Figure 6.

Protein detection device. A. Top view of the device showing important parts. The device consists of one nitrocellulose test strip, and three source legs, one feeder channel, and one timing wick, all made of glass fiber. There are three on-switches, V_ON,1, V_ON,2, V_ON,3, between the test strip and source legs 1, 2, and 3, respectively, and an off-switch, V_OFF, that, when actuated, disconnects the feeder channel from all three source legs. Scale bar is 1 cm. B. The shape of the glass fiber timing wick and the location of the four valves. The wick splits at the point indicated by the green asterisk – one branch actuates V_OFF and the other actuates the three on-switches sequentially. C. Schematic of a step-by-step procedure of conducting the protein detection test. The test is initiated by adding 30 μl sample in the sample inlet port and 2 ml water in the fluid reservoir. No further user steps are required and the result can be read in the detection zone after 20 minutes. D. The operation of the device is demonstrated using colored fluids. Time-lapse images show the sequential flow over the detection zone of i) red fluid introduced through the sample port (t = 5 min), ii) yellow fluid (t = 10 min), iii) a wash fluid (t = 14 min), and iv) green fluid (t = 23 min), rehydrated from legs 1, 2, and 3, respectively. The status of valves is tabulated at each time point; a green check indicates an actuated valve. Scale bar is 1 cm. E. Montage of time-lapse images over a square region indicated by the yellow box (t = 23 min) in the detection zone. F. Time-lapse images of the detection zone of the device that was used to conduct a PfHRP2 protein detection assay. The two spots represent test result (bottom) and control (top). The sample flows over the detection zone first (t = 5 min), followed by the labeling antibody (t = 10.3 min), wash buffer (t = 16 min), and gold enhancement reagents (t = 23 min).