Affiliation:
1. Institut für Physik Johannes Gutenberg Universität Staudinger Weg 7 55128 Mainz Germany
2. Institute for Condensed Matter Physics Department of Physics Technische Universität Darmstadt Hochschulstr. 8 64289 Darmstadt Germany
3. Huazhong University of Science and Technology Luoyu Road 1037 Wuhan 430074 China
Abstract
AbstractWriting is an ancient communication technique dating back at least 30 000 years. While even sophisticated contemporary writing techniques hinge on solid surfaces for engraving or the deposition of ink, writing within a liquid medium requires a fundamentally different approach. The study here demonstrates the writing of lines, letters, and complex patterns in water by assembling lines of colloidal particles. Unlike established techniques for underwater writing on solid substrates, these lines are fully reconfigurable and do not require any fixation onto the substrate. Exploiting gravity, an ion‐exchange bead (pen) is rolled across a layer of sedimented colloidal particles (ink). The pen evokes a hydrodynamic flow collecting ink‐particles into a durable, high‐contrast line along its trajectory. Deliberate substrate‐tilting sequences facilitate pen‐steering and thus drawing and writing. The experiments are complemented with a minimal model that quantitatively predicts the observed parameter dependence for writing in fluids and highlights the generic character of writing by line‐assembly. Overall, the approach opens a versatile route for writing, drawing, and patterning fluids—even at the micro‐scale.
Subject
Biomaterials,Biotechnology,General Materials Science,General Chemistry