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<\/div>A new technique can precisely steer drops of water around obstacle courses and into chemical reactions<\/p>\n
Jonathan Knowles\/Getty Images<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
Putting tiny magnetic particles inside ordinary water droplets can turn them into liquid acrobats \u2013 the droplets can climb steps, leap over obstacles and jump-start chemical reactions. This level of control could be useful in drug delivery or to make more complex lab-on-a-chip technologies.<\/p>\n
Shilin Huang<\/a> at Sun Yat-sen University in China and his colleagues made a surface with tiny grooves and covered it in a varnish that is superhydrophobic, or nearly impossible to wet<\/a>. They knew water droplets sitting on top of such grooves can spontaneously jump up because of the pressure difference between a droplet\u2019s bottom, which is deformed by the small channel, and its rounder and less restrained top.<\/p>\n The researchers wanted to create this pressure difference on demand. They added a tiny magnetic particle<\/a> into each droplet and placed an electromagnet underneath the groove. When they turned on the electromagnet, it pulled the particle \u2013 and therefore some of the droplet \u2013 into the groove. When they switched it off, the droplet\u2019s shape rebounded and it flew upwards as if flying from a slingshot.<\/p>\n <\/p>\n With this technique, the team made liquid droplets hop up millimetre-scale stairs and over miniature obstacles. The researchers even steered a droplet into a narrow space between two wires, thus connecting a circuit and lighting a light bulb.<\/p>\n