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Slips for ew-enhanced condensation

Slippery surface for reliable vapor condensation under electrowetting

 Objective and task description

Electrowetting (EW) is versatile tool to manipulate drops on solid surfaces by applying a voltage [1]. Next to lab-on-a-chip systems, tunable lenses, displays, and various other applications, it was recently in the PCF group that EW can also be used to control the condensation of water vapor onto solid surfaces [2]. This novel approach can lead to substantial improvements of heat transfer. Yet, at present, the solid Teflon surfaces used in these experiments tend to degrade within hours due to the accumulation of permanently trapped charges. So-called liquid-infused surfaces provide a possible solution to this problem. Liquid-infused surfaces consist of a porous material that is filled with oil [3]. Basically, the solid matrix acts a scaffold that holds the oil in place – and the oil film acts as a slippery and replenishable lubricant layer.

Your task will be to explore whether liquid-infused surfaces can be used to overcome the degradation problems of the surfaces currently used for EW-enhanced condensation. To this end you will first characterize the EW response of liquid-infused porous Teflon membranes on substrates with interdigitated electrodes. Subsequently, you will expose the surfaces to vapor for extended periods of time in a condensation chamber and test the EW response again. Variations in both the equilibrium contact angle and the contact angle hysteresis can be seen as indications of surface degradation. If they can be suppressed, this will be an enormous boost for the practical applicability of EW-enhanced condensation.

 

What will you learn?

You will learn about electrowetting and liquid-infused surfaces, both hot topics in current wetting science, and you will acquire practical skills in:

  •  Preparation of liquid-infused slippery surfaces
  • Performing electrowetting and condensation experiments (handling function generator, imaging, analysis)
  • Working with an Optical Contact Angle goniometer

 Contact Information & daily supervision

  •   Dr Jun Gao, Meander 160, tel. 1239

Recommended reading

1.            Mugele, F. and J.C. Baret, Electrowetting: From basics to applications. Journal of Physics-Condensed Matter, 2005. 17(28): p. R705-R774.

2.            Baratian, D., et al., Breath Figures under Electrowetting: Electrically Controlled Evolution of Drop Condensation Patterns. Physical Review Letters, 2018. 120: p. 214502.

3.            Wong, T.-S., et al., Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature, 2011. 477(7365): p. 443-447.