3D printed monolithic microfluidic device with an integrated porous filter: Application to pH measurement of water

Despite the available 3D printing technologies, fabrication of miniaturized analytical systems with integrated functional components is still one of the largest impediments. Here, we integrate a permeable porous filter into a 3D printed fluidic device capable of withstanding moderate hand pressure for in-field colorimetric pH measurements. The pH indicator is loaded and dried into the device, and the pH determined from converting images taken by a smartphone camera to a chromaticity diagram in International Commission on Illumination (CIE) 1931 color space and compared to calibration standards. The portable miniaturized device was fabricated with an integrated porous structure using a PolyJet 3D printer. One hundred and thirty-six devices could be printed in a single run (136 min), with cost of $0.6 per device. The 3D printed devices are capable of filtering particulate matter from the sample before mixing with an indicator avoiding optical interferences. Different environmental samples with a wide pH range (3-10) can be measured rapidly within 1 min.