Figure 4.

Folding card design for timed sequential delivery using a 2DPN with sugar time delays and volume-limited fluid source pads. A) Photo of the folding card. The 2DPN with sugar-treated legs was adhered to one leaf of the card, and glass fiber fluid source pads were adhered to the other leaf. B) Schematic of card and fluid sources prior to card activation. The sugar solution applied to each leg is indicated as a percent of saturation at room temperature. Dyed PBST was added to each source pad (11 microliters), and the card was activated by folding. C) Images corresponding to arrival of each fluid at the detection line. White rectangles around the card perimeter are adhesive pads used to hold the card closed. D) Time course of color at the detection line. White arrows indicate transitions between multiple videos used to generate the data; time gaps of <10 seconds between each video are not included in the time course, but these represent a small fraction of the overall time (time gaps were included in all reported numbers). E) Arrival time of each reagent at the detection zone. Errors in arrival time (n=5 devices) are comparable to those for simple strips in Figure 2.