plane diffusivity with increasing \(f\) is understood: the stickiest particles have the shortest rolling regime prior to arrest, so that their motion is dominated by untethered phase.