Direction-Switchable\nSelf-Thermophoresis Motor with\nChiral Antihelical Resonators

The thermophoresis effect has revolutionized adjustable\nmanipulation\nbased on physical, chemical, and even biomolecular mechanisms. However,\ntraditional self-propelled and thermophoresis devices lack reconfigurability\nof their motion, hindering the dynamic switching and artificial spatial\nlocation of the motors. Through numerical simulation, this paper delves\ninto the underexplored concept of tunable antihelical resonators,\nwhich offer rich managing channels on differential optical absorption,\nthermal gradient, and propulsion. Utilizing a pair of oppositely helical\ngold nanostructures, we demonstrate the achievement of direction-switchable\nself-thermophoresis motion, along with artificially controllable forward\nand backward propulsion as well as the retrace operation. To clarify\nthe mechanism in detail, the chiral circular dichroism related resonant\nlight energy absorption and temperature gradient distribution around\nan antihelical particle are observed under various circularly polarized\nlight sources. We further elucidate the rapid responses and principles\nof photothermal propulsion and successfully manipulate photothermal\nself-propulsion. Additionally, we establish a linear relationship\nbetween the laser power and multiphysical quantities such as velocity\nand force, enabling quantitative modulation in motion. Our work paves\nthe way for chiroptics enabled direction-switchable self-propelled\nmotion and provides a practically rational basis for direction-switchable\nmotors, nanoparticle transport, tracking techniques, and so on.