Authors: Lester Li Victor Breedveld Dennis W Hess
Publish Date: 2012/08/21
Volume: 291, Issue: 2, Pages: 417-426
Abstract
Fabrication of surfaces with heterogeneous contact angle hysteresis enables extraction of droplet samples from bulk liquid volumes These surfaces are created by printing high hysteresis wax islands onto low hysteresis superhydrophobic paper The volume of the sampled droplets depends on the hysteresis of the printed islands which can be controlled through both physical and chemical means Physically hysteresis is modified through the addition of surface roughness Chemical hysteresis is tuned by changing the active chemical groups present on the wax surface The observed control of the volume of sampled droplets which is necessary for quantitative biochemical or chemical assays extends to scenarios in which multiple droplet samples are extracted simultaneously from a single bulk droplet Demonstration of the capacity of this technique to perform colorimetric glucose immunoassays is described The ability to obtain welldefined microliter sample volumes and to extract several samples simultaneously from the same source enables the development of twodimensional paperbased microfluidic devices for biomedical testingThe authors thank Dr Ashwini Sinha Praxair for generously donating the pentafluoroethane PFE gas Stephanie Didas for materials support and Yan Liu for support with CA measurements The authors are also grateful to the Institute for Paper Science and Technology IPST at Georgia Tech for fellowship support for LL
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