10.1371/journal.pone.0115993.g006 George Korir George Korir Manu Prakash Manu Prakash (A) One-to-one mapping demonstrated for the punched code and sequence of droplets generated. Public Library of Science 2015 paper tapes example colorimetric water quality assays punch card programming volume fluid handling Card Programmable Microfluidics microfluidic paper tape encodes information PUNCHCARD microfluidics 2015-03-04 03:42:02 Figure https://plos.figshare.com/articles/figure/_A_One_to_one_mapping_demonstrated_for_the_punched_code_and_sequence_of_droplets_generated_/1325879 <p>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.</p>