Multifurcate Assembly of Slanted Micropillars Fabricated by Superposition of Optical Vortices and Application in High-Efficiency Trapping Microparticles

Self-assembly induced by capillary force is abundant in nature and has been widely used in fabrication as a bottom-up method. Here a rapid and flexible method for achieving an even number of furcate slanted micropillars by single-exposure under a spatial phase modulated laser beam is reported, which is produced by designing a superimposed hologram with opposite topological charges to split the incident beam into several equal-weighting sectors. These furcate micropillars with intentional spatial arrangement can be directed to capillary-assisted self-assembly process for generating designable hierarchical functional arrays. Due to the slanted characteristic of micropillars (8 degrees-13 degrees), the assembled arrays are very stable and can be used as an effective tool for trapping SiO2 particles to form honeycomb patterns with an ultrahigh trapping ratio (>90%), which can image as a microlens array. The investigation reveals that micropillars with a height of 6 mu m exhibit the high trapping ratio of particles, which maintain a fine imaging performance. The fast fabrication (more than 2 orders of magnitude enhancement) of furcate slanted pillars paves an avenue for developing innovative microoptics, microfluidics and biological scaffold engineering.