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INTELLECTUAL MERITS

RUI: “ Coffee Ring ” Formation Dynamics on Smooth, Defect-Free Substrates with Controlled Wettability Wei Chen, Mount Holyoke College, DMR 1005324. INTELLECTUAL MERITS

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INTELLECTUAL MERITS

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  1. RUI: “Coffee Ring” Formation Dynamics on Smooth, Defect-Free Substrates with Controlled WettabilityWei Chen, Mount Holyoke College, DMR 1005324 • INTELLECTUAL MERITS • The commonly observed “coffee ring” phenomenon prevents uniform spreading of particles/solutes on solid substrates. This has important implications in printing, assembling catalysts on support, and manufacturing micro-arrays. Physically and chemically well-controlled substrates and particles have not been used in the previous studies • Clean silicon wafers modified with tris(trimethylsiloxy)chlorosilane afforded smooth substrates with controllable dynamic contact angles up to to 84°/74°. Poly(vinyl alcohol) (PVOH) adsorbed gold nanoparticles (AuNPs) were used as the colloids so that particles do not aggregate during evaporation. • Drying dynamics (drying stages) and deposit patterns (deposit size and ring width) strongly depend on substrate wettability. Interesting, clean silicon wafer (0°/0°) is the only substrate that does not result in coffee-ring formation. Four drying stages: 1st pinning depinning 2nd pinning final deposit

  2. RUI: “Coffee Ring” Formation Dynamics on Smooth, Defect-Free Substrates with Controlled WettabilityWei Chen, Mount Holyoke College, DMR 1005324 BROADER IMPACTS Education: Four undergraduate students, Lanhe Zhang 12’, My-Linh Nguyen 13’, Yen Nguyen 13’, and Elizabeth Laudadio 15’, have been carrying out the NSF-supported research this year. Elizabeth joined the research group this summer and successfully prepared AuNPs of different sizes. This allowed Yen and My-Linh to expand the PVOH-AuNP adsorption studies. Lanhe’s senior thesis on drying patterns of PVOH-AuNPs from sessile drops was awarded the Summa Cum Laude distinction. This summer she adopted an improved substrate system to elucidate factors affecting drying dynamics and criteria for coffee-ring formation. We are in the process of writing a manuscript on the findings. The PI will present the research in the upcoming ACS National Meeting. Lanhe is starting her Ph.D. study in the Materials program at Northwestern University in the fall. Outreach: We continue to work with Hypatia, a local nonprofit organization helping teen mothers to get GEDs. It was one of the Arts and Humanity Programs for Youth honored by the First Lady last November. In addition, the PI served on a career panel for graduate students and postdoctoral researchers at the University of Massachusetts, Amherst last fall. Summer Research 2012

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