Laser-induced rotary micromotor with high energy convert efficiency

Light is a precious resource that nature has given to human beings. Converting green, recyclable light energy into the mechanical energy of a micromotor is undoubtedly an exciting challenge. However, the performance of current light-induced micromotor devices is unsatisfactory, the conversion efficiency of the light-to-work is only 10-15-10-12. In this paper, we propose and demonstrate a laser-induced rotary micromotor operated by Δα-type photopheresis in the pure liquid glycerol, whose energy conversion ratio researches to as high as 10-9, which is 3-6 orders of magnitude higher than previous light-induced micromotor devices. In addition, we perform the micromotor neither with a light field carrying angular momentum nor with a rotor with a special rotating symmetrical shape. We just employ an annular-core fiber to configure a conical-shaped light field and select a piece of graphite sheet (with an irregular shape) as the micro-rotor. The Δα-type photophoretic force introduced by the conical-shaped light field drives the rotation of the graphite sheet. We perform the rotating rate up to 818.2 r.p.m., which can be controlled by tuning the incident laser power. This optical rotary micromotor is available for twisting macromolecules or generating vortex and shear force in a medium at the nanoscale.