Multiphysics numerical investigation of photothermal self-driving characteristics of SiO2@Au Janus microparticles for drug delivery

The photothermal self-driving process of Janus microparticles has wide application prospects in the fields of biomedicine. Since silica and gold have good biocompatibility and high photothermal conversion efficiency, the SiO2@Au Janus microparticles are widely used as drug carriers. Based on the multiphysics coupling method, the photothermal self-driving process of SiO2@Au Janus microparticles was investigated, wherein the substrate was SiO2 particles and one side of the particles was coated with gold film. Under a continuous wave laser with irradiation of 20 W/cm2, the distance covered by the Janus particles was increased by increasing the thickness of the gold film and reducing the size of the SiO2 particles; the self-driving characteristics of the Janus particles were controlled substantially by increasing the intensity of the incident laser. Based on the simulation results, the thermophoretic motion and Brownian motion of particles can be measured by comparing the absolute values of the thermophoretic force impulse, Brownian force impulse, and drag force impulse. The Brownian force acting on Janus microparticles under low laser power cannot be ignored. Furthermore, the minimum laser power required for Janus particles to overcome Brownian motion was calculated. The results can effectively guide the design of Janus particles in biomedicine and systematically analyze the mechanism of particle thermophoretic motion during drug delivery.