Water is sticky stuff. Attractive forces between its molecules create surface tension, which keeps it running across windscreens, curling up at the edges of cups, and explains why fat raindrops linger on leaves. Investigating droplets resting on thin fibres, researchers found that bent fibres hold more water. Crafted corners like those shown holding blue and red liquid can hold up to three times as much water as horizontal fibre (green drop) – an angle of around 36 degrees creates a bend with the perfect mix of sticky forces. This water bearing knowledge may come in useful when designing microfluidic devices to mix or pump biological fluids. Or perhaps the techniques involved might investigate sticky angles at play in the human body, where bends in blood vessels, for example, change with posture, age and disease.
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