Journal: Nature Communications

Article Title: Rich complex behaviour of self-assembled nanoparticles far from equilibrium

doi: 10.1038/ncomms14942

Figure Lengend Snippet: ( a ) Illustration showing colloidal solution of polystyrene spheres sandwiched between two thin microscope glass slides with an ultrafast laser beam focused to ∼10 μm. ( b ) Image displaying velocity field simulation of Marangoni-type microfluidic flow, where red and dark blue areas denote highest and lowest flow speeds, respectively. Simulated area is a 1 cm by 1 cm cell and a bubble of 50 μm diameter is located at the centre of this cell. Magnified image shows that the laser is introduced as a boundary heat source at the lower right quarter of the bubble, depicted by a red line. ( c ) Image showing numerical simulation of the Brownian nanoparticles that are released from a location close to the bubble and aggregate at its boundary. ( d ) Images showing velocity field simulations of the flow before and after an aggregate forms, where the black lines are streamlines. The dark area on the right, magnified image denotes the self-assembled aggregate. ( e ) Schematic description of the nonlinear feedback mechanisms. ( f ) Plot of as a function of φ (filling ratio), showing stable and unstable fixed points for F =0.001 and 〈 ξ ( t )〉 rms =0.1. ( g ) Plot comparing toy model and three measurements with the sigmoid function, confirming the autocatalysis characteristics. Experimental data are extracted from the temporal evolution of number of particles in a selected region while forming an aggregate. Toy model data are the evolution of φ over time (blue line) for F =0.001 and 〈 ξ ( t )〉 rms =0.1 with the initial condition of φ (0)=0.21, fitted with a sigmoid function (red line) of the general form 1/(1+ e − t ).

Article Snippet: Colloidal solution of polystyrene nanoparticles (500 nm in diameter) was purchased from Microparticles GmbH.

Techniques: Microscopy