Sample transport with thermocapillary force for microfluidics

This paper presents a novel concept for transport of aqueous sample in capillaries. The concept is based on the thermocapillary effect, which utilizes the temperature dependency of surface tension to drive a sample droplet. To date, the major problem of this concept was the evaporation of the aqueous sample. In our approach, a liquid-liquid system was used for delivering the sample. The aqueous sample is protected by silicone oil, thus evaporation can be avoided. A transient temperature field drives both liquids away from a heater. The paper first presents a theoretical model for the coupled thermocapillary problem. Next, the paper compares and discusses experimental results with different capillary sizes. The results show the huge potential of this concept for handling sample droplets dispersed in oil, which are often created by droplet-based microfluidics.