Why a Coffee Mark Stays in a Ring
Why a Coffee Mark Stays in a Ring
  • Reporter Reo Ye-jin
  • 승인 2013.02.15 21:35
  • 댓글 0
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Professor Jung Ho Je (MSE) and Research Assistant Professor Byung Mook Weon (MSE) discovered why coffee marks remain in a ring. Colloidal particles suspended in a fluid usually inhibit complete wetting of the fluid on a solid surface and cause pinning of the contact line, known as self-pinning. The research team showed difference in spreading and drying behaviors of pure and colloidal droplets using optical and confocal imaging methods. The study showed that the difference comes from the spreading inhibition by colloids. By tracking individual colloids near the contact lines of evaporating colloidal droplets, the team observed a self-pinning mechanism based on the spreading inhibition. The discovery was posted in Physical Review Letters on Jan. 11.