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.