(A) One-to-one mapping demonstrated for the punched code and sequence of droplets generated.
A binary code was implemented (every alphabet assigned a 5 bit code, example “U” = 10101) spelling “PUNCHCARD MICROFLUIDICS”. The presence of a hole in punch card tape (top) results in a single droplet representing a binary value of “1” while the absence of a hole results in no droplet representing a binary value of “0”. Vertical height of each plug represents droplet volume, which is approximately 2.5 nL. (B) Results of a qualitative colorimetric assay to test pH, ammonia, nitrates and nitrites in three samples: deionized water, pond water and seawater. Photographs compare bulk reactions (left image) with microfluidic outlet (right image); (1) pH readings with deionized water having a pH of 7.8, pond water at 8.2 and seawater at 8.8, (2) Ammonia levels in parts per million with deionized water at 0 ppm, pond water at 0.25 ppm and seawater at 0 ppm, (3) Nitrite levels with the deionized and sea water samples showing none and pond water at 2 ppm, (4) Nitrate levels in the water samples with pond water at 160 ppm and the deionized water and sea water samples having none.