Marangoni-driven micromotor in liquid medium

Marangoni flow, the flow of liquids induced by a temperature gradient at a liquid-gas interface, can be utilized in microfluidic actuation. In this paper, we describe the rotary motion, by Marangoni flow, of a micromotor made of stainless steel immersed in a thin layer of liquid. A 128-pixel heater array is suspended ≈500 μm above the liquid of height 2 mm. By applying 1 W to each of the four heaters directly above the four rotor blades, a temperature gradient of 0.8 K/mm is created at the surface. A rotor of diameter 4.1 mm with a blade angle of 34° experiences a maximum torque of 5.6 pN.m and takes 28 sec to make a complete rotation in a liquid with viscosity 5 cSt. The speed of rotation is affected by the blade angle of the rotor, temperature gradient of liquid surface and liquid viscosity.