Issue Date: November 7, 2011
With a few quick folds of a sheet of photolithographically patterned paper, Hong Liu and Richard M. Crooks of the University of Texas, Austin, have devised a more functional assembly of paper microfluidic devices (J. Am. Chem. Soc., DOI: 10.1021/ja2071779). In years past, George M. Whitesides and coworkers at Harvard University have reported making three-dimensional paper microfluidic devices, which have potential as low-cost medical diagnostic tools. In these devices, microfluidic channels and reservoirs are patterned on chromatography paper using hydrophobic photoresist material or wax. Aqueous samples are driven along the hydrophilic paper channels by capillary action, and multiple target analytes such as glucose and proteins in a drop of urine can be detected by colorimetric chemistry. The Harvard versions were prepared by patterning individual layers sequentially, stacking them using double-sided tape, and then laser-punching holes to provide connections between layers. Liu and Crooks achieved the same effect, with quantitative fluorescence measurements now possible, by creating patterns in one step on a single sheet of paper and then folding it to obtain the desired stacking order. The Texas team next plans to integrate more sophisticated chemical and biological functions into their origami paper analytical devices, which they are calling oPADs.
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