Test strips were imaged by a portable imaging device similar to one previously described by Lu et al.21 . Briefly, the device consists of a 5 megapixel 1080p HD CMOS camera (Raspberry Pi, Cambridge, UK), focusing lens and LEDs (Thorlabs Inc., Newton, NJ, USA), Raspberry Pi computer board, rechargeable lithium ion battery pack (Adafruit Industries, New York, NY, USA), and cassette tray, all surrounded by a 3D-printed light-tight container. The device used in this work is different from the one used by Lu et al21 . in that it does not have any filters, as the measurements in this paper are all colorimetric rather than fluorescent.
After the test strip cassette was placed in the device, we started the imaging. We ran the imaging program via a laptop connected to the imaging device through Wi-Fi. The device then took an image approximately every 10 seconds for a total of 100 images. We processed the images using a Python script which cropped each picture to contain the appropriate portion of the image and determined the test and control line intensities.
After the test strip cassette was placed in the device, we started the imaging. We ran the imaging program via a laptop connected to the imaging device through Wi-Fi. The device then took an image approximately every 10 seconds for a total of 100 images. We processed the images using a Python script which cropped each picture to contain the appropriate portion of the image and determined the test and control line intensities.