microgravity conditions aboard sounding rockets to observe the Marangoni effect without the influence of gravity. Research on heat pipes performed on the International Space Station revealed that whilst heat pipes exposed to a temperature gradient on Earth cause the inner fluid to evaporate at one end and migrate along the pipe, thus drying the hot end, in space (where the effects of gravity can be ignored) the opposite happens and the hot end of the pipe is flooded with liquid. This is due to the Marangoni effect, together with capillary action. The fluid is drawn to the hot end of the tube by capillary action. But the bulk of the liquid still ends up as a droplet a short distance away from the hottest part of the tube, explained by Marangoni flow. The temperature gradients in axial and radial directions makes the fluid flow away from the hot end and the walls of the tube, towards the center axis. The liquid forms a droplet with a small contact area with the tube walls, a thin film circulating liquid between the cooler droplet and the liquid at the hot end. The effect of the Marangoni effect on heat transfer in the presence of gas bubbles on the heating surface (e.g., in subcooled nucleate boiling) has long been ignored, but it is currently a topic of ongoing research interest because of its potential fundamental importance to the understanding of heat transfer in boiling. Examples and application A familiar example is in soap films: the Marangoni effect stabilizes soap films. Another instance of the Marangoni effect appears in the behavior of convection cells, the so-called Bénard cells. One important application of the Marangoni effect is the use for drying silicon wafers after a wet processing step during the manufacture of integrated circuits. Liquid spots left on the wafer surface can cause oxidation that damages components on the wafer. To avoid spotting, an alcohol vapor (IPA) or other organic compound in gas, vapor, or aerosol form is blown through a nozzle over the wet wafer surface (or at the meniscus formed between the cleaning liquid and wafer as the wafer is lifted from an immersion bath), and the subsequent Marangoni effect causes a surface-tension gradient in the liquid allowing gravity to more easily pull the liquid completely off the wafer surface, effectively leaving a dry wafer surface. A similar phenomenon has been creatively utilized