Colloidal Pixel-Based Micropatterning Using Uniform Janus Microparticles with Tunable Anisotropic Particle Geometry

A new platform for designing 2D colloidal arrays by using Janus microparticles (JMPs) with tunable anisotropic particle geometry is introduced. The JMPs are synthesized by the photopolymerization of biphasic emulsion droplets produced by capillary-based microfluidics while adjusting the spreading coefficient between -4.4 and -7.2 mN m(-1). The unidirectional rubbing of JMPs leads to their exact positioning in the stencil holes. The ratio of the hole diameter to the bigger bulb diameter of JMPs, ranging from 1.05-1.16, is critical for maximizing the positioning rate. When the anisotropic geometry factor is near zero, a standing particle configuration with a protrusion in the stencil hole is obtained more efficiently due mainly to the enhanced steric constraint. Finally, it is demonstrated that different types of JMPs with controlled sizes and geometries can be arrayed at specific hole sites of the stencil, thus enabling development of a colloidal pixel-based micropatterning technology.