The temperature distribution of droplet surface directly influences the microflow inside the droplet

but most of the papers about droplet surface temperature are based on substrate heating mode. In this study

with the aid of the infrared thermograph and MEMS technology

both the surface temperature and the temperature gradient of the droplet were investigated based on local heating mode. It was found that different from the concave distribution of surface temperature in the substrate heating mode

the surface temperature of the droplet in the local heating mode showed a convex distribution with a higher temperature at the apex but a lower temperature at the edge. With the increase of heating power

both the surface temperature and the temperature gradient were increased. However

as the heating power reached a certain value

the surface temperature gradient increased less and finally tended to a uniform distribution.  The surface temperature of the droplet before and after the bubble burst under local boiling was also investigated. The results presented in this paper help to understand the internal microflow of droplets in the local heating mode and manipulate the microflow inside droplets.