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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Poster 1

CPP 12.16: Poster

Montag, 5. September 2022, 18:00–20:00, P1

Scaling mechanical instabilities in drying micellar droplets — •Jayant Kumar Dewangan¹, Nandita Basu², and Mithun Chowdhury¹ — ¹Lab of Soft Interfaces, Metallurgical Engineering and Materials science, IIT Bombay, Mumbai 400076, India — ²Department of Chemistry, IIT Bombay, Mumbai 400076, India

We present unique wrinkling patterns produced by evaporating sessile micellar aqueous droplets on rigid and soft substrates kept at temperatures far above ambient. The wrinkling patterns vary dramatically depending on the material's elastic modulus and substrate, the concentration of the micellar solution, and the temperature of the substrate. Coffee-ring-like morphologies are observed at very low concentration regimes (CTAB concentration < 0.0364 wt%), devoid of any wrinkling morphology, regardless of substrate temperature. Droplets deposited at a temperature above 85°C wrinkle formation begins at the droplet peripheral zone, radial on the stiff glass annular on soft cross-linked PDMS substrate, at the high initial concentration regime (CTAB concentration > 0.0364 wt%). Radial wrinkles on the glass substrate and annular wrinkles on the cross-linked PDMS substrate nucleate from the edges connecting to the deposit's central region at CTAB concentration > 2.73 wt%. The ratio of the width of the gel-like deposit to the radius of the droplet scales with surfactant concentration is dependent on the initial equilibrium contact angle of micellar droplets. Our findings support previous literature on mechanical instabilities of dried deposits by interdependent scaling relationships between deposit radius, wavelength of wrinkle, thickness, and elastic modulus.