%0 Online Multimedia %A Zhang, Kai %A Liang, Qionglin %A Ai, Xiaoni %A Hu, Ping %A Wang, Yiming %A Luo, Guoan %D 2011 %T Comprehensive Two-Dimensional Manipulations of Picoliter Microfluidic Droplets Sampled from Nanoliter Samples %U https://acs.figshare.com/articles/media/Comprehensive_Two_Dimensional_Manipulations_of_Picoliter_Microfluidic_Droplets_Sampled_from_Nanoliter_Samples/2601823 %R 10.1021/ac2017458.s003 %2 https://acs.figshare.com/ndownloader/files/4250686 %K Picoliter Microfluidic Droplets Sampled %K droplet manipulations %K method %K droplet arrays %K microwell %X A facile method is presented for achieving comprehensive two-dimensional droplet manipulations in closed microstructures consisting of microwell arrays and a straight microchannel. In this method, picoliter/nanoliter droplets with controllable sizes and numbers are sampled from nanoliter samples/reagents with almost 100% efficiency. Droplet motions are precisely controlled in the ±X-direction and ±Y-direction by managing hydrostatic pressure and magnetic repulsion, respectively. As a demonstration, a fluorescein-labeled droplet and a deionized droplet are successively generated and trapped in adjacent microwells. Then their positions are quickly exchanged without cross-contamination and fusion is implemented on-demand. After operations, hydrophobic ferrofluid can be completely replaced by mineral oil and droplets still remain in microwells safely. A typical fluorescence intensity-based assay is demonstrated: droplet arrays containing copper ion are diluted disproportionately first and then detected by addition of droplet arrays containing Calcein. With the ability of comprehensive two-dimensional droplet manipulations, this method could be used in various miniaturized biochemical analyses including requirements of multistep procedures and in situ monitoring. %I ACS Publications