BELSPO IAP 7/38 - Thermocapillary micromanipulation
Manipulation of objects in the microscale (object size below one mm) is still a challenge. The scaling process of classic manipulation techniques does not provide satisfactory solutions. Therefore it is necessary to develop new techniques that take into consideration the physical limitations of this scale. Manipulation without contact, is a promissing solution which is based on external force fields. This project proposes to use laser induced thermocapillary convection to move objects placed in the interface air/water. The increase in temperature changes the properties of the air/water interface and a flow is generated towards the cold regions. The goal of this project is to model this physical phenomena to automatize the movement of objects.
Thermocapillary flow is generated due to an thermal gradient generated at the the fluid/air interface which also generate a surface tension gradient. The surface tension gradient will produce a force that will pull the liquid from the low surface tension region (hot region) towards the high surface tension region (cold region).
The main novelty of this project is the combination of 3 characteristics: Thermocapillary flow, laser heating and manipulation of object at the air/water interface.
1 Thermocapillary flow is advantageus because it is not an instability, meaning that its onset does not depend on the value of a dimensionless number (which is the case of Natural and Marangoni convection which depend on the Rayleigh and Marangoni numbers respectively).
2 Laser heating allows to generate significant thermal gradients on small regions which means that important flows can be generated without disturbing the entire water surface, so manipulation can be performed locally.
3 When the water/air interface is heated from the top, the velocity at the top region is the highest. Therefore, an object placed there would be affect by the fastest flow region which would allow it to attain a maximal velocity.
The final goal of this project is to design an experimental setup that can deterministically manipulate objects placed at the water/air interface on a closed-loop system.