Can QR Codes be used to readout Colorimetric Gas Sensors? A Back-Compatible Color QR Code with an Embedded CO2 Sensor Dye

Devices to readout colorimetric dyes have been presented before, often these kinds of devices try to fix the illuminant and capture conditions by creating an ad hoc complex hardware setup attached to smartphones or other digital cameras. Here, we present a cost-effective sensor fabrication pipeline to embed a colorimetric dye in a QR Code, which can be read by any smartphone. QR Codes present themselves as a standard well-established machine-readable patterns in which to place gasometric active dyes. Which this proposal we preserved the integrity of the QR Code data by using a novel approach to back-compatibility across the pattern creation, e.g. not only placing the dye in the middle of -or outside- the QR Code. We demonstrate this concept by embedding a CO2 sensor dye in a QR Code, which can be read by any smartphone, while the QR Code presents a link to our website and a traceability ID. The dye is based on a pH-sensitive dye that changes color in the presence of CO2, focused on Modified Atmosphere Packaging (MAP) applications.