Fast lipid vesicles and dielectric particles migration using thermal-gradient-induced forces

Abstract

Lipid vesicles represent small biological particles that can be used for both targeted drug delivery systems and clinical studies. However, their optical manipulation is hindered by the small difference in the refractive indices with the surrounding medium and the high trapping laser powers that are required. In this work, we combine gradient force, thermophoresis, and diffusiophoresis to deliver and trap individual lipid vesicles with low trapping laser powers. The total optothermal force exerted on liposomes causes them to migrate rapidly toward the laser focus with a high average migration velocity of 1.77 µm under 7.3% w/v PEG concentration and low trapping laser power of 1 mW. A high normalized experimental trap stiffness of 0.88 (pN/µm)/mW was obtained at 7.3% w/v PEG/water solution. This work opens new ways for bioparticle sorting and manipulation with potential applications in cellular studies, drug delivery, biosensing, and medicine