Precise Fabrication of Elongated Janus Microparticles

Abstract

Janus particles that have regions with different properties (e.g., a metal and a polymer) are of great interest for extensive technological aspects such as material and environmental sciences, surface and functional chemistry, drug delivery, biomedicals, and micro/nanomotors. Numerous techniques, including masking, phase separation, and self-assembly, have been presented in Janus particle fabrication. Nonetheless, a method for precise fabrication is challenging and necessary to control the properties of Janus particles accurately. Here, truncated-cone elongated Janus microparticles with one surface of epoxy-based negative photoresist (SU-8) microparticles deposited with gold are fabricated. The microparticles in SU-8 are produced by micropatterning with height to width design aspect ratios of 1, 2, 5, and 10 using a proton beam writing. Gold coating on the surface of SU-8 microparticles is subsequently performed using a magnetron sputtering technique. Experimental results showed that the design aspect ratio had to exceed 2 for coating the side surfaces. These Janus microparticles can be produced with uniform sizes, shapes, and coating thickness. This method for fabricating well-defined Janus microparticles can be adapted to many applications, particularly as metal-polymer particles for microplastic research.