Tunable rose petal effect of cobalt coated zinc surfaces via a facile electroless galvanic deposition process

<p>The rose petal effect (large apparent contact angles accompanied by high affinity to water) has greatly inspired researchers recently. In this paper, the rose-petal surfaces with tunable high water adhesion have been prepared successfully via a facile electroless galvanic deposition process as well as the subsequent modification with stearic acid on zinc substrates. We have regulated the concentration of CoSO<sub>4</sub> solution in the process of electroless galvanic deposition to control the surface topography. After being modified with stearic acid, the as-prepared cobalt coated films showed similar apparent contact angles larger than 150° but contrast high water adhesion. To the best of our knowledge, the fabrication of rose petal surfaces with tunable water adhesion is still scarce. The largest water droplet volumes suspended on the tunable rose petal surfaces were 8, 24 and 28 μL, respectively. In addition, based on the different water adhesion on the rose petal surfaces, the selective transportation of microdroplets with different volumes has been demonstrated. We believe that these tunable adhesive rose petal surfaces would have great potential in the droplet-based microreactors.</p>