Influence of temperature on the performance of an evaporation driven micro pump
article
Microfluidic devices are important for health care applications. Some of the applications require a continuous liquid flow over a sensor surface, which can be accomplished by an evaporation driven pump. We have realized an evaporation driven pump on a multilayer substrate foil fabricated by lasers. The structures are ablated on polyethylene terephthalate (PET) stacked foils with an inlet and an outlet, and connected by a microchannel. At the outlet, the liquid evaporates via a porous structure. The capillarity of the channel surface keeps the meniscus in the pores and pushes the liquid towards it thereby generating a flow in the channel with a magnitude that is determined by the evaporation rate. The temperatures of the liquid and the ambient determine the vapor concentration difference and thereby influence the evaporation rate. The goal of this paper is to investigate the effects of temperature on the flow rate in the evaporative micro pump in order to achieve appropriate and controllable flow rates. In our experiments, the flow in the channel is measured using 2D-particle tracking velocimetry. The results are compared with values estimated from an evaporation theory that includes a correction factor for the geometry of the porous structure, since the distribution of pores influences the evaporation. By heating the device creating a temperature difference of 9.4 °C between the substrate and the ambient, the flow rate is increased by 130% compared to the unheated case . These experimental values are in a good agreement with predictions by the evaporation model.
Topics
TNO Identifier
868250
Publisher
SHF
Source title
Proceedings of the 4th European Conference on Microfluidics - Microfluidics 2014 - Limerick, December 10-12, 2014
Pages
μFLU14-18
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